Maharashtra Board Class 7 Science Chapter 11 Cell Structure and Micro organisms Solutions

1. Answer The Following Questions.

Question a. What is a cell?
Answer: The cell is the fundamental, structural and functional unit of living organism.
In simple words: A cell is the smallest basic unit that makes up all living things and carries out all life functions.

🎯 Exam Tip: Remember the three key terms: fundamental, structural, and functional unit of life for a complete definition.

Question b. Name the different organelles in a cell.
Answer: The nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids, chloroplasts are the different organelles in a cell.
In simple words: Cell organelles are specialized structures within a cell that perform specific tasks, such as the nucleus for control, mitochondria for energy, and chloroplasts for photosynthesis in plants.

🎯 Exam Tip: Listing at least 5-7 organelles accurately can fetch full marks. Focus on those with distinct functions.

Question c. What are micro-organisms?
Answer: The organisms which cannot be seen with our eyes but can only be observed under a microscope are called micro-organisms.
In simple words: Micro-organisms are tiny living beings, like bacteria and viruses, that are too small to be seen without a microscope.

🎯 Exam Tip: Highlight the inability to see them with the naked eye and the necessity of a microscope for observation.

Question d. Which are the different types of micro-organisms?
Answer: Algae, fungi, bacteria, protozoa and viruses are various types of micro-organism. Some are unicellular and others are multicellular. Some of them are useful and some are harmful.
In simple words: Micro-organisms include algae, fungi, bacteria, protozoa, and viruses; they can be single-celled or multi-celled and have both beneficial and harmful roles.

🎯 Exam Tip: Provide at least three distinct examples and briefly mention their diversity in terms of cellularity and effects.

2. Fill In The Blanks With The Proper Word.

Question a. The organelle called the ................. is present in the plant cells only.
Answer: chloroplasts
In simple words: Chloroplasts are special parts found only in plant cells, where they capture sunlight to make food.

🎯 Exam Tip: Focus on unique structures for plant cells, like chloroplasts and cell walls, which are often distinguishing features.

Question b. Garbage is converted into by microorganisms.
Answer: fertilizer
In simple words: Microorganisms help break down garbage into useful fertilizer, enriching the soil.

🎯 Exam Tip: Understand the role of microorganisms in decomposition and nutrient cycling, often yielding beneficial products like fertilizer.

Question c. In the cell, photosynthesis is carried out with the help of ........... .
Answer: chloroplast
In simple words: Photosynthesis, the process plants use to make food, happens inside chloroplasts within their cells.

🎯 Exam Tip: Link photosynthesis directly to chloroplasts, as it's their primary function in plant cells.

Question d. An electron microscope is necessary for the study of ................. .
Answer: micro-organism
In simple words: An electron microscope is required to clearly observe very tiny things like micro-organisms because they are too small for regular microscopes.

🎯 Exam Tip: Differentiate between the types of microscopes and what they are used to observe, noting the high magnification needed for microorganisms.

Question e. The process of preparing their own food in presence of sunlight and chloroplast by plants cells is known as ............. .
Answer: photosynthesis.
In simple words: Photosynthesis is the process where plants use sunlight and chloroplasts to create their own food.

🎯 Exam Tip: This question tests the definition of photosynthesis; ensure you include sunlight and chloroplasts as key components.

3. What Is The Difference Between Us?

Question a. Plant cell and animal cell.
Answer:

In simple words: Plant cells have a rigid cell wall, a large central vacuole, and chloroplasts for making food, while animal cells lack a cell wall and chloroplasts, and have many small vacuoles.

🎯 Exam Tip: Focus on 3-4 major differentiating features like cell wall, chloroplasts, and vacuole size for clear comparison.

Question b. Prokaryotic cell and Eukaryotic cell
Answer:

In simple words: Prokaryotic cells are simpler, lacking a true nucleus and membrane-bound organelles, while eukaryotic cells are more complex, possessing a well-defined nucleus and many specialized organelles.

🎯 Exam Tip: The presence or absence of a well-defined nucleus and membrane-bound organelles are the primary distinguishing features to highlight.

4. Sketch And Describe In Your On Words, The Plant Cell And Animal Cell.

Question a. Sketch and describe in your on words, the plant cell and animal cell.
Answer: There are two types of cell-animal cells and plant cells. These cells contain various types of membrane beyond cell-organelles. Plant cells have a definite shape due to the presence of cell wall. Besides, unlike animal cells, plant cells contain single large vacuole. All these cells are known as eukaryotic cells. It cell has four main parts: the cell wall, cell membrane, cytoplasm and cell organelles.
1. Cell wall: The cell wall is the outermost covering of a cell. It is present only in plant cells.
2. Plasma membrane: The plasma membrane, also called the cell membrane, is a kind of thin covering,
(a) It is extremely delicate and flexible,
(b) It is the outermost covering of animal cells.
3. Cytoplasm: The liquid part in the cell, present around the nucleus is called cytoplasm,
(a) It occupies the space between the plasma membrane and nucleus,
(b) Cell organelles are scattered in the cytoplasm.
4. Cell organelles: These mainly include the nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids etc.
Plant cells contain chloroplasts.
(a) The nucleus is the most important organelle of the cell,
(b) There is a porous double membrane around it.
(c) The nucleus controls all functions of the cell,
(d) The endoplasmic reticulum is a sprawling net-like organelle. Its function is to make necessary changes in the proteins produced by ribosomes and send them to the Golgi bodies,
(e) Golgi bodies are made up of several flat sacs. Their function is the proper distribution of proteins.
(f) Mitochondria and plastids are organelles with double outer coverings,
(g) As mitochondria produce energy, they are called the powerhouses of the cell,
(h) The chloroplasts in plant cells carry out the function of photosynthesis,
(i) Vacuoles help to throw out waste products of the cell,
(j) Vacuoles in animal cells are small whereas there is only one large vacuole in a plant cell.
In simple words: Plant and animal cells are eukaryotic and share basic parts like cytoplasm and a cell membrane, but plant cells have a cell wall, chloroplasts, and a large central vacuole that animal cells lack.

🎯 Exam Tip: While diagrams are not rendered, a detailed description of the major parts of both plant and animal cells, highlighting their unique features and commonalities, is essential for this type of question. Ensure all sub-points are covered.

5. Explain The Uses And The Harmful Effects Of Micro-Organisms.

Question a. Explain the uses and the harmful effects of, micro-organisms.
Answer: Micro-organisms which are helpful are called useful micro-organisms.
Uses:
1. Micro-organisms present in nodules of leguminous plants, convert atmospheric nitrogen into its compounds and these compounds help to increase the soil fertility and protein content in the soil.
2. Some micro-organisms are useful in process of fermentation, making the food easily digestible and more nutritious. For producing milk products like butter, buttermilk, cheese, paneer, etc.
3. Microbes present in soil, dung etc. decompose garbage and convert into manure of best quality and surrounding is kept clean.
4. Microbes are also useful for sewage disposal. They help in decomposition of organic compounds in it.
5. Microbes are used in production of vaccines.
6. Microbes are also used in processes like tanning of skin, production of ropes and strings, from agave.
7. Some microbes use oil for their growth. Such microbes are used to clear a layer of oil floating on the surface of an ocean or lake formed due to leak or spill.
8. Farm waste, human urine and faeces, wet garbage etc. is collected and used in a biogas plant to produce biogas and fertilizer.
Harmful effects:
1. Disease producing micro-organisms are called pathogens, they are harmful micro-organisms.
2. Fungus grows on moist food, and microbes release enterotoxins into the food. Such toxins spoil the foods. Eating such spoiled food causes food poisoning i.e. loose motions and vomiting.
3. Pathogens may be present in water bodies contaminated with sewage, and dirt from surroundings, in food with flies sitting on it. If such contaminated food or water is consumed, we may fall ill with diseases like amoebiasis, typhoid, cholera, hepatitis, gastro, etc.
4. Pathogens are released in the air by a person having infection of the respiratory, sneezes or coughs. A healthy person may get infected by pathogens on breathing in the same air and contract diseases like common cold, cough, diphtheria, pneumonia, tuberculosis, etc.
5. Microbes that cause diseases like malaria, dengue, elephantiasis, yellow fever, chikunguniya, zike fever etc. gain entry into the human body through the bite of a female mosquito.
In simple words: Micro-organisms are both beneficial, aiding in soil fertility, food production (fermentation), waste decomposition, and vaccine creation, and harmful, causing diseases in humans, animals, and plants, and spoiling food.

🎯 Exam Tip: Provide at least three points for both 'uses' and 'harmful effects' to demonstrate a comprehensive understanding of microorganisms' impact.

6. Give Reasons.

Question a. Diseases spread on a large scale during periods of heavy rainfall and floods.
Answer:
1. Due to floods there is shortage of clean, safe drinking water.
2. It gets contaminated with sewage and dirt having disease causing pathogens, causing disease of alimentary canal, typhoid, cholera, dysentery.
3. Due to stagnant water, many mosquitoes breed on it and cause diseases like malaria, dengue, etc.
In simple words: Diseases spread during heavy rainfall and floods because clean water becomes scarce and contaminated, and stagnant water becomes a breeding ground for disease-carrying mosquitoes.

🎯 Exam Tip: Focus on the immediate consequences of heavy rainfall and floods – water contamination and mosquito breeding – as direct causes of disease spread.

Question b. There is a possibility of food poisoning if we eat stale food.
Answer:
1. Fungus grows quickly on moist and stale food. Micro-organisms grown on the food release toxic materials like enterotoxin into the food.
2. Such toxins spoil the food.
3. Eating such spoiled food may cause loose motions and vomiting. So, we should eat food which is freshly prepared.
In simple words: Eating stale food can lead to food poisoning because fungi and other microorganisms grow on it, producing harmful toxins that cause illness.

🎯 Exam Tip: Clearly explain the link between microbial growth, toxin production (e.g., enterotoxins), and the resulting symptoms of food poisoning.

Question c. Soil is turned over during tilling.
Answer:
1. Tilling is done to loosen the soil in initial agricultural practice.
2. Loose soil allows the penetration of roots of the plant.
3. By turning of soil, it allows uniform mixing of manure and fertilizer.
4. It increases the fertility of soil. Seeds also germinate easily in aerated soil. Hence, soil is turned during tilling.
In simple words: Soil is tilled to loosen it, which helps roots grow better, mixes nutrients evenly, and improves aeration for seed germination and overall soil fertility.

🎯 Exam Tip: Provide at least three reasons related to soil structure, nutrient distribution, and root/seed health to explain the importance of tilling.

Question d. Fungus grows quickly in moist or humid condition.
Answer:
1. Fungus needs water and moisture for its growth.
2. Humidity brings about spore germination and the fungus is able to grow and reproduce quickly in moist and humid condition.
In simple words: Fungus thrives in moist or humid conditions because moisture is essential for its growth and triggers the germination of its spores, allowing rapid reproduction.

🎯 Exam Tip: Emphasize that moisture is a critical requirement for fungal growth and spore germination, leading to rapid proliferation in humid environments.

Question e. A refrigerator is used in almost every home.
Answer:
1. Refrigerator is used to keep food item in healthy condition and to keep them fresh.
2. If the food items are kept outside, they spoil very fast due to growth of micro-organisms and they make food spoiled and harmful.
3. The optimum temperature for the growth of micro-organism is 15°C to 35°C.
4. In refrigerator the temperature is kept very low. So, the food is preserved in refrigerator.
In simple words: Refrigerators are widely used to preserve food by keeping temperatures low, which slows down or stops the growth of spoilage-causing microorganisms that thrive at warmer room temperatures.

🎯 Exam Tip: Explain how low temperatures inhibit microbial growth, contrasting it with the optimal growth range for microorganisms, thereby preserving food.

Question f. Bread rises during baking.
Answer:
1. The process of fermentation is used in baking, for example, in making bread. Yeast is added to make the dough rise.
2. The fermentation is a chemical process of conversion of one type of carbon compound into another type of carbon compound by the action of micro-organisms.
3. Heat is generated in this process. Carbon dioxide (CO2) and some other gases are released.
4. These gases cause an increase in volume so the bread dough rises.
In simple words: Bread rises during baking because yeast, a microorganism, ferments sugars in the dough, producing carbon dioxide gas which gets trapped and expands, making the dough light and airy.

🎯 Exam Tip: Key points include yeast, fermentation, and the production of carbon dioxide (CO2) gas, which causes the dough to rise.

Question g. Fodder is soaked in water before offering to cattle.
Answer:
1. In dry fodder only some part of it is useful for cattle and rest is wasted.
2. When fodder is soaked in water, it sprouts.
3. So, to make the fodder more nutritious and more easy to digest it is soaked in water before offering to cattle.
In simple words: Fodder is soaked in water to allow it to sprout, which increases its nutritional value and makes it easier for cattle to digest, reducing waste.

🎯 Exam Tip: Connect soaking to sprouting, which enhances nutrition and digestibility, making the fodder more efficient for cattle consumption.

7. When Will You Use A Simple Microscope And When A Compound Microscope?

Question a. When will you use a simple microscope and when a compound microscope?
Answer:
1. I will use a simple microscope to magnify the objects and to see the growth of a fungi or mucor on a piece of moist bread.
2. I will use a compound microscope in Research Laboratory and high school science lab to observe micro-organisms which we are not able to see with our naked eye.
In simple words: A simple microscope is used for magnifying larger, easily visible objects like mold on bread, while a compound microscope is needed in labs to see much smaller microorganisms invisible to the naked eye.

🎯 Exam Tip: Distinguish between the two types based on their magnification power and the size of the objects they are used to observe (simple for slightly magnified, compound for very tiny microbes).

Fill In The Blanks And Rewrite The Sentences:

Question 1. ............. is the fundamental, structural and functional unit of living organism.
Answer: Cell
In simple words: The cell is the basic building block and functional unit of all living things.

🎯 Exam Tip: This is a fundamental definition; remember "cell" as the answer to this core concept.

Question 2. The four main parts of the plant cell are ............., ............., ............. and ............. .
Answer: cell wall, cell membrane, cytoplasm, cell organelle
In simple words: The four major parts of a plant cell are the cell wall, cell membrane, cytoplasm, and various cell organelles.

🎯 Exam Tip: List the four main structural components that define a plant cell, ensuring accuracy in terms.

Question 3. Plant cell contains ............. which carry out the process of photosynthesis.
Answer: chloroplast
In simple words: Chloroplasts are the parts in plant cells responsible for photosynthesis, which is how plants make food.

🎯 Exam Tip: Connect chloroplasts directly to their function of photosynthesis in plant cells.

Question 4. ............. are called the power houses of the cell.
Answer: Mitochondria
In simple words: Mitochondria are known as the powerhouses of the cell because they generate energy.

🎯 Exam Tip: Remember "Mitochondria" as the organelle responsible for energy production in cells.

Question 5. The outermost covering of plant cell is ............. .
Answer: cell wall
In simple words: The cell wall forms the outermost protective layer of a plant cell.

🎯 Exam Tip: Clearly identify the cell wall as the defining outer boundary of a plant cell.

Question 6. The outermost covering of animal cell is ............. .
Answer: plasma membrane
In simple words: The plasma membrane is the outer boundary that encloses an animal cell.

🎯 Exam Tip: Note that for animal cells, the plasma membrane is the outermost layer, unlike plant cells which have a cell wall.

Question 7. The ............ is the most important organelle of the cell.
Answer: nucleus
In simple words: The nucleus is the cell's control center, managing all its activities and housing genetic material.

🎯 Exam Tip: The nucleus is crucial as it controls cell functions and contains genetic information, making it highly important.

Question 8. ............. is a national movement started several years ago to increase awareness about public hygiene and personal hygiene.
Answer: Swach Bharat Abhiyan
In simple words: Swachh Bharat Abhiyan is a national campaign launched to promote cleanliness and sanitation across India.

🎯 Exam Tip: Recognize this as a general knowledge question related to public health initiatives in India.

Question 9. The body temperature of a healthy human being is about ............ .
Answer: 37°C
In simple words: The normal body temperature for a healthy human is approximately 37 degrees Celsius.

🎯 Exam Tip: Remember the standard healthy human body temperature in Celsius.

Question 10. Micro-organisms use food stuffs for their own nutrition and release toxic materials called ............. .
Answer: enterotoxins
In simple words: Microorganisms consume food for energy and can release harmful enterotoxins, which are toxins specifically affecting the intestines.

🎯 Exam Tip: Understand that toxins produced by microorganisms, especially those affecting the gut, are called enterotoxins.

Name The Following:

Question 1. An instrument used to observe cells.
Answer: Microscope
In simple words: A microscope is a tool used to magnify and observe tiny cells and organisms that are invisible to the naked eye.

🎯 Exam Tip: Know the primary tool for cell observation.

Question 2. I control the function of a cell.
Answer: Nucleus
In simple words: The nucleus acts as the control center of the cell, directing all its activities.

🎯 Exam Tip: The nucleus is the 'brain' of the cell, responsible for its overall control.

Question 3. I am like a policeman. I do not allow anything and everything to get in and out of the cell.
Answer: Cell membrane
In simple words: The cell membrane regulates what enters and exits the cell, acting as a selective barrier.

🎯 Exam Tip: The function of selective permeability is key to understanding the cell membrane.

Question 4. Outermost layer of the plant cell.
Answer: Cell wall
In simple words: The cell wall is the rigid outer layer that provides structural support and protection to plant cells.

🎯 Exam Tip: Remember the cell wall as the unique and outermost protective layer of plant cells.

Question 5. Outermost layer of the animal cell.
Answer: Cell membrane
In simple words: The cell membrane is the protective outer boundary of an animal cell.

🎯 Exam Tip: For animal cells, the cell membrane forms the outer boundary, distinguishing it from plant cells with their cell walls.

Question 6. I am the jelly like substance containing all the organelles.
Answer: Cytoplasm
In simple words: Cytoplasm is the jelly-like substance filling the cell, where organelles are suspended and many cell processes occur.

🎯 Exam Tip: Recognize cytoplasm as the internal fluid environment of the cell where various organelles are located.

Question 7. I contain thread like structures called chromosome.
Answer: Nucleus
In simple words: The nucleus contains thread-like structures called chromosomes, which carry genetic information.

🎯 Exam Tip: Understand the nucleus as the location of chromosomes, which are crucial for heredity.

Question 8. Which part of the cell contain organelles.
Answer: Cytoplasm
In simple words: Cell organelles are found floating within the cytoplasm, the jelly-like substance inside the cell.

🎯 Exam Tip: The cytoplasm is the medium where most cellular activities, including the functioning of organelles, take place.

Question 9. The unit of measurement used for expressing dimension, size of the cell.
Answer: Nanometer, micrometer
In simple words: Cells are measured using very small units like nanometers and micrometers due to their microscopic size.

🎯 Exam Tip: Remember that cells are measured in microscopic units such as micrometers (µm) or nanometers (nm).

Question 10. The power house of the cell.
Answer: Mitochondria
In simple words: Mitochondria are the cell structures that produce energy, earning them the nickname "power house."

🎯 Exam Tip: This is a common question; clearly state mitochondria as the energy-producing organelle.

Question 11. Largest organelle in the plant cell.
Answer: Vacuole
In simple words: The vacuole is often the largest organelle in a plant cell, storing water, nutrients, and waste, and maintaining turgor pressure.

🎯 Exam Tip: In plant cells, the large central vacuole is typically the most prominent organelle.

Question 12. It is necessary for photosynthesis.
Answer: Chlorophyll
In simple words: Chlorophyll is the green pigment in plants essential for capturing sunlight during photosynthesis.

🎯 Exam Tip: Connect chlorophyll directly to its role in absorbing light energy for photosynthesis.

Question 13. The living substance in the cell.
Answer: Cytoplasm
In simple words: The cytoplasm is the living, jelly-like material within the cell where organelles are suspended.

🎯 Exam Tip: Cytoplasm refers to the entire contents within the cell membrane, excluding the nucleus, and is considered the 'living substance'.

Question 14. A group of cells.
Answer: Tissue
In simple words: A tissue is a collection of similar cells that work together to perform a specific function.

🎯 Exam Tip: Understand the hierarchy of biological organization: cells form tissues, tissues form organs, and so on.

Question 15. Empty structures in cytoplasm.
Answer: Vacuole
In simple words: Vacuoles are sac-like structures within the cytoplasm that store various substances and waste.

🎯 Exam Tip: Vacuoles appear as empty spaces but are filled with cell sap and play important storage and maintenance roles.

State Whether The Following Statements Are True Or False. Correct And Rewrite The False Statement:

Question 1. Cells can be easily seen with naked eyes.
Answer: False. We can't see cells with naked eyes, can be seen under microscope
In simple words: Cells are microscopic and cannot be seen with the unaided eye; they require a microscope for observation.

🎯 Exam Tip: This statement tests basic knowledge about the visibility of cells. Emphasize the need for a microscope.

Question 2. A single cell can perform all the functions in a unicellular organism.
Answer: True
In simple words: In single-celled organisms, one cell carries out all necessary life functions, like eating, breathing, and reproducing.

🎯 Exam Tip: For unicellular organisms, the single cell is a complete living entity performing all vital processes.

Question 3. Cell wall is present in both plant cells and animal cells.
Answer: False. Cell wall is present only in plant cell
In simple words: The cell wall is a distinguishing feature of plant cells, providing structure and protection, and is not found in animal cells.

🎯 Exam Tip: Clearly differentiate between plant and animal cells based on the presence or absence of a cell wall.

Question 4. Vacuoles are not found in plant cell.
Answer: False. Large vacuole is found in plant cell
In simple words: Plant cells typically have a large central vacuole that stores water, nutrients, and waste, and helps maintain cell rigidity.

🎯 Exam Tip: Remember that plant cells usually have a prominent, large central vacuole, which is a key structural feature.

Question 5. Tissue is a group of dissimilar cells.
Answer: False. Tissue is a group of similar cells.
In simple words: A tissue is formed by a collection of similar cells that work together to perform a specific function in an organism.

🎯 Exam Tip: The definition of tissue emphasizes "similar cells" working cooperatively, not dissimilar ones.

Question 6. Unicellular organisms have one celled body.
Answer: True.
In simple words: Unicellular organisms are composed of only a single cell that performs all life processes.

🎯 Exam Tip: The term "unicellular" itself means "single-celled," directly answering the statement.

Question 7. The basic living unit of an organism is an organ.
Answer: False. The basic living unit of an organism is the cell.
In simple words: The cell is considered the fundamental unit of life, not an organ, as organs are made up of many cells and tissues.

🎯 Exam Tip: Reiterate that the cell is the most fundamental unit of life, from which all larger structures are built.

Question 8.
The unit of measurement used for expressing dimension size of the cell is centimetre.
Answer:
False. It is nanometer.
In simple words: The unit of measurement for cell size is not centimetre; it's much smaller, typically nanometers or micrometers.

🎯 Exam Tip: Remember the appropriate units for measuring microscopic structures like cells, which are nanometer and micrometer, not larger units like centimeter.

Question 9.
Micro-organism cannot grow in extreme adverse conditions.
Answer:
False. Some micro-organisms can survive in extreme adverse conditions e.g. ocean floor, ice polar region, hot water spring.
In simple words: Some microorganisms are extremophiles, meaning they can thrive in harsh environments like deep oceans, icy regions, or hot springs, contrary to the idea that they cannot grow in adverse conditions.

🎯 Exam Tip: Understanding extremophiles is key to grasping the diversity and adaptability of microorganisms in various environmental conditions.

Question 10.
Some micro-organisms can grow without oxygen.
Answer:
True
In simple words: Yes, some microorganisms are anaerobic, meaning they can grow and survive in environments completely devoid of oxygen.

🎯 Exam Tip: Differentiate between aerobic and anaerobic microorganisms based on their oxygen requirements for growth.

Question 11.
Amoeba has irregular shape.
Answer:
True
In simple words: Amoebas are known for their ability to change shape constantly, hence having an irregular form.

🎯 Exam Tip: Recognize Amoeba's irregular shape as a characteristic feature, often associated with its pseudopodal movement.

Question 12.
The process of fermentation is used for making yogurt from milk.
Answer:
True
In simple words: Fermentation, carried out by bacteria, is indeed the process that transforms milk into yogurt.

🎯 Exam Tip: Connect fermentation to food production, specifically how microorganisms contribute to making dairy products like yogurt.

Question 13.
Micro-organisms need an optimum temperature of 55°C to 70°C to grow.
Answer:
False. They need temperatures between 15°C to 35°C to grow well.
In simple words: Most common microorganisms thrive in a moderate temperature range, typically between 15°C and 35°C, not the higher range mentioned.

🎯 Exam Tip: Be aware of the optimal temperature ranges for microbial growth, as it's crucial for understanding food spoilage and preservation.

Question 14.
Cells with membrane bound organelles inside them are called prokaryotic cells.
Answer:
False. Cells with membrane bound organelles inside them are called eukaryotic cells.
In simple words: Cells that have membrane-bound organelles, like a nucleus and mitochondria, are classified as eukaryotic cells, not prokaryotic cells.

🎯 Exam Tip: Clearly distinguish between prokaryotic and eukaryotic cells based on the presence or absence of membrane-bound organelles.

Question 15.
Golgi bodies are the power houses of the cells.
Answer:
False. Mitochondria are the power houses of the cell.
In simple words: Mitochondria are responsible for generating energy (ATP) for the cell, earning them the title of "powerhouses," while Golgi bodies are involved in packaging and transport.

🎯 Exam Tip: Memorize the specific functions of key cell organelles, such as mitochondria as the powerhouse and Golgi bodies for modification and transport.

Choose The Correct Word.

Question 1.
Which one of the following terms is not a part of the nucleus?
(a) ribosome
(b) DNA
(c) chromosome
(d) gene
Answer: (a) ribosome
In simple words: Ribosomes are found in the cytoplasm and on the endoplasmic reticulum, not typically inside the nucleus, though they are synthesized in the nucleolus (part of the nucleus). DNA, chromosomes, and genes are all components within the nucleus.

🎯 Exam Tip: Know the distinct locations of major organelles and genetic material within a cell to correctly identify what belongs to the nucleus.

Question 2.
A suitable term for the various components of cell is.
(a) tissue
(b) cell organelle
(c) chromosome
(d) gene
Answer: (b) cell organelle
In simple words: The specialized structures within a cell that perform specific functions are collectively called cell organelles.

🎯 Exam Tip: Understand the hierarchy of biological organization, where cell organelles are components of a cell, which then form tissues, organs, etc.

Question 3.
The jelly like fluid substance present in the cells is called.
(a) protoplasm
(b) chromosome
(c) chloroplast
(d) cytoplasm
Answer: (d) cytoplasm
In simple words: The jelly-like material filling the cell and surrounding the organelles is known as cytoplasm.

🎯 Exam Tip: Distinguish between cytoplasm (the jelly-like substance where organelles are suspended) and protoplasm (which includes both cytoplasm and nucleus).

Question 4.
The units of measurement used for expressing dimension size of the cell are,
(a) centimetre
(b) micrometre
(c) nanometre
(d) metre
Answer: (c) nanometre, (b) micrometre.
In simple words: Cells are incredibly small, so their size is measured in microscopic units like micrometers and nanometers.

🎯 Exam Tip: Be precise with units of measurement; for cells, micrometers (μm) and nanometers (nm) are standard, indicating very small scales.

Question 5.
The largest cell in the human body
(a) nerve
(b) muscle
(c) liver
(d) kidney
Answer: (a) nerve
In simple words: Nerve cells, particularly some neurons, can be very long, making them among the largest cells in the human body.

🎯 Exam Tip: Remember that cell size can vary greatly depending on their function; nerve cells are notable for their length.

Question 6.
The barrier between protoplasm and other environment in animal cell
(a) plasma membrane
(b) cell wall
(c) nucleus membrane
Answer: (a) plasma membrane
In simple words: In animal cells, the plasma membrane acts as the outer boundary, controlling what enters and exits the cell, thus separating the protoplasm from the external environment.

🎯 Exam Tip: Understand that the plasma membrane is the outer boundary for animal cells, while plant cells have an additional cell wall outside it.

Question 7.
The term cell wall is given by
(a) Leeuwenhoek
(b) Robert Hooke
(c) Fleming
Answer: (b) Robert Hooke
In simple words: Robert Hooke was the scientist who first observed and coined the term "cell" after looking at cork tissue, and in doing so, described the cell wall.

🎯 Exam Tip: Associate key scientific discoveries with their discoverers, such as Robert Hooke's contribution to cell biology.

Question 8.
The cell theory was proposed by.
(a) Watsonar Cricks
(b) Schleiden
(c) Schwann
(d) Mengal Morgan
Answer: (b) Schleiden, (c) Schwann.
In simple words: The foundational cell theory, stating that all living things are made of cells and cells are the basic unit of life, was developed by Matthias Schleiden and Theodor Schwann.

🎯 Exam Tip: Know the main proponents of the cell theory and its core principles, as it's a fundamental concept in biology.

Question 9.
Which of the following features will help you in distinguishing a plant cell from an animal cell.
(a) cell wall
(b) cell membrane
(c) mitochondria
(d) nucleus
Answer: (a) cell wall
In simple words: The presence of a rigid cell wall is a defining characteristic that distinguishes a plant cell from an animal cell, which lacks this structure.

🎯 Exam Tip: Focus on the unique structures of plant cells (cell wall, chloroplasts, large central vacuole) and animal cells (centrioles, small vacuoles) for differentiation.

Question 10.
The gas released during the preparation of bread,
(a) O₂
(b) CO₂
(c) nitrogen
(d) sulphur oxide
Answer: (b) CO2
In simple words: During bread making, yeast ferments sugars and produces carbon dioxide gas, which causes the dough to rise.

🎯 Exam Tip: Understand the role of yeast in fermentation and the gas it produces, which is essential for leavening bread.

Question 11.
The structural-functional unit of life is called.
(a) cell
(b) tissue
(c) organ
(d) organism
Answer: (a) cell
In simple words: The cell is considered the fundamental building block and smallest unit that can perform all life processes.

🎯 Exam Tip: Recognize the cell as the basic unit of life, a cornerstone concept in biology.

Question 12.
Which organelle is called power house of the cell?
(a) centrosome
(b) lysosome
(c) plastid
(d) mitochondria
Answer: (d) mitochondria
In simple words: Mitochondria are responsible for generating most of the cell's supply of adenosine triphosphate (ATP), which is used as a source of chemical energy, hence called the power house.

🎯 Exam Tip: Always remember that mitochondria are the primary sites of ATP production in eukaryotic cells.

Question 13.
Living substance of cell is called.
(a) cytoplasm
(b) protoplasm
(c) nucleus
(d) chromosome
Answer: (a) cytoplasm
In simple words: The cytoplasm refers to the jelly-like substance that fills the cell, encompassing all organelles and the cytosol, vital for cell life.

🎯 Exam Tip: Differentiate between cytoplasm (all contents within the cell membrane, excluding the nucleus) and protoplasm (cytoplasm + nucleus).

Give Scientific Reasons:

Question 1.
Mitochondria are called the power houses of the cell.
Answer:
1. Mitochondria are tiny organelles inside the cells that are involved in releasing energy from food.
2. This process is known as cellular respiration.
3. It is for this reason that mitochondria are often referred to as the power houses of the cell.
In simple words: Mitochondria are called the powerhouses because they perform cellular respiration, a process that extracts energy from food molecules and converts it into ATP, the cell's main energy currency.

🎯 Exam Tip: Focus on the energy production role of mitochondria through cellular respiration when explaining why they are called "powerhouses."

Question 2.
A compound microscope is used for observing cells.
Answer:
1. Cell are extremely minute in size.
2. We cannot see cells with naked eye.
3. An object when kept on a glass slide is magnified many times by the lenses of this microscope.
4. Hence, compound microscope is used for observing cells.
In simple words: Cells are too small to be seen with the naked eye, so a compound microscope is essential because its multiple lenses provide high magnification, making these minute structures visible and allowing for detailed observation.

🎯 Exam Tip: Emphasize the high magnification capability of a compound microscope, which is necessary to visualize the minute structures of cells.

Question 3.
Cells are the basic structural units of living organism.
Answer:
1. Cells are the smallest unit from which a living organism is made.
2. A cell contains all the necessary structures which are required to carry out various biological processes.
3. A group of cells makes a tissue, which further makes an organ and many organs together make an organ system and finally organism. Thus, the cells are the basic structural units of living organism.
In simple words: Cells are the fundamental structural units of all living organisms because they are the smallest entities capable of independent life and perform all essential biological functions, forming the building blocks for tissues, organs, and entire organisms.

🎯 Exam Tip: Highlight the cell's role as the fundamental unit of structure and function, capable of independent existence and forming higher levels of organization.

Answer The Following In Short:

Question 1.
What is a vaccine?
Answer:
Vaccine is a live micro-organism which is weak but in a very small amount, and is injected into a person so that antibodies are produced against that micro-organism.
In simple words: A vaccine is a biological preparation containing weakened or inactive forms of disease-causing microorganisms or their components, which, when administered, stimulates the body's immune system to produce antibodies and develop immunity without causing the actual disease.

🎯 Exam Tip: Focus on the mechanism of vaccines-introducing a weakened pathogen to stimulate antibody production and build immunity.

Question 2.
What are the similarities between the Plant cell and Animal cell?
Answer:
They both have cell membrane, cytoplasm, nucleus, ribosomes, golgi bodies, mito-chondria, vacuoles and chromosomes.
In simple words: Both plant and animal cells are eukaryotic and share many common structures like a cell membrane, cytoplasm, nucleus, ribosomes, Golgi bodies, mitochondria, and chromosomes, all essential for basic cellular functions.

🎯 Exam Tip: List the common organelles found in both plant and animal cells, such as nucleus, cytoplasm, cell membrane, mitochondria, Golgi bodies, and ribosomes.

Question 3.
What do micro-organisms need for growth?
Answer:
Micro-organisms need soil, water and decaying material. Temperature suitable for microbial growth is 15 to 35°C moist, humid and warm climate.
In simple words: Microorganisms primarily need a source of nutrients (like decaying material or specific chemical compounds), sufficient water, and suitable environmental conditions, particularly a moderate temperature (15-35°C) and appropriate humidity, to grow and multiply.

🎯 Exam Tip: Remember the critical factors for microbial growth: nutrients, water, and optimal temperature and humidity, which are often why food spoils.

What Is The Difference Between Us:

Question 1.
Simple microscope and Compound microscope.
Answer:

In simple words: A simple microscope uses a single lens for limited magnification of larger objects, relying on natural light, while a compound microscope uses multiple lenses to achieve much higher magnification for viewing extremely small objects like cells, using an artificial light source.

🎯 Exam Tip: Differentiate microscopes based on the number of lenses, magnification power, and type of light source, understanding that compound microscopes are for microscopic cellular details.

Answer In Details:

Question 1.
Explain the functions of organelles in a cell.
Answer:
1. Functions of cell wall: It consist of cellulose. It is present in plant cell only. It is a protective layer outside the cell membrane. It provides structural support and protection.
2. Function of cell membrane: It controls the movement of substances in and out of the cell. It protect the cell from its surrounding.
3. Function of cytoplasm: It is the jelly like liquid, it occupies space between cell membrane and nucleus. All the organelles are scattered in it.
4. Function of Nucleus: It is the brain of the cell. It directs all cell activities, and contains genetic material called chromosomes made of DNA.
5. Function of mitochondria: It is the power house of cell. It produces energy in the form of ATP from the food.
6. Vacuoles: It is the largest organelle in the plant cell surrounded by membrane. It holds material and waste. It maintains proper pressure. It helps to throw out waste products of cell.
In simple words: Each organelle within a cell has a specialized role: the cell wall provides structure and protection (in plants), the cell membrane controls entry/exit, the cytoplasm is where organelles reside and reactions occur, the nucleus manages cell activities and stores genetic material, mitochondria generate energy, and vacuoles store substances and manage waste.

🎯 Exam Tip: For detailed answers, list each organelle's name and its primary function clearly, emphasizing how their collective actions maintain cell life.

Explain:

Question 1.
Ram ate chaat from a street hawker, when he reached home he fell ill and complained of stomach ache. What could be the reason?
Answer:
1. he chaat Ram ate from a street hawker must be contaminated with harmful micro-organism due to dirty water used in it or stale potato used in it.
2. Toxins are produced by micro-organisms in food.
3. Ram ate that and suffered from food poisoning.
In simple words: Ram likely suffered from food poisoning because the chaat was probably contaminated with harmful microorganisms due to unsanitary preparation, such as using dirty water or stale ingredients, which produced toxins causing his stomach ache.

🎯 Exam Tip: When addressing foodborne illness scenarios, consider factors like hygiene, freshness of ingredients, and microbial contamination leading to toxin production.

Question 2.
With the help of diagram describe Prokaryotic cell.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक प्रोकैरियोटिक कोशिका की संरचना को दर्शाता है। इसमें कोशिका भित्ति, प्लाज्मा झिल्ली, न्यूक्लियोइड (जहां आनुवंशिक सामग्री होती है), कोशिका द्रव्य, राइबोसोम, प्लास्मिड, कैप्सूल और फ्लैगेलम जैसे विभिन्न घटक स्पष्ट रूप से लेबल किए गए हैं। यह छात्रों को एक विशिष्ट जीवाणु कोशिका के आंतरिक और बाहरी भागों को समझने में मदद करता है।
1. Prokaryotic cell do not have well-defined nucleus.
2. The plasma membrane, cytoplasm and nucleoid are the only components.
3. The prokaryotic cells have smaller ribosomes compared to eukaryotic cells.
4. Bacteria and blue green algae are examples of prokaryotic cell.
In simple words: A prokaryotic cell is a simple cell type lacking a membrane-bound nucleus and other membrane-bound organelles; its genetic material (nucleoid) floats in the cytoplasm, and it typically has a cell wall and plasma membrane, with bacteria being a common example.

🎯 Exam Tip: When describing prokaryotic cells, highlight the absence of a true nucleus and membrane-bound organelles, along with their simpler structure compared to eukaryotic cells.

Question a.
Draw neat and labelled diagram of plant cell.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एक पादप कोशिका की विस्तृत और नामांकित संरचना को दिखाता है। इसमें कोशिका भित्ति, कोशिका झिल्ली, राइबोसोम, गॉल्जी बॉडी, क्लोरोप्लास्ट, केंद्रक, एंडोप्लाज्मिक रेटिकुलम, रिक्तिकाएँ, साइटोप्लाज्म और माइटोकॉन्ड्रिया जैसे प्रमुख अंग स्पष्ट रूप से दर्शाए गए हैं। यह छात्रों को पादप कोशिका के विभिन्न भागों और उनके स्थान को समझने में मदद करता है।
In simple words: (No simple words needed for drawing instruction, but the diagram explanation above covers it.)

🎯 Exam Tip: For drawing diagrams, ensure all key organelles are clearly visible and accurately labeled to score maximum marks.

Question b.
Draw neat and labelled diagram of animal cell.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक जंतु कोशिका की संरचना को दर्शाता है। इसमें लाइसोसोम, राइबोसोम, गॉल्जी बॉडी, केंद्रक, एंडोप्लाज्मिक रेटिकुलम, रिक्तिकाएँ और माइटोकॉन्ड्रिया जैसे विभिन्न कोशिकांग स्पष्ट रूप से लेबल किए गए हैं। यह छात्रों को जंतु कोशिका के मुख्य घटकों और उनकी व्यवस्था को समझने में मदद करता है।
In simple words: (No simple words needed for drawing instruction, but the diagram explanation above covers it.)

🎯 Exam Tip: Pay attention to the absence of a cell wall and chloroplasts in animal cell diagrams, and accurately label structures like the nucleus, cytoplasm, and mitochondria.

Name The Types Of Cells Shown In The Diagrams.

Question 1.
(a)
(b)
(c)
(d)
(e)
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न प्रकार की कोशिकाओं को प्रदर्शित करता है, जिसमें अमीबा, लाल रक्त कोशिकाएँ, सतही कोशिकाएँ, वसा कोशिका, मांसपेशी कोशिकाएँ, स्पाइरोगाइरा, एक अंडा कोशिका, एक अस्थि कोशिका, एक शुक्राणु और एक तंत्रिका कोशिका (न्यूरॉन) शामिल हैं। यह छात्रों को जीवित जीवों में पाई जाने वाली कोशिकाओं की विविधता और उनके विशिष्ट आकारों को समझने में मदद करता है।
Answer:
(a) A fat cell
(b) A nerve cell
(c) A sperm cell
(d) Spirogyra
(e) Red Blood cells
In simple words: The diagrams illustrate various specialized cells like fat cells, nerve cells, sperm cells, Spirogyra, and red blood cells, each with a distinct shape and function, highlighting the diversity of cellular forms in living organisms.

🎯 Exam Tip: Learn to identify different cell types based on their characteristic shapes, which often reflect their specific functions in an organism.

Answer The Following Questions:

Question 1.
Keep a moistened piece of bread or bhakari in a closed box. What will you observe after 3-4 days?
Answer:
1. I will observe growth of fungus or mucor. White cotton like layer or black spots.
2. As we know fungus grows in presence of moisture.
In simple words: After a few days, fungus or mucor will grow on the moistened bread or bhakari, appearing as white cotton-like layers or black spots, because fungi thrive in moist environments.

🎯 Exam Tip: This experiment demonstrates the conditions necessary for fungal growth: moisture and a food source, leading to spoilage.

Question 2.
Observe a drop of muddy water or water from a stagnant puddle, under the compound microscope.
Answer:
1. We will observe, living things, micro-organism, bacteria, fungi.
2. It will be swarming withbacteria,paramoecium, amoeba, ciliated bacteria and protozoa, etc.
In simple words: Under a microscope, muddy or stagnant water will reveal a vibrant world of living microorganisms, including various bacteria, fungi, amoeba, and paramecium, actively moving and interacting.

🎯 Exam Tip: Microscopic observation of pond water is a classic experiment to demonstrate the ubiquity and diversity of microorganisms in the environment.

Question 3.
Take a drop of yoghurt or buttermilk on a glass slide and observe it under a compound microscope.
Answer:
1. I will see Lactobacillus rod shapted bacteria and streptococcus spherical shape bacteria which may be in clusters.
2. Lactobacillus use lactose present in the milk and produce lactic acid which gives tangy taste to yoghurt.
In simple words: Observing yogurt or buttermilk under a microscope will show rod-shaped Lactobacillus and spherical Streptococcus bacteria, which ferment lactose into lactic acid, giving yogurt its characteristic tangy flavor.

🎯 Exam Tip: This observation highlights the beneficial role of bacteria in food production, specifically in dairy fermentation, and allows students to visualize these microorganisms.

Answer The Following Questions:

Question 1.
Which diseases do micro-organism cause in plants and animals?
Answer:
Diseases caused by micro-organism in plants and animals are:

In simple words: Microorganisms cause a wide range of diseases in plants, such as cankers and rusts, leading to crop damage, and in animals, including anthrax in cattle and tuberculosis in various species, impacting health and productivity.

🎯 Exam Tip: Be prepared to list specific examples of plant and animal diseases caused by microorganisms to demonstrate a comprehensive understanding.

Question 2.
Why are infants vaccinated according to fixed time schedule?
Answer:
Vaccination is done to protect the child against diseases.
1. If a baby is vaccinated by true vaccine schedule, that baby will have immunity to over 14 diseases by the age of two. With the recommended schedule, babies visit their doctor 5 times in the first 15 months and receive protection against upto 14 diseases in as little as 18 shots.
2. We immunize children so young against these diseases because infancy is the time period that kids are most vulnerable to life threatening diseases.
3. It is not advisable to skip or delay vaccines as this will leave the child vulnerable to disease for a longer period of time.
In simple words: Infants are vaccinated on a fixed schedule because they are highly vulnerable to life-threatening diseases during early childhood, and following the schedule ensures timely development of immunity against numerous pathogens, providing crucial protection.

🎯 Exam Tip: Emphasize that vaccination schedules are designed to provide maximum protection during the most vulnerable periods of a child's life, preventing severe infections.

Answer The Following Questions:

Question 1.
Observe cells from various parts of plants like leaves, bark, root tips, etc.

Question a.
Are the cells that you observed, all alike?
Answer:
No, all cells do not look alike, each one has different shape and size.
In simple words: No, cells from different plant parts vary in shape and size, reflecting their specialized functions.

🎯 Exam Tip: Understand that cell diversity is a fundamental biological principle, where structure is adapted for specific functions.

Question b.
What are their shapes?
Answer:
1. The cells of leaves, show a green pigment because of chloroplast.
2. The shape of the cell may be spherical or polygonal.
3. The shape of root tips are oval or polygonal and the cells of back are hexagonal in shape.
In simple words: Leaf cells are often spherical or polygonal due to chloroplasts, root tip cells are typically oval or polygonal, and bark cells are hexagonal, showcasing diverse shapes adapted for their specific roles.

🎯 Exam Tip: Relate the shape of plant cells (e.g., polygonal for bark, varied for leaves and roots) to their function and the presence of specific organelles like chloroplasts.

Question 2.
Observe the roots of the pea, bean and fenugreek plants. What could be the functions of the nodules on their roots.
Answer:
1. Micro-organisms are present in the root nodules.
2. They fix the atmospheric nitrogen and make it available for plants.
In simple words: The nodules on the roots of pea, bean, and fenugreek plants contain beneficial microorganisms that perform nitrogen fixation, converting atmospheric nitrogen into a form usable by the plant, thus enriching soil fertility.

🎯 Exam Tip: Recognize the symbiotic relationship between leguminous plants and nitrogen-fixing bacteria in root nodules as a key process in nutrient cycling.

Question 3.
What happens if clothes remain damp in the rainy season?
Answer:
1. During rainy season the humidity in the air is quite high and also.
2. Due to presence of moisture in clothes it becomes breeding ground for fungus.
3. It is the favourable condition for growth of fungus.
4. We can see white cotton like growth of fungus on clothes.
In simple words: Damp clothes in the rainy season provide an ideal moist and humid environment for fungi to grow, leading to visible white cotton-like layers or mold and a musty smell.

🎯 Exam Tip: Connect high humidity and moisture in the rainy season to the rapid growth of fungi on organic materials like clothes, emphasizing environmental conditions for microbial proliferation.

Question 4.
What are the black or white spots sometimes seen on gunny bags?
Answer:
These spots are the growth of many microbes such as fungi, mucus, mold, etc.
In simple words: The black or white spots on gunny bags are colonies of various microorganisms, primarily fungi and mold, that thrive on the organic fibers of the bags in damp conditions.

🎯 Exam Tip: Explain that visible spots on organic materials are usually microbial growths like fungi or mold, indicating degradation of the material.

Question 5.
Why are leather articles like purses, wallets, belts, footwear always polished before storing away?
Answer:
They are polished so as to protect them from the growth of fungus.
1. Polish creates a layer of wax on them so that moisture cannot enter from atmosphere.
2. It prevents the growth of fungus, which damages the leather.
In simple words: Leather articles are polished before storage to create a protective wax layer that prevents moisture absorption, thereby inhibiting the growth of fungi and mold which can damage the leather.

🎯 Exam Tip: Focus on the role of polish in creating a moisture barrier, which is key to preventing fungal growth and preserving leather goods.

Question 6.
What is the powdery material found on old currency notes or old rubber or paper?
Answer:
1. The powdery material is the spores of fungi.
2. All the materials like gunny bags, cotton clothes, paper, rubber, etc. are plant products and leather is an animal product.
3. In a humid atmosphere, fungi and some other micro-organisms grow on these articles and spoil or damage them.
In simple words: The powdery material found on old currency notes, rubber, or paper consists of fungal spores and growth, indicating microbial decomposition of these organic materials in humid conditions.

🎯 Exam Tip: Explain that powdery growths on old organic items are typically fungal spores or mycelium, a sign of microbial activity in humid environments.

Question 8. Try this and answer the following questions:

Keep both pots in garden
Observe after 3-4 weeks.

Question a. Did the garbage in pot B remain unchanged.
Answer:
1. Yes, the garbage in pot B remained unchanged because micro-organisms need nutrients for their growth.
2. In pot B there was no medium for growth of micro-organisms.
In simple words: Garbage in pot B remained unchanged as it lacked organic matter for microbial growth, essential for decomposition.

🎯 Exam Tip: Understanding the conditions required for decomposition is key, especially the role of organic nutrients for microorganisms.

Question b. Where did the garbage in pot 'A' disappear? Why?
Answer:
1. Microbes present in soil, dung, etc. decompose the garbage to obtain food material.
2. As a result garbage is soon converted into manure of the best quality and our surroundings are kept clean.
In simple words: The garbage in pot A decomposed due to microbes in the soil and dung, which converted the organic waste into nutrient-rich manure, cleaning the surroundings.

🎯 Exam Tip: Focus on the role of microbes in decomposing organic waste and their contribution to natural cycles like manure production.

Question 9. What does your mother do to make yoghurt from milk?
Answer:
1. Few drops of yoghurt or buttermilk are mixed with lukewarm milk and it is kept at room temperature for 8-10 hours.
2. Microbes present in the drops of yoghurt quickly multiply and the milk gets converted into yoghurt. This is a process of fermentation.
In simple words: To make yoghurt, a small amount of existing yoghurt or buttermilk (containing microbes) is added to lukewarm milk and left at room temperature. The microbes ferment the milk, turning it into yoghurt.

🎯 Exam Tip: This question highlights the practical application of fermentation in food production and the role of microorganisms.

Question 10. Who discovered the process of fermentation?
Answer:
1. Louis Pasteur established that fermentation is initiated by living organisms.
2. It involves yeast microbes, breaking down molecules of complex carbohydrates into simple sugar, alcohol and CO2.
In simple words: Louis Pasteur discovered that living organisms, specifically yeast microbes, are responsible for initiating fermentation, which breaks down complex carbohydrates into simpler substances like alcohol and carbon dioxide.

🎯 Exam Tip: Remember Louis Pasteur's contribution to understanding microbial processes, particularly fermentation.

Use Your Brain Power!

Answer The Following Questions:

Question 1. How will you know that a foodstuff is spoilt?
Answer:
1. When the food is kept for a long time it allows the growth of bacteria and fungi.
2. We can see the white layer of bacterial or fungal growth on it, it causes a typical odour, or smell, and also the food tastes sour due to presence of enterotoxins produced by fungi in the food.
In simple words: Spoiled food will show visible signs like white fungal growth, emit a bad odor, and taste sour because of the toxins produced by growing bacteria and fungi.

🎯 Exam Tip: Focus on the sensory indicators (sight, smell, taste) that suggest food spoilage and the microbial activity behind it.

Question 2. What precautions will you take while purchasing food? Why?
Answer:
1. We will see the expiry date. If the food is kept for a long period of time, it may allow the growth of many microbes which can cause disease or food poisoning.
2. We will check for any fungal growth, any white or black spots on it.
In simple words: When buying food, always check the expiry date and inspect for any visible signs of spoilage like fungal growth or spots, as these indicate potential microbial contamination that can cause illness.

🎯 Exam Tip: Prioritize checking expiry dates and visual cues of spoilage to ensure food safety and prevent foodborne illnesses.

Question 3. Why do food poisoning incidents occur during marriage or other community feasts?
Answer:
1. During marriage feast, food is prepared in very large quantity and food may not be properly washed or if it is cooked with water contaminated, with sewage or dirt which has many disease causing microbes, or the people handling the food may be having dirty hands
2. Also the utensils used for cooking and storing food may be dirty, contaminated with dirt and may produce microbes. The consumption of such food is responsible for food poisoning.
In simple words: Food poisoning at large gatherings often occurs because of mass production, potential use of contaminated water, improper handling by unhygienic staff, or unclean utensils, all of which facilitate microbial growth and spread.

🎯 Exam Tip: Emphasize the factors contributing to microbial contamination in mass food preparation, such as hygiene, water quality, and handling practices.

Question 4. How do the cells acquire definite shapes?
Answer:
The cells acquire definite shapes due to the presence of cell wall.
In simple words: Cells maintain their definite shapes primarily due to the presence of a rigid cell wall, which provides structural support.

🎯 Exam Tip: Understand that the cell wall is the primary determinant of a cell's fixed shape, especially in plant cells.

Question 5. How are cells protected?
Answer:
1. Plant cells are protected due to presence of cell wall.
2. Animal cells are protected by the double plasma membrane.
In simple words: Plant cells are protected by a strong cell wall, while animal cells are protected by their double plasma membrane.

🎯 Exam Tip: Differentiate the protective structures in plant (cell wall) and animal (plasma membrane) cells.

Question 6. What are the needs of cells?
Answer:
1. The most important things for a cell are oxygen and glucose.
2. Cell uses these during process of glycolysis and makes ATP which is energy source.
In simple words: Cells primarily need oxygen and glucose to perform glycolysis and produce ATP, which is their main energy source.

🎯 Exam Tip: Focus on oxygen and glucose as essential inputs for cellular respiration and ATP production, the cell's energy currency.

Question 7. Can the point of a needle accommodate micro-organism?
Answer:
Yes, they are smaller than the point of a needle.
In simple words: Yes, microorganisms are much smaller than the tip of a needle, so many can easily fit on its point.

🎯 Exam Tip: This illustrates the extremely small size of microorganisms, emphasizing why they require microscopes for observation.

Question 8. Why should dry and wet waste be collected separately?
Answer:
1. Dry waste consist of plastic, glass, metals, paper, etc. It is easier to segregate dry waste so that it is easier for treatment and recycling of waste.
2. Wet waste consists of organic matter. Wet garbage is converted into manure of the best quality and surroundings are kept clean.
In simple words: Dry waste (e.g., plastic, glass) is separated for recycling and proper treatment, while wet waste (organic matter) is separated for composting into manure, helping to manage waste efficiently and keep the environment clean.

🎯 Exam Tip: Highlight the different disposal and recycling methods for dry and wet waste, and their environmental benefits.

Question 9. Why is yoghurt mixed in the batter or dough for making rava-idli, butter naan?
Answer:
1. The microbes present in yoghurt are allowed to grow in batter or dough.
2. They break down these substances producing new compound and gases are released as they grow and multiply in them which allows the batter, dough to rise.
3. This process is called fermentation.
4. This makes the food soft and nutritious.
In simple words: Yoghurt is added to batter or dough because its microbes ferment the mixture, producing gases that make the dough rise, resulting in soft, nutritious food like rava-idli or butter naan.

🎯 Exam Tip: Focus on the fermentation process, the role of microbes, and the resulting changes in food texture and nutritional value.

Question 10. How do preparation like yoghurt, idli, dosa become easy to digest?
Answer:
Fermentation does detoxification and splits complex carbohydrates and proteins into simple ones. Thus, making it easy to digest.
In simple words: Preparations like yoghurt, idli, and dosa become easy to digest because fermentation breaks down complex carbohydrates and proteins into simpler forms, and also helps in detoxification.

🎯 Exam Tip: Emphasize how fermentation improves digestibility by breaking down complex food components and detoxifying them.

Question 11. What is the co-relation between the normal body temperature of humans which is 37°C and the optimum temperature for the growth of micro-organism, 15 °C to 35 °C?
Answer:
1. Each micro-organism needs a specific environment for growth and reproduction.
2. Optimum temperature for the growth of micro-organism is 15°C to 35°C.
3. Normal body temperature of human body is 37°C. At that temperature micro-organism can not grow and cause disease.
In simple words: Microorganisms thrive optimally between 15°C and 35°C. The human body's normal temperature of 37°C is generally above this optimal range, which helps to inhibit the rapid growth and disease-causing potential of many common microorganisms.

🎯 Exam Tip: Understand the concept of optimum temperature for microbial growth and how human body temperature acts as a protective mechanism.

Question 12. How do micro-organism survive the adverse conditions?
Answer:
1. During adverse conditions micro-organisms form a thick covering around themselves and stop their life processes.
2. On return of favourable conditions they come out of the protective covering and continue their life processes.
In simple words: Microorganisms survive adverse conditions by forming a protective thick covering, halting their life processes until favorable conditions return, at which point they emerge and resume normal activity.

🎯 Exam Tip: Focus on the formation of protective structures (like spores or cysts) that enable microorganisms to endure harsh environments.