Chapter 15. Our Environment | CBSE Class 10th Science | Solved Exercises
Why are some substances biodegradable and some non-biodegradable?
Answer. Substances which can be decomposed and broken down to simpler substances by microorganisms acting on it is called bio-degradable and those substances which cannot be acted upon by micro-organisms and are not broken down into simpler
substances are called non-biodegradable substance.
Give any two ways in which biodegradable substances would affect the environment.
Answer.
Two ways in which biodegradable substances would affect the environment are
(i) During decomposition of the substances lot of foul smell spreads in the surrounding areas.
(ii) The place where these bio-degradable substance are present with some moisture becomes breeding ground for insects like mosquitoes, housefly which are vectors in carrying parasites that cause different diseases.
or
(i) The non-biodegradable substance gets accumulated and doesn't get decomposed hence it remains in the ecosystem and causes pollution, chokes the system of many animals and kill them.
(ii) These Substances due to accumulation cause water and soil pollution e.g.,pesticides, detergents, polythene.
Question 3. Give any two ways in which non-biodegradable substances would affect the environment
Answer. The non-biodegradable substances affect the environment in the following ways:
- They persist in the environment for a long time and thus damage the environment.
- Such substances cause land pollution and water pollution.
Chapter 15. Our Environment | CBSE Class 10th Science | Solved Exercises
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer. A trophic level is the level of species in an ecosystem on the basis of the source of nutrition such as producers, primary consumers, secondary consumers, etc.
The producers form the first trophic level as they manufacture food. The primary consumers form the second trophic level, the secondary consumers form the third, and the tertiary consumers form the fourth trophic level.
Trophic levels :Various
trophic levels are connected through
food chains. For example, in an aquatic food chain, phytoplanktons are the producers, zooplanktons are the primary consumers, and small fish is the secondary consumer and so on.
Aquatic food chain
What is the role of decomposers in the ecosystem?.
Answer. The decomposers break down the complex organic substances into simple inorganic substances that go into the soil. These are used up once more by the plants. Natural replenishment of soil nutrients takes place like this. Decomposers are natural scavengers. They clean the world of all dead things.
or
Decomposers decompose dead remains of plants and animals. By doing so, they serve two purposes. One; they reduce the burden on the environment by clearing dead remains. Two; they channelize the raw materials back to the environment.
or
Decomposers break down the complex organic substances like plant's and animal's dead body and convert them into simpler inorganic substances.
All the elements that are present in the body on which decomposers act is released back to the nature. Decomposers maintain balance in the nature and plays an important role in the environment.
Chapter 15. Our Environment / CBSE Class 10th Science /
What is ozone? How does it affect any ecosystem?
Answer.
Ozone is a molecule formed by three atoms of oxygen (O3). Ozone is a deadly poison. At higher levels of atmosphere it shields the surface of the earth from ultraviolet radiation from the sun. This radiation is highly damaging to organisms. In humans it causes skin cancer.
Or
Ozone is a form of oxygen. Ozone is a triatomic molecule while oxygen is a diatomic molecule. Ozone forms the ozone layer in our atmosphere. Ozone plays an important role in the ecosystem. The ozone layer wards off harmful ultraviolet radiations from the sun and thus protects the living beings
.
How can you help in reducing the problem of waste disposal? Give any two methods.
Answer.
The problem of waste disposal can be reduced in many ways. Two methods are given below:
By using more of biodegradable substances and reducing the use of non-biodegradable substances. For example; instead of plastic bags, one should carry jute bags or cloth bags for shopping.
By proper segregation of waste before disposing.
or
Every individual should play a role in reducing the problem of
waste disposal. They can do that by-
(i) Improved packing methods.
(ii) Increased use of disposable items.
(iii) Use of compost in the field.
or
1.Reduce the usage of non-biodegradable products such as plastics.
2.Make a compost pit for decomposing biodegradable waste.
or
Reduce the usage of non-biodegradable products such as plastics. Also use the plastics for other purposes .Make a compost pit for decomposing biodegradable waste. 3. Use different bins for different materials. Segregation of waste following the 3R 's-reduce, reuse, recycle.
or
Plastic is found in virtually everything these days. Your food and hygiene products are packaged in it. Your car, phone and computer are made from it. And you might even chew on it daily in the form of gum.
Chapter 15. Our Environment / CBSE Class 10th Science / Solved Exercises
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
Answer. (c) (d).
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
Answer. (b)
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
Answer. (d)
What will happen if we kill all the organisms in one trophic level?
Answer.
if we kill all the organisms in one trophic level it will adversly affect the food chain leading to ecological imbalance
for eg : grass ----------------> deer --------------> lion
in the given food chain if we kill all the deer than the numer of grass (autotrophs ) will increase as there would be no deer to feed on it whereas all the lions will die one by one as now they don 't have deer to feed upon.
so removal of all the organisms from one trophic level leads to increase in the number of organisms in the previous trophic level whereas decrease , resulting in perishing away of the organisms of the successive trophic level.
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?
Answer.
Removal of all the organisms of a trophic level will affect the entire ecosystem of that area. Its impact on different trophic levels will be different because of the organisms of a trophic level are directly dependent on them while the organisms of other trophic level are indirectly depend on them for their food. For example, killing of herbivores will increase the number of carnivores and killing of carnivores will increase the number of herbivores. Most of the organisms will die of starvation.
or
The impact of removing all the organisms in a trophic level shall be similar for different trophic levels; although their manifestations can be different. Organisms of any trophic level cannot be removed without causing any damage to the ecosystem. The examples of lions and deer in the previous answer illustrate this.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer.
The accumulation of a particular substance through different trophic levels is called biological magnification. Let us take example of lead poisoning which may affect plants because of water pollution. The level of lead would be at a particular level in plants. When an herbivore would eat these plants, the level of lead shall be more in the body of herbivore because it would eat a large number of plants. When this herbivore would be eaten by a carnivore, the level shall rise further because the carnivore would at a large number of herbivores. Hence, the level of this magnification will increase as we move to higher trophic levels.
or
Biological magnification, also known as biomagnification or bioamplification, explains why a substance appears in higher concentrations in organisms higher in a given food chain than in organisms lower in a food chain. This happens because creatures high up in the food chain, such as predators, feed on creatures that are lower in the food chain and absorb the substances from the organisms they consume in addition to the substances they directly absorb from the environment. In some cases, the process of biological magnification can be harmful to the organisms that are high in a food chain because they absorb harmful substances from all of the organisms they consume.
While the tiny amounts absorbed from the environment could be completely harmless, the amounts consumed from food sources could add up and be harmful.
What are the problems caused by the non-biodegradable wastes that we generate?
Answer. The problems are caused when we don't recycle these non-biodegradable wastes. Without recycling, the raw material resources that went into this product are considered "used" with no renewable action. Therefore the resources are lessened by these products and ultimately we will run out of the resource.
However, with our current technology, and developing technologies, it is within our grasp to convert these wastes into new resources. Therefore the problems may be temporary.
Ah, back to the question, so we have dwindling resources because of this, and we also then have waste that is occupying space and having an effect on the environment around the space it is occupying.
I can't get more specific than that unless you specify which non-biodegradable waste you mean. Mercury? Metals? Plastics?
If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer.
If all the waste we generate is biodegradable, this would also have an impact on the environment but most of the impacts would be positive. After decomposition, the biodegradable substance produces different raw materials which are sent back to the ecosystem. The solid remains would add to the humus content of soil.
There can be some negative impacts; like obnoxious smell which is created during the process of decomposition. There can also be a possibility of sparking an epidemic if the waste is dumped near a residential area or is allowed to contaminate the water bodies. So, it is not the biodegradable waste which is going to create the problem, rather the way we dispose it.
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer. Ozone layer works like a protective shield for living beings. The ozone layers wards off harmful ultraviolet radiations from the sun. Damage to the ozone layer can result in increased level of ultraviolet radiations in our atmosphere. This would be very dangerous for all life forms.
In 1987, the UNEP (United Nations Environment Programme) succeeded in forging an agreement among different nations to freeze the CFC production at 1986 level. Later, an agreement was signed among different nations to phase out CFCs. It is important to note that CFC is used in refrigerators and aerosol spray. India is also a signatory of that agreement and thanks to the efforts by the United Nations and different environmentalists, the CFC emission has been put under some control.
