Download App

Environmental Issues — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYEnvironmental Issues4 Marks
Question
What is Green House Effect? How is smog formed?
✓

Answer

Green House Effect: Energy from the Sun that makes its way to Earth can have trouble finding its way back out to space. The greenhouse effect causes some of this energy to be way laid in the atmosphere, absorbed and released by greenhouse gases. Without the greenhouse effect, Earth's temperature would be below freezing. It is, in part, a natural process. However, Earth's greenhouse effect is getting stronger as we add greenhouse gases to the atmosphere. That is warming the climate of our planet.
Solar energy absorbed at Earth's surface is radiated back into the atmosphere as heat. As the heat makes its way through the atmosphere and back out to space, greenhouse gases absorb much of it. Why do greenhouse gases absorb heat? Greenhouse gases are more complex than other gas molecules in the atmosphere, with a structure that can absorb heat. They radiate the heat back to the Earth's surface, to another greenhouse gas molecule, or out to space.
There are several different types of greenhouse gases. The major ones are carbon dioxide, water vapour, methane, and nitrous oxide. These gas molecules all are made of three or more atoms. The atoms are held together loosely enough that they vibrate when they absorb heat. Eventually, the vibrating molecules release the radiation, which will likely be absorbed by another greenhouse gas molecule. This process keeps heat near the Earth's surface. Most of the gas in the atmosphere is nitrogen and oxygen, which cannot absorb heat and contribute to the greenhouse effect.
Image
Common Greenhouse Gases
Carbon Dioxide : Made of one carbon atom and two oxygen atoms, carbon dioxide molecules make up a small fraction of the atmosphere, but have a large effect on climate. There was about 270 parts per million volume (ppmv) of carbon dioxide in the atmosphere in the mid- 19th Century at the start of the Industrial Revolution. The amount is growing as burning fossil fuels releases carbon dioxide into the atmosphere. There is about 400 parts per million volume (ppmv) now.
Methane : A powerful greenhouse gas, able to absorb far more heat than carbon dioxide, methane is made of one carbon and four hydrogen atoms. It is found in very small quantities in the atmosphere but is able to make a big impact on warming. Methane gas is also used as a fuel. When burned, it releases carbon dioxide greenhouse gas into the atmosphere.
Smog : Smog is a kind of air pollution, originally named for the mixture of smoke and fog in the air. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulphur dioxide. Ozone can be helpful or harmful. The ozone layer high up in the atmosphere protects us from the sun's dangerous ultraviolet radiation. But when ozone is close to the ground, it is bad for human health. Ozone can damage lung tissue, and it is especially dangerous to people with respiratory illnesses like asthma. Ozone can also cause itchy, burning eyes. Smog is unhealthy to humans and animals, and it can kill plants. Smog is also ugly. It makes the sky brown or gray. Smog is common in big cities with a lot of industry and traffic.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "4 Marks Questions" from Environmental Issues→Environmental Issues — all question types→BIOLOGY STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

Give reasons why:
Most zygotes in angiosperms divide only after certain amount of endosperm is formed.
→
Explain in detail the various reagents of pollination.###How many types of pollination are there? Write a brief note and explain any one abiotic factor of pollination with an example.
→
For selection of recombinants, insertional inactivation of antibiotic marker has been superceded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons.
→
How is sex determined in human beings?
→
Compare the characteristic features of insect pollinated and wind pollinated flowers. Explain how the respective features assist in pollination.
→
What is meant by the term bio-pesticide? Name and explain the mode of action of a popular bio-pesticide.
→
Give the term/ reason:
Sperm cannot reach ovum without seminal plasma.
→
During her tour to a renowned forest, Sakshi saw a highway being constructed, which passes through the middle of the forest. She was unhappy seeing that and on return, she contacted the local eco-club and approached the concerned department to stop the work.
  1. What would be the effect on biodiversity, if the highway is constructed?
  2. How forests are useful to mankind?
  3. What values of Sakshi reflect here?
→
With a neat diagram explain the 7-celled 8-nucleate nature of the female gametophyte.
→
  1. State one difference and one similarity between geitonogamy and xenogamy.
  2. Explain any three devices developed in flowering plants to discourage self pollination and encourage cross-pollination.
→