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?
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –
(a) 100 W (b) 75 W (c) 50 W (d) 25 W
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
(a) A convex lens of focal length 50 cm.
(b) A concave lens of focal length 50 cm.
(c) A convex lens of focal length 5 cm.
(d) A concave lens of focal length 5 cm.
What were the limitations of Döbereiner’s classification?
What effect does the concentration of H+(aq) ions have on the nature of the solution?
Which one of the following materials cannot be used to make a lens?
(a) Water (b) Glass (c) Plastic (d) Clay
How could the Modern Periodic Table remove various anomalies of Mendeléev’s Periodic Table?
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
Draw magnetic field lines around a bar magnet.
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
What are the components of the transport system in human beings? What are the functions of these components?