Human activities in the recent past have caused the increased concentration of carbon dioxide in the atmosphere, but a lot of it does not remain in the lower atmosphere because of 1. its escape into the outer stratosphere. 2. the photosynthesis by phytoplankton in the oceans. 3. the trapping of air in the polar ice caps. Which of the statements given above is/are correct?

If a tropical rain forest is removed, it does not regenerate quickly as compared to a tropical deciduous forest. This is because

Consider the following: 1. Photosynthesis 2. Respiration 3. Decay of organic matter 4. Volcanic action. Which of the above add carbon dioxide to the carbon cycle on Earth?

Biodiversity forms the basis for human existence in the following ways: 1. Soil formation 2. Prevention of soil erosion 3. Recycling of waste 4. Pollination of crops