RBSE Solutions Class 9 Science Chapter 8 Major Activities of Living Organisms

Major Activities of Living Organisms

Major Activities of Living Organisms Textbook Questions Solved

Objective Type Questions

 

Question 1. The water in plants is conducted by-
(a) Phloem
(b) Xylem
(c) Sieve tubes
(d) Epidermis
Answer: (b) Xylem
In simple words: Xylem is like tiny pipes that carry water from the roots all the way up to the leaves of a plant.

🎯 Exam Tip: Remember that xylem transports water and minerals, while phloem transports food.

 

Question 2. The water which a plant receives from soil is-
(a) Hygroscopic water
(b) Gravitational water
(c) Guttated water
(d) Capillary water
Answer: (d) Capillary water
In simple words: Plants drink the capillary water from the soil. This is the water that stays stuck between soil particles and is easy for roots to take in.

🎯 Exam Tip: Capillary water is the most available form of water for plants, making it crucial for their survival.

 

Question 3. The stomata exchange-
(a) Water vapour and gases.
(b) Oxygen and hydrogen.
(c) Oxygen and carbohydrate.
(d) Nitrogen and water vapour
Answer: (a) Water vapour and gases.
In simple words: Stomata are small openings on leaves. They help plants breathe, letting out water vapor and swapping gases like carbon dioxide and oxygen.

🎯 Exam Tip: Stomata also regulate transpiration, which is the process of water loss from plants, balancing gas exchange with water conservation.

 

Question 4. The conduction of food material is by-
(a) Xylem
(b) Phloem
(c) Lenticles
(d) Red blood corpuscles
Answer: (b) Phloem
In simple words: Phloem is a special tissue in plants that carries the food made in the leaves to all other parts of the plant, like roots and fruits.

🎯 Exam Tip: Food is transported as sugar solution through the phloem to areas where it's needed for growth or storage.

 

Question 6. What is a higher side blood pressure of the normal body-
(a) 120 nm
(b) 90 nm
(c) 140 nm
(d) 80 nm
Answer: (a) 120 nm
In simple words: For a healthy person, the top number when measuring blood pressure, called systolic pressure, is usually around 120 units.

🎯 Exam Tip: Blood pressure measurements include systolic (the higher number, when the heart beats) and diastolic (the lower number, when the heart rests between beats).

 

Question 7. Which is not a function of the stomach-
(a) Storage of food
(b) Absorption
(c) Digestion
(d) Complete digestion of fat
Answer: (d) Complete digestion of fat
In simple words: The stomach stores food and starts digesting proteins, but it does not finish digesting fats. Fat digestion mainly happens in the small intestine.

🎯 Exam Tip: The stomach's main roles are mixing food with digestive juices, breaking down proteins, and killing harmful bacteria with acid.

 

Question 8. The main example of fission is-
(a) Spirogyra
(b) Bryophyllum
(c) Yeast
(d) Amoeba
Answer: (d) Amoeba
In simple words: Amoeba reproduces by splitting into two new organisms, which is a type of fission.

🎯 Exam Tip: Fission is a form of asexual reproduction where a single organism divides into two or more new organisms.

 

Question 9. The reproduction in Rhizopus takes place by-
(a) Binary fission
(b) Budding
(c) Spore formation
(d) Fragmentation
Answer: (c) Spore formation
In simple words: Rhizopus, a type of fungus, reproduces by making tiny spores. These spores can grow into new Rhizopus plants when conditions are right.

🎯 Exam Tip: Spore formation is a common asexual reproduction method in fungi and some plants, allowing them to spread widely.

 

Question 10. Ovules are arranged upon-
(a) Ovary
(b) Style
(c) Anther
(d) Embryo
Answer: (a) Ovary
In simple words: In flowering plants, the small structures called ovules, which later become seeds, are found inside the ovary.

🎯 Exam Tip: The ovary protects the ovules and develops into the fruit after fertilization, while the ovules inside become seeds.

 

Question 11. The metabolic process in plants is dependent on-
(a) Proteins
(b) Fats
(c) Carbohydrates
(d) Vitamins
Answer: (c) Carbohydrates
In simple words: Plant metabolism, which includes all the chemical reactions that keep a plant alive, relies heavily on carbohydrates for energy and building blocks.

🎯 Exam Tip: Carbohydrates are primary energy sources for plants, produced during photosynthesis, and are key to various metabolic pathways.

 

Question 12. Guard cells are found in-
(a) Root
(b) Stem
(c) Leaf
(d) Flower
Answer: (c) Leaf
In simple words: Guard cells are special cells found on the surface of plant leaves. They control the tiny pores called stomata, which help the plant breathe.

🎯 Exam Tip: Guard cells open and close stomata to regulate gas exchange and water loss, adapting to environmental conditions.

 

Question 13. Guttation is seen, when-
(a) Respiration is high
(b) High absorption and low transpiration
(c) Photosynthesis is high
(d) Diffusion is more
Answer: (b) High absorption and low transpiration
In simple words: Guttation happens when plants take in a lot of water from the soil, but they don't lose much water through their leaves (low transpiration). This causes water to push out from the leaf edges.

🎯 Exam Tip: Guttation usually occurs during the night or early morning when the air is humid, reducing the plant's need to transpire.

 

Question 14. Ureotelic excretion is found in-
(a) Amoeba and frog
(b) Human and frog
(c) Birds and lizard
(d) Humans and mammals
Answer: (d) Humans and mammals
In simple words: Ureotelic animals, like humans and other mammals, get rid of waste nitrogen by turning it into urea, which they then excrete in urine.

🎯 Exam Tip: Knowing the different types of excretion (ammonotelic, ureotelic, uricotelic) and examples of animals for each is important for biology.

Major Activities of Living Organisms Very Short Answer Type Questions

 

Question 15. What is the method of excretion in aquatic plants?
Answer: In hydrophytes (aquatic plants), waste products diffuse out from the cell membrane into the surrounding water. Aquatic plants release their waste directly into the water they live in, a simple and efficient process.
In simple words: Water plants get rid of their waste by simply letting it flow out of their cells into the water around them.

🎯 Exam Tip: Aquatic plants have simple excretory mechanisms because water is readily available to dilute and carry away waste products.

 

Question 16. What is the function of guard cells?
Answer: Guard cells contain chlorophyll and carry out photosynthesis. When guard cells swell up with water, they open the stomata. When they lose water and contract, the stomata close. This controls gas exchange and water loss.
In simple words: Guard cells help plants breathe by opening and closing tiny holes on leaves called stomata. They also do a little bit of food making, like other plant cells.

🎯 Exam Tip: The turgor pressure within guard cells directly controls the opening and closing of stomata, regulating vital plant processes.

 

Question 17. What is uricotelic excretion?
Answer: Uricotelic excretion is the process where animals remove nitrogenous waste products mainly in the form of uric acid. This type of excretion helps conserve water. Animals like birds, lizards, and snakes are examples of uricotelic organisms.
In simple words: Uricotelic excretion is when animals get rid of their waste by making uric acid. This helps them save water because uric acid doesn't need much water to be removed from the body.

🎯 Exam Tip: Uric acid is a less toxic form of nitrogenous waste compared to ammonia, allowing animals in arid environments to conserve water.

 

Question 18. Name the two main parts of a plant.
Answer: The two main parts of a plant are the root system and the shoot system. The shoot system includes the stem and leaves.
In simple words: The two main parts of a plant are the roots, which are underground, and the stem with leaves, which is above the ground.

🎯 Exam Tip: The root system anchors the plant and absorbs water and nutrients, while the shoot system is responsible for photosynthesis and reproduction.

 

Question 19. From which vascular tissue, the water reaches to the leaves?
Answer: Water reaches the leaves from the xylem tissue. Xylem forms a network of tubes throughout the plant, from the roots to the leaves, for water transport.
In simple words: Water gets to the leaves through special tubes called xylem, which act like tiny straws carrying water all the way from the roots.

🎯 Exam Tip: Xylem is a crucial vascular tissue composed of dead cells that form a continuous pipeline for efficient water and mineral transport.

 

Question 20. What is the function of phloem?
Answer: The main function of phloem is to transport food, primarily sugars made during photosynthesis, from the leaves (where food is produced) to other parts of the plant, such as roots, fruits, and growing tips. This process is called translocation.
In simple words: Phloem's job is to carry the sugar food made in the leaves to all the other parts of the plant that need energy, like the roots or new shoots.

🎯 Exam Tip: Phloem is a living tissue, unlike xylem, and uses active transport to move sugars against their concentration gradient.

 

Question 22. What is respiration?
Answer: Respiration is a catabolic (breaking down) reaction where food substances like carbohydrates, fats, and proteins are broken down within the body's tissues. This process releases energy, which is stored as ATP. Respiration also helps carry oxygen from the lungs to the tissues and brings carbon dioxide back to the lungs.
In simple words: Respiration is how our body gets energy from food. It breaks down food to make energy and also helps move oxygen into our body and carbon dioxide out.

🎯 Exam Tip: Cellular respiration occurs in all living cells to produce energy, and it's essential for all life processes.

 

Question 23. What is binary fission?
Answer: Binary fission is a method of asexual reproduction where a parent organism divides into two similar, equally sized daughter organisms. This involves a complex process of mitotic division. For example, Amoeba, Euglena, and Paramecium reproduce this way.
In simple words: Binary fission is a way some tiny living things make copies of themselves. One parent simply splits into two identical new living things, like cutting an apple in half.

🎯 Exam Tip: Binary fission is common in prokaryotes (like bacteria) and some single-celled eukaryotes (like Amoeba), leading to rapid population growth.

 

Question 24. What is the floral part?
Answer: The floral part refers to the flower, which is a swollen structure found on the upper side of the flower stalk. A complete flower typically consists of four main sets of parts: (1) Calyx (sepals), (2) Corolla (petals), (3) Androecium (male reproductive parts), and (4) Gynaecium (female reproductive parts).
In simple words: The floral part is the flower itself, which is the reproductive part of a plant. It has four main sections: sepals, petals, male parts, and female parts.

🎯 Exam Tip: Understanding the structure of a flower is key to comprehending plant reproduction and identifying different plant species.

 

Question 25. Write the main example of air layering?
Answer: Air layering is a propagation technique often used for plants like raspberries, Magnolia, Jasmine, and Pomegranate. This method encourages roots to form on a stem while it's still attached to the parent plant.
In simple words: Air layering is a way to grow new plants from a branch while it's still connected to the main plant. Good examples are jasmine and pomegranate plants.

🎯 Exam Tip: Air layering is a valuable asexual propagation technique that allows for the production of new plants that are genetically identical to the parent plant.

Major Activities of Living Organisms Short Answer Type Questions

 

Question 27. Point out the differences between taproot and adventitious root?
Answer:
1. Taproot: This root system develops directly from the radicle of the seed and has a main primary root with smaller side roots. It is typical for dicot plants.
2. Adventitious root: These roots grow from parts of the plant other than the radicle, such as from nodes, internodes, leaves, or the base of the stem. They are common in monocot plants.
The main taproot grows downwards and provides strong anchorage, while adventitious roots often spread out and help with support or storage.
In simple words:
1. Taproot: Grows straight down from the seed, like a main strong root with little branches.
2. Adventitious root: Grows from other parts of the plant, like the stem or leaves, not just from the seed's root part.

🎯 Exam Tip: Taproots are good for deep anchoring and reaching groundwater, while adventitious roots often provide extra support or can be used for vegetative propagation.

 

Question 28. Clarify the differences between xylem and phloem?
Answer:

Both xylem and phloem are essential vascular tissues that work together to ensure the plant's survival and growth.
In simple words: Xylem carries water from the roots to the leaves. Phloem carries the food made in the leaves to the rest of the plant.

🎯 Exam Tip: Xylem typically transports in one direction (upwards), while phloem transports in multiple directions (source to sink).

 

Question 29. Define the following:
Answer:
1. Diffusion: This is the movement of molecules from an area where they are highly concentrated to an area where they are less concentrated. It continues until the molecules are evenly spread out.
2. Osmosis: This is a special type of diffusion where water molecules move through a semipermeable membrane. They move from a solution with more water (weaker solution) to a solution with less water (stronger solution).
3. Plasmolysis: This happens when a plant cell is placed in a solution that has a higher concentration of solutes than inside the cell. Water leaves the cell, causing the protoplasm to shrink away from the cell wall.
4. Imbibition: This is a process where a solid substance absorbs water, causing it to swell. It's how seeds take in water to start germination or how wood swells when wet.
These processes are fundamental to how plants absorb water and nutrients and manage internal cellular conditions.
In simple words:
1. Diffusion: Things spread out from where there's a lot of them to where there's less.
2. Osmosis: Water moves through a special skin from where there's lots of water to where there's less.
3. Plasmolysis: Plant cells shrink when they lose water to a salty outside.
4. Imbibition: Solids soak up water and swell, like a sponge.

🎯 Exam Tip: Diffusion and osmosis are passive processes, meaning they don't require the cell to expend energy.

 

Question 30. Explain the theory pertaining to the ascent of water from root to leaves?
Answer: The ascent of water from roots to leaves involves several processes. Water is absorbed by root hairs from the soil, which contains capillary water (water available between soil particles). This water contains dissolved minerals, forming a dilute solution. Inside the root hair cells, the cell sap is more concentrated. Due to osmosis, water moves from the soil into the root hair cells. This movement creates root pressure that pushes water upwards into the xylem vessels. From there, water is pulled upwards to the leaves through transpiration.
The combined effects of root pressure and transpiration pull ensure water reaches all parts of the plant.
In simple words: Plants get water from the soil through tiny root hairs. The water then moves up through tubes in the stem, like straws, all the way to the leaves. This happens partly because roots push water up and partly because leaves pull water up as they let some water vapor out.

🎯 Exam Tip: The "Cohesion-Tension Theory" is the widely accepted explanation, where transpiration creates a pulling force, and water molecules stick together (cohesion) to form a continuous column.

 

Question 31. Describe the functions of the stomach?
Answer: The stomach wall has gastric glands that produce gastric juice. This juice contains mucus, hydrochloric acid, and pepsin (a protein-digesting enzyme).
- Role of Hydrochloric Acid: It makes the stomach contents acidic, which is necessary for pepsin to work correctly and digest proteins. It also helps kill bacteria that come in with food.
- Role of Mucus: Mucus forms a protective layer on the inner wall of the stomach. This layer protects the stomach lining from being damaged by the strong hydrochloric acid and pepsin.
- Role of Pepsin: Pepsin is an enzyme that starts breaking down proteins into smaller peptide molecules.
These combined functions ensure efficient chemical and mechanical digestion within the stomach.
In simple words: The stomach helps break down food. Acid in the stomach kills germs and helps an enzyme called pepsin start digesting proteins. A slimy layer called mucus protects the stomach wall from its own strong acid.

🎯 Exam Tip: The stomach's acidic environment and enzyme pepsin are crucial for initiating protein digestion, but fat digestion primarily occurs in the small intestine.

 

Question 32. How many types of circulatory systems are found in animals?
Answer: Animals have two main types of circulatory systems:
- Open type circulation: In this system, blood flows out of vessels and directly bathes the body tissues in large open spaces called sinuses. Body tissues are in direct contact with the blood. The amount of blood flowing to specific tissues cannot be easily controlled. There is usually no complex heart. Examples include insects like grasshoppers and cockroaches.
- Closed type circulation: In this system, blood is always contained within blood vessels (arteries, veins, capillaries) and does not directly bathe the tissues. The volume of blood to organs can be regulated by vessel contraction and relaxation. A pumping heart is present. Examples include earthworms and humans.
Both systems efficiently transport nutrients and remove waste, adapted to the organism's size and metabolic needs.
In simple words: Animals have two ways their blood moves around. In "open" systems, blood flows freely inside the body, touching all parts. In "closed" systems, blood stays inside tubes, like our veins and arteries, and a heart pumps it.

🎯 Exam Tip: Open circulatory systems are less efficient at directing blood to specific organs, which is why they are common in smaller, less active animals.

 

Question 33. What are catabolic and anabolic processes?
Answer: Metabolic processes in living organisms are broadly divided into two types:
- Catabolic Processes: These are reactions that break down complex compounds into simpler ones. During these processes, energy is released, which the body then uses for various biological activities.
- Anabolic Processes: These are reactions that build complex compounds from simpler ones. These newly formed complex compounds are vital for building and organizing cell structures.
These two processes, catabolism and anabolism, work together to maintain life, growth, and repair within an organism.
In simple words:
- Catabolic Processes: These are like breaking down big building blocks into smaller ones to get energy.
- Anabolic Processes: These are like using small building blocks to make bigger, new parts for the body.

🎯 Exam Tip: Catabolism releases energy (exergonic), while anabolism consumes energy (endergonic), forming a fundamental cycle of energy and matter in living systems.

 

Question 34. Why specific excretory organs are not found in plants? Explain.
Answer: Plants generally do not have specialized excretory organs like animals because their excretion process is quite simple. There are several reasons for this:
1. The rate of catabolism (breaking down processes) in plants is much slower than in animals, so waste products build up slowly.
2. Green plants reuse many of their waste products from catabolism in their anabolic processes, for example, water and carbon dioxide from respiration are used in photosynthesis. Nitrogen compounds can be reused for protein synthesis.
3. Plant metabolism is largely based on carbohydrates, which produce less toxic waste products compared to protein metabolism in animals.
4. Waste products like carbon dioxide, oxygen, and water vapor are released through stomata (in leaves) and lenticels (in stems).
Plants store some waste in old leaves or bark, which are later shed, or in specialized compartments like vacuoles.
In simple words: Plants don't need special organs to get rid of waste like animals do because they make less waste, use some waste again, and can simply let out gases and water through tiny holes. They also store some waste in parts they will shed.

🎯 Exam Tip: Plants often store waste products in vacuoles or convert them into less harmful substances, making their excretory needs less complex than animals.

Major Activities of Living Organisms Long Answer Type Questions

 

Question 36. What is reflex action? Give some examples.
Answer: A reflex action is an automatic, involuntary response to a stimulus that does not involve conscious thought. These actions are rapid and protect the body from harm. Examples include sneezing, blinking of eyes, and coughing. The brainstem and spinal cord usually control reflex actions.
In simple words: A reflex action is when your body reacts automatically without you thinking about it, like quickly pulling your hand away from something hot, or sneezing.

🎯 Exam Tip: Reflex actions are an important part of the nervous system, providing immediate responses to protect the body.

 

Question 37. What is guttation? Explain with examples.
Answer: Guttation is the exudation (release) of water from plants in liquid form, typically as small drops, from the edges or tips of leaves. This usually happens when environmental conditions are favorable for water absorption but transpiration (water loss through evaporation) is low, often due to high humidity. Examples include water droplets seen on the margins of peepal leaves, tomato plants, Nasturtium, and lawn grass in the morning.
- Conditions for guttation:
* Guttation increases when the plant absorbs water faster than it loses it through transpiration.
* It is more common when the air humidity is high, reducing the rate of transpiration.
This process ensures water moves through the plant even when transpiration is minimal.
In simple words: Guttation is when plants push out small drops of water from their leaves, usually when they have soaked up too much water from the soil but can't release it into the humid air easily. You might see these drops on grass in the morning.

🎯 Exam Tip: Guttation is different from dew, which is condensation from the atmosphere. Guttation involves water actively secreted by the plant.

 

Question 38. Explain the Internal structure of the leaf?
Answer: The internal structure of a leaf is designed for efficient photosynthesis and gas exchange. It primarily consists of three main portions:
- (a) Upper Epidermis: This is the outermost protective layer on the top surface of the leaf.
- (b) Lower Epidermis: This is the outermost protective layer on the bottom surface of the leaf, often containing stomata.
- (c) Mesophyll: This is the tissue between the upper and lower epidermis, divided into two types:
* Palisade parenchyma: Located just below the upper epidermis, these cells are tightly packed and rich in chloroplasts, where most photosynthesis occurs.
* Spongy parenchyma: Located below the palisade parenchyma, these cells have large air spaces for gas circulation throughout the leaf.
- (d) Vascular bundles: These are the veins of the leaf, containing xylem (for water transport) towards the upper side and phloem (for food transport) towards the lower side. Each bundle is surrounded by a bundle sheath.
The arrangement of these tissues maximizes light absorption, gas exchange, and water/nutrient delivery for photosynthesis.
In simple words: Inside a leaf, there are top and bottom skin layers called epidermis. In between, there's a middle layer called mesophyll, which has cells that make food (photosynthesis) and air spaces for gases. Tiny tubes called vascular bundles, or veins, carry water and food all over the leaf.

🎯 Exam Tip: The palisade layer, with its high concentration of chloroplasts, is the primary site of photosynthesis in most leaves.

 

Question 39. Explain root pressure in plants with the help of an experiment.
Answer: Root pressure is the positive pressure that develops in the xylem of roots due to the active absorption of water by root cells. This pressure helps push water upwards in the plant stem, especially when transpiration is low.
- Experiment:
1. Take a well-watered potted plant and cut its main stem about 7 cm above the soil surface.
2. Attach a glass tube to the cut end of the stem using a rubber tube joint and seal it airtight with wax or grease.
3. Fill some water in the glass tube up to a marked level.
4. After some time (e.g., an hour), water will be observed rising in the glass tube.
This rise in water shows that pressure from the roots is pushing water upwards into the stem and tube. The continuous pulsation of cortical cells drives this process.
Root pressure plays a role in water movement, especially when transpiration is not actively pulling water upwards.
In simple words: Root pressure is when the roots of a plant push water up into the stem. You can see this by cutting a plant's stem and attaching a tube; water will slowly rise in the tube because the roots are pushing it up. This push helps water move through the plant.

🎯 Exam Tip: While root pressure is important for pushing water over short distances, transpiration pull is the primary force for moving water to the tops of tall trees.

 

Question 40. Describe respiration in human beings with a labelled diagram?
Answer: Human respiration involves a complex system of organs that work together to take in oxygen and release carbon dioxide. The primary respiratory organs are the lungs, supported by accessory organs like the nostrils, pharynx, and trachea.
1. Nostrils: Air first enters through the nostrils, which filter out dirt with hair and moist mucous membranes.
2. Pharynx: From the nasal passage, air moves into the pharynx (throat), which leads to the windpipe (trachea) and food pipe (oesophagus). A flap called the epiglottis ensures food goes into the food pipe, not the windpipe.
3. Trachea: The trachea is a tube leading to the lungs, supported by C-shaped cartilaginous rings. It branches into two bronchi, which further divide into bronchioles and then into tiny air sacs.
- Main respiratory organ: Lungs: Humans have two lungs, enclosed in the chest cavity by a double-walled pleural membrane. Inside the lungs, the bronchioles end in numerous tiny air sacs called alveoli. These alveoli have thin, moist membranes and are surrounded by a rich network of capillaries. This is where the actual exchange of gases (oxygen into blood, carbon dioxide out of blood) takes place efficiently due to their large surface area.
The overall process ensures oxygen reaches body cells for energy production and carbon dioxide is removed.
In simple words: Humans breathe using a system of organs. Air goes in through the nose, down the throat, into a tube called the trachea, and then into the lungs. Inside the lungs are tiny air sacs (alveoli) where oxygen from the air gets into the blood, and waste carbon dioxide from the blood goes into the air to be breathed out.

🎯 Exam Tip: The alveoli's thin walls and large surface area are perfectly adapted for efficient gas exchange, a key principle in human respiration.

 

Question 41. Explain the method of Grafting?
Answer: Grafting is a method of asexual reproduction where two parts from different plants, usually closely related varieties, are joined so they grow together as one plant. The lower part with roots, staying in the soil, is called the 'stock,' and the small shoot from the other plant to be joined is called the 'scion.' The cambium layers of both stock and scion must be fused to form a successful connection.
- (C) Crown grafting: If the stock plant has a thicker stem than the scion, several scions can be grafted onto a single stock. The scions are cut into long wedges and inserted into matching cuts on the stock, then tied firmly.
- (D) Bud grafting: In this method, a single bud with a small piece of living tissue is taken as the scion. A T-shaped cut is made in the bark of the stock, and the bud is inserted into this cut. Both are then tied to prevent drying, and after a few days, the bud grows as part of the stock plant.
Grafting is commonly used to combine desirable traits from two plants, such as a strong root system with a high-yielding fruit variety.
In simple words: Grafting is like joining two different plants together so they grow as one. You take a piece from one plant (the scion) and attach it to another plant with roots (the stock). If done right, they grow together, combining their best features.

🎯 Exam Tip: Successful grafting requires the cambium layers of the scion and stock to align well, enabling vascular connections for nutrient and water transport.

 

Question 42. Describe double fertilisation?
Answer: Double fertilization is a unique process in flowering plants that involves two separate fusion events.
1. After a pollen tube delivers two male gametes to the ovule, one male gamete fuses with the egg cell. This forms a diploid zygote (2n), which develops into the embryo. This is known as true fertilization or syngamy.
2. The second male gamete fuses with the central cell's secondary nucleus (which is diploid, 2n). This forms a triploid (3n) nucleus called the endosperm mother nucleus. This event is known as triple fusion.
Since two fusions occur, it is called double fertilization. The zygote develops into the embryo, and the endosperm mother nucleus develops into the endosperm, which provides nutrition to the growing embryo.
In simple words: Double fertilization is when a plant's egg gets fertilized twice. One part of the sperm joins with the egg to make a baby plant, and another part joins with a different cell to make food for that baby plant.

🎯 Exam Tip: Double fertilization ensures that the endosperm, which nourishes the embryo, only develops if fertilization of the egg has successfully occurred.

 

Question 43. Briefly explain pollination?
Answer: Pollination is the process of transferring pollen grains from the anther (the male part of a flower) to the stigmatic surface (the receptive female part of a flower). This transfer is a crucial step in plant reproduction, allowing for fertilization and seed formation.
In simple words: Pollination is simply when pollen, which contains male plant cells, moves from one part of a flower (or one flower) to the female part of another flower, so new seeds can grow.

🎯 Exam Tip: Pollination can occur through various agents like wind, water, insects, birds, and even bats, each adapted to specific flower structures.

 

Question 44. Describe the reproductive organs of a human with the help of a labelled diagram?
Answer: The male reproductive system includes the following parts:
1. Testes: These are the male reproductive organs, which are two in number. They are located in a special skin pouch called the scrotum sac, found outside the body between the two legs. Their main job is to produce sperm. Each testis contains many coiled tubes called seminiferous tubules, which open into a collecting duct called the epididymis. Sperms are made by the epithelial layer of the seminiferous tubules and stored in the epididymis. Each sperm has three parts: the head (front end) contains the nucleus with chromosomes, the middle portion, and the tail, which helps it move. This complex system ensures the efficient production and storage of sperm.
2. Vas deferens: From each epididymis, a duct called vas deferens arises, which then opens into a wide structure called the seminal vesicles.
3. Seminal vesicle: This is located in the front part of the urethra. A tube called the ejaculatory duct comes from the seminal vesicle. Before sperm are released, they are stored in this duct.
4. Urethra: The ejaculatory duct leads into the urethra, which is a long, muscular tube passing through the penis. This tube has a small opening at the end. Both urine and sperm exit the body through this opening, which is why it's also called the urino-genital aperture.
In simple words: The male reproductive system makes and delivers sperm. It has testes to produce sperm, tubes (vas deferens and ejaculatory duct) to carry them, seminal vesicles for storage, and the urethra which is used for both urine and sperm to leave the body.

🎯 Exam Tip: When describing organ systems, always list the main organs and briefly state their primary function. A clear, labeled diagram is very important for full marks in such questions.

 

Question 1. The gas liberated (given out) in photosynthesis is-
(A) Carbon dioxide gas
(B) Oxygen gas
(C) Nitrogen gas
(D) Hydrogen gas
Answer: (B) Oxygen gas
In simple words: During photosynthesis, plants take in carbon dioxide and release oxygen as a byproduct, which is essential for breathing.

🎯 Exam Tip: Remember the main inputs and outputs of photosynthesis: plants use carbon dioxide and water to make food, releasing oxygen in the process.

 

Question 2. Examples of chemosynthetic organisms are-
(A) Sulphur bacteria and Ficus
(B) Copper bacteria and Ficus
(C) Margosa bacteria and Ficus
(D) Sulphur and copper bacteria
Answer: (D) Sulphur and copper bacteria
In simple words: Chemosynthetic organisms are special types of bacteria, like sulphur and copper bacteria, that make their own food using chemical energy, not sunlight.

🎯 Exam Tip: Distinguish between photosynthetic (using light) and chemosynthetic (using chemicals) organisms, often identified by the type of bacteria involved.

 

Question 3. Dark reaction in photosynthesis is called because-
Answer: The dark reaction in photosynthesis is also known as the light-independent reaction. It is named this way because it does not directly need sunlight to happen. Instead, it uses the energy (ATP and NADPH) produced during the light-dependent reactions to convert carbon dioxide into sugars. This process can occur in both light and dark conditions, as long as the necessary energy carriers are available.
In simple words: The dark reaction in photosynthesis is called that because it doesn't need sunlight directly. It uses stored energy from the light reactions to make food.

🎯 Exam Tip: Emphasize that "dark" means light-independent, not that it only occurs in the dark. It relies on the products of the light reactions.

 

Question 4. The animals that depend on the blood of other animals, for their food are called-
(A) Herbivores
(B) Carnivores
(C) Sanguivorous
(D) Omnivorous
Answer: (C) Sanguivorous
In simple words: Animals that feed on blood are called sanguivorous.

🎯 Exam Tip: Remember specific terms for different feeding habits in biology, such as herbivore (plants), carnivore (meat), omnivore (both), and sanguivorous (blood).

 

Question 5. The acidic food coming from the stomach is neutralised in the small intestine by-
(A) Saliva
(B) Trypsin
(C) Lipase
(D) Bile
Answer: (D) Bile
In simple words: When food leaves the stomach, it's very acidic. Bile, made in the liver and stored in the gallbladder, helps to make it less acidic in the small intestine so other enzymes can work.

🎯 Exam Tip: Recall the role of bile in digestion, specifically its function in emulsifying fats and neutralizing acidic chyme from the stomach, which is crucial for enzyme activity in the small intestine.

 

Question 6. Digestion is extracellular in-
(A) Animals like human
(B) Amoeba
(C) Fungi
(D) Both A and C
Answer: (D) Both A and C
In simple words: Extracellular digestion means food is broken down outside the cells. This happens in both humans and fungi.

🎯 Exam Tip: Understand that extracellular digestion means enzymes are secreted outside the cells to break down food, which is then absorbed. This differs from intracellular digestion, where food is engulfed and digested inside the cell.

 

Question 7. The exchange of gases occurs in human beings takes place in-
(A) Skin
(B) Mouth
(C) Nose
(D) Lungs
Answer: (D) Lungs
In simple words: In humans, oxygen from the air enters the blood, and carbon dioxide leaves the blood, mainly in the lungs.

🎯 Exam Tip: Focus on the primary organ for gas exchange in humans, which is the lungs, specifically in the tiny air sacs called alveoli.

 

Question 9. In anaerobic respiration is produced.
(A) Pyruvic Acid
(B) Lactic Acid
(C) Citric Acid
(D) Malic Acid
Answer: (B) Lactic Acid
In simple words: When there isn't enough oxygen, our bodies do anaerobic respiration, which creates lactic acid.

🎯 Exam Tip: Remember that anaerobic respiration in animals produces lactic acid, while in yeast, it produces ethanol and carbon dioxide.

 

Question 10. In normal expiration the diaphragm is-
(A) Arched
(B) Flattened
(C) Not involved
(D) Perforated
Answer: (A) Arched
In simple words: When you breathe out normally, your diaphragm relaxes and goes back to its curved, arched shape.

🎯 Exam Tip: Visualize the diaphragm's movement: it flattens during inhalation (contraction) and arches during exhalation (relaxation).

 

Question 11. The trachea is prevented from collapsing by-
(A) Complete cartilaginous rings
(B) incomplete cartilaginous ring
(C) bony rings
(D) Chitinous rings
Answer: (B) incomplete cartilaginous ring
In simple words: The windpipe (trachea) has C-shaped cartilage rings that keep it open all the time, stopping it from collapsing.

🎯 Exam Tip: Note that the rings are incomplete (C-shaped) on the back, allowing the esophagus behind it to expand when food is swallowed.

 

Question 12. The circulatory system of cockroach is-
(A) Closed type
(B) Open type
(C) Both type
(D) By diffusion
Answer: (B) Open type
In simple words: Cockroaches have an open circulatory system, meaning their blood flows freely in body spaces, not just inside blood vessels.

🎯 Exam Tip: Recall that an open circulatory system means blood (hemolymph) is pumped into a body cavity (hemocoel) and directly bathes the organs, unlike a closed system where blood stays in vessels.

 

Question 14. Our body temperature is regulated by-
(A) Blood
(B) Veins
(C) Arteries
(D) Capillaries
Answer: (A) Blood
In simple words: Blood helps keep our body at the right temperature by moving heat around.

🎯 Exam Tip: Blood plays a crucial role in thermoregulation by distributing heat throughout the body and releasing it at the surface through mechanisms like vasodilation.

 

Question 15. The flow of water from a cell to outside in more concentrated solution results in shrinking and rounding of protoplasm, this is due to-
(A) Absorption
(B) Plasmolysis
(C) Imbibition
(D) Exosmosis
Answer: (B) Plasmolysis
In simple words: When a plant cell loses water to a salty environment and its insides shrink away from the cell wall, this process is called plasmolysis.

🎯 Exam Tip: Plasmolysis happens when a cell is placed in a hypertonic solution (higher concentration of solutes outside), causing water to leave the cell by osmosis.

 

Question 16. The process of transpiration in plants help in-
(A) opening of stomata
(B) absorption of CO2
(C) upward conduction of water and mineral
(D) absorption of O2
Answer: (C) upward conduction of water and mineral
In simple words: Transpiration, which is water evaporating from plant leaves, helps pull water and minerals up from the roots to the rest of the plant.

🎯 Exam Tip: Understand that transpiration creates a "pull" (transpirational pull) that is essential for moving water and dissolved minerals against gravity from roots to leaves.

 

Question 17. Malpighian tubules are found in-
(A) Amoeba
(B) Earthworm
(C) Hydra
(D) None of these
Answer: (D) None of these
In simple words: Malpighian tubules are a type of excretory organ found in insects, not in amoeba, earthworms, or hydra.

🎯 Exam Tip: Malpighian tubules are characteristic excretory and osmoregulatory organs of insects and myriapods.

 

Question 19. Which of the following nitrogenous waste product is excreted by Hydra-
(A) Ammonia
(B) Urea
(C) Uric acid
(D) All of the options
Answer: (A) Ammonia
In simple words: Hydra gets rid of waste nitrogen as ammonia, which is easily dissolved and passed out in water.

🎯 Exam Tip: Remember that aquatic animals often excrete ammonia because it is highly soluble in water and can be easily diluted and removed from the body.

 

Question 20. Excretion of nitrogenous wastes mainly as uric acid by birds is helpful for-
(A) Conserving body water
(B) Eliminating excess body water
(C) Eliminating excess body heat
(D) Conserving body heat
Answer: (A) Conserving body water
In simple words: Birds excrete waste as uric acid, which helps them save water, which is very important for animals that fly and need to be light.

🎯 Exam Tip: Uric acid is a semi-solid, less toxic nitrogenous waste product that requires very little water for its excretion, making it ideal for animals in dry environments or those needing to conserve water, like birds.

 

Question 21. In comparison to animals, the rate of excretion in plants is-
(A) more
(B) less
(C) equal
(D) absent
Answer: (B) less
In simple words: Plants produce much less waste and get rid of it slower than animals do.

🎯 Exam Tip: Plants have simpler excretory systems and often store waste products in non-toxic forms or release them through stomata, making their overall excretion rate lower than animals.

 

Question 22. Metabolism of which group of organic compound produces more harmful waste products-
(A) Fats
(B) Starch
(C) Proteins
(D) Sugar
Answer: (C) Proteins
In simple words: When proteins are broken down in the body, they create more toxic waste products compared to fats, starches, or sugars.

🎯 Exam Tip: Protein metabolism produces nitrogenous wastes like ammonia, urea, and uric acid, which are generally more toxic and require more complex excretion mechanisms than the waste products of carbohydrate or fat metabolism.

 

Question 24. By which method asexual reproduction occurs in amoeba-
(A) Fission
(B) Budding
(C) Germination
(D) All of the options
Answer: (A) Fission
In simple words: Amoeba reproduces by fission, which means it splits into two or more new amoebas.

🎯 Exam Tip: Fission is a common asexual reproduction method for single-celled organisms like amoeba, where the parent cell divides into two or more daughter cells.

 

Question 25. Rupturing of ovarian follicle and discharge of ovum is known as-
(A) Copulation
(B) Ovulation
(C) Conjugation
(D) Oviposition
Answer: (B) Ovulation
In simple words: When a mature egg is released from the ovary, it's called ovulation.

🎯 Exam Tip: Ovulation is a key event in the female reproductive cycle, indicating the release of a fertilizable egg.

 

Question 26. Menstruation in human females stops after the age of about-
(A) 65
(B) 60
(C) 45
(D) 35
Answer: (C) 45
In simple words: Menstruation in women usually stops around the age of 45.

🎯 Exam Tip: This event is known as menopause, marking the end of a woman's reproductive years.

 

Question 27. The largest part of the brain is-
(A) Cerebrum
Answer: (A) Cerebrum
In simple words: The cerebrum is the biggest part of our brain and is responsible for thinking, memory, and our senses.

🎯 Exam Tip: The cerebrum is involved in higher-level functions such as voluntary movement, intelligence, memory, and sensory processing.

 

Question 28. The cerebellum is concerned with-
(A) Coordination and muscular movements
(B) Perception
(C) Memory
(D) Vision
Answer: (A) Coordination and muscular movements
In simple words: The cerebellum helps us with balance and making our movements smooth and coordinated.

🎯 Exam Tip: The cerebellum is vital for fine-tuning motor activity, balance, and posture, allowing for smooth and precise movements.

 

Question 29. Endocrine glands are those which put their secretions into-
(A) Ducts
(B) Blood
(C) Both
(D) None of the options
Answer: (B) Blood
In simple words: Endocrine glands release their hormones directly into the bloodstream, which then carries them to different parts of the body.

🎯 Exam Tip: Contrast endocrine glands (ductless, secrete into blood) with exocrine glands (have ducts, secrete onto surfaces or into cavities).

 

Question 30. Reflex action is controlled by-
(A) Spinal cord
(B) Peripheral Nervous System
(C) Autonomous Nervous System
(D) Brain
Answer: (A) Spinal cord
In simple words: Reflex actions, like quickly pulling your hand away from something hot, are handled by the spinal cord without the brain being directly involved first.

🎯 Exam Tip: Reflex actions are involuntary and rapid responses mediated by the spinal cord, allowing for quick reactions to stimuli without conscious thought.

 

Major Activities of Living Organisms Very Short Answer Type Questions

 

Question 1. Define Nutrition?
Answer: Nutrition is the complete process where an organism takes in food and uses it to grow, repair itself, and get energy. It involves several steps from eating to using the food's components.
In simple words: Nutrition is how living things get and use food for energy and growth.

🎯 Exam Tip: Define nutrition as the process of obtaining and utilizing nutrients, highlighting its importance for energy, growth, and body maintenance.

 

Question 2. What are chemotrophs?
Answer: Chemotrophs are organisms that get their energy by breaking down chemical compounds, instead of using sunlight. They use energy from chemical reactions to make their own food. This is different from how plants use light to make food.
In simple words: Chemotrophs are living things that get energy from chemicals to make their food.

🎯 Exam Tip: Differentiate chemotrophs (chemical energy source) from phototrophs (light energy source), noting they are often bacteria found in unique environments.

 

Question 4. What are Nutrients?
Answer: Nutrients are substances found in food that living organisms need to survive and grow. They provide energy, help build and repair body tissues, and keep body processes working correctly. Examples include carbohydrates, fats, proteins, vitamins, and minerals.
In simple words: Nutrients are things in food that give us energy and help our bodies grow and stay healthy.

🎯 Exam Tip: List the main categories of nutrients (carbohydrates, proteins, fats, vitamins, minerals, water) and their general roles for a complete answer.

 

Question 5. What are finger-like projections of the intestinal wall called?
Answer: The finger-like projections found on the inner surface of the small intestine are called villi. These tiny folds greatly increase the surface area of the intestine, which helps absorb nutrients from digested food more efficiently. This large surface is crucial for nutrient uptake.
In simple words: The tiny finger-like bumps inside our small intestine are called villi, and they help absorb food.

🎯 Exam Tip: Highlight that villi, along with microvilli, are crucial for maximizing the absorption of digested nutrients due to their increased surface area.

 

Question 6. For what purpose, energy is required by a living organism?
Answer: Living organisms need energy for all their life processes. This includes growing, moving, repairing damaged cells, reproducing, and maintaining their body temperature. Energy is like the fuel that keeps all biological activities running smoothly, from the smallest cell function to large-scale body movements.
In simple words: Living things need energy to grow, move, fix their bodies, and stay alive.

🎯 Exam Tip: Emphasize that energy is fundamental for metabolic processes, mechanical work (movement), transport, and maintaining homeostasis (stable internal conditions).

 

Question 7. What is the importance of air sacs?
Answer: Air sacs, or alveoli, are extremely important in the lungs because they are the main places where oxygen enters the blood and carbon dioxide leaves it. They have very thin walls and a large total surface area, which allows gases to be exchanged very quickly and efficiently. This makes breathing effective.
In simple words: Air sacs are tiny bags in our lungs that help oxygen get into our blood and carbon dioxide leave.

🎯 Exam Tip: Focus on the two key features of alveoli: large surface area and thin walls, which are perfectly adapted for efficient gas exchange.

 

Question 8. Which type of process is respiration?
Answer: Respiration is a catabolic process. This means it involves breaking down complex substances, like glucose, into simpler ones, which releases energy. This energy is then used by the body for various functions. It is the opposite of an anabolic process, which builds things up.
In simple words: Respiration is a catabolic process, meaning it breaks down food to make energy.

🎯 Exam Tip: Clearly define catabolic (breaking down) and anabolic (building up) processes to distinguish them in biological contexts like respiration and photosynthesis.

 

Question 9. What is epiglottis?
Answer: The epiglottis is a small, leaf-shaped flap of cartilage located at the back of the tongue, at the entrance to the larynx (voice box). Its main job is to act like a lid, closing over the windpipe when you swallow food or liquid. This prevents food from going down into your lungs and causing you to choke. It is crucial for safe eating.
In simple words: The epiglottis is a small flap that covers your windpipe when you swallow, stopping food from going into your lungs.

🎯 Exam Tip: Emphasize the protective role of the epiglottis during swallowing to prevent aspiration (food entering the trachea).

 

Question 11. Write any two functions of blood.
Answer: Here are two important functions of blood:
(1) Blood carries oxygen from the lungs to all the cells in the body, which need it for energy. It also picks up carbon dioxide waste from the cells to take it back to the lungs to be breathed out.
(2) Blood helps stop bleeding by forming clots when a blood vessel is damaged. This prevents too much blood loss and helps the body heal.
In simple words: Blood carries oxygen to cells and removes carbon dioxide. It also helps stop bleeding by forming clots.

🎯 Exam Tip: Focus on blood's primary roles: transport (gases, nutrients, hormones, waste) and protection (clotting, immune response) for a comprehensive answer.

 

Question 12. Define heart-beat.
Answer: A heartbeat is one full cycle of the heart contracting (squeezing) and relaxing (filling with blood). This continuous rhythm pumps blood throughout the entire body. The sound you hear is the heart valves opening and closing during this cycle.
In simple words: A heartbeat is when your heart squeezes and then relaxes once to pump blood.

🎯 Exam Tip: Explain that a heartbeat involves both systole (contraction) and diastole (relaxation) of the atria and ventricles, working together to circulate blood.

 

Question 13. What is normal blood pressure?
Answer: Normal blood pressure is the healthy force exerted by circulating blood against the walls of the arteries. It is typically expressed as two numbers: systolic pressure (the higher number, when the heart beats) and diastolic pressure (the lower number, when the heart rests between beats). A healthy adult usually has a blood pressure around 120/80 mmHg or lower, though this can vary slightly.
In simple words: Normal blood pressure is the healthy force of blood pushing on your artery walls, usually around 120 over 80.

🎯 Exam Tip: Specify the two components of blood pressure (systolic and diastolic) and provide the general healthy range to demonstrate complete understanding.

 

Question 14. What are capillaries?
Answer: Capillaries are the smallest and thinnest blood vessels in the body. They form a network connecting arteries (which carry blood away from the heart) to veins (which carry blood back to the heart). Their extremely thin walls allow for the exchange of oxygen, nutrients, and waste products between the blood and body cells. They are like tiny bridges for blood.
In simple words: Capillaries are very tiny blood vessels that connect arteries and veins, helping to pass oxygen and food to cells and pick up waste.

🎯 Exam Tip: Emphasize the crucial role of capillaries as the primary sites for nutrient and gas exchange due to their single-cell thick walls and extensive networks.

 

Question 15. What is lymph?
Answer: Lymph is a clear to yellowish fluid that flows through the lymphatic system. It comes from blood plasma that leaks out of capillaries and surrounds cells. Lymph contains water, proteins, inorganic salts, and waste products, but fewer red blood cells. It plays an important role in the immune system and transporting fats, like a cleaner for the body's tissues.
In simple words: Lymph is a clear liquid that comes from blood, helps fight sickness, and carries waste from body tissues.

🎯 Exam Tip: Remember that lymph is similar to blood plasma but lacks red blood cells, and its main functions are immunity, fluid balance, and fat transport.

 

Question 16. What is transpiration?
Answer: Transpiration is the process where plants release water vapor into the atmosphere from their leaves, stems, and flowers. Most of this water loss occurs through tiny pores called stomata on the leaves. It's like sweating for plants, helping them draw water up from the roots and cool down. This process is essential for water movement through the plant.
In simple words: Transpiration is when plants release water vapor from their leaves into the air.

🎯 Exam Tip: Connect transpiration to the water cycle and understand its importance in creating the transpirational pull that moves water and minerals up a plant.

 

Question 18. What is osmosis?
Answer: Osmosis is a special type of diffusion where water molecules move from an area of higher water concentration (more water, less dissolved stuff) to an area of lower water concentration (less water, more dissolved stuff) across a semi-permeable membrane. This membrane allows water to pass through but blocks larger molecules. This movement tries to make the concentration of water equal on both sides.
In simple words: Osmosis is when water moves through a special skin (membrane) from a place with lots of water to a place with less water.

🎯 Exam Tip: Clearly state that osmosis involves the movement of water (solvent) only, across a semi-permeable membrane, from high to low water potential.

 

Question 19. What is the function of the root cap?
Answer: The root cap is a protective layer of cells covering the very tip of a plant root. Its main job is to shield the delicate growing cells underneath as the root pushes through rough soil. It prevents damage from friction and allows the root to grow deeper into the ground without harm. This protection is vital for root growth.
In simple words: The root cap is like a protective helmet on the tip of a plant's root, keeping it safe as it grows through the soil.

🎯 Exam Tip: Highlight that the root cap provides mechanical protection to the meristematic (growing) tissue of the root tip, enabling it to penetrate soil particles.

 

Question 20. Give two functions of contractile vacuoles of an amoeba?
Answer: The contractile vacuoles in an amoeba perform two main functions:
1. Osmoregulation: They collect excess water that enters the amoeba's body from its environment and then pump it out. This helps maintain the correct water balance inside the amoeba, preventing it from bursting.
2. Releasing waste water: Along with excess water, they also help remove some dissolved waste products from the cell. They act like a tiny pump and waste disposal system.
In simple words: Contractile vacuoles help amoebas get rid of extra water to stop them from bursting and also remove some liquid waste.

🎯 Exam Tip: For unicellular organisms like amoeba, osmoregulation (water balance) is a critical function performed by contractile vacuoles, especially in freshwater environments.

 

Question 21. What are sweat glands?
Answer: Sweat glands are tiny, coiled tubes located within the skin that produce sweat. Each gland has a duct that leads up to the surface of the skin, where sweat is released through pores. Their main function is to help cool the body down when it gets too hot, and they also excrete small amounts of waste. They are essential for temperature control.
In simple words: Sweat glands are small tubes in your skin that make sweat to cool you down and remove a little waste.

🎯 Exam Tip: Connect sweat glands directly to their primary role in thermoregulation (body temperature control) through evaporative cooling.

 

Question 22. Define metabolic waste.
Answer: Metabolic wastes are substances that are produced as byproducts during the normal chemical processes (metabolism) inside a living organism's cells, but are not useful and can even be harmful if they build up. These wastes, like carbon dioxide, urea, and uric acid, need to be removed from the body to keep it healthy. They are just leftover materials from daily body work.
In simple words: Metabolic wastes are leftover harmful things made by the body's normal processes that need to be removed.

🎯 Exam Tip: Provide examples of metabolic wastes (carbon dioxide, urea, uric acid) to illustrate your definition and emphasize their potential toxicity if not excreted.

 

Question 23. Why is excretion process more simple in plants than animals? Give one reason.
Answer: The excretion process is simpler in plants compared to animals for several reasons. One key reason is that plants have a much lower metabolic rate than animals. This means they produce waste products at a much slower rate. Also, many of their waste products, like oxygen (from photosynthesis) and carbon dioxide (from respiration), are released as gases or reused in other processes. They don't have specialized excretory organs like kidneys, instead relying on simpler mechanisms like shedding leaves, storing waste in vacuoles, or releasing gases through stomata.
In simple words: Plant excretion is simpler because they make less waste and can reuse some of it, unlike animals that produce more harmful waste quickly.

🎯 Exam Tip: Focus on either the low metabolic rate, the reuse of waste products, or the lack of specialized excretory organs as primary reasons for simpler excretion in plants.

 

Question 25. What is the period of heat? (Oestrous cycle)
Answer: The "period of heat," also known as the oestrous cycle, is a recurring physiological period in many female mammals when they are fertile, receptive to mating, and capable of conceiving. During this time, there is a strong desire for reproduction, usually peaking around ovulation. This cycle ensures that mating occurs at the optimal time for fertilization. This cycle is a natural part of mammalian reproduction.
In simple words: The period of heat, or oestrous cycle, is a time when female mammals are ready to mate and can get pregnant.

🎯 Exam Tip: Explain that the oestrous cycle is hormonally controlled and varies in length and frequency among different mammalian species, directly linked to reproductive readiness.

 

Question 26. Write two functions of flower relating to reproduction.
Answer: Here are two functions of flowers related to reproduction:
1. Flowers produce male and female gametes: They contain the reproductive organs (stamens for male gametes/pollen, and carpels/pistils for female gametes/ovules). These gametes are essential for the formation of new seeds.
2. Flowers facilitate fertilization: They are designed to attract pollinators (like insects or birds) through their colors, scents, and nectar. This attraction helps in the transfer of pollen, leading to fertilization and the eventual development of seeds and fruits. This ensures the continuation of the plant species.
In simple words: Flowers make the plant's reproductive cells (pollen and eggs) and attract animals to help spread pollen for new seeds.

🎯 Exam Tip: Clearly state the two main reproductive functions: gamete production and aiding fertilization, often through pollination mechanisms.

 

Question 27. Name the hormone secreted by thyroid gland?
Answer: The thyroid gland mainly produces two important hormones: thyroxine (T4) and tri-iodothyronine (T3). These hormones contain iodine and are crucial for regulating the body's metabolism, growth, and development. They affect almost every cell in the body.
In simple words: The thyroid gland makes hormones called thyroxine and tri-iodothyronine, which control how our body uses energy and grows.

🎯 Exam Tip: Always remember to mention both thyroxine (T4) and tri-iodothyronine (T3) as the primary hormones secreted by the thyroid gland.

 

Question 28. Name three parts of the nervous system of an earthworm.
Answer: The nervous system of an earthworm has three main parts:
1. Central nervous system: This includes the brain (a pair of cerebral ganglia) and a ventral nerve cord. The nerve cord runs along the belly side of the worm and has swellings (ganglia) in each segment. This central part helps coordinate all body activities.
2. Peripheral nervous system: This consists of nerves that extend from the central nervous system to different parts of the body, allowing for sensory input and motor output.
3. Autonomic nervous system: This controls involuntary actions like digestion and blood circulation.
In simple words: An earthworm's nervous system has a central part (brain and nerve cord), a peripheral part (nerves to the body), and an autonomic part (controls inside organs).

🎯 Exam Tip: For simple organisms, understand that their nervous systems are often segmented and less centralized than vertebrates, focusing on basic coordination and reflexes.

 

Question 30. What is reflex action? Give some examples.
Answer: A reflex action is a quick, automatic, and involuntary response to a stimulus, meaning it happens without conscious thought or control. These actions help the body react very quickly to avoid harm. Examples include:
- Sneezing: An automatic expulsion of air to clear irritants from the nasal passages.
- Blinking of eyes: An involuntary closing of the eyelids to protect the eyes from foreign objects or bright light.
- Coughing: A sudden expulsion of air from the lungs to clear the throat of irritants.
These rapid responses help keep the body safe from immediate threats.
In simple words: A reflex action is a fast, automatic body reaction you don't think about, like sneezing or blinking, to keep you safe.

🎯 Exam Tip: Emphasize that reflex actions are involuntary, rapid, and protective, and provide at least two clear examples to illustrate the concept.

 

Major Activities of Living Organisms Short Answer Type Questions

 

Question 1. Describe the pigments which are essential in photosynthesis?
Answer: Photosynthesis relies on specific pigments to capture light energy. The three main types found in plants are:
1. Chlorophyll: This is the primary pigment, responsible for the green color of plants. Chlorophyll a and chlorophyll b are found within chloroplasts and directly absorb light energy, especially red and blue wavelengths, to power photosynthesis.
2. Carotenoids: These pigments are yellow, orange, or red. They are also found in chloroplasts and absorb light energy, then transfer it to chlorophyll. They also protect chlorophyll from damage by intense light.
3. Phycobilins: These are water-soluble pigments found in some algae and cyanobacteria. They absorb light in green and yellow regions and pass the energy to chlorophyll. While other pigments like anthocyanins (giving red/purple color) and xanthophylls (yellow) exist, chlorophyll and carotenoids are the most essential for the core process in higher plants.
In simple words: Plants use pigments like chlorophyll (green), carotenoids (yellow/orange), and phycobilins to catch sunlight for photosynthesis. Chlorophyll does most of the work, and the others help it.

🎯 Exam Tip: List chlorophyll as the main pigment and mention carotenoids as accessory pigments, explaining their role in light absorption and protection.

 

Question 2. What is respiration?
Answer: Respiration is a vital catabolic process where living organisms break down food substances, such as carbohydrates, fats, and proteins, to release energy. This happens within the cells' tissues. The energy released is stored in molecules like ATP, which the body then uses for all its activities. In humans, respiration also includes taking in oxygen from the lungs to the tissues and bringing carbon dioxide from the tissues back to the lungs to be breathed out. It is a continuous process for life.
In simple words: Respiration is how living things break down food to get energy. In humans, it also means breathing in oxygen and breathing out carbon dioxide.

🎯 Exam Tip: Distinguish between cellular respiration (biochemical process) and external respiration (breathing) while explaining the overall energy-releasing function.

 

Question 3. Give two dissimilarities and similarities between respiration and combustion?
Answer: Respiration and combustion both release energy by breaking down organic compounds, but they have key differences:
**Dissimilarities:**
1. Respiration releases energy slowly, step-by-step, at normal body temperature, with enzymes controlling each stage. Combustion releases energy quickly and suddenly as heat and light, usually at high temperatures, without enzymes.
2. Respiration captures a significant portion of the released energy in ATP molecules for biological use. Combustion mostly releases energy as uncontrolled heat and light, with little or no energy stored in usable forms.
**Similarities:**
1. Both processes consume organic compounds (like fuel or food) and oxygen.
2. Both processes produce carbon dioxide and water as end products.
3. Both involve oxidation reactions that break down complex molecules into simpler ones, releasing energy.
In simple words: Both respiration and burning use oxygen and release energy, carbon dioxide, and water. But respiration is slow and controlled in our bodies, making useful energy, while burning is fast and uncontrolled, releasing heat and light.

🎯 Exam Tip: For comparing respiration and combustion, focus on the differences in control (enzymes vs. uncontrolled), temperature, and efficiency of energy capture (ATP vs. heat/light), while noting shared inputs and outputs.

 

Question 4. Clarify the difference between the two types of Respiration?
Answer: There are two main types of respiration: aerobic and anaerobic respiration.
**Aerobic Respiration:**
1. Requires oxygen: This process needs oxygen to occur.
2. Complete breakdown: Glucose is completely broken down.
3. End products: The final products are carbon dioxide, water, and a large amount of energy (around 38 ATP molecules per glucose).
4. Energy yield: Produces much more energy.
5. Occurrence: Common in most living cells and organisms.
**Anaerobic Respiration:**
1. No oxygen needed: This process happens without oxygen.
2. Incomplete breakdown: Glucose is only partially broken down.
3. End products: The final products vary but commonly include lactic acid (in animals during intense exercise) or ethyl alcohol and carbon dioxide (in yeast fermentation), along with a small amount of energy (around 2 ATP molecules per glucose).
4. Energy yield: Produces much less energy.
5. Occurrence: Found in some microorganisms or in animal muscle cells during oxygen shortage. Both types are important for energy production depending on the environment.
In simple words: Aerobic respiration uses oxygen to fully break down food for lots of energy, producing water and carbon dioxide. Anaerobic respiration happens without oxygen, partly breaking down food for less energy, and producing things like lactic acid or alcohol.

🎯 Exam Tip: Clearly state whether oxygen is required, the completeness of glucose breakdown, and the amount of energy (ATP) produced for each type to highlight their key distinctions.

 

Question 6. How does circulation in the cockroach? occur? Explain.
Answer: In cockroaches, nutrients and waste products move around the body through an open circulatory system. The main vessel is a dorsal tube called the heart or aorta, which has 13 chambers. This heart pulses, pushing blood from the back part to the front part. The aorta then opens up, releasing blood into large open spaces in the body called sinuses. The blood flows backwards through these sinuses to reach all cells. After that, it returns to the aorta through a valve. This completes the blood circulation. Cockroach blood does not have any pigment, so it does not help in gas exchange; this is done by a tracheal system instead.
In simple words: Cockroaches have an open blood system where blood flows through spaces, not just vessels. Their simple heart pushes blood around the body to all cells.

🎯 Exam Tip: Remember that cockroaches have an open circulatory system and lack respiratory pigments in their blood, unlike humans.

 

Question 7. Define vessels present in a human being.
Answer: Humans have three main types of blood vessels:

1. Arteries: These are thick-walled blood vessels that carry blood from the heart to all body parts. The main artery carries oxygen-rich blood from the left ventricle. Only the pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
2. Capillaries: These are very thin and narrow tubes that connect arteries to veins. Arteries branch into smaller tubes called arterioles, which then divide into even thinner capillaries.
3. Veins: Veins carry deoxygenated blood from various body parts back to the heart. They have valves to prevent blood from flowing backward.

Blood vessels are like a network of roads that transport blood, oxygen, and nutrients throughout the body.
In simple words: Humans have arteries that take blood away from the heart, veins that bring blood back, and tiny capillaries that connect them and allow exchange.

🎯 Exam Tip: Focus on the direction of blood flow and the relative wall thickness of arteries, veins, and capillaries, as these are key distinguishing features.

 

Question 8. Describe the structure and function of sieve tubes.
Answer: Sieve tubes are long, thin-walled, living cells that join end-to-end to form continuous tubes. They have tiny pores on their end walls, which form a sieve plate. Cytoplasmic strands pass through these pores, connecting one cell to another. Mature sieve tubes do not have a nucleus. Companion cells are always found next to sieve elements, and their nucleus helps control the sieve tubes' functions. The main job of sieve tubes is to transport food, which is made during photosynthesis, in liquid form from the leaves to other parts of the plant.
In simple words: Sieve tubes are plant tubes that move food from leaves to the rest of the plant. They are long cells joined together with small holes.

🎯 Exam Tip: Remember that sieve tubes are part of the phloem and are responsible for food transport, unlike xylem which transports water.

 

Question 9. Explain plasmolysis in a plant cell. Draw a diagram showing stages in plasmolysis.
Answer: Plasmolysis happens when a plant cell is placed in a solution that has a higher concentration of solutes (a stronger solution) than the cell's internal fluid. Because of this, water molecules move out of the cell sap into the surrounding solution. This causes the cell's protoplasm (the living content inside the cell wall) to shrink and pull away from the cell wall, losing its turgidity. This shrinking of the protoplasm is called plasmolysis. This process shows how water movement is affected by concentration differences across a cell membrane.

In simple words: When a plant cell is in very salty water, it loses water, and its inside (protoplasm) shrinks away from the cell wall. This shrinking is called plasmolysis.

🎯 Exam Tip: Always specify that plasmolysis occurs in a hypertonic solution and involves the shrinking of the protoplasm, not just the cell wall itself.

 

Question 10. How does excretion occur in earthworm?
Answer: Earthworms excrete waste using special organs called nephridia. These are many small, glandular tubules arranged in sequence throughout the earthworm's body. Each nephridium has a coiled excretory duct. The walls of these nephridia are glandular and have many blood vessels. The body cavity of the earthworm contains a fluid where waste products like ammonia and urea collect. These nephridia then gather these waste products from the body fluid and help remove them.
In simple words: Earthworms use many small tubes called nephridia to filter out waste like ammonia and urea from their body fluid.

🎯 Exam Tip: The key term for earthworm excretion is "nephridia," which are specialized tubules for filtering waste.

 

Question 11. What is the role of Malphigian tubules in cockroach?
Answer: Malpighian tubules are the excretory organs in cockroaches. There are about 80 to 90 yellow, glandular, and tubular Malpighian tubules. One end of these tubules floats freely in the body cavity, while the other end opens into the alimentary canal (the proctodeum). These tubules collect waste products from the body fluids through diffusion and pass them into the gut. The undigested food (faeces) then leaves the body through the anus, along with the collected waste. This system efficiently removes waste and helps maintain water balance.
A diagram for Malpighian tubules in cockroaches would typically show:

• **Ileum** (part of the alimentary canal)
• **Mid Gut**
• **Colon**
• **Group of Malpighian Tubules** connected to the gut.

This shows how the tubules are associated with the digestive system to facilitate excretion.
In simple words: Malpighian tubules in cockroaches collect waste from their body fluids and send it to the gut to be removed.

🎯 Exam Tip: Remember that Malpighian tubules are crucial for excretion in insects like cockroaches and connect to the alimentary canal for waste removal.

 

Question 12. Explain the method of excretion in Amoeba.
Answer: Amoeba is a single-celled organism (protozoan) and does not have any special organs for excretion. Carbon dioxide and ammonia, which are waste products from its metabolism, simply diffuse out of the cell body through the cell membrane (plasmalemma) into the surrounding water. For water regulation and some waste removal, Amoeba uses a contractile vacuole. This vacuole appears near the nucleus, collects excess water and waste products, and then periodically expels them from the cell. This keeps the Amoeba from swelling too much with water.
A diagram for excretion in Amoeba would show:

• **Food particle** being ingested (phagocytosis)
• **Food vacuole** forming
• **Nucleus**
• **Pseudopodia** for movement and engulfing food
• A **Contractile vacuole** near the nucleus, expanding and contracting to expel water and waste.

This illustrates the simple but effective methods of waste removal in a single-celled organism.
In simple words: Amoeba gets rid of waste gases and ammonia by letting them pass through its skin (cell membrane). It also uses a "contractile vacuole" to pump out extra water and some waste.

🎯 Exam Tip: Highlight that Amoeba uses diffusion for gases and ammonia, and the contractile vacuole for osmoregulation and liquid waste, due to its unicellular nature.

 

Question 13. Excretion in Hydra. What is Hydathode? Explain with a diagram?
Answer:Excretion in Hydra: Hydra is a simple organism without specialized excretory structures. Its body is made of two layers of cells. Carbon dioxide and ammonia are produced as waste and simply pass out of the body through diffusion directly into the water. Any solid waste left after food digestion is expelled through its mouth, which also functions as its anus.
Hydathode: Hydathodes are special water pores found in plants. They are located at the very ends of veins on the edges of leaves. These water pores open into a small cavity, which is surrounded by delicate parenchyma cells. Hydathodes play a role in guttation, which is the exudation of water in liquid form from plant leaves when transpiration is low and water absorption is high. This shows how plants manage excess water.
A diagram for Hydathode would show:

• **Hydathode** pore at the leaf margin
• **Guard cell** surrounding the pore (though these are modified stomata, not typical guard cells)
• **Intercellular spaces** beneath the pore
• **Epidermis** layer of the leaf
• **Parenchyma** cells forming the surrounding tissue
• **Vascular tissue** (vein ending) leading to the hydathode

This structure facilitates the release of water droplets from the plant.
In simple words: Hydra gets rid of waste by simple diffusion through its body. Hydathodes are tiny pores on plant leaves that let out extra water as droplets when the air is very wet.

🎯 Exam Tip: For Hydra, emphasize diffusion due to its simple body plan. For hydathodes, remember their role in guttation (liquid water release) rather than transpiration (water vapor release).

 

Question 16. What happens, if ovum (egg) is not fertilised by the sperms?
Answer: If an ovum (egg) is not fertilized by sperm, the corpus luteum in the ovary degenerates. The ovaries produce two hormones, progesterone and estrogen. When fertilization does not occur, the amount of progesterone hormone in the blood decreases over time. This drop in progesterone causes the lining of the uterus, which was prepared for a possible pregnancy, to break down. As a result, blood vessels burst, and blood along with uterine fluid is shed from the body. This process is called menstruation, which occurs in a cyclic manner, typically every 28 days, marking the menstrual cycle. This shedding cleans the uterus to prepare for a new cycle. If fertilization does occur, these hormones maintain the uterine lining to support the embryo.
In simple words: If an egg is not fertilized, the hormones that prepare the uterus drop. This causes the uterus lining to break down and shed, leading to menstruation.

🎯 Exam Tip: Connect the non-fertilization of an ovum directly to the degeneration of the corpus luteum and the subsequent decrease in progesterone, leading to menstruation.

 

Question 17. Explain reproduction in earthworm? diagram?
Answer: Earthworms are hermaphrodites, meaning each individual has both male and female sex organs. The female genital pore is located on the 18th segment, and the male genital pore is on the 11th segment. Although they have both organs, earthworms usually reproduce through cross-fertilization. During mating, two earthworms exchange sperm. The ova (eggs) and sperm are produced at different times to prevent self-fertilization. Fertilization happens within the female reproductive organ, which includes the ovary, oviduct, and seminal vesicles. The fertilized eggs are then protected in a cocoon, where development takes place. This process ensures the continuation of the species.
A diagram for earthworm reproduction would show the male and female reproductive structures:

• **Testis sacs**
• **Spermiducal funnel**
• **Seminal vesicle**
• **Ovary**
• **Oviducal funnel**
• **Oviduct**
• **Vasa deferentia**
• **Accessory gland**
• **Common prostatic and spermatic duct**
• **Prostate gland**

These structures highlight the dual nature of their reproductive system.
In simple words: Earthworms have both male and female parts. They mate to exchange sperm, and then the fertilized eggs are laid in a protective cocoon to grow.

🎯 Exam Tip: Emphasize that while earthworms are hermaphrodites, they typically practice cross-fertilization, which is key for genetic diversity.

 

Question 18. What effect will be produced on the embryo, if the placenta does not develop?
Answer: The placenta is a crucial structure formed by the inner walls of the uterus and the embryo (fetus). It is responsible for controlling all vital processes for the developing fetus, including respiration (oxygen supply), nutrition (food supply), and excretion (waste removal). If the placenta does not develop or becomes inactive, the fetus will not be able to perform these essential functions. This means the fetus would not get oxygen or nutrients and would not be able to get rid of its waste products. As a direct result, the fetus would likely die within the uterus. This highlights the placenta's indispensable role in supporting fetal life.
In simple words: If the placenta does not grow, the baby inside the womb will not get oxygen, food, or a way to remove waste. This would cause the baby to die.

🎯 Exam Tip: Understand the three critical functions of the placenta: respiration, nutrition, and excretion, as these are the core reasons for its importance.

 

Question 19. Describe the structure of medulla oblongata.
Answer: The medulla oblongata is a part of the brain that connects the forebrain and the hindbrain. It has a somewhat triangular shape and continues downwards, eventually becoming the spinal cord. Inside, it is hollow and contains the fourth ventricle, which is a fluid-filled space. This region is vital for connecting different parts of the brain and linking the brain to the spinal cord, allowing important signals to pass through. It controls many involuntary actions, such as breathing and heart rate.
In simple words: The medulla oblongata is a triangular part of the brain that links the front and back parts of the brain and connects to the spinal cord. It helps control basic body functions.

🎯 Exam Tip: Note the medulla oblongata's position (connecting brain parts to the spinal cord) and its vital role in involuntary functions, like breathing.

 

Question 21. Explain the structure of female reproductive gland and name the hormones secreted by them?
Answer: The primary female reproductive glands are the ovaries. They are found only in females, located in the abdominal region. Ovaries are oval-shaped and typically white or cream-colored. Their inner layer consists of germinal epithelium cells, which produce eggs through a process called oogenesis. In front of each ovary, there is a funnel-shaped structure called the ostium. The ovaries secrete three important hormones:

1. Estrogen: This hormone, controlled by FSH from the anterior pituitary, helps in the development of female secondary sexual characteristics. Its secretion is highest during ovulation and, along with progesterone, prepares the uterus for pregnancy.
2. Progesterone: Secreted by the corpus luteum (formed after ovulation), this hormone prepares the inner lining of the uterus for receiving an embryo. It is crucial for maintaining pregnancy and is often called the "pregnancy hormone." If pregnancy does not occur, the corpus luteum breaks down.
3. Relaxin: This hormone is secreted during the later stages of pregnancy. It helps relax the muscles of the pelvic area, making childbirth easier by easing pressure on the fetus.

These hormones ensure proper reproductive function and support pregnancy.
In simple words: The female reproductive glands are ovaries, which make eggs and hormones. They produce estrogen and progesterone to help with female traits and pregnancy, and relaxin to help with childbirth.

🎯 Exam Tip: Remember the two main hormones, Estrogen and Progesterone, and their distinct roles in developing female characteristics and supporting pregnancy, respectively.

 

Question 22. Write a note on-Application of hormones in Agriculture?
Answer: Plant hormones, also known as phytohormones, are naturally occurring chemicals that regulate plant growth and development. They are widely used in agriculture to improve crop yield, quality, and management. Here are some key applications:

1. Fruit Development: Auxins are used to prevent fruits from dropping prematurely and to promote uniform fruit growth. Gibberellins can increase fruit size, especially in grapes.
2. Seed Germination and Dormancy: Gibberellins help break the dormancy of seeds, buds, and tubers, promoting faster germination in crops like lettuce and cereals.
3. Preventing Sprouting: Chemicals like naphthalene acetic acid (NAA) are sprayed on potato tubers in cold storage to prevent unwanted sprouting of buds, extending their shelf life.
4. Ripening and Storage: Plant hormones are used to ripen fruits more uniformly and to produce resistance against low temperatures, which is useful for storing seeds and protecting crops.
5. Sterility Control: Hormones can also be used to check sterility in plants, ensuring healthy reproduction.

These applications allow farmers to manipulate plant processes for better agricultural outcomes.
In simple words: Plant hormones are used in farming to make plants grow better, produce more fruit, help seeds sprout, stop potatoes from growing sprouts, and protect plants from cold.

🎯 Exam Tip: Focus on how plant hormones are used to control specific plant processes, such as growth, fruit development, dormancy, and ripening, for agricultural benefit.

 

Major Activities of Living Organisms Long Answer Type Questions

 

Question 1. Explain the light reaction and dark reaction of photosynthesis?
Answer: Photosynthesis is a process where plants use sunlight to make food. It happens in two main phases:
(A) Light Reaction (or Hill Reaction): This part of photosynthesis needs light to happen. It occurs in the chloroplasts. During this phase:

1. Chlorophyll, a green pigment, absorbs light energy from specific wavelengths.
2. Water molecules are split using this light energy (a process called photolysis).
3. Oxygen gas is released as a byproduct, which comes from the water that was absorbed.
4. Energy-carrying molecules, ATP and NADPH2, are produced. This process of ATP formation in light is called photophosphorylation. The H ion from water splitting is picked up by NADP, which then becomes activated.

These ATP and NADPH2 molecules are then used in the next phase. The light reaction converts light energy into chemical energy, which is then used to fuel the dark reaction.
(B) Dark Reaction (or Blackmann Reaction): This part of photosynthesis does not directly need light, but it uses the energy (ATP) and reducing power (NADPH2) created during the light reaction. It is a biochemical process that takes place in the stroma (fluid-filled space) of the chloroplast.
In the dark reaction, carbon dioxide (\( \text{CO}_2 \)) is converted into sugars. This process is also known as the Calvin cycle (or C3 cycle) because the first stable compound formed contains three carbon atoms (Phosphoglyceric acid or PGA). Some plants use a slightly different pathway called the C4 cycle, where the first stable compound has four carbon atoms. The carbon assimilation in this stage forms the actual food for the plant.
A diagram for light and dark reactions would show:

• **Light reaction** in the thylakoid membranes, showing light input, water splitting, oxygen release, and ATP/NADPH production.
• **Dark reaction** (Calvin cycle) in the stroma, showing \( \text{CO}_2 \) intake, use of ATP/NADPH, and sugar production.

These two reactions are interconnected, with the light reaction providing the energy for the dark reaction to synthesize glucose.
In simple words: Photosynthesis has two steps: the "light reaction" where plants use sunlight and water to make energy and oxygen, and the "dark reaction" where they use that energy and carbon dioxide to make sugar.

🎯 Exam Tip: Clearly differentiate between the light-dependent (thylakoid) and light-independent (stroma) phases, noting the inputs and outputs for each. Emphasize that the dark reaction uses the products of the light reaction.

 

Question 2. Describe the factors affecting photosynthesis.
Answer: Photosynthesis, the process by which plants make their own food, is affected by several external and internal factors:
External Factors:

1. Light Intensity: As light intensity increases, the rate of photosynthesis generally increases up to a certain point. Very high light intensity can lead to stomata closure, reducing \( \text{CO}_2 \) intake and transpiration, which can then inhibit photosynthesis.
2. Oxygen: A higher concentration of oxygen in the air or inside the leaf can decrease the rate of photosynthesis. This is because oxygen can compete with carbon dioxide for binding sites on enzymes involved in photosynthesis.
3. Carbon Dioxide: Carbon dioxide concentration is often a limiting factor, as it's usually low in the atmosphere (around 0.035%). Increasing \( \text{CO}_2 \) levels (up to about 1%) typically increases the rate of photosynthesis.
4. Temperature: The dark reaction of photosynthesis is highly dependent on temperature, while the light reaction is less so. The rate of photosynthesis generally doubles for every \( 10^{\circ}\text{C} \) rise in temperature between \( 5^{\circ}\text{C} \) and \( 30^{\circ}\text{C} \). Extreme temperatures can denature enzymes and reduce the rate.
5. Water: Water is essential for photosynthesis (it's a reactant). A lack of water (deficiency) can severely reduce photosynthesis. It causes stomata to close, limiting \( \text{CO}_2 \) entry and reducing the turgor pressure needed for cell functions.
6. Air Pollutants: Pollutants like sulfur dioxide (\( \text{SO}_2 \)) and nitrogen oxides can harm plant tissues and reduce the rate of photosynthesis.

Internal Factors:

1. Chlorophyll Content: Chlorophyll is the main pigment that captures light energy. The more chlorophyll a plant has, the higher its photosynthetic capacity.
2. Protoplasmic Factors: The protoplasm contains enzymes and other substances that influence photosynthesis. These internal factors affect the timing and efficiency of the process.
3. Accumulation of Carbohydrates: If the sugars produced during photosynthesis are not moved away from the leaves to other parts of the plant, they can accumulate. This build-up can slow down or inhibit further photosynthesis.

Understanding these factors helps in optimizing conditions for plant growth.
In simple words: Photosynthesis is affected by outside things like light, carbon dioxide, oxygen, water, and temperature. Inside the plant, the amount of green chlorophyll and how well the plant uses its stored food also change how much food it can make.

🎯 Exam Tip: Categorize factors into external and internal, and for each, provide a concise explanation of how it impacts the rate of photosynthesis.

 

Question 3. How does the exchange of gases occur as a result of respiration in human beings?
Answer: Gas exchange in human respiration involves two main phases: inspiration (breathing in) and expiration (breathing out).
(1) Inspiration (Breathing In): During inspiration, the ribs and the muscles of the diaphragm contract. The diaphragm moves downwards and flattens, causing the pleural cavity (space around the lungs) to expand. This expansion also makes the lungs expand. As a result, the air pressure inside the lungs becomes lower than the outside air pressure. This pressure difference creates a gradient, causing air to rush through the nasal passage into the air sacs (alveoli) of the lungs.
(2) Expiration (Breathing Out): During expiration, the ribs and diaphragm muscles relax. The chest cavity contracts, and the lungs recoil. This pushes the air out of the lungs with pressure, through the nostrils. We breathe in and out because of the changing air pressure caused by the movement of our chest muscles; the lungs themselves are passive in this movement. Gas exchange (oxygen in, carbon dioxide out) happens primarily in the alveoli due to differences in partial pressures of these gases.
A simple diagram for inspiration/expiration typically shows:

• **Inspiration:** Diaphragm moves down, rib cage expands, arrows show air entering lungs.
• **Expiration:** Diaphragm moves up, rib cage contracts, arrows show air leaving lungs.

These movements create pressure changes, allowing us to breathe and exchange gases.
In simple words: When we breathe in, our diaphragm and rib muscles move to make space for air to enter our lungs. When we breathe out, these muscles relax, pushing air back out. This is how oxygen enters our body and carbon dioxide leaves.

🎯 Exam Tip: Focus on the role of the diaphragm and rib muscles in changing chest cavity volume, leading to pressure differences that drive air in and out of the lungs.

 

Question 4. Describe with the help of diagrams the internal and external structure of the heart.
Answer: The human heart is a vital muscular organ that pumps blood throughout the body.
External Structure of Heart: The human heart is a four-chambered organ, roughly the size of a fist. It weighs about 300 grams and is located in the thoracic cavity, between the two lungs. It is enclosed within a double-walled membranous sac called the pericardium, which protects it. The heart has two upper chambers called auricles (or atria) and two lower chambers called ventricles. An inter-arterial septum separates the left and right auricles, and an interventricular septum separates the left and right ventricles. These septa ensure that oxygenated and deoxygenated blood do not mix.
Internal Structure of Heart: The heart's internal structure reveals its efficiency as a pump:

1. Chambers: The heart has four chambers – the right atrium, left atrium, right ventricle, and left ventricle. The atria are thin-walled and receive blood from veins. The right atrium receives deoxygenated blood from the body through the vena cava, while the left atrium receives oxygenated blood from the lungs via the pulmonary veins.
2. Ventricles: The ventricles are thick-walled, especially the left ventricle, which pumps blood to the entire body. The right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery.
3. Valves: Valves ensure one-way blood flow. The bicuspid (mitral) valve is between the left atrium and left ventricle. The tricuspid valve is between the right atrium and right ventricle. Semilunar valves are at the exits of the ventricles into the aorta and pulmonary artery. These valves prevent blood from flowing backward into the atria or ventricles during contraction.
4. Muscular Contraction: All atria and ventricles contract and relax in a coordinated manner, making the heart function as a powerful pump. The entire muscular heart is protected by the pericardium.

A diagram of the heart would illustrate:

• **External:** Aorta, vena cava, pulmonary arteries/veins, auricles, ventricles.
• **Internal:** All four chambers, the septa, and the various valves (tricuspid, bicuspid/mitral, semilunar) at their correct locations, showing the path of blood flow.

This complex structure allows for efficient circulation of blood throughout the body.
In simple words: The human heart is a powerful muscle with four parts (two upper, two lower). It has valves that act like doors to keep blood flowing in one direction. The right side pumps dirty blood to the lungs, and the left side pumps clean blood to the rest of the body.

🎯 Exam Tip: Accurately label the four chambers, major blood vessels (aorta, vena cava, pulmonary artery/veins), and the key valves (tricuspid, bicuspid/mitral, semilunar) in any diagram. Understand the path of blood flow through these structures.

 

Question 5. Explain Cohesion-transpiration theory.
Answer: The Cohesion-Transpiration theory, proposed by Dixon and Jolly in 1894, explains how water moves from the roots to the leaves in tall plants. This theory is based on three main points:

1. Cohesion of Water Molecules: Water molecules have a strong attraction to each other (cohesion) due to hydrogen bonds. This force keeps the water column in the xylem vessels continuous and unbroken, like a long, thin chain.
2. Transpiration Pull: Plants release water vapor from their leaves into the atmosphere through tiny pores called stomata (this process is called transpiration). This evaporation creates a reduced pressure, or "suction pressure," in the leaves. This suction pull is the main force that draws the continuous column of water upwards from the roots.
3. Adhesion to Xylem Walls: Water molecules also stick to the walls of the xylem vessels (adhesion), preventing the water column from breaking. The root pressure, which pushes water from the soil into the xylem, also helps maintain this continuous water column, though it is a weaker force than transpiration pull.

In essence, transpiration from the leaves creates a pull, and because water molecules stick together and to the xylem walls, this pull is transmitted down the entire water column, drawing water from the roots all the way up to the leaves.
An experiment to demonstrate this involves:

• A glass tube with water, inverted into mercury.
• A freshly cut twig is fitted into the top end.
• The apparatus is sealed and kept airtight.

As the twig transpires, water is pulled upwards, and the mercury in the tube rises, showing the upward pull of water. This helps us understand how water defying gravity reaches the top of even the tallest trees.
In simple words: The cohesion-transpiration theory says that water travels up plants like a continuous chain because water molecules stick together (cohesion). As water evaporates from leaves (transpiration), it pulls the whole chain of water up from the roots, like a giant straw.

🎯 Exam Tip: Focus on the three key aspects: cohesion of water molecules, transpiration pull (the main driving force), and adhesion to xylem walls. These three forces work together to move water up the plant.

 

Question 6. Show experimentally that liquid food is conducted by phloem.
Answer: To show that liquid food is conducted by phloem, we can perform a girdling experiment:
Experiment:

1. Take a well-watered potted plant.
2. About 6 inches above the soil surface, carefully remove a complete ring (girdle) of bark from the stem. This ring should include the bark, cortex, and phloem tissue, but leave the xylem (the innermost wood) intact.
3. Observe the plant over some time.

Observation: After some time, you will notice that the part of the stem above the girdle will swell up, and sometimes even sprout roots. The growth of the plant part below the girdle will be significantly reduced, or it may even die.
Explanation: This happens because the leaves manufacture organic food material through photosynthesis, which is then transported downwards through the phloem. By removing the phloem in the girdled section, this downward transport of food is interrupted. The food accumulates above the girdle, leading to swelling and promoting root growth in that area. Below the girdle, the cells do not receive enough food, causing reduced growth and eventual death.
A diagram of this experiment would show:

• A plant with **roots**, **stem**, and **leaves**.
• A **band (girdle)** where the bark and phloem have been removed.
• **Swelling** of the stem above the girdle.
• **Reduced growth** of roots and stem below the girdle.

This experiment clearly demonstrates that the phloem tissue is responsible for translocating liquid food material (sugars) from the leaves to other parts of the plant, especially the roots. This is crucial for the plant's overall development and survival.
In simple words: To prove phloem moves food, we remove a ring of bark from a plant stem. The part above the cut swells with stored food, and the part below it starves and stops growing. This shows phloem carries food.

🎯 Exam Tip: When describing the girdling experiment, clearly explain why removing the phloem above a certain point leads to accumulation above the girdle and lack of nourishment below it, thus linking phloem directly to food transport.

 

Question 7. What is osmosis? Explain with the help of an experiment.
Answer:Osmosis: Osmosis is a special type of diffusion. It is the movement of water molecules (or other solvent molecules) across a semi-permeable membrane. This movement always occurs from a region of higher water potential (where water is more concentrated or "pure") to a region of lower water potential (where solutes are more concentrated). In plant cells, this process is essential for water absorption from the soil and movement between cells, as the plasma membrane acts as a semi-permeable barrier that allows water to pass but restricts most solute particles.
Experiment to Demonstrate Osmosis:
Setup:

1. Take a small bag made of cellophane. Cellophane acts as a semi-permeable membrane.
2. Fill this cellophane bag with a 2% sugar solution. This means the bag contains 2% sugar and 98% water.
3. Tie the mouth of the bag securely with a thread.
4. Suspend this bag in a beaker filled with pure water. The pure water in the beaker has 100% water concentration and 0% sugar.

Observation:

1. After some time (e.g., an hour), you will observe that the cellophane bag swells up.
2. The level of liquid inside the bag may also rise.

Explanation:

1. The beaker has pure water (100% water, higher water potential), while the bag contains a 2% sugar solution (98% water, lower water potential).
2. Due to osmosis, water molecules from the beaker move through the semi-permeable cellophane membrane into the bag. This influx of water causes the bag to swell.
3. Although sugar molecules are more concentrated inside the bag, they will try to diffuse out into the beaker. However, the cellophane membrane is semi-permeable, meaning it mostly restricts the passage of larger solute molecules (like sugar) but allows smaller solvent molecules (like water) to pass through easily. Therefore, the net movement of water into the bag is significant, causing it to swell.

This experiment effectively demonstrates osmosis and the pressure it generates, known as osmotic pressure, which is crucial for water movement in plants, helping cells maintain turgidity and affecting stomata opening and closing.
In simple words: Osmosis is when water moves from a watery area to a less watery (more sugary) area through a special filter-like wall. In an experiment, a sugar-filled bag placed in pure water will swell because water moves into it.

🎯 Exam Tip: Clearly define a semi-permeable membrane and water potential. In the experiment, ensure you explain the concentration gradient of water and how the membrane acts as a selective barrier.

 

Question 8. Explain the internal structure of the kidney?
Answer: The kidney has two main internal parts. The outer part is called the cortex, and the inner part is called the medulla. These parts work together to filter blood and produce urine, which helps keep the body clean.

(a) **Nephrons:** Inside the kidney's medulla, there are about one million tiny, coiled tubes called nephrons. These nephrons are the basic working units of the kidney. Each nephron has two parts: the Malpighian capsule and a tubule. The Malpighian capsule is shaped like a cup (Bowman's capsule) and contains a cluster of tiny blood vessels called the glomerulus. The capsule leads into a twisted tube called the proximal convoluted tubule. After this, there is a U-shaped thin loop called the Loop of Henle. This loop is followed by another twisted tube, the distal convoluted tubule, which then opens into a larger collecting tubule. This collecting tubule eventually leads to the funnel-shaped part (pelvis) of the ureter in the kidney.In simple words: The kidney has an outer part (cortex) and an inner part (medulla). Inside, there are millions of tiny filtering units called nephrons, which look like a cup with a twisted tube, that clean the blood.

🎯 Exam Tip: Remember to clearly label the cortex, medulla, and major components of the nephron in diagrams, as these are key to understanding kidney function.

 

Question 9. What is excretion? How is urine excreted out by kidney?
Answer: **Excretion:** Excretion is the process where the body removes metabolic waste products. During daily activities, our body creates different waste products like carbon dioxide and urea through various metabolic reactions. These wastes are harmful and must be removed. **Formation of Urine:** Urine is formed in the kidneys through a physical process. Tiny filtering units called nephrons in the kidney are responsible for making urine. Each kidney has millions of nephrons. Three main processes happen in the nephrons to form urine:
• Glomerulus ultra-filtration (initial filtering)
• Selective re-absorption (taking back useful things)
• Tubular excretion (removing extra waste) Blood enters the kidney through the renal artery, which then divides into many small capillaries. These capillaries form a dense network called the glomerulus inside Bowman's capsule. Blood flows into the glomerulus through a wider vessel (afferent arteriole) and leaves through a narrower one (efferent arteriole). This difference in width creates high blood pressure, forcing water, urea, glucose, uric acid, and some salts from the blood into Bowman's capsule. This first step is called ultrafiltration. As this filtered liquid (filtrate) passes through the tubule part of the nephron, useful substances like glucose, some salts, and most of the water are re-absorbed back into the blood. This careful reabsorption ensures the body keeps what it needs. The liquid remaining after reabsorption is urine. This urine then flows from the kidney through tubes called ureters into the urinary bladder. The urinary bladder has muscles that are not under our conscious control. When the bladder fills with urine, these muscles contract, pushing the urine out of the body through the urethra.In simple words: Excretion is how the body gets rid of waste. Kidneys filter blood to make urine. First, they filter everything out, then they take back what the body needs, and finally, the waste (urine) goes to the bladder and leaves the body.

🎯 Exam Tip: When describing excretion, highlight that it removes HARMFUL metabolic wastes, and for urine formation, emphasize the three distinct steps: filtration, reabsorption, and excretion.

 

Question 10. Draw the diagram of the excretory system of human?
Answer: The human excretory system includes kidneys, ureters, urinary bladder, and urethra. These organs work together to filter waste from the blood and remove it from the body as urine.

Other excretory organs:
1. **Skin:** Our skin has many small pores where sweat ducts open. Excess salt and urea, along with water, pass through these ducts and come out as perspiration (sweat).
2. **Liver:** The liver changes ammonia, a harmful waste, into urea. This urea is then sent to the kidneys through the blood, where it is filtered and removed in the urine. The liver helps detoxify the body.
3. **Spleen:** The spleen and liver cells destroy old and damaged red blood cells. They also help make bile pigment, which is then passed into the small intestines along with bile.In simple words: The diagram shows the kidneys, tubes (ureters), bladder, and the exit tube (urethra). Other body parts like skin (sweat), liver (changes waste), and spleen (cleans blood) also help remove waste.

🎯 Exam Tip: When drawing, make sure the kidneys are bean-shaped, ureters connect to the bladder, and major blood vessels (aorta and vena cava) are correctly shown with their branches to the kidneys.

 

Question 11. Explain the different methods of artificial vegetative reproduction in plants. Write the importance of vegetative reproduction?
Answer: Vegetative propagation is a common way plants multiply using their body parts (like stems or roots) instead of seeds. This method is very useful in farming and gardening to grow specific types of flowering and fruit plants, such as roses, jasmine, mango, and sugarcane. It allows growers to choose which plant part helps in reproduction. There are four main methods of artificial vegetative propagation:
(a) **Cutting:** In this method, a part of a plant's stem, like a rose or croton, is cut and planted in moist soil. The bottom part of the cutting grows roots, and the buds on the stem grow into new shoots, forming a new plant. This ensures the new plant is identical to the parent.
(b) **Budding:** Here, a bud from a desired plant (superior variety) is joined onto the stem of another ordinary plant of the same type. The bud grows to form a new shoot, resulting in a plant that has the good qualities of the budded plant. This is used for ornamental plants.
(c) **Grafting:** In grafting, a shoot (called a scion or graft) from a superior plant is attached to the root system of another plant (called the stock). The two parts grow together as one plant. This method is used for many fruit trees like mango, oranges, and seedless grapes to create desired varieties.
(d) **Layering:** This method is often used for plants with flexible, soft branches, like jasmine or magnolia. A branch is bent to the ground and covered with soil while still attached to the parent plant. Roots grow from the buried part, and then the branch is cut off to become a new plant.In simple words: Artificial vegetative reproduction means growing new plants from parts like stems or branches. Methods like cutting, budding, grafting, and layering help us grow many plants that are exactly like the parent plant, especially for fruits and flowers, or if seeds are hard to grow.

🎯 Exam Tip: When explaining each method, state what part of the plant is used and give a relevant example. For importance, focus on genetic consistency and faster growth.

 

Question 12. Describe asexual reproduction in lower groups of animals.
Answer: **Asexual reproduction:** All living organisms begin their life from a single cell. If a new organism comes from only one parent, without the fusion of sex cells, it is called asexual reproduction. This method is common in simpler animals. The main methods of asexual reproduction are as follows:
(1) **Budding:** In this method, a small outgrowth, or 'bud', forms on the body of the parent animal. This bud grows bigger and eventually separates from the parent, developing into a new, independent animal. A common example is Hydra and Vorticella. This allows rapid population growth in stable environments.

🎯 Exam Tip: When listing methods of asexual reproduction, always give a clear definition and a classic example for each, such as Hydra for budding.

 

Question 13. Describe the structure of the nerve cell with the help of a diagram. How does the conduction of nerve impulse take place? Explain.
Answer: A nerve cell, or neuron, is the basic unit of the nervous system. It helps our body communicate by sending electrical signals. It is made of three main parts: the cell body (soma), dendrites, and an axon. The soma is like a simple cell, with a nucleus and other cell parts inside. Dendrites are small, branched extensions that receive signals from other nerve cells and bring them to the soma. The axon is a long, thin extension that carries signals away from the soma to other nerve cells or muscles.

**Conduction of impulse:** Nerve impulses are like electrical signals that travel along the nerve cells. The brain and spinal cord (controlling centers) receive signals from sensory nerves, which pick up information from our senses. The brain then decides how to react. Motor nerves carry these reaction signals from the brain to the muscles or glands, telling them what to do. This entire process happens very quickly, allowing our body to respond to its environment.In simple words: Nerve cells have dendrites that get signals, a body that processes them, and an axon that sends them out. Signals travel like electricity from one nerve cell to the next, helping our body react quickly.

🎯 Exam Tip: When explaining nerve impulse conduction, focus on the roles of sensory nerves (carrying signals to the brain/spinal cord) and motor nerves (carrying responses to muscles/glands).

 

Question 14. Describe with the help of a diagram, the structure of the human nervous system and functions of the brain?
Answer: The human nervous system is very complex and highly developed. It helps us control our actions, thoughts, and feelings. It has two main parts: the central nervous system and the peripheral nervous system. Nerve impulses are electrical signals that travel through nerve cells. When a signal is received by dendrites, the electrical charges change, creating an impulse. This impulse moves along the nerve cell. When it reaches the end of the axon, special chemicals (hormones) are released, helping the signal pass to the next nerve cell.

The nervous system of man consists of two parts:
(a) The central nervous system.
(b) The peripheral nervous system.
**Nervous system**
• Central Nervous System
• Brain
• Spinal cord
• Peripheral Nervous System
• Voluntary Nervous System
• Autonomic Nervous System
• Sympathetic Nervous System
• Para Sympathetic Nervous System
(a) **The Central Nervous System:** This system includes the brain and spinal cord. It is responsible for all our thoughts, emotions, and movements.
1. **Brain:** The human brain looks like a large mushroom and is located inside the skull, which is a bony cavity called the cranium. The brain is protected by three membranes (meninges), and a fluid (cerebrospinal fluid) fills the space between these membranes, cushioning the brain from shocks. The brain has three main parts:
(a) Forebrain
(b) Midbrain
(c) Hindbrain The forebrain is the largest part, making up about two-thirds of the brain. It mainly contains the cerebrum, which is responsible for higher thinking. The midbrain is small and connects the cerebrum to other parts of the brain and the spinal cord. The hindbrain has three main parts: the medulla oblongata, pons, and cerebellum. This complex structure allows the brain to process vast amounts of information and coordinate body functions.
2. **Spinal cord:** The spinal cord is a collection of nerve cells and fibers, forming a cylindrical mass that extends from the brain down to the lower back. It is also protected by meninges and lies within the vertebral column. The spinal cord has two main jobs: it carries signals to and from the brain, and it controls reflexes.In simple words: The nervous system has a central part (brain and spinal cord) and a peripheral part (nerves that go everywhere else). The brain helps us think and move, and the spinal cord sends messages between the brain and the body, also controlling quick reactions.

🎯 Exam Tip: When explaining the nervous system, ensure you distinguish between the central (brain, spinal cord) and peripheral (all other nerves) parts, and for the brain, name its three main regions and their general roles.

 

Question 15. Describe any four endocrine glands and explain the effects of hormones secreted by them.
Answer: Endocrine glands are special glands in our body that produce hormones. These hormones are like chemical messengers that travel through the blood and control many important body functions. Here are some of these glands and their hormones:

1. **Pineal gland:** This small gland is located in the middle of the brain. It produces melatonin, a hormone that helps control sleep and wake cycles. It also affects other body rhythms and the development of reproductive organs.
2. **Thymus gland:** Located in the chest, above the heart, the thymus gland produces hormones called thymosins. These hormones are very important for our immune system, as they help in the production of lymphocytes, which fight off germs and infections.
3. **Parathyroid glands:** These are usually four small glands found on the back of the thyroid gland in the neck. They produce parathormone, which controls the levels of calcium and phosphate in the blood. This hormone is vital for healthy bones and teeth. If there's too little parathormone, it can lead to muscle spasms, and too much can weaken bones.
4. **Adrenal gland:** We have two adrenal glands, one on top of each kidney. They are divided into an outer part (cortex) and an inner part (medulla). The cortex produces several hormones called corticosteroids, including mineralocorticoids.
**Mineralocorticoid:** This hormone helps maintain the balance of sodium and potassium salts in the blood. If this hormone is lacking, the body can lose too much sodium, which can be very dangerous. It is sometimes called the "life-saving hormone" because of its critical role. These glands play a crucial role in maintaining overall health and proper functioning of the body.In simple words: Endocrine glands make hormones that control many body activities. Examples include the pineal gland (sleep), thymus gland (immunity), parathyroid glands (calcium), and adrenal glands (salt balance).

🎯 Exam Tip: For each endocrine gland, clearly name the gland, the hormone(s) it produces, and at least one major effect or function of that hormone in the body.

 

Question 11. Explain the different methods of artificial vegetative reproduction in plants. Write the importance of vegetative reproduction?
Answer: Vegetative propagation is a common way plants multiply using their body parts (like stems or roots) instead of seeds. This method is very useful in farming and gardening to grow specific types of flowering and fruit plants, such as roses, jasmine, mango, and sugarcane. It allows growers to choose which plant part helps in reproduction. There are four main methods of artificial vegetative propagation:
(a) **Cutting:** In this method, a part of a plant's stem, like a rose or croton, is cut and planted in moist soil. The bottom part of the cutting grows roots, and the buds on the stem grow into new shoots, forming a new plant. This ensures the new plant is identical to the parent.
(b) **Budding:** Here, a bud from a desired plant (superior variety) is joined onto the stem of another ordinary plant of the same type. The bud grows to form a new shoot, resulting in a plant that has the good qualities of the budded plant. This is used for ornamental plants.
(c) **Grafting:** In grafting, a shoot (called a scion or graft) from a superior plant is attached to the root system of another plant (called the stock). The two parts grow together as one plant. This method is used for many fruit trees like mango, oranges, and seedless grapes to create desired varieties.
(d) **Layering:** This method is often used for plants with flexible, soft branches, like jasmine or magnolia. A branch is bent to the ground and covered with soil while still attached to the parent plant. Roots grow from the buried part, and then the branch is cut off to become a new plant.In simple words: Artificial vegetative reproduction means growing new plants from parts like stems or branches. Methods like cutting, budding, grafting, and layering help us grow many plants that are exactly like the parent plant, especially for fruits and flowers, or if seeds are hard to grow.

🎯 Exam Tip: When explaining each method, state what part of the plant is used and give a relevant example. For importance, focus on genetic consistency and faster growth.

 

Question 12. Describe asexual reproduction in lower groups of animals.
Answer: **Asexual reproduction:** All living organisms begin their life from a single cell. If a new organism comes from only one parent, without the fusion of sex cells, it is called asexual reproduction. This method is common in simpler animals. The main methods of asexual reproduction are as follows:
(1) **Budding:** In this method, a small outgrowth, or 'bud', forms on the body of the parent animal. This bud grows bigger and eventually separates from the parent, developing into a new, independent animal. A common example is Hydra and Vorticella. This allows rapid population growth in stable environments.

🎯 Exam Tip: When listing methods of asexual reproduction, always give a clear definition and a classic example for each, such as Hydra for budding.

 

Question 13. Describe the structure of the nerve cell with the help of a diagram. How does the conduction of nerve impulse take place? Explain.
Answer: A nerve cell, or neuron, is the basic unit of the nervous system. It helps our body communicate by sending electrical signals. It is made of three main parts: the cell body (soma), dendrites, and an axon. The soma is like a simple cell, with a nucleus and other cell parts inside. Dendrites are small, branched extensions that receive signals from other nerve cells and bring them to the soma. The axon is a long, thin extension that carries signals away from the soma to other nerve cells or muscles.

**Conduction of impulse:** Nerve impulses are like electrical signals that travel along the nerve cells. The brain and spinal cord (controlling centers) receive signals from sensory nerves, which pick up information from our senses. The brain then decides how to react. Motor nerves carry these reaction signals from the brain to the muscles or glands, telling them what to do. This entire process happens very quickly, allowing our body to respond to its environment.In simple words: Nerve cells have dendrites that get signals, a body that processes them, and an axon that sends them out. Signals travel like electricity from one nerve cell to the next, helping our body react quickly.

🎯 Exam Tip: When explaining nerve impulse conduction, focus on the roles of sensory nerves (carrying signals to the brain/spinal cord) and motor nerves (carrying responses to muscles/glands).

 

Question 14. Describe with the help of a diagram, the structure of the human nervous system and functions of the brain?
Answer: The human nervous system is very complex and highly developed. It helps us control our actions, thoughts, and feelings. It has two main parts: the central nervous system and the peripheral nervous system. Nerve impulses are electrical signals that travel through nerve cells. When a signal is received by dendrites, the electrical charges change, creating an impulse. This impulse moves along the nerve cell. When it reaches the end of the axon, special chemicals (hormones) are released, helping the signal pass to the next nerve cell.

The nervous system of man consists of two parts:
(a) The central nervous system.
(b) The peripheral nervous system.
**Nervous system**
• Central Nervous System
• Brain
• Spinal cord
• Peripheral Nervous System
• Voluntary Nervous System
• Autonomic Nervous System
• Sympathetic Nervous System
• Para Sympathetic Nervous System
(a) **The Central Nervous System:** This system includes the brain and spinal cord. It is responsible for all our thoughts, emotions, and movements.
1. **Brain:** The human brain looks like a large mushroom and is located inside the skull, which is a bony cavity called the cranium. The brain is protected by three membranes (meninges), and a fluid (cerebrospinal fluid) fills the space between these membranes, cushioning the brain from shocks. The brain has three main parts:
(a) Forebrain
(b) Midbrain
(c) Hindbrain The forebrain is the largest part, making up about two-thirds of the brain. It mainly contains the cerebrum, which is responsible for higher thinking. The midbrain is small and connects the cerebrum to other parts of the brain and the spinal cord. The hindbrain has three main parts: the medulla oblongata, pons, and cerebellum. This complex structure allows the brain to process vast amounts of information and coordinate body functions.

2. **Spinal cord:** The spinal cord contains many nerve cells and fibers, extending from the brain to the lower part of the back. It is covered by similar protective membranes as the brain. The spinal cord has two main functions: it sends nerve impulses to and from the brain, and it acts as a center for reflex actions.
(b) **Peripheral nervous system:** This system includes all the nerves outside the brain and spinal cord. It consists of three parts: Cranial nerves, Spinal nerves, and the Autonomic nervous system.
**Cranial nerves:** These nerves come directly from the brain. In humans, there are twelve pairs of cranial nerves, which mainly supply organs in the head region, helping with things like sight, smell, and facial movements.
**Autonomic nervous system:** This system controls internal body functions automatically and without us thinking about them. It manages smooth muscles in organs like the digestive tract, respiratory system, and blood vessels, as well as cardiac muscles and glands. It has two parts: sympathetic and parasympathetic, which often have opposite effects to keep the body in balance. This system regulates:
1. The contraction of involuntary muscles.
2. The rate and force of the heartbeat.
3. The secretion of digestive glands.
4. The size of the pupil of the eye.
**Functions of Brain:**
1. The brain receives signals from all sensory organs (like eyes and ears) and processes them.
2. After processing, the brain sends instructions to muscles and glands, telling them how to respond.
3. It connects different sensory information, helping us understand the world around us.
4. The brain helps coordinate all our body activities efficiently.
5. It stores information, which forms our knowledge and memories.
6. The brain is essential for thinking, learning, and intelligence.In simple words: The brain is like the body's control center, protected in the skull. It has a forebrain (for thinking), midbrain, and hindbrain (for basic body functions). It works with the spinal cord to send and receive messages, helping us think, move, and react.

🎯 Exam Tip: When describing brain functions, mention its role in sensory processing, motor control, memory, and coordinating body activities. Use simple language to explain complex ideas.

 

Question 15. Describe any four endocrine glands and explain the effects of hormones secreted by them.
Answer: Endocrine glands are special glands in our body that produce hormones. These hormones are like chemical messengers that travel through the blood and control many important body functions. Here are some of these glands and their hormones:

1. **Pineal gland:** This small gland is located in the middle of the brain. It produces melatonin, a hormone that helps control sleep and wake cycles. It also affects other body rhythms and the development of reproductive organs.
2. **Thymus gland:** Located in the chest, above the heart, the thymus gland produces hormones called thymosins. These hormones are very important for our immune system, as they help in the production of lymphocytes, which fight off germs and infections.
3. **Parathyroid glands:** These are usually four small glands found on the back of the thyroid gland in the neck. They produce parathormone, which controls the levels of calcium and phosphate in the blood. This hormone is vital for healthy bones and teeth. If there's too little parathormone, it can lead to muscle spasms, and too much can weaken bones.
4. **Adrenal gland:** We have two adrenal glands, one on top of each kidney. They are divided into an outer part (cortex) and an inner part (medulla). The cortex produces several hormones called corticosteroids, including mineralocorticoids.
**Mineralocorticoid:** This hormone helps maintain the balance of sodium and potassium salts in the blood. If this hormone is lacking, the body can lose too much sodium, which can be very dangerous. It is sometimes called the "life-saving hormone" because of its critical role. These glands play a crucial role in maintaining overall health and proper functioning of the body.In simple words: Endocrine glands make hormones that control many body activities. Examples include the pineal gland (sleep), thymus gland (immunity), parathyroid glands (calcium), and adrenal glands (salt balance).

🎯 Exam Tip: For each endocrine gland, clearly name the gland, the hormone(s) it produces, and at least one major effect or function of that hormone in the body.