Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ozone layer is formed of three oxygen atoms and known as the layer of protection which protects the earth from the UV rays. The photodissociation of ozone and generation are present in the equilibrium state. This ozone layer releases the energy of ultraviolet radiations as heat. So, ozone layer acts as the shield in the stratosphere which protect us from the harmful radiations. Decline in the thickness of the ozone layer over a restricted area is known as ozone hole. And, the chlorofluorocarbons are the main cause of the ozone depletion. CFCs are used as the coolants in refrigerators and air conditioners or as cleaning solvents etc. They get released into the troposphere and then they reach into the stratosphere and produce chlorine in the presence of the UV rays and these chlorine radicals does the ozone depletion by converting them into the oxygen.
This damage can be overcome by minimizing the release of chlorofluorocarbons. CFCs used as air conditioners or refrigerators should be replaced with environment friendly alternatives. Or CFCs released through the industries, should be controlled.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Give any two ways in which biodegradable substances would affect the environment.
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
If all the waste we generate is biodegradable, will this have no impact on the environment?
Why are some substances biodegradable and some non-biodegradable?
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
How can you help in reducing the problem of waste disposal? Give any two methods.
What is ozone and how does it affect any ecosystem?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What is the role of decomposers in the ecosystem?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
State Fleming’s left-hand rule.
Explain the importance of fossils in deciding evolutionary relationships.
What are fossils? What do they tell us about the process of evolution?
How is the equal genetic contribution of male and female parents ensured in the progeny?
What were the limitations of Newlands’ Law of Octaves?
In evolutionary terms, we have more in common with
(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium.
An example of homologous organs is
(a) our arm and a dog’s fore-leg.
(b) our teeth and an elephant’s tusks.
(c) potato and runners of grass.
(d) all of the above.
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
How are the areas of study – evolution and classification – interlinked?
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?