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

Explanation

Millennium Ecosystem Assessment (MA) was initiated in 2001 by the United Nations. The objective of the MA was to evaluate how changing ecosystems might affect human well-being as well as the scientific foundation for any necessary action to improve the systems’ conservation and sustainable us-age, as well as their contribution to human well-being. Ecosystem services to the society are in the form of:

1. Provisioning services: food, raw materials, genetic resources, water, etc

2. Regulating services: carbon sequestration and climate regulation

3. Cultural services: tourism and religion

4. Supporting services: that are necessary for the production of all other ecosystem services such as nutrient recycling, crop pollination and soil formation, etc.

Explanation

Phytoplanktons are the primary producers in the marine food chain and hence they are called the ‘grass of the sea’. They contribute more than half of the oxygen in the environment and help in reducing global warming by absorbing human-in-duced carbon dioxide. They are important bioindicators regulating life in oceAns:

Statements 1 is correct: If phytoplankton are destroyed then less CO₂ will be absorbed thereby increasing atmospheric carbon and contributing to global warming. Phytoplankton are responsible for carbon fixation through photosynthesis. They absorb CO₂ from the atmosphere and convert it into organic matter. When phytoplankton die, some of this carbon sinks to the ocean floor, sequestering it for long periods. Statements 2 is correct: Phytoplankton are the primary producers in marine ecosystems forming the base of the food web. They are consumed by zooplankton which in turn are eaten by larger organisms like fish, marine mammals, and seabirds. The destruction of phytoplankton would disrupt the entire marine food chain and can lead to the collapse of fisheries and the decline of marine biodiversity.

Statement 3 is incorrect: The density of ocean water is primarily determined by temperature and salinity and not by the presence of phytoplankton. While phytoplankton can slightly affect water properties through their metabolic activities but their destruction would not cause a drastic decrease in ocean water density.