Our EnvironmentClass 10 Biology NCERT Solutions
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Q1Exercises
Which of the following groups contain only biodegradable items?
(a)
Grass, flowers and leather
(b)
Grass, wood and plastic
(c)
Fruit-peels, cake and lime-juice
(d)
Cake, wood and grass
Solution
The correct options are (a), (c), and (d) as all items listed in these groups are of natural origin and can be broken down by microorganisms.
- (a) Grass, flowers and leather: All are natural products and are biodegradable.
- (b) Grass, wood and plastic: Plastic is a non-biodegradable substance.
- (c) Fruit-peels, cake and lime-juice: All are food items and are biodegradable.
- (d) Cake, wood and grass: All are derived from plants and are biodegradable.
Since multiple options are correct, this question may be intended to identify the group that does not belong. Option (b) is the only one containing a non-biodegradable item.
Q2Exercises
Which of the following constitute a food-chain?
(a)
Grass, wheat and mango
(b)
Grass, goat and human
(c)
Goat, cow and elephant
(d)
Grass, fish and goat
Solution
The correct answer is (b) Grass, goat and human.
- A food chain shows a sequence of who eats whom.
- In option (b), grass is the producer, the goat (herbivore) eats the grass, and a human (omnivore) can eat the goat. This represents a valid flow of energy.
- Option (a) consists only of producers.
- Option (c) consists only of herbivores (primary consumers).
- Option (d) is incorrect because a goat does not eat fish.
Q3Exercises
Which of the following are environment-friendly practices?
(a)
Carrying cloth-bags to put purchases in while shopping
(b)
Switching off unnecessary lights and fans
(c)
Walking to school instead of getting your mother to drop you on her scooter
(d)
All of the above
Solution
The correct answer is (d) All of the above.
- (a) Carrying cloth bags reduces the use of plastic bags, which are non-biodegradable and cause pollution.
- (b) Switching off unnecessary lights and fans conserves electricity, which helps reduce the burning of fossil fuels and associated pollution.
- (c) Walking to school reduces the consumption of fuel and prevents air pollution from vehicle emissions.
Q4Exercises
What will happen if we kill all the organisms in one trophic level?
Solution
If we kill all the organisms in one trophic level, it will cause a serious imbalance in the ecosystem and disrupt the food web.
- The organisms in the subsequent (higher) trophic level will be deprived of their food source, leading to their starvation and death. Their population will decline drastically or they might migrate.
- The organisms in the preceding (lower) trophic level will experience a population explosion due to the removal of their predators. This overpopulation can lead to the depletion of their own food source, causing them to die of starvation eventually.
For example, if all the deer (primary consumers) in a forest are killed, the tigers (secondary consumers) will not have food and will die, while the grass (producers) might grow unchecked initially but could be affected by other factors later.
Q5Exercises
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Solution
Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels.
- Removing Producers (First Trophic Level): This would have the most catastrophic impact. Producers form the base of the food chain, converting solar energy into food. Their removal would mean no energy is available for any other trophic level, leading to the collapse of the entire ecosystem.
- Removing Primary Consumers (Herbivores): This would lead to the starvation and death of secondary and tertiary consumers. The producers would overgrow due to the lack of herbivores to eat them.
- Removing Top Consumers (Tertiary Carnivores): This would lead to a population increase in the secondary consumers (their prey). This, in turn, could cause a sharp decline in the population of primary consumers.
No, the organisms of any trophic level cannot be removed without causing any damage to the ecosystem. Every trophic level plays a vital role in maintaining the flow of energy and the balance of nature. The removal of any level will lead to an imbalance and can cause irreversible damage.
Q6Exercises
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Solution
Biological magnification (or biomagnification) is the phenomenon where the concentration of certain harmful, non-biodegradable chemicals, such as pesticides, increases progressively at each successive trophic level in a food chain.
These chemicals are not metabolized or excreted by organisms; instead, they get accumulated in their fatty tissues. When an organism is eaten by another, these accumulated chemicals are passed on to the next trophic level.
Yes, the levels of this magnification will be different at different levels of the ecosystem. The concentration of the harmful chemical is lowest at the producer level and increases at each subsequent level. Therefore, the top-level consumers, such as humans or large carnivores, will have the highest concentration of these chemicals accumulated in their bodies, which can be highly toxic.
Q7Exercises
What are the problems caused by the non-biodegradable wastes that we generate?
Solution
The non-biodegradable wastes that we generate cause several environmental problems:
- Land and Water Pollution: Since these wastes, like plastics and glass, do not decompose, they persist in the environment for very long periods. They accumulate in landfills, taking up valuable land space, and pollute the soil. When washed into rivers and oceans, they cause water pollution.
- Harm to Wildlife: Animals can mistake plastic waste for food and ingest it, leading to internal injuries, choking, and death. They can also get entangled in plastic debris, which can cause injury and drowning.
- Clogging of Drains: Waste materials like plastic bags and wrappers can block sewage and drainage systems, leading to waterlogging, especially during heavy rains, and providing breeding grounds for disease-carrying insects like mosquitoes.
- Biological Magnification: Harmful non-biodegradable chemicals like pesticides can enter the food chain and accumulate at higher trophic levels, causing health issues in animals and humans.
Q8Exercises
If all the waste we generate is biodegradable, will this have no impact on the environment?
Solution
No, even if all the waste we generate is biodegradable, it would still have an impact on the environment, especially if produced in large quantities. The impacts include:
- Air Pollution: The process of decomposition by microorganisms is slow and can release large amounts of foul-smelling and harmful gases, such as methane (a potent greenhouse gas) and hydrogen sulphide, into the atmosphere.
- Water Pollution: If biodegradable waste is disposed of in water bodies, the bacteria and other microorganisms involved in decomposition will consume a large amount of dissolved oxygen. This rapid depletion of oxygen can lead to the death of fish and other aquatic organisms, a process known as eutrophication.
- Resource Consumption: Generating large amounts of biodegradable waste still implies the consumption of resources. For example, large-scale paper waste means a high rate of deforestation.
Q9Exercises
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Solution
Damage to the ozone layer is a major cause for concern because this layer, located in the stratosphere, protects life on Earth by absorbing most of the harmful ultraviolet (UV) radiation from the sun. The depletion of the ozone layer allows more UV radiation to reach the Earth's surface, which can lead to severe consequences:
- Increased incidence of skin cancer and cataracts in humans.
- Damage to the immune system in humans and animals.
- Harm to plant life, including crops, by affecting photosynthesis.
- Disruption of aquatic ecosystems by harming phytoplankton, which are at the base of the aquatic food web.
Steps being taken to limit this damage:
The international community has taken significant steps to address this issue. The most prominent step is the Montreal Protocol, an international treaty signed in 1987 under the United Nations Environment Programme (UNEP). This agreement aims to phase out the production and consumption of ozone-depleting substances, such as chlorofluorocarbons (CFCs), which were widely used in refrigerants and aerosol sprays. As a result of this protocol, it is now mandatory for manufacturing companies worldwide to produce CFC-free refrigerators and other products.
Q1In-text Questions 1
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Solution
Trophic levels are the various steps or levels in a food chain at which the transfer of food or energy takes place.
An example of a simple food chain is:
Grass → Deer → Lion
In this food chain, the different trophic levels are:
- First Trophic Level: Grass (Producer) - They produce their own food using sunlight.
- Second Trophic Level: Deer (Primary Consumer/Herbivore) - They feed on the producers.
- Third Trophic Level: Lion (Secondary Consumer/Carnivore) - They feed on the primary consumers.
Q2In-text Questions 1
What is the role of decomposers in the ecosystem?
Solution
Decomposers, such as bacteria and fungi, play a crucial role in the ecosystem. Their primary functions are:
- Decomposition: They break down the complex organic substances present in dead organisms (plants and animals) and their waste products into simple inorganic substances.
- Nutrient Recycling: By breaking down organic matter, they release essential nutrients back into the soil, water, and air. These nutrients are then available to be used again by producers (like plants). This process is vital for the natural replenishment of the soil and the continuation of life cycles in the ecosystem.
In the absence of decomposers, dead remains and waste would pile up, and the nutrients locked within them would not be returned to the ecosystem, eventually halting the flow of life.
Q1In-text Questions 2
Why are some substances biodegradable and some non-biodegradable?
Solution
The ability of a substance to be broken down by biological processes determines whether it is biodegradable or non-biodegradable. This process is carried out by microorganisms which secrete specific enzymes.
-
Biodegradable substances: These are substances that can be broken down by the action of microorganisms like bacteria and fungi. This is because these microorganisms have the specific enzymes required to digest and decompose these materials (e.g., paper, kitchen waste, cotton). These materials are typically of natural origin.
-
Non-biodegradable substances: These are substances that cannot be broken down by microorganisms. This is because the microorganisms lack the specific enzymes needed to act on these materials. Many human-made materials, such as plastics, glass, and metals, fall into this category. They persist in the environment for a very long time.
Q2In-text Questions 2
Give any two ways in which biodegradable substances would affect the environment.
Solution
Two ways in which biodegradable substances can affect the environment are:
- Pollution through Decomposition: When biodegradable waste decomposes in large quantities, it can produce foul smells and release harmful gases like methane () and hydrogen sulphide (), which contribute to air pollution.
- Water Pollution: If large amounts of biodegradable waste are dumped into water bodies, the microorganisms that decompose this waste will use up a significant amount of dissolved oxygen from the water. This reduction in oxygen can harm or kill aquatic organisms like fish.
Q3In-text Questions 2
Give any two ways in which non-biodegradable substances would affect the environment.
Solution
Two ways in which non-biodegradable substances can affect the environment are:
- Land and Water Pollution: Since these substances do not decompose, they persist in the environment for thousands of years. They accumulate in landfills, pollute soil, and can clog drainage systems. When they find their way into water bodies, they cause water pollution and can harm aquatic life.
- Biological Magnification: Certain non-biodegradable chemicals, like pesticides (e.g., DDT), can enter the food chain. Their concentration increases at each successive trophic level. This phenomenon, known as biological magnification, can lead to harmful levels of these chemicals in top consumers, including humans, causing various health problems.
Q1In-text Questions 3
What is ozone and how does it affect any ecosystem?
Solution
Ozone () is a molecule formed by three atoms of oxygen. While it is a deadly poison at ground level, it performs an essential function at higher levels of the atmosphere.
In the stratosphere, ozone forms a protective layer that shields the Earth's surface from most of the harmful ultraviolet (UV) radiation coming from the Sun. This protection is crucial for ecosystems because high-energy UV radiation is highly damaging to living organisms. It can cause skin cancer and cataracts in humans, damage eyesight, and harm plants and other aquatic life, thereby disrupting entire ecosystems.
Q2In-text Questions 3
How can you help in reducing the problem of waste disposal? Give any two methods.
Solution
We can help reduce the problem of waste disposal in the following two ways:
- Segregation of Waste: We can separate our household waste into biodegradable and non-biodegradable categories. Biodegradable waste (like kitchen scraps) can be composted to create manure for plants. Non-biodegradable waste (like plastic, glass, and metal) can be sent for recycling.
- Practicing the 3 R's (Reduce, Reuse, Recycle):
- Reduce: Minimize the use of disposable items. For example, using a cloth bag for shopping instead of plastic bags.
- Reuse: Use items again instead of throwing them away. For example, using empty jars to store kitchen items.
- Recycle: Ensure that recyclable materials like paper, plastic, and glass are collected and sent to recycling facilities.