Class 10 Biology Chapter 5 - Our environment Important Questions
Class 10 Biology Chapter 5 - Our environment Important Questions
Most important questions:-
Question 1.
Why is the maximum concentration of pesticides found in human beings?
Answer:
The pesticides are not biodegradable, they get accumulated progressively at each trophic level. As human beings occupy the topmost level in food chain, their concentration becomes maximum in our bodies.
Question 2.
Give one method which could be applied to reduce our intake of pesticides through food to some extent.
Answer:
By using biological methods for controlling insects in fields and by washing fruits and vegetables before eating could help to reduce our intake of pesticides through food to some extent.
Question 3.
Various steps in a food chain represent:
(a) food web
(b) trophic level
(c) ecosystem
(d) biomagnification.
Answer:
(b) trophic level
Question 4.
What is an ecosystem?
Answer:
An ecosystem is defined as a structural and functional unit of the biosphere. It comprises of living organisms and their non-living environment that interact by means of food chains and biogeo-chemical cycles resulting in energy-flow, biotic diversity and material cycling to form stable self-supporting system.
Question 5.
Why is a lake considered to be a natural ecosystem?
Answer:
Lake is an ecosystem where living organisms grow, reproduce and interact among each other as well as with abiotic components and carry out other activities in nature by themselves without any human interference, therefore it is referred to as a natural ecosystem.
Question 6.
List two biotic components of a biosphere.
Answer:
Two biotic components of a biosphere are:
(i) Producers – Include organisms which can produce their food using simple inorganic compounds, e.g., all green plants, blue green algae (cyanobacteria).
(ii) Consumers – Include organisms which are unable to synthesise their food, therefore, utilise materials and energy stored by the producers or eat other organisms, e.g., all the animals.
Question 7.
Why are green plants called producers?
Answer:
Green plants are called producers because they manufacture their own food with the help of CO2 and H2O in the presence of sunlight and chlorophyll
Question 8.
In a food chain, if 10,000 joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer?
Answer:
According to ten percent law, 10% of the energy of producer will be available to primary consumer, and 10% of this energy will be available to secondary consumer and so on.
Hence, 100 J of energy will be available to the secondary consumer to transfer it to tertiary level.
Question 9.
What is meant by biological magnification?
Answer:
Biological magnification or biomagnification refers to the process of accumulation of non- biodegradable chemicals (pesticides, etc.) into the body of organisms through the food chain which go on increasing in its concentration at each trophic level.
Question 10
Give an example to illustrate that indiscriminate use of pesticides may result in the degradation of the environment.
Answer:
Pesticides are the chemicals used to kill plant and animal pests. They are non-biodegradable and toxicants. For example, excessive use of DDT resulted in reduced population of fish eating birds. DDT accumulated in such birds through the food chain. It interfered with the egg shell formation. The shell being thin broke due to weight of the bird during incubation. Hence, their population declined.
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