Rajasthan Board RBSE Solutions for Class 10 Science Chapter 15 Our Environment Textbook Exercise Questions and Answers.
RBSE Class 10 Science Solutions Chapter 15 Our Environment
RBSE Class 10 Science Chapter 15 Our Environment InText Questions and Answers
What are trophic levels ? Give an example of a food chain and state the different trophic levels in it.
Trophic level Autotrophs or green plants prepare their own food using solar energy. These green plants are eaten by herbivores and these herbivores are then eaten by carnivores. This series or organisms taking part at various biotic levels form a food chain. Each step or level of the food chain forms a trophic level.
One food chain is as follows: Grass Grasshopper Chameleon Eagle There are four trophic levels in this food chain.
- First trophic level: It is grass, which is autotrophs and called primary producer.
- Second trophic level: It is grasshopper which is heterotrophs and called primary consumer.
- Third trophic level: It is chameleon, which is carnivore and called secondary consumer.
- Fourth trophic level: It is eagle, which is carnivore and called tertiary consumer.
What is the role of decomposers in the ecosystem ?
Decomposers have a special role in the ecosystem. Bacteria and other micro-organisms acts as decomposers in the ecosystem. They attack the dead plants and animals and convert complex organic material into simple substances. Similarly, waste such as vegetable peels and fruit peels, animal excreta and dead parts of plants are decomposed by decomposers. In this way decomposers help in recycling these material and make environment clean.
Why are some substances biodegradable and some non – biodegradable?
Some substances are biodegradable and some are non – biodegradable because micro – organisms like bacteria and fungi have an important role in this. They can only decompose natural substances such as paper, wood, etc. but many human made materials like plastics will not be broken down by the action of bacteria or other saprophytes, therefore, some substances are biodegradable and some are non – biodegradable.
Give any two ways in which biodegradable substances would affect the environment.
The two ways in which biodegradable substances would affect the environment are
- They decompose easily, hence, keeping the environment clean.
- With the help of decomposers, they are easily incorporated into the geochemical cycle and become available again.
Give any two ways in which non- biodegradable substances would affect the environment.
The two ways in which non – biodegradable substances would affect the environment are
- Useful herbicides, pesticides and insecticides, etc. are used to increase agricultural yield. These chemicals flow into the soil and water bodies and pollute them.
- These substances become bio – magnified in the food chain and ultimately affect humans.
What is ozone and how does it affect any organism?
Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation coming from the sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings.
How can you help in reducing the problem of waste disposal? Give any two methods.
We can contribute in the following way in reducing the problems of waste material.
- Reuse of non – biodegradable waste materials after recycling. Like plastic metals etc.
- iodegradable waste materials like kitchen wastes, remaining material after cooking food, leaves etc. can be put into deep pits in the ground and be left for natural breakdown. After some time it will convert into compost manure, by this the plants could get the high quality of manure.
RBSE Class 10 Science Chapter 15 Our Environment Textbook Questions and Answers
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.
In (a), (c) and (d).
Which of the following constitue a food chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat.
(b) Grass, goat and human.
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
(d) All of the above.
What will happen if we kill all the organisms in one trophic level?
If we kill all the organisms in one trophic level there will be an end of food chain and ecosystem balance would be effected. In nature all food chains are interlinked to each other. If we destroy any one stage (trophical level) of food chain, the number of organisms will increase in previous tropical level and due to non availability of food the number will be decreased in post stage of food chain. For example:
- If herbivores are destroyed, carnivores will be unable to get food and will die.
- If carnivores are destroyed of a trophic level, herbivores will increase in number causing overcrowding. This results in competition and consequently number of producers once again decreases to near normal.
- If we destroy the producers of a trophic level, the cycle of nutrient element of that area will not be completed.
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?
No, if organisms of any trophic level are removed all organisms of pre and post trophic level will be effected. All trophic level will be affected fast in beginning and slowely afterwards. No, organisms of any trophic level can not be removed without causing any damage to the ecosystem because in nature all food chains are linked together.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Biological magnification Non – biodegradable pesticides like DDT are mostly used for protecting the crops. Once they enter in food chain then gradually increase their concentration in each trophic level (steps of food chain). As a result after long duration these compounds are accumulated in the body of top consumer. Progressive increases in the concentration of harmful non – biodegradable substances at successive trophic level of a food chain is called biological magnification. Yes, the level gradually increases. It is lowest at producer level but highest in top consumers, like human.
What are the problems caused by the non – biodegradable wastes that we generate?
The non – biodegradable waste that we generate develop the following problems:
- Non – biodegradable substances are not degraded by microorganisms.
- Disposing of their increasing quality is a serious problem.
- Non – biodegradable waste cause water pollution and water can not be used for drinking purpose.
- Due to this waste the flow of water in river – drainage will be stopped.
- Eating the plastic bags by animals results in death.
- Soil will not be suitable for agriculture and its productivity will be reduced.
- By the entrance of non – biodegradable chemicals in food chain will develop different diseases in human beings. For examples in cow milk and mother’s milk there is the presence of high concentration of DDT, which develop various defects in newly bom babies.
- The balance of ecosystem will be destroyed.
If all the waste we generate is biodegradable, will this have no impact on the environment?
If all the waste we generate in biodegradable its disposal will be easy. Biodegradable materials are easily decomposed by microorganisms. These wastes do not persist for a long time. But if their quantity increases then many problems will arise, such as
- Since their decomposition is a slow process, so this process evolves poisonous and toxic gases which have harmful effect of organisms.
- Increase in their quantity will results in the increase in the number of harmful microorganisms which will have adverse effect on organisms.
- Such substances can flow with water into the reservoirs where they will act as nutrients, which will increase the number of aquatic animals and will have adverse effect on other organisms.
Why is damage to the ozone layer a cause of concern? What steps are being taken to limitise this damage?
The ozone layer present in the atmosphere of the earth check the harmful ultraviolet rays of sun coming on the surface of the earth. Refrigeration, air conditioners, puring solvents, fire extinguishers and aerosol (perfume, insecticides, medicines, spray etc. used in boxes) emmit chemicals like chlorofluorocarbons (CFCs) which harms the ozone layer.
The depletion of ozone layer may cause the following danger:
- Skin cancer, skin abscission, black face, cataract, cancer of eye retina etc.
- Genetical defect.
- Loss in productivity of sea and forests.
For controlling the depletion of ozone layer, in 1987 the united nations environment programme (UNEP) succeeded in forgoing an agreement to keep the production of CFCs at the level of 1986.