Samacheer Kalvi Class 9 Science Solutions Chapter 24 Environmental Science

I. Choose the correct answer:

 

Question 1. All the factors of biosphere which affect the ability of organisms to survive and reproduce are called as ...............
(a) biological factors
(b) abiotic factors
(c) biotic factors
(d) physical factors
Answer: (c) biotic factors
In simple words: Biotic factors are the living parts of an ecosystem that influence other living things, like plants, animals, fungi, and bacteria. These living components can affect how well organisms survive and grow.

🎯 Exam Tip: Remember that biotic factors are living components, while abiotic factors are non-living components like water, sunlight, and temperature.

 

Question 2. The ice sheets from the north and south poles and the icecaps on the mountains, get converted into water vapour through the process of ...............
(a) evaporation
(b) condensalion
(c) sublimation
(d) infiltration
Answer: (c) sublimation
In simple words: Sublimation is when ice or snow turns directly into water vapor without first melting into liquid water. This process is common in very cold, dry, and windy conditions.

🎯 Exam Tip: Distinguish sublimation from evaporation; evaporation is liquid turning to gas, while sublimation is solid turning directly to gas.

 

Question 3. The atmospheric carbon dioxide enters into the plants through the process of ...............
(a) photosynthesis
(b) assimilation
(c) respiration
(d) decomposition
Answer: (a) photosynthesis
In simple words: Plants take in carbon dioxide from the air to make their own food using sunlight. This process is called photosynthesis and is crucial for all life on Earth.

🎯 Exam Tip: Photosynthesis is the primary way carbon dioxide is removed from the atmosphere and converted into organic matter by plants.

 

Question 4. Increased amount of ............... in the atmosphere, results in greenhouse effect and global warming.
(a) carbon monoxide
(b) sulphur dioxide
(c) nitrogen dioxide
(d) carbon dioxide
Answer: (d) carbon dioxide
In simple words: Too much carbon dioxide in the air traps heat and warms up the planet. This is known as the greenhouse effect, which leads to global warming.

🎯 Exam Tip: Carbon dioxide is the most significant greenhouse gas contributing to climate change, largely due to human activities like burning fossil fuels.

II. Match the following:

 

Question 1. Match the following.

Answer:

In simple words: Each microorganism has a specific job in the nitrogen cycle. Nitrosomonas turns ammonia into nitrites, Azotobacter helps fix nitrogen from the air, Pseudomonas changes nitrates back into nitrogen gas, and putrefying bacteria break down dead matter to release ammonia.

🎯 Exam Tip: Understanding the role of each microorganism in the nitrogen cycle is key to explaining how nitrogen moves through ecosystems.

III. Say true or false. Correct the false statements:

 

Question 1. Nitrogen is a greenhouse gas.
Answer: False.
Correct statement: Carbon dioxide is a greenhouse gas.
In simple words: Nitrogen is a common gas in the air, but it does not trap heat like greenhouse gases do. Carbon dioxide is the main gas that causes the greenhouse effect.

🎯 Exam Tip: Be precise about which gases are greenhouse gases; nitrogen (N2) is a major atmospheric component but not a greenhouse gas, while nitrous oxide (N2O) is.

 

Question 2. Poorly developed root is an adaptation of mesophytes.
Answer: False.
Correct statement: Poorly developed root is an adaptation of Hydrophytes.
In simple words: Mesophytes live in moderate water conditions and have well-developed roots. Plants that live in water (hydrophytes) often have small, poorly developed roots because they can absorb water directly from their surroundings.

🎯 Exam Tip: Remember the specific adaptations for each plant type: hydrophytes (water plants), xerophytes (desert plants), and mesophytes (moderate conditions).

 

Question 3. Bats are the only mammals that can fly.
Answer: True
In simple words: Bats are unique because they are the only mammals that can truly fly. Their wings are specially adapted for active flight.

🎯 Exam Tip: While some mammals like flying squirrels can glide, only bats possess the ability for sustained, powered flight.

 

Question 4. Earthworms use the remarkable high frequency system called echoes.
Answer: False.
Correct statement: Earthworms do not use a high-frequency system called echoes; bats use echolocation.
In simple words: Earthworms do not use echoes to find their way. Instead, bats use a high-frequency sound system, called echolocation, to navigate and hunt in the dark.

🎯 Exam Tip: Avoid confusing the senses and adaptations of different animals; echolocation is a specific adaptation for bats and some other species.

 

Question 5. Aestivation is an adaptation to overcome cold condition.
Answer: False.
Correct statement: Aestivation is an adaptation to overcome hot and dry conditions.
In simple words: Aestivation is a state of rest some animals enter during hot or dry weather. It helps them survive when water is scarce, unlike hibernation, which is for cold conditions.

🎯 Exam Tip: Differentiate between aestivation (summer sleep for hot/dry conditions) and hibernation (winter sleep for cold conditions).

IV. Give reason for the following:

 

Question 1. Roots grow very deep and reach the layers where water is available. Which type of plants develop the above adaptation? Why?
Answer: Xerophytes have well-developed, deep roots. They develop this adaptation because they grow in dry places where water is hard to find. Their deep roots help them search for and absorb water from far below the ground.
In simple words: Xerophytes, or desert plants, have long roots to find water deep underground because they live in very dry areas.

🎯 Exam Tip: When explaining adaptations, always link the specific feature (e.g., deep roots) to the environmental challenge (e.g., water scarcity).

 

Question 2. Why streamlined bodies and presence of setae is considered as adaptations of earthworm?
Answer: Earthworms have a streamlined body shape and setae (small bristles) as adaptations for living underground.
• Streamlined bodies help earthworms move easily through narrow burrows in the soil, allowing for smooth penetration.
• Setae act like anchors, helping the earthworm grip the soil and pull itself forward, making movement and burrowing more effective.
In simple words: Earthworms have smooth bodies and tiny bristles to help them push through soil and move around underground easily.

🎯 Exam Tip: Clearly state each adaptation and then explain how it specifically benefits the organism in its environment.

 

Question 3. Why is it impossible for all farmers to construct farm ponds it in their fields?
Answer: It is impossible for all farmers to construct farm ponds in their fields for several reasons.
• Constructing ponds requires a large area, and many farmers have small land holdings, making it impractical to dedicate a significant portion to a pond.
• Additionally, the cost of excavation and maintenance can be high, which might be unaffordable for all farmers. Building a pond can also impact water availability for other farms in lower-lying areas, which could lead to resource conflicts if everyone built one.
In simple words: Not all farmers can build farm ponds because they might not have enough land, or the cost to dig and care for the pond is too high.

🎯 Exam Tip: Consider both physical constraints (like land size) and economic factors (like cost) when explaining limitations in agricultural practices.

V. Answer briefly:

 

Question 1. What are the two factors of biosphere?
Answer: The biosphere is the part of the earth where life exists. All resources within the biosphere can be grouped into two main categories:
1. Biotic factors: These are living factors, including plants, animals, fungi, bacteria, and all other living organisms.
2. Abiotic factors: These are non-living factors, such as temperature, pressure, water, soil, air, and sunlight. These factors influence an organism's ability to survive and reproduce. Both types of factors interact constantly to support life.
In simple words: The two main factors of the biosphere are living things (biotic factors) like plants and animals, and non-living things (abiotic factors) like water and air.

🎯 Exam Tip: When defining biotic and abiotic factors, always provide clear examples for each category to illustrate your understanding.

 

Question 2. How do human activities affect nitrogen cycle?
Answer: Human activities significantly impact the nitrogen cycle, often causing imbalances in ecosystems.
• Human actions like deforestation and pollution alter the biodiversity, which can reduce the number of nitrogen-fixing organisms.
• They change the food web structure by impacting plants and animals that play a role in nitrogen transfer.
• Overall, human activities destroy the general habitat of many organisms, disturbing the natural flow of nitrogen through the environment.
In simple words: Human actions like cutting down trees and polluting can harm the nitrogen cycle by changing living things, disrupting food chains, and destroying natural places.

🎯 Exam Tip: Focus on specific human activities and their direct consequences on each stage or component of the nitrogen cycle when answering this type of question.

 

Question 3. Define adaptation.
Answer: An adaptation is any special feature of an organism or a part of it that allows it to live and thrive in the specific conditions of its habitat. These features help organisms survive challenges in their environment.
In simple words: Adaptation means a living thing has a special body part or behavior that helps it live well in its home.

🎯 Exam Tip: A good definition of adaptation should emphasize both the "feature" and its "benefit" for survival in a particular habitat.

 

Question 4. What are the challenges faced by hydrophytes in their habitat?
Answer: Hydrophytes, or water plants, face several unique challenges in their aquatic habitats:
• They deal with more water availability than they need, which means they don't need extensive root systems to search for water.
• They must withstand the damaging forces of water currents, especially in moving water bodies.
• Regular changes in water level can expose or submerge them, requiring flexible adaptations.
• Maintaining buoyancy in water is crucial for many hydrophytes to keep their leaves and flowers at the water's surface for sunlight and pollination.
In simple words: Water plants face problems like too much water, strong water currents, changing water levels, and needing to float correctly.

🎯 Exam Tip: When discussing challenges for hydrophytes, consider how their submerged or floating lifestyle creates unique environmental pressures.

 

Question 5. Why is it important to conserve water?
Answer: Water conservation is very important for several reasons:
• It leads to a more efficient use of our limited water resources, making sure we don't waste precious supplies.
• It helps to ensure that we always have enough usable water for drinking, farming, and other needs, especially as the population grows.
• It helps decrease water pollution, as less water is drawn from natural sources and less wastewater is discharged.
• It also helps increase energy saving, because less energy is needed to pump, heat, and treat water.
In simple words: Saving water is important so we always have enough clean water, use it smartly, keep it clean, and save energy too.

🎯 Exam Tip: Focus on the interconnected benefits of water conservation, including resource availability, environmental protection, and energy efficiency.

 

Question 6. List some of the ways in which you could save water in your home and school?
Answer: We can save water in our homes and schools through several simple actions:
• Install low-flow taps and showerheads to reduce water usage.
• Use recycled water for watering lawns and gardens instead of fresh water.
• Regularly check and repair any leaks in taps, pipes, or toilets to prevent waste.
• Practice recycling and reusing water whenever possible, such as using leftover water from washing vegetables to water plants. These small steps make a big difference.
In simple words: We can save water by using low-flow taps, recycling water for plants, fixing leaks, and reusing water whenever possible.

🎯 Exam Tip: Provide practical and actionable examples of water-saving methods that are relevant to everyday life at home and school.

 

Question 7. What are the uses of recycled water?
Answer: Recycled water, after proper treatment, has many valuable uses. It can be used for:
• Agriculture, to irrigate crops and livestock.
• Landscaping, for watering public parks, sports fields, and golf courses.
• Industrial processes, such as cooling water for power plants and oil refineries.
• Non-potable purposes in buildings, like toilet flushing.
• Dust control on construction sites and in mining operations.
• Various construction activities.
Recycling water reduces the demand on fresh water sources and helps manage water resources sustainably.
In simple words: Recycled water can be used for watering farms, parks, and golf courses, for cooling in factories, flushing toilets, and controlling dust.

🎯 Exam Tip: When listing uses for recycled water, categorize them (e.g., agricultural, industrial, urban) for a comprehensive answer.

 

Question 8. What is IUCN? What is the vision of IUCN?
Answer: IUCN stands for the International Union for Conservation of Nature and Natural Resources. Its vision is to create a just world that values and conserves nature. IUCN works globally to address environmental challenges and promote sustainable development through scientific research and policy recommendations.
In simple words: IUCN is an international group focused on protecting nature. Its goal is a fair world that cares for and saves natural environments.

🎯 Exam Tip: When defining organizations like IUCN, always state the full name and briefly explain their core mission or vision.

VI. Answer in detail:

 

Question 1. Describe the processes involved in the water cycle.
Answer: The water cycle, also called the hydrological cycle, is the continuous movement of water on Earth. Water constantly moves from one place to another, like from rivers to oceans or from oceans to the sky. This happens through several key processes:
• Evaporation: Water changes from a liquid to a gas (water vapor) from the surface of oceans, seas, lakes, ponds, and rivers, rising into the atmosphere.
• Sublimation: Ice and snow from the poles and mountains directly turn into water vapor without first melting into liquid water.
• Transpiration: Plants release water vapor into the atmosphere through tiny pores in their leaves and stems.
• Condensation: High in the sky, water vapor cools down and turns into very tiny water droplets. These droplets gather to form clouds and fog. This change from gas to liquid is essential for rain to form.
• Precipitation: When clouds get heavy with water droplets, they release water back to Earth. This can be in forms like drizzle, rain, snow, or hail.
• Runoff: As water falls to Earth, some of it flows over the land surface, forming channels, rivers, and eventually flowing into lakes, seas, and oceans.
• Infiltration: Some of the water seeps deep into the soil. This process helps to replenish groundwater levels.
• Percolation: The water that infiltrated continues to flow downward through soil and rock layers. Infiltration and percolation are related but describe movement at different depths.
In simple words: The water cycle is how water moves around the Earth. It starts with water turning into vapor (evaporation and sublimation), then forming clouds (condensation), falling back as rain or snow (precipitation), and then flowing over or into the ground (runoff, infiltration, and percolation).

🎯 Exam Tip: Clearly define each process in the water cycle and explain its role in the continuous movement of water.

 

Question 2. Explain carbon cycle with the help of a flow chart.
Answer: The carbon cycle describes how carbon moves through the Earth's atmosphere, oceans, land, and living organisms. It is a vital biogeochemical cycle that supports all life. Here is a flow chart illustrating its main processes:

The carbon cycle involves the following key processes:
1. Photosynthesis: Green plants (producers) take in atmospheric carbon dioxide to create organic compounds using sunlight.
2. Respiration: Both plants and animals release carbon dioxide back into the atmosphere through breathing, breaking down organic compounds for energy.
3. Consumption: Animals obtain carbon by eating plants or other animals.
4. Death and Excretion: When plants and animals die, or excrete waste, their organic matter contains carbon.
5. Decomposition: Decomposers (like bacteria and fungi) break down dead organic matter, returning carbon dioxide to the atmosphere and soil.
6. Fossilization: Over millions of years, under specific conditions, dead organic matter can be converted into fossil fuels (coal, oil, gas), storing carbon underground.
7. Combustion: Burning fossil fuels and biomass releases large amounts of stored carbon dioxide into the atmosphere. Human activities like burning wood and driving cars significantly contribute to this process, impacting the balance of the carbon cycle.
In simple words: The carbon cycle shows how carbon moves between the air, plants, animals, and the ground. Plants take carbon from the air, animals eat plants, and both release carbon back. Burning fossil fuels also adds a lot of carbon to the air.

🎯 Exam Tip: When explaining the carbon cycle, ensure your flow chart clearly labels all reservoirs (like atmosphere, plants, fossil fuels) and the processes that move carbon between them.

 

Question 3. List out the adaptations of xerophytes.
Answer: Xerophytes are plants adapted to live in very dry environments. Their adaptations help them to absorb as much water as possible, retain water for a long time, and reduce water loss. Here are some key adaptations:
1. Well-developed roots: They have deep root systems that grow extensively to reach water sources far below the surface, as seen in plants like Calotropis. This helps them find scarce water.
2. Water-storing tissues: Many xerophytes store water in specialized succulent parenchymatous tissues within their stems or leaves, allowing them to conserve water for extended dry periods.
3. Small or modified leaves: They often have small-sized leaves, sometimes with a waxy coating (e.g., Acacia), to reduce the surface area for transpiration (water loss). In some plants, leaves are modified into spines (e.g., Opuntia) for further water conservation and protection.
4. Short life cycle: Some xerophytes complete their entire life cycle very quickly during brief periods when moisture is available, avoiding prolonged exposure to dry conditions. This ensures they reproduce before harsh dry seasons.
In simple words: Xerophytes, or desert plants, have special ways to live in dry places. They have very deep roots to find water, store water in their parts, or have small, waxy leaves or spines to stop water from escaping. Some even grow very fast when it rains.

🎯 Exam Tip: When listing xerophyte adaptations, always explain how each feature helps the plant conserve water or access it more effectively in dry conditions.

 

Question 4. How does a bat adapt itself to its habitat?
Answer: Bats have several unique adaptations that allow them to thrive in their habitats, particularly during nocturnal activity:
• Shelter in caves: Most bats live in caves, which provide excellent protection from predators during the day and help maintain a stable, cool temperature. Caves offer a safe resting place.
• Nocturnal activity: Bats are active at night. This is a crucial adaptation as it helps them avoid many predators that are active during the day. It also allows them to hunt insects that are more active after sunset. Flying requires a lot of energy, so hunting at night in cooler temperatures can be more efficient.
• Hibernation: During winter, some bats reduce their body temperature and metabolic rate. This state of hibernation helps them conserve energy when food sources are scarce.
• Reduced internal temperature during rest: Bats can lower their internal body temperature during periods of rest, which helps in saving energy, similar to a mini-hibernation.
• Echolocation: Bats use a remarkable system called echolocation, emitting high-frequency ultrasonic sound waves. They listen to the echoes to create a sound map of their surroundings, helping them identify and locate prey and navigate in complete darkness. This is a highly specialized hunting and navigation tool.
In simple words: Bats adapt by living in caves for safety, being active at night to avoid danger, and hibernating to save energy in winter. They also use special sound waves (echolocation) to find their way and hunt in the dark.

🎯 Exam Tip: For bat adaptations, emphasize both their behavioral adaptations (nocturnality, hibernation) and unique physiological features (echolocation, flight) for a complete answer.

 

Question 5. What is water recycling? Explain the conventional wastewater recycling treatment?
Answer: Water recycling is the process of reusing treated wastewater for beneficial purposes. This includes applications such as agricultural and landscape irrigation, industrial processes, toilet flushing, and groundwater replenishment, reducing the demand for fresh water.
Conventional wastewater recycling treatment typically involves a combination of physical, chemical, and biological processes, which are divided into stages:

Each stage removes different types of impurities, making the water progressively cleaner and safer for reuse. Advanced treatments might follow depending on the intended use of the recycled water, ensuring it meets specific quality standards. This multi-step process effectively purifies wastewater to a reusable state.
In simple words: Water recycling is cleaning used water to use it again for things like farming or factories. The cleaning process has three main steps: first, removing big solid waste; second, using tiny living things to break down organic waste; and third, taking out small particles and germs with chemicals.

🎯 Exam Tip: For wastewater treatment, remember the three main stages (primary, secondary, tertiary) and the specific types of waste removed at each step.

ACTIVITY -1

 

Question. Create your own water cycle. Take a small container and place it in the middle of the large bowl. Fill water in the large container and cover it with plastic wrap. Fasten the plastic wrap around the rim of the large container with the rubber band. Place a stone on the top of the plastic wrap. Keep this under sun for few hours. Record your observation. Aim: To understand utilisation and recycling of water. Materials: A large transparent bowl, plastic wrap, a stone, a smaller container and a rubber band.
Answer:
**Procedure:**
1. The small container is placed in the middle of a larger bowl. Water is filled into the larger container and then covered with plastic wrap.
2. The plastic wrap is secured around the rim of the large container using a rubber band.
3. A stone is placed on top of the plastic wrap, above the smaller container, creating a slight dip.
4. The entire setup is left under the sun for several hours.

**Observation:**
1. Looking closely at the plastic wrap, water droplets are seen forming on its inner surface. This clearly shows that condensation is taking place.
2. Over time, the water level in the large bowl decreases. This indicates that a part of the water has evaporated into the air.
3. After some time, the water droplets collected on the plastic wrap grow larger and drip into the small container below. This demonstrates the phenomenon of precipitation.

**Conclusion:**
Through this activity, the fundamental processes of the water cycle, including evaporation, condensation, and precipitation, are effectively demonstrated. This simple model helps to visualize how water moves and recycles in nature.
In simple words: We put water in a bowl, cover it with plastic, and put a stone on top. In the sun, water turns into vapor (evaporation), forms drops on the plastic (condensation), and then drips into a small cup (precipitation). This shows how the water cycle works.

🎯 Exam Tip: When describing an experiment, always clearly state the procedure, observations, and conclusion, linking each step to the scientific concept being demonstrated.

9th Science Guide Environmental Science Additional Important Questions and Answers

I. Choose the correct answer:

 

Question 1. Which of the following is NOT an adaptation of hydrophytes?
(a) poorly developed root system
(b) reduced plant body
(c) water storing parenchymatous tissues
(d) finely divided submerged leaves
Answer: (c) water storing parenchymatous tissues
In simple words: Water plants (hydrophytes) usually have small roots, small bodies, and thin leaves. Storing water in special tissues is a trick used by desert plants, not water plants.

🎯 Exam Tip: Remember that water-storing tissues are an adaptation for plants in dry environments (xerophytes), not for water plants (hydrophytes).

 

Question 2. In some xerophytes, leaves are modified into spines as an adaptation ...............
(a) to reduce transpiration rate
(b) to store water
(c) to reduce consumption of water
(d) all of the options
Answer: (d) all of the options
In simple words: Xerophytes change their leaves into spines to lose less water, store some water, and reduce how much water they use overall to survive in dry places.

🎯 Exam Tip: Spines in xerophytes serve multiple purposes, primarily protecting against herbivores while also significantly reducing water loss through transpiration.

 

Question 3. Identify the incorrect statement with respect to adaptations of earthworm.
(a) Earthworm has a streamlined body with no antennae or fins.
(b) Each segment of earthworm has setae.
(c) Many earthworms become inactive in a process called hibernation, during winter season.
(d) Earthworms remain in its burrow during day time, to avoid sunlight.
Answer: (c) Many earthworms become inactive in a process called hibernation, during winter season
In simple words: Earthworms have smooth bodies and bristles, and they stay underground in the day. However, they become inactive in dry, hot conditions, a process called aestivation, not hibernation (which is for cold).

🎯 Exam Tip: Clearly distinguish between aestivation (inactivity during hot/dry periods) and hibernation (inactivity during cold periods) to avoid common mistakes.

 

Question 5. Specific constituents such as nitrogen, phosphorus, suspended solids and heavy metals found in the wastewater are removed during ............ recycling process.
(a) primary
(b) secondary
(c) tertiary
(d) none of the options
Answer: (c) tertiary
In simple words: Tertiary treatment is the final stage of wastewater cleaning, where tiny dissolved particles like nitrogen, phosphorus, and other complex substances are removed. This ensures the water is very clean before being returned to the environment or reused.

🎯 Exam Tip: Remember that tertiary treatment targets specific pollutants like nutrients and microorganisms, while primary and secondary treatments focus on larger solids and organic matter, respectively.

 

Question 6. Free-living soil bacteria such as Pseudomonas sp. are responsible for the ............. process in the nitrogen cycle.
(a) ammonification
(b) nitrogen fixation
(c) nitrification
(d) denitrification
Answer: (d) denitrification
In simple words: Pseudomonas bacteria help change nitrates in the soil back into nitrogen gas, releasing it into the atmosphere. This process completes the nitrogen cycle.

🎯 Exam Tip: Clearly distinguish the roles of different bacteria in each stage of the nitrogen cycle (fixation, ammonification, nitrification, denitrification).

 

Question 7. Environmental science provides holistic knowledge about ....................
(a) Natural processes
(b) Effects of human interventions
(b) Solutions to environmental issues
(d) All of the options
Answer: (d) All of the options
In simple words: Environmental science covers everything about our planet, including how nature works on its own, how humans change things, and how we can solve environmental problems. It's a broad field that links many different sciences together.

🎯 Exam Tip: When given "All of the options" in a science question, consider if each individual option is true before selecting it. In this case, all options are indeed aspects of environmental science.

 

Question 8. Which one the following is not an abiotic factor?
(a) water
(b) air
(c) soil
(d) None of the options
Answer: (d) None of the options
In simple words: Abiotic factors are the non-living parts of an environment that affect living organisms. Since water, air, and soil are all non-living components, none of them are *not* abiotic factors; they all *are* abiotic factors.

🎯 Exam Tip: Remember that "a-" often means "not" or "without," so abiotic means "not living." Biotic factors are living organisms.

 

Question 9. The process of water cycle that related with the plants is called ....................
(a) Percolation
(b) Evaporation
(c) Transpiration
(d) Precipitation
Answer: (c) Transpiration
In simple words: Transpiration is like plants sweating. They release water vapor from tiny pores on their leaves into the air, which is a major part of the water cycle. This process helps move water up through the plant.

🎯 Exam Tip: Focus on the specific roles of living organisms in the water cycle, such as plants through transpiration and animals through respiration.

 

Question 11. .................... is the primary nutrient, important for survival of all living organisms.
(a) Nitrogen
(b) Carbon
(c) Hydrogen
(d) Oxygen
Answer: (a) Nitrogen
In simple words: Nitrogen is a fundamental building block for all life, essential for making proteins and nucleic acids (like DNA). It's a key element in every living cell.

🎯 Exam Tip: Understand the concept of limiting nutrients, where the availability of a particular nutrient (like nitrogen or phosphorus) can control the growth of organisms.

 

Question 12. The bacteria present in the root nodules of leguminous plants is .....................
(a) Nitrobacter
(b) Rhizobium
(c) Pseudomonas sp
(d) Nitrosomonas
Answer: (b) Rhizobium
In simple words: Rhizobium bacteria live in a special partnership with leguminous plants (like beans and peas). They take nitrogen gas from the air and convert it into a form the plants can use. This symbiotic relationship helps enrich the soil.

🎯 Exam Tip: Recognize the importance of nitrogen-fixing bacteria like Rhizobium in making atmospheric nitrogen available to plants, a crucial step in the nitrogen cycle.

 

Question 13. In the Nitrification process, the ammonium compounds are oxidised to .....................
(a) Ammonia
(b) Urea
(c) Nitrites
(d) Nitrates
Answer: (d) Nitrates
In simple words: Nitrification is a two-step process where special bacteria first change ammonium into nitrites, and then other bacteria change nitrites into nitrates. Plants can easily absorb and use these nitrates for their growth.

🎯 Exam Tip: Remember the sequence of compounds in nitrification: Ammonium -> Nitrites -> Nitrates. Each step is carried out by specific types of nitrifying bacteria.

 

Question 14. The atmospheric carbon dioxide enters into the plants through the process of photosynthesis to form
(a) Proteins
(b) Carbohydrates
(c) Water
(d) Carbon monoxide
Answer: (b) Carbohydrates
In simple words: During photosynthesis, plants take in carbon dioxide from the air and use sunlight to turn it into glucose, which is a simple carbohydrate. This glucose is the plant's food and energy source.

🎯 Exam Tip: Recall the basic equation for photosynthesis: Carbon Dioxide + Water + Light Energy → Glucose (Carbohydrate) + Oxygen.

 

Question 15. Carbon dioxide is also returned to atmosphere through .....................
(a) Decomposition of dead organic matter
(b) Burning fossil fuels
(c) Volcanic activities
(d) All of the options
Answer: (d) All of the options
In simple words: Carbon dioxide naturally goes back into the air when dead plants and animals decompose. Human activities like burning fossil fuels also release a lot of carbon dioxide, and volcanoes add some too. These processes are all part of the carbon cycle.

🎯 Exam Tip: Think about both natural (decomposition, respiration, volcanic eruptions) and anthropogenic (burning fossil fuels, deforestation) sources that release carbon dioxide into the atmosphere.

 

Question 16. The plants that has air chambers is .....................
(c) Eichhornia
(d) Acacia
Answer: (c) Eichhornia
In simple words: Eichhornia, commonly known as water hyacinth, is an aquatic plant that has special air-filled spaces, or air chambers. These chambers help the plant float on the surface of the water, which is a key adaptation for its watery environment.

🎯 Exam Tip: Connect structural adaptations like air chambers to the specific environment a plant lives in, especially for hydrophytes (water plants).

 

Question 17. Which plant is called as “Cinderella of the plant kingdom"?
(a) Hydrilla
(b) Water hyacinth
(c) Calotropis
(d) Aloevera
Answer: (b) Water hyacinth
In simple words: Water hyacinth is often called the "Cinderella of the plant kingdom" because it has beautiful flowers but can also grow very quickly and become an invasive weed. It quickly covers water bodies, blocking sunlight and harming other aquatic life.

🎯 Exam Tip: While some plants are admired for their beauty, remember that invasive species can have significant negative impacts on ecosystems.

 

Question 18. Root caps is a characteristic .................... adaptation of .....................
(a) Xerophytes
(b) Hydrophytes
(c) Mesophytes
(d) All of the options
Answer: (c) Mesophytes
In simple words: Root caps are protective layers found at the tips of roots. They are a common feature of mesophytes, which are plants adapted to environments with a moderate supply of water. The root cap protects the growing tip as it pushes through the soil.

🎯 Exam Tip: Understand that different plant groups (xerophytes, hydrophytes, mesophytes) have distinct adaptations based on water availability in their habitat.

 

Question 19. The presence of .................... in leaves traps the moisture and lessens water loss in Mesophytes.
(a) Waxy Cuticle
(c) stalk
(d) None of the options
Answer: (a) Waxy Cuticle
In simple words: Mesophytes, which grow in normal conditions, have a waxy layer called a cuticle on their leaves. This layer helps to keep water inside the leaf and reduce how much water is lost to the air, especially on hot or windy days.

🎯 Exam Tip: The waxy cuticle is a key adaptation for plants to regulate water loss, particularly important in preventing desiccation.

 

Question 20. .................... supports and controls movements during flight of a bat.
(a) Forelimbs
(b) Hind limbs
(c) Tail
(d) Muscles
Answer: (a) Forelimbs
In simple words: Bats are the only mammals that can truly fly, and they do this using their forelimbs, which are specially modified into wings. These wings are essential for lifting, steering, and controlling their flight.

🎯 Exam Tip: Understand that the wings of bats are homologous to the arms of other mammals, showing evolutionary adaptation for flight.

 

Question 21. Find the incorrect statement
(a) Vermicompost is prepared by using earthworms
(b) Vermicompost decomposes the plant and animal waste
(c) Vermicompost is an inorganic compound
(d) Vermicompost contains water soluble nutrients.
Answer: (c) Vermicompost is an inorganic compound
In simple words: Vermicompost is a rich, organic fertilizer made by earthworms breaking down plant and animal waste. It is full of natural nutrients and beneficial microbes, making it an organic compound, not inorganic.

🎯 Exam Tip: Remember that vermicompost is a natural, sustainable method of composting that enriches soil with organic matter, improving its fertility and structure.

 

Question 22. World Water Day is celebrated on ....................
(a) 22nd February
(b) 22nd March
(c) 5th June
Answer: (b) 22nd March
In simple words: Every year on March 22nd, people around the world celebrate World Water Day. This day is used to highlight how important fresh water is and to advocate for the sustainable management of freshwater resources.

🎯 Exam Tip: Being aware of important environmental days and their significance can demonstrate a broader understanding of environmental issues.

 

Question 23. Which one of the following is not an advantage of farm ponds?
(a) Reduce soil erosion
(b) Recharge ground water
(c) Reduce water flow to other parts
(d) Improve drainage
Answer: (c) Reduce water flow to other parts
In simple words: Farm ponds offer several benefits like preventing soil erosion, helping to refill underground water, and improving the drainage on farmlands. Reducing water flow to other areas is not considered an advantage for the wider ecosystem, but rather an impact on downstream areas.

🎯 Exam Tip: Consider the broader ecological and community impacts when evaluating the advantages and disadvantages of water management practices.

 

Question 24. Biological oxidation is the method used in ....................
(a) Primary Treatment
(b) Secondary Treatment.
(c) Tertiary Treatment
(d) None of the options
Answer: (b) Secondary Treatment
In simple words: In secondary treatment of wastewater, microorganisms are used to break down dissolved organic matter through a process called biological oxidation. This step cleans the water further after the initial removal of large solids.

🎯 Exam Tip: Remember that biological processes are central to secondary wastewater treatment, making use of microbes to purify water.

 

Question 25. The wastes removed in tertiary treatment are ....................
(c) Inorganic substances
Answer: (c) Inorganic substances
In simple words: Tertiary treatment is an advanced stage of wastewater purification that specifically targets and removes inorganic substances such as nitrogen and phosphorus compounds. It also effectively removes any remaining disease-causing microorganisms.

🎯 Exam Tip: Focus on the specific types of pollutants removed at each treatment stage: primary (large solids), secondary (dissolved organic matter), and tertiary (inorganic nutrients, pathogens).

 

Question 26. India accounts for ....................% of all recorded species.
(a) 2-4%
(b) 5-6%
(c) 6-7%
(d) 7-8%
Answer: (d) 7-8%
In simple words: India is recognized globally as a megadiverse country, home to a significant portion of the world's biodiversity. It contains about 7-8% of all the known plant and animal species found on Earth.

🎯 Exam Tip: Understand the concept of biodiversity hotspots and why countries like India hold such a high percentage of global species diversity.

II. Fill in the Blanks:

 

Question 1. .................... is the study of patterns, processes in the natural world and their modifications by human activities.
Answer: Environmental Science
In simple words: Environmental Science is a field of study that looks at how nature works, how people affect it, and how we can find solutions to environmental problems. It combines many subjects like biology, chemistry, and ecology.

🎯 Exam Tip: A clear definition of key terms is crucial. Environmental Science integrates natural sciences with social sciences to understand environmental issues.

 

Question 2. Biosphere is a .................... and .................... and system.
Answer: dynamic, stable
In simple words: The biosphere is the part of Earth where life exists. It is constantly changing (dynamic) due to natural processes and living organisms, but it also maintains a certain balance (stable) over long periods.

🎯 Exam Tip: Remember that "dynamic" means constantly changing or active, while "stable" implies a tendency to return to a balanced state after disturbance.

 

Question 3. Cyclic flow of nutrients between non-living and living factors of the environment are termed as .................... cycle.
Answer: Biogeochemical
In simple words: The continuous movement and recycling of important elements like carbon, nitrogen, and water between living organisms and the non-living parts of the Earth (like air, water, and soil) are called biogeochemical cycles.

🎯 Exam Tip: Break down the word "biogeochemical" into its parts: "bio" (life), "geo" (Earth), and "chemical" (elements) to remember its meaning.

 

Question 4. .................... is the reverse of vapourisation.
Answer: Condensation
In simple words: Condensation is the process where a gas, like water vapor, changes back into a liquid. It's the opposite of vaporization (evaporation), where a liquid turns into a gas. This often happens when warm, moist air cools down.

🎯 Exam Tip: Understanding the terms "vaporization," "evaporation," and "condensation" is key to grasping the water cycle.

 

Question 5. Atmosphere is a rich source of ....................
Answer: Nitrogen
In simple words: The air around us, the atmosphere, is mostly made up of nitrogen gas. This makes it a very large store of nitrogen, which is an essential element for all living things.

🎯 Exam Tip: Recall that nitrogen makes up about 78% of Earth's atmosphere, making it the most abundant gas, although it's not directly usable by most organisms in its atmospheric form.

 

Question 6. The blue-green algae that take part in nitrogen fixation is also called ....................
Answer: Cyanobacteria
In simple words: Blue-green algae are actually a type of bacteria known as cyanobacteria. They are special because they can capture nitrogen gas from the air and convert it into a form that plants can use, a process called nitrogen fixation.

🎯 Exam Tip: Cyanobacteria are ancient organisms that played a critical role in Earth's early atmosphere and continue to be important in nutrient cycles today.

 

Question 7. .................... animals convert plant proteins into animal proteins.
Answer: Herbivorous
In simple words: Herbivorous animals are those that eat only plants. When they digest plants, they break down plant proteins and then use those building blocks to create their own animal proteins for growth and repair.

🎯 Exam Tip: Differentiate between herbivores (plant-eaters), carnivores (meat-eaters), and omnivores (both) based on their diet and how they obtain nutrients.

 

Question 8. Carnivorous animals synthesize .................... from their food.
Answer: Protein
In simple words: Carnivorous animals eat other animals, which are rich in protein. They digest these proteins and then use the amino acids (protein building blocks) to make their own proteins for building muscles and other body tissues.

🎯 Exam Tip: All living organisms need proteins for growth and repair; the source of these proteins varies depending on the organism's trophic level.

 

Question 9. Charcoal, diamond and graphite are .................... forms of carbon.
Answer: Elemental
In simple words: Charcoal, diamond, and graphite are all different ways the element carbon can exist in its pure form. They are called allotropes, meaning they are different structures of the same element.

🎯 Exam Tip: Remember that allotropes are different physical forms in which an element can exist, with distinct properties due to different atomic arrangements.

 

Question 10. All living organisms are made up of carbon-containing molecules like .................... and ....................
Answer: Proteins, nucleic acids
In simple words: Every living thing, from tiny bacteria to large animals, is built from molecules that contain carbon. Two very important types of these carbon-based molecules are proteins (which do most of the work in cells) and nucleic acids (like DNA, which carries genetic instructions).

🎯 Exam Tip: Recognize carbon as the fundamental element of organic chemistry and life, forming complex macromolecules essential for biological functions.

 

Question 11. Floating leaves have long .................... to enable the leaves move up and down in response to changes in water level.
Answer: Leaf stalks
In simple words: Plants that have leaves floating on water often have very long, flexible leaf stalks. These stalks allow the leaves to stay on the surface, moving up or down as the water level changes, ensuring they get enough sunlight.

🎯 Exam Tip: This is a clear adaptation for aquatic plants (hydrophytes) to maximize light absorption while anchored in the substrate.

 

Question 12. .................... is the plant in which leaves are modified into spines.
Answer: Opuntia
In simple words: Opuntia, also known as the prickly pear cactus, is a desert plant that has adapted to dry conditions by modifying its leaves into sharp spines. These spines help protect the plant from animals and reduce water loss through transpiration.

🎯 Exam Tip: Spines in xerophytes serve dual purposes: defense against herbivores and reduction of surface area to minimize water loss.

 

Question 13. The function of stomata in leaves of mesophytes is to prevent ....................
Answer: Transpiration
In simple words: Stomata are tiny openings on the surface of plant leaves that allow for gas exchange. In mesophytes (plants adapted to moderate water), these stomata can close to prevent excessive loss of water vapor to the atmosphere, a process called transpiration.

🎯 Exam Tip: Stomata regulate both gas exchange (carbon dioxide intake for photosynthesis) and water loss, balancing these vital processes.

 

Question 14. In bats, the excessive heat absorption during the day is caused by ....................
Answer: Patagium
In simple words: The patagium is the thin, leathery membrane that forms the wings of a bat. Because it has a large surface area and is thin, it can absorb a lot of heat during the day, which is why bats prefer to rest in cool, dark places like caves.

🎯 Exam Tip: The patagium is not only crucial for flight but also plays a role in thermoregulation due to its extensive surface area and vascularization.

 

Question 15. In bats modified forelimbs serve as ....................
Answer: Wings
In simple words: Bats have evolved their front limbs to become wings, allowing them to fly. This adaptation is unique among mammals and enables them to navigate and hunt in the air.

🎯 Exam Tip: Emphasize that bat wings are homologous to human arms, demonstrating how a basic skeletal structure can be adapted for vastly different functions over evolutionary time.

 

Question 16. .................... of hind limbs in bat provides a tight grasp when the animals
Answer: Tendons
In simple words: The strong tendons in a bat's hind limbs are crucial for providing a firm grip. This allows bats to hang upside down effortlessly while resting, conserving energy.

🎯 Exam Tip: Specific anatomical features like strong tendons highlight how animals are perfectly adapted to their unique lifestyles and habitats.

 

Question 17. Bats are .................... blooded animals
Answer: warm
In simple words: Bats are mammals, and like all mammals, they are warm-blooded (endothermic). This means they can maintain a constant, warm body temperature regardless of the external environment.

🎯 Exam Tip: Differentiate between warm-blooded (endothermic) and cold-blooded (ectothermic) animals and their methods of temperature regulation.

 

Question 18. Earthworm belongs to Phylum .....................
Answer: Annelida
In simple words: Earthworms are classified under the phylum Annelida, which includes segmented worms. This means their bodies are made up of many ring-like segments.

🎯 Exam Tip: Knowing the phylum for common animals like earthworms helps in understanding broader biological classification.

 

Question 19. Moist skin in earthworm helps in .................... of blood.
Answer: Oxygenation
In simple words: Earthworms breathe through their skin. Their skin must stay moist for oxygen from the air to dissolve and pass into their blood, a process known as oxygenation. This allows them to absorb the oxygen needed for survival.

🎯 Exam Tip: Cutaneous respiration (breathing through the skin) is an important adaptation for earthworms, highlighting the need for a moist environment.

 

Question 20. The theme for World Water Day 2018 is ....................
Answer: Nature for water
In simple words: In 2018, World Water Day focused on the theme "Nature for Water." This theme encouraged using natural solutions, like planting trees or restoring wetlands, to manage water resources better.

🎯 Exam Tip: Understanding the themes of international environmental days helps contextualize global efforts towards sustainable development.

 

Question 21. The microorganism used in secondary treatment must be separated from treated wastewater by ....................
Answer: Sedimentation
In simple words: After microorganisms break down waste in secondary treatment, they themselves form a sludge. This sludge, full of microbes, is then separated from the clean water by allowing it to settle at the bottom through sedimentation.

🎯 Exam Tip: Sedimentation is a crucial physical process used in various stages of water and wastewater treatment to separate solids from liquids.

 

Question 22. There are .................... globally identified biodiversity hotspots in India.
Answer: Four
In simple words: India is home to four major biodiversity hotspots: the Himalayas, Indo-Burma, Western Ghats and Sri Lanka, and Sundaland. These areas are incredibly rich in unique species but are also facing significant threats, making their conservation vital.

🎯 Exam Tip: Biodiversity hotspots are regions with high levels of endemic species that are also under severe threat, requiring focused conservation efforts.

 

Question 23. IUCN was founded on .................... at Gland, Switzerland.
Answer: 5th October 1948
In simple words: The International Union for Conservation of Nature (IUCN) was established on October 5, 1948. Its headquarters are in Gland, Switzerland, and it works to protect nature and promote sustainable use of natural resources worldwide.

🎯 Exam Tip: Knowing the full form, founding date, and location of key environmental organizations like IUCN is important for environmental awareness.

III. Match the Following:

 

Question 1. Match the following.

Answer:In simple words: This table correctly matches each microorganism with its specific role in the nitrogen cycle. For example, Nitrosomonas is involved in nitrification, converting ammonia to nitrites. Azotobacter performs nitrogen fixation, turning atmospheric nitrogen into usable forms. Pseudomonas handles denitrification, returning nitrogen gas to the atmosphere, and putrefying bacteria are responsible for ammonification, breaking down organic matter into ammonia.

🎯 Exam Tip: Memorize the key microorganisms involved in each stage of the nitrogen cycle and their precise functions to accurately match them.

 

Question 2. Match the following.

Answer:In simple words: This matching exercise helps us understand plant adaptations. Xerophytes, which live in dry places, often have small leaves to save water. Mesophytes grow in moderate conditions and typically have broad, thin leaves for efficient photosynthesis. Hydrophytes, or water plants, usually have a reduced plant body, and an example is the water hyacinth, which can also be used as green manure.

🎯 Exam Tip: Relate plant features directly to their habitat. For instance, reduced leaves/spines for dry areas, broad leaves for temperate areas, and reduced root systems for aquatic environments.

 

Question 3. Match the following.

Answer:In simple words: This match identifies various animal adaptations. Aestivation is a state of dormancy (like summer sleep) with low metabolism, helping animals survive hot, dry periods. Echolocation is a navigation system using ultrasonic sounds, like bats do. Hibernation is a winter dormancy marked by a significant drop in body temperature. The patagium, a bat's wing membrane, can absorb a lot of heat.

🎯 Exam Tip: Differentiate between aestivation (summer dormancy) and hibernation (winter dormancy) and understand the physiological changes involved in each.

 

Question 4. Match the following.

Answer:In simple words: This match correctly pairs wastewater treatment stages and water types with their associated processes. Primary treatment uses flotation to remove larger floating solids. Secondary treatment uses sedimentation to separate microbial sludge after biological processing. Tertiary treatment involves disinfection to kill remaining pathogens. Grey water refers to used household water that can be reused for certain purposes like gardening.

🎯 Exam Tip: Understand the sequence and purpose of each wastewater treatment stage and the concept of water reuse for sustainability.

IV. Say True or False. Correct the False Statements:

III. Say True or False. Correct the False Statements:

 

Question 1. Sublimation is conversion of solid into liquid.
Answer: False. Sublimation is actually when a solid changes directly into a gas without first becoming a liquid. For example, dry ice changes directly into carbon dioxide gas.
In simple words: This is false. Sublimation is when a solid turns straight into a gas.

🎯 Exam Tip: Remember the key direct conversion in sublimation: solid to gas. Don't confuse it with melting (solid to liquid) or evaporation (liquid to gas).

 

Question 2. Nitrogen is an essential component of protein, DNA and chlorophyll.
Answer: True. Nitrogen is a very important building block for life. It is found in proteins, DNA, and even chlorophyll, which helps plants make food.
In simple words: This is true. Nitrogen is a vital part of proteins, DNA, and chlorophyll.

🎯 Exam Tip: Recall the major macromolecules (proteins, nucleic acids) and their elemental composition to confirm such statements.

 

Question 3. Plant proteins are excreted in the form of urea, uric acid or ammonia.
Answer: False. It is animal proteins, not plant proteins, that are broken down and excreted as urea, uric acid, or ammonia. Plants typically do not excrete proteins in these forms; they reuse their nitrogen compounds.
In simple words: This is false. Animals excrete proteins as urea, uric acid, or ammonia, not plants.

🎯 Exam Tip: Distinguish between plant and animal metabolism when answering questions about waste products.

 

Question 4. During respiration, plants and animals release carbon into the atmosphere in the form of carbon monoxide.
Answer: False. During respiration, both plants and animals release carbon into the atmosphere as carbon dioxide \( (\text{CO}_2) \), not carbon monoxide \( (\text{CO}) \). Carbon dioxide is a natural part of the carbon cycle, while carbon monoxide is a harmful gas.
In simple words: This is false. Plants and animals breathe out carbon dioxide, not carbon monoxide.

🎯 Exam Tip: Understand the difference between carbon monoxide \( (\text{CO}) \), which is a poisonous gas, and carbon dioxide \( (\text{CO}_2) \), which is a product of respiration and essential for photosynthesis.

 

Question 5. Bats are not blind.
Answer: True. Bats are not blind; they can see. Many bats also use echolocation, which is like a natural sonar, to navigate and find food in the dark, but this doesn't mean they can't see with their eyes.
In simple words: This is true. Bats can see, and they also use sound to find their way around.

🎯 Exam Tip: Recognize that echolocation in bats is an additional sense for navigation, not a replacement for sight, dispelling a common misconception.

 

Question 6. Earthworm come out of their burrow during summer season.
Answer: False. Earthworms usually come out of their burrows during the rainy season, not summer. This is because the soil becomes too wet, and they need to come to the surface to breathe and avoid drowning. During summer, they typically burrow deeper to escape dryness and heat.
In simple words: This is false. Earthworms come out in the rainy season when the soil is very wet.

🎯 Exam Tip: Remember that earthworms thrive in moist, not overly dry or overly wet, conditions. They surface to avoid waterlogging during heavy rains.

 

Question 7. Earthworm reacts positively to brighter light.
Answer: False. Earthworms react negatively to brighter light, meaning they move away from it. They prefer dark, moist environments, and direct sunlight can be harmful to their skin and survival.
In simple words: This is false. Earthworms do not like bright light and move away from it.

🎯 Exam Tip: Always associate earthworms with dark, damp conditions, as direct light and dryness are detrimental to them.

 

Question 8. Clean and Fresh water is essential for every human activity.
Answer: True. Clean and fresh water is absolutely necessary for almost all human activities, including drinking, cooking, washing, farming, and industrial uses. Access to clean water is fundamental for health and development.
In simple words: This is true. Clean, fresh water is needed for almost everything humans do.

🎯 Exam Tip: Emphasize the wide range of human needs for clean water, from daily survival to economic activities.

 

Question 9. Nicobar island is one of the biodiversity hotspots in India.
Answer: True. The Nicobar Islands are indeed recognized as a biodiversity hotspot in India, known for their rich variety of plant and animal species, many of which are unique to the region. These areas are crucial for conserving global biodiversity.
In simple words: This is true. Nicobar Island is a special place with many different kinds of plants and animals, making it a biodiversity hotspot.

🎯 Exam Tip: Remember key biodiversity hotspots in India (e.g., Western Ghats, Eastern Himalayas, Indo-Burma region, Nicobar Islands) as they are important for environmental studies.

V. Assertion and Reason Type Questions:

 

Question 1. Assertion (A) : Biosphere is a dynamic and stable system. Reason (R) : There is a constant interaction between biotic and abiotic components in the biosphere.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
Answer: (a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
In simple words: The biosphere is always changing but stays balanced because living things (biotic) and non-living things (abiotic) constantly work together. This interaction helps explain why it's dynamic yet stable.

🎯 Exam Tip: When evaluating assertion-reason questions, first check if both statements are true individually. Then, see if the reason directly explains the assertion.

 

Question 2. Assertion (A): Infiltration and Percolation are two related but different processes. Reason (R) : They describe the movement of water through atmosphere.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
Answer: (c) If assertion is true but reason is false.
In simple words: Infiltration and percolation are different ways water moves into and through the ground, so the assertion is true. However, these processes happen in the soil, not in the atmosphere, making the reason false.

🎯 Exam Tip: Clearly understand the definitions of infiltration (water entering the soil surface) and percolation (water moving deeper through soil layers) to correctly identify their medium of movement.

 

Question 3. Assertion (A) : Plants and animals can utilize atmospheric nitrogen. Reason (R) : Atmosphere is a rich source of nitrogen.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
Answer: (d) If assertion is false but reason is true.
In simple words: Plants and animals cannot directly use the nitrogen gas from the air, even though there is a lot of it. Special bacteria change this nitrogen into a form that plants can use.

🎯 Exam Tip: Recall the nitrogen cycle, specifically the role of nitrogen-fixing bacteria, to understand why atmospheric nitrogen cannot be directly used by most organisms.

 

Question 4. Assertion (A) : By increasing the amount of carbon dioxide, earth becomes warmer. Reason (R) : Carbon dioxide is a greenhouse gas.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
Answer: (a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
In simple words: When there is more carbon dioxide in the air, the Earth gets warmer because carbon dioxide is a greenhouse gas that traps heat. So, the reason correctly explains why the Earth warms up.

🎯 Exam Tip: Connect the role of greenhouse gases like carbon dioxide directly to their ability to trap heat, leading to global warming.

 

Question 5. Assertion (A) : The moist skin in earthworm helps in oxygenation of blood. Reason (R) : The slippery skin of earthworm is kept moist.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
Answer: (b) If both assertion and reason are true but reason is not the correct explanation of assertion.
In simple words: Both statements are true: moist skin helps earthworms get oxygen into their blood, and their skin is kept slippery. However, the reason only states that the skin is moist, not why this moisture helps with oxygenation, so it's not the full explanation. The moisture is crucial because earthworms breathe through their skin, and gases exchange only when dissolved.

🎯 Exam Tip: For respiration in earthworms, the key is cutaneous respiration (breathing through skin), which requires the skin to be moist for oxygen to dissolve and diffuse.

VI. Very Short Answer Questions

 

Question 1. Name three Biogeochemical cycles.
Answer: Three important biogeochemical cycles are:
1. Water cycle
2. Nitrogen cycle
3. Carbon cycle
These cycles ensure that elements essential for life are continuously reused and circulated throughout the Earth's ecosystems.
In simple words: The three main cycles are the water cycle, the nitrogen cycle, and the carbon cycle.

🎯 Exam Tip: Remember that biogeochemical cycles describe the movement of chemical elements through both living (bio) and non-living (geo) parts of an ecosystem.

 

Question 2. List the forms of Precipitation.
Answer: Precipitation refers to any form of water that falls from the atmosphere to the Earth's surface. Its forms include:

• Drizzle
• Rain
• Snow

Other forms also exist, such as hail and sleet, depending on atmospheric conditions.
In simple words: Precipitation can be drizzle, rain, or snow.

🎯 Exam Tip: Enumerate all major forms of precipitation, not just the common ones, to ensure a comprehensive answer.

 

Question 3. Mention the excretory forms of Animal proteins.
Answer: When animal proteins are broken down, they produce nitrogenous waste. The main excretory forms of these wastes are:

• Urea
• Uric acid
• Ammonia

Different animals excrete these in varying forms depending on their habitat and water availability. For example, fish excrete ammonia, birds excrete uric acid, and mammals excrete urea.
In simple words: Animals get rid of protein waste as urea, uric acid, or ammonia.

🎯 Exam Tip: Remember these three main forms and their association with different animal groups based on water conservation strategies.

 

Question 4. What are the effects of carbon dioxide in the atmosphere?
Answer: Carbon dioxide \( (\text{CO}_2) \) in the atmosphere has two main effects:

• It contributes to the greenhouse effect, which is the natural warming of Earth's surface and atmosphere.
• Increased levels of \( \text{CO}_2 \) lead to global warming, causing climate change.

This gas traps heat, acting like a blanket around the Earth.
In simple words: Carbon dioxide causes the greenhouse effect and leads to global warming.

🎯 Exam Tip: Clearly link carbon dioxide to both the greenhouse effect (a natural process) and global warming (an enhanced, human-caused effect).

 

Question 5. How are plants classified on the basis of water availability?
Answer: Plants are classified into different groups based on the amount of water available in their habitat:

• Hydrophytes: These plants live in water or very wet places.
• Xerophytes: These plants live in dry places and can survive with very little water.
• Mesophytes: These plants live in places with a moderate amount of water, neither too wet nor too dry.

Each group has special adaptations to survive in its specific water environment.
In simple words: Plants are grouped as hydrophytes (water), xerophytes (dry), and mesophytes (moderate) based on water in their living areas.

🎯 Exam Tip: Understand the environmental conditions and typical adaptations associated with each plant classification based on water availability.

 

Question 6. How are bats important to humans?
Answer: Bats play several important roles that benefit humans:

• They help control insect populations by eating many insects, including pests that harm crops.
• Many bats help pollinate plants, just like bees, which is crucial for the reproduction of certain crops and wild flowers.

Some bats also help spread seeds, aiding in forest regeneration. Their diverse roles highlight their ecological importance.
In simple words: Bats help people by eating insects and by pollinating plants.

🎯 Exam Tip: Focus on the ecological services bats provide, such as pest control and pollination, when discussing their importance to humans.

 

Question 7. What is the Ideal temperature range of earthworm?
Answer: The ideal temperature range for earthworms is between 60-80°F (15-27°C). Within this range, they are most active and healthy. Temperatures outside this range can stress them, affecting their growth and reproduction.
In simple words: Earthworms like temperatures from 60 to 80 degrees Fahrenheit to live best.

🎯 Exam Tip: Knowing the optimal environmental conditions for organisms like earthworms is important for understanding their biology and ecological role.

VII. Answer Briefly:

 

Question 1. Define : Environmental Science.
Answer: Environmental science is the study of how the natural world works, including all its patterns and processes. It also looks at how human activities change these natural systems. This field helps us understand our impact on the planet and find solutions.
In simple words: Environmental science studies nature and how humans change it.

🎯 Exam Tip: A good definition of environmental science should include both the study of natural processes and the impact of human activities.

 

Question 2. What is biogeochemical cycle?
Answer: A biogeochemical cycle describes the continuous movement of nutrients and elements between the living parts (biotic factors) and non-living parts (abiotic factors) of an environment. These cycles, like the carbon and nitrogen cycles, are vital for maintaining life on Earth. They ensure that essential substances are constantly recycled.
In simple words: A biogeochemical cycle is how important materials move from living things to non-living things and back in nature.

🎯 Exam Tip: When defining biogeochemical cycles, emphasize the "cyclic flow" and the involvement of both "living" (bio) and "non-living" (geo) components.

 

Question 3. How are clouds and fogs formed?
Answer: Clouds and fogs are formed through a process called condensation:

• At higher altitudes, the air temperature is much lower.
• The water vapor in the air cools down and changes into tiny water droplets or ice crystals.

These tiny droplets gather around dust particles in the air, becoming visible as clouds high up or as fog close to the ground. When these droplets get too heavy, they fall as rain.
In simple words: Clouds and fog form when water vapor in the air gets cold and turns into tiny water droplets.

🎯 Exam Tip: Focus on the key process of condensation, the role of temperature, and the formation of tiny water droplets around nuclei (like dust) when explaining cloud and fog formation.

 

Question 4. How is carbon dioxide returned to atmosphere? :
Answer: Carbon dioxide \( (\text{CO}_2) \) is released back into the atmosphere through several natural and human-caused processes:

• Decomposition of dead organic matter: When plants and animals die, decomposers break them down, releasing \( \text{CO}_2 \).
• Burning fossil fuels: Human activities like burning coal, oil, and gas for energy release large amounts of stored carbon.
• Volcanic activities: Volcanic eruptions naturally release \( \text{CO}_2 \) and other gases.

Respiration by living organisms is another major natural process returning carbon dioxide to the atmosphere.
In simple words: Carbon dioxide goes back into the air when dead things rot, when fossil fuels are burned, and from volcanoes.

🎯 Exam Tip: List both natural processes (decomposition, volcanic activity, respiration) and human-induced processes (burning fossil fuels) that contribute to \( \text{CO}_2 \) release.

 

Question 5. Explain briefly the role of earth-worm in soil atmosphere, (or) soil health?
Answer: Earthworms play a vital role in keeping soil healthy:

• They create tunnels in the soil, which helps with aeration (allowing air to get in) and water infiltration (allowing water to soak in deeper).
• They break down organic matter and their castings (waste) add nutrients, increasing the organic content of the soil and improving crop growth.

By moving soil particles around, they also help mix nutrients throughout the soil.
In simple words: Earthworms make tunnels that help air and water get into the soil. Their waste also adds good stuff to the soil, helping plants grow better.

🎯 Exam Tip: When discussing earthworms' role, highlight their contributions to soil structure (aeration, infiltration) and nutrient cycling (organic matter, castings).

 

Question 6. What is worm castings? How is it useful?
Answer: Worm castings are the faecal waste products of earthworms, essentially their poop. These castings are very useful for soil because:

• They are rich in nitrogen and other essential nutrients.
• This rich content adds fertility to the soil, helping plants grow stronger and healthier.

Castings also improve soil structure, making it easier for roots to grow and water to penetrate. Many farmers use vermicompost, which is rich in these castings, to naturally enrich their soil.
In simple words: Worm castings are earthworm waste. They are useful because they add nitrogen and other important nutrients to the soil, making it more fertile for plants.

🎯 Exam Tip: Define worm castings correctly as earthworm waste and explain their utility by mentioning nutrient enrichment and improved soil structure.

 

Question 7. Point out the importance of water conservation.
Answer: Water conservation is very important for several reasons:

• It helps us use water resources more efficiently, ensuring enough water for everyone.
• It ensures that we have enough usable water for drinking, farming, and other needs, especially as populations grow and climates change.
• It helps decrease water pollution by reducing runoff and the strain on treatment plants.
• It also helps save energy because less energy is used to pump, heat, and treat water.

By saving water, we protect our environment and secure future water supplies.
In simple words: Saving water helps us use it better, makes sure we have enough clean water, reduces pollution, and saves energy.

🎯 Exam Tip: When discussing water conservation, include benefits like efficient resource use, pollution reduction, and energy saving, not just ensuring availability.

 

Question 8. According to you, which process of water cycle is adversely affected by human activities?
Answer: Transpiration is a process in the water cycle that is significantly affected by human activities. Transpiration is when plants release water vapor through tiny pores in their leaves and stems.
Human actions like deforestation (cutting down forests) and urbanization (building cities) reduce the number of plants, leading to less water being released into the atmosphere through transpiration. This can change local rainfall patterns. When trees are cut down, less water moves from the ground into the air.
In simple words: Human activities like cutting down trees and building cities reduce transpiration, which is when plants release water vapor into the air.

🎯 Exam Tip: Focus on how large-scale human land-use changes, like deforestation, directly impact the biological components of the water cycle, such as transpiration.

 

Question 9. Identify the given plant. How does it adapt itself to its habitat?
Answer: The plant shown is Hydrilla, which is an aquatic plant (hydrophyte). It adapts to its watery habitat in the following ways:

• It has poorly developed roots because it can absorb water and nutrients directly from the surrounding water.
• Its leaves are narrow or finely divided and submerged. This shape helps reduce resistance to water currents and increases the surface area for absorbing dissolved gases and light.

These features allow Hydrilla to thrive completely underwater.
In simple words: The plant is Hydrilla. It has small roots and thin leaves that stay underwater, which helps it live well in water.

🎯 Exam Tip: When describing plant adaptations, link each feature directly to how it helps the plant survive in its specific environment (e.g., small roots in water, thin leaves for light/gas absorption).

 

Question 10. What is grey water?
Answer: Grey water is wastewater that comes from residential, commercial, and industrial sources, but it does not contain human waste. It typically comes from bathroom sinks, bathtubs, shower drains, and washing machines. This type of water can often be reused for non-drinking purposes, such as watering gardens or flushing toilets, after minimal treatment. Using grey water reduces the demand for fresh, clean water.
In simple words: Grey water is used water from sinks, showers, and washing machines that does not have human waste in it. It can often be cleaned and used again for things like watering plants.

🎯 Exam Tip: Distinguish grey water from black water (which contains human waste) and emphasize its potential for reuse as a water conservation strategy.

VIII. Answer in Detail:

 

Question 1. Draw a neat flow chart of Nitrogen cycle. Briefly explain the various processes involved in nitrogen cycle.
Answer: The Nitrogen cycle shows how nitrogen moves through the environment in different forms. Here is a flowchart and an explanation of the processes:

The various processes involved in the nitrogen cycle are:
1. Nitrogen Fixation:
Process: This is the conversion of atmospheric nitrogen gas \( (\text{N}_2) \), which is inert, into reactive compounds like ammonia. This makes nitrogen usable for living organisms.
Agents: Special bacteria (like Rhizobium in leguminous plant root nodules) and blue-green algae (cyanobacteria), as well as lightning, carry out this process.
Occurrence: It happens in soil by free-living bacteria and in root nodules of plants like peas and beans.
2. Nitrogen Assimilation:
Process: Plants absorb usable forms of nitrogen (like nitrates and ammonium) from the soil and use them to build their own organic molecules, such as proteins and nucleic acids. Animals get nitrogen by eating plants or other animals.
3. Ammonification:
Process: When plants and animals die, or when animals excrete waste, decomposers (like putrefying bacteria and fungi) break down the nitrogenous waste into ammonium compounds.
4. Nitrification:
Process: Ammonium compounds are oxidized by nitrifying bacteria in the soil. First, ammonia is converted to nitrites \( (\text{NO}_2^-) \) by Nitrosomonas bacteria. Then, nitrites are converted to nitrates \( (\text{NO}_3^-) \) by Nitrobacter bacteria. Nitrates are the main form of nitrogen absorbed by plants.
5. Denitrification:
Process: This is the reduction of nitrates back into nitrogen gas \( (\text{N}_2) \) by denitrifying bacteria (like Pseudomonas species) in the soil. This nitrogen gas then returns to the atmosphere, completing the cycle. This step balances the amount of usable nitrogen in the soil.
In simple words: The nitrogen cycle shows how nitrogen moves from the air to the soil, then into plants and animals, and finally back to the air. It involves steps like fixing nitrogen from the air, changing it into different forms for plants to use, and then sending it back to the air.

🎯 Exam Tip: When explaining complex cycles, always include a clear diagram or flowchart. For each step, mention the process name, what happens, and the organisms or conditions involved.

 

Question 2. Write the adaptations of mesophytes.
Answer: Mesophytes are plants that live in environments with a moderate amount of water. They have several adaptations to thrive in these conditions, where water is neither too scarce nor too abundant:

• Roots: They have well-developed root systems with root caps to help absorb water and nutrients from the soil effectively.
• Stems: Their stems are typically straight and branched, providing support and allowing leaves to capture sunlight.
• Leaves: They have broad and thin leaves, which are good for capturing sunlight for photosynthesis.
• Waxy Cuticles: Their leaves often have a waxy coating (cuticle) that helps to trap moisture and reduce water loss from the leaf surface.
• Stomata: They have stomata (small pores) on their leaves that can close in very hot or windy conditions. This helps them control the rate of transpiration and prevent excessive water loss.

These adaptations allow mesophytes to maintain a good water balance within their tissues. For example, most common garden plants and agricultural crops are mesophytes.
In simple words: Mesophytes, which live in places with normal water, have strong roots, branched stems, wide leaves with a waxy layer to keep water in, and pores that close to stop too much water from leaving.

🎯 Exam Tip: Focus on how mesophyte adaptations enable them to balance water uptake and loss in average conditions, as opposed to the extreme adaptations of hydrophytes or xerophytes.

 

Question 3. Discuss the adaptations of earthworm with its applications.
Answer: Earthworms have several adaptations that help them survive and thrive in their soil habitat:
1. Streamlined Body:
Adaptation: An earthworm has a cylindrical, long, and segmented body. This shape allows it to move easily through tight spaces.
Application: This body shape helps the earthworm live in narrow burrows and easily push its way through the soil.
2. Skin:
Adaptation: Its skin is covered with mucus and is always kept moist and slippery.
Application: The mucus prevents soil particles from sticking to its body. The moist skin is essential for respiration, as oxygen from the air dissolves in the mucus and passes into the blood, while carbon dioxide moves out. This process is called cutaneous respiration.
3. Burrowing:
Adaptation: Earthworms have both circular and longitudinal muscles in their body wall. Each segment on their lower surface has small bristles called setae.
Application: The muscles help in movement and digging tunnels under the soil. The setae act like anchors, gripping the soil and helping the earthworm push itself forward or backward, and stay firm in its burrow.
4. Aestivation:
Adaptation: During very dry or hot conditions, earthworms burrow deep into the soil and become inactive. They secrete mucus and reduce their metabolic rate.
Application: This behavior helps them survive harsh conditions by reducing water loss and conserving energy until favorable conditions return.
5. Nocturnality:
Adaptation: Earthworms have light-sensitive cells in their skin, but they do not see images. They prefer darkness.
Application: They remain in their burrows during the day to avoid direct sunlight, which can dry out their skin, and come out at night for feeding and other activities. They are more active in low light.
In simple words: Earthworms have a long, segmented body to burrow easily. Their moist, slippery skin helps them breathe. Muscles and tiny bristles (setae) help them move and dig. They go deep into the soil and slow down in dry heat to save water. They also stay in the dark during the day, coming out at night.

🎯 Exam Tip: For each adaptation, clearly state the feature (e.g., streamlined body) and then explain how it helps the earthworm survive or function in its environment (its application).

 

Question 4. Describe layout of a Farm pond.
Answer: A farm pond is a man-made dugout structure designed to collect and store water for agricultural purposes. Here's a description of its layout:
1. Structure: It is a dug-out area in the ground with a specific shape and size. The pond's sides are usually sloped to prevent erosion and for stability.
2. Inlet and Outlet: Farm ponds are designed with proper inlet structures to collect surface runoff water from the surrounding farm area. They also have outlet structures to manage excess water, preventing overflow and damage.
3. Size and Depth: The dimensions (size and depth) of the pond are decided based on several factors:

• The amount of land available for digging the pond.
• The type of soil, which affects how well the pond can hold water and the stability of its banks.
• The water requirements of the farmers, which determines how much water needs to be stored.
• The cost of digging and constructing the pond.

4. Water Use: The water collected and stored in the farm pond is primarily used for irrigation of crops, especially during dry periods. It helps farmers manage water resources efficiently.
Farm ponds are an effective way to conserve rainwater and recharge groundwater.
In simple words: A farm pond is a dug-out area with a clear shape and size. It has pipes for water to flow in from the farm and out when it's full. Its size depends on the land, soil, how much water farmers need, and how much it costs to dig. The water collected is then used to water crops.

🎯 Exam Tip: When describing a farm pond, include its physical characteristics (dugout, shape, size), water management features (inlet/outlet), and the factors determining its design.

 

Question 5. What are all the strategies used to support water conservation?
Answer: Many strategies can be used to conserve water, helping us use this precious resource wisely:

• Rainwater Harvesting: Collecting and storing rainwater for later use, reducing reliance on other water sources.
• Improved Irrigation Techniques: Using efficient methods like drip irrigation or sprinklers to deliver water directly to plants, minimizing waste.
• Use of Traditional Water Harvesting Structures: Reviving old methods like check dams, tanks, and ponds to store water.
• Minimizing Domestic Water Consumption: Being mindful of water use in homes, such as taking shorter showers and turning off taps.
• Awareness on Water Conservation: Educating people about the importance of saving water and how to do it.
• Construction of Farm Ponds: Building small ponds on farms to collect rainwater and surface runoff for irrigation.
• Recycling of Water: Treating used water (like grey water) so it can be reused for non-drinking purposes, such as gardening or industrial cooling.

These strategies help ensure sustainable water management for current and future needs.
In simple words: To save water, we can collect rainwater, use better ways to water crops, use less water at home, tell others to save water, build farm ponds, and reuse old water.

🎯 Exam Tip: Provide a diverse list of strategies for water conservation, covering individual actions, technological improvements, and community-level initiatives.

 

Question 6. List out any five advantages of Farm ponds.
Answer: Farm ponds offer many benefits, especially for agriculture and local communities. Here are some of their advantages:

• They provide water for growing crops, allowing farmers to irrigate their fields even during dry spells or without waiting for the next rainfall.
• Farm ponds help reduce soil erosion by collecting surface runoff, preventing valuable topsoil from being washed away.
• They contribute to recharging groundwater levels as stored water slowly seeps into the ground.
• These ponds can improve drainage in agricultural fields by collecting excess water, thus preventing waterlogging.
• The soil dug out to create the pond can be used to enrich other fields or level uneven land on the farm.
• Farm ponds can be used for fish rearing, providing an additional source of income and food for farmers.
• They serve as a source of water for domestic purposes and for livestock, especially in areas with limited access to other water sources.

These benefits make farm ponds a valuable asset for sustainable farming.
In simple words: Farm ponds give water for crops, stop soil from washing away, fill up underground water, make drainage better, provide useful soil, help in raising fish, and give water for home use and animals.

🎯 Exam Tip: When listing advantages, try to cover different aspects: direct agricultural benefit (irrigation), environmental benefit (erosion control, groundwater), and socio-economic benefits (income, domestic use).