Ecology, Ecosystem and Functions of Ecosystem: UPSC Previous Year Questions (Environment and Ecology)

Explanation

Upwelling is a process in which deep, cold water of the ocean rises toward the surface. Winds blowing across the ocean surface push water away. Water then rises up from beneath the surface to replace the water that was pushed away. This process is known as "upwelling."

Statement 1 is incorrect: Decomposer microorganisms primarily reside in the deep ocean and play a role in breaking down organic matter. Upwelling does not bring decomposers to the surface. Most decomposition occurs at depth and decomposer microbes are not significantly transported to the surface by upwelling.

Statement 2 is correct: Upwelling regions bring nutrients like nitrogen, phosphorus, and iron from deep waters to the surface. These nutrients enhance phytoplankton growth which supports higher trophic levels such as fish and marine mammals. Major upwelling zones include the coasts of Peru, California, and West Africa. These regions contribute to high fishery productivity (Ex: Peru-vian anchovy fishery).

Statement 3 is incorrect: Bottom-dwelling (benthic) organisms such as crustaceans and mollusks are not brought to the surface by upwelling. Upwelling affects water movement but does not displace benthic creatures from the ocean floor.

Explanation

Tropical rainforests and tropical deciduous forests differ in their nutrient cycles, soil composition, and regeneration capacity. When a tropical rainforest is removed, it does not regenerate quickly because of the nutrient-poor soil. In tropical rainforests, the warm and humid conditions promote rapid decomposition of organic matter by bacteria and fungi. But due to the high density of plant life the nutrients released are immediately absorbed by plants leaving the soil infertile. In contrast the tropical deciduous forests have richer soils be-cause the leaf litter decomposes and replenishes soil nutrients more effectively. Options (b), (c) and (d) are incorrect:

Propagules (seeds, spores, or other reproductive structures) of rainforest trees generally have high viability. However, the regeneration of rainforests is hindered more by soil nutrient deficiencies than by the viability of propagules. Many rainforest species are fast-growing especially pioneer species that colonize disturbed areas. However, the lack of nutrients in the soil limits their growth and the overall regeneration of the forest. In rainforests slow regeneration is due to nutrient loss and not exotic/invasive species. If soils were fertile, native plants would recover quickly but rainforest soils are typically nutrient-poor which limits their regrowth.