Shankar IAS Test: Functions Of Ecosystem - UPSC

• The consumers which start the food chain, utilising the plant or plant part as their food, constitute the grazing food chain.

• This food chain begins from green plants at the base and the primary consumer is a herbivore.

The first statement is correct, but the second statement is incorrect.

Explanation:

An ecosystem consists of several interrelated food chains, and these food chains can be interconnected to form a complex network of feeding relationships called a food web. The food web shows how different organisms in an ecosystem are interconnected through their feeding relationships.

Therefore, the first statement is correct as an ecosystem may consist of several interrelated food chains.

The second statement is incorrect as the food web does not trace only one pathway of the food. In fact, the food web shows all the possible feeding relationships in an ecosystem, including the different pathways of the food. The food web is a more accurate representation of the feeding relationships in an ecosystem as it takes into account the complexity of the interactions between different organisms.

Therefore, the correct answer is only statement 1 is correct.

Pyramid of numbers:

• It depicts the numbers of individual organisms at different trophic levels of the food chain.
• It is helpful to calculate the changes observed in the number of organisms in each trophic level.
• An upright pyramid of numbers, the number of individuals decreases from the lower level to the higher level.
• This type of pyramid is usually found in the grassland ecosystem and the pond ecosystem.
• The grass in a grassland ecosystem occupies the lowest trophic level because of its abundance  
• We can identify which level is in the endangered zone and need to be saved. But its limitation is we cannot count a number of all organisms accurately.

Both statements are correct.

1. In a pyramid of biomass, the weight (biomass) of all individuals in each trophic level is considered instead of counting the number of individuals. This gives a more accurate representation of the energy available in each trophic level, as larger organisms typically have more energy stored in their tissues.

2. The pyramid of biomass is structured with producers at the bottom, representing the largest amount of biomass in the ecosystem. Producers (e.g., plants) convert sunlight into energy through photosynthesis and form the base of the food chain. As energy transfers up the trophic levels through consumption, energy is lost in the form of waste and heat, resulting in a decrease in biomass as you move up the pyramid. This is why the biomass of producers is at the bottom of the pyramid, as they represent the largest amount of available energy in the ecosystem.

The correct answer is 1, 2, 3 and 4.
Key Points

• ​Mangroves are the characteristic littoral plant formation of tropical and subtropical sheltered coastlines.
• Mangroves are trees and bushes growing below the high water level of spring tides which exhibits a remarkable capacity for saltwater tolerance.
• They are basically evergreen land plants growing on sheltered shores, typically on tidal flats, deltas, estuaries, bays, creeks and barrier islands.
• Mangroves have many special features for adapting to such a stressful coastal environment.
• Mangroves occur in a variety of configurations.
• Some species (e.g. Rhizophora) send arching prop roots down into the water.
• While others (e.g. Avicennia) send vertical Pneumatophores or air roots up from the mud.
• Most mangrove vegetation has lenticellate bark which facilitates more water loss, produces coppices.
• Mangroves exhibit a Viviparity mode of reproduction. i.e. seeds germinate in the tree itself (before falling to the ground).
• This is an adaptative mechanism to overcome the problem of germination in saline water.
• Some secrete excess salt through their leaves and some others block absorption of salt at their roots.
• The roots of some mangrove species (e.g. Bruguiera gymnorrhiza, Kandelia obovata) form into "knees" that project above the mud surface to facilitate gaseous exchange.
• Salt glands are present in the leaves of some mangrove species (e.g. Aegiceras corniculatum).
• Salt glands are used to concentrate and actively excrete the absorbed salts so as to regulate the salt concentration inside the mangroves.

• In bioaccumulation, there is an increase in the concentration of a pollutant from the environment to the first organism in a food chain. In biomagnification, there is an increase in the concentration of a pollutant from one link in a food chain to another.

• For biomagnification to occur, the pollutant must be long-lived, mobile, soluble in fats', biologically active. If the pollutant is soluble in water, it will be excreted by the organism. Pollutants that dissolve in fats, however, may be retained for a long time. E.g. DDT

• If a pollutant is not active biologically, it may biomagnify, but we really don't worry about it much, since it probably won't cause any problems Examples: DDT.

• Mutualism is defined as an interaction between individuals of different species that results in positive (beneficial) effects on per capita reproduction and/or survival of the interacting populations.

•  

  Commensalism is a long-term biological interaction in which members of one species gain benefits while those of the other species neither benefit nor are harmed.

In any particular environment, the nutrient cycle must be balanced and stable if the organisms that live in that environment are to flourish and be maintained in a constant population

A nutrient cycle is defined as the cyclic pathway by which nutrients pass-through, in order to be recycled and reutilised. The pathway comprises cells, organisms, community and ecosystem.
Hence both statements are correct.

All of the statements about the Carbon Cycle are correct.

Explanation:

The carbon cycle is the process by which carbon is cycled through various stages in the ecosystem. The cycle includes both atmospheric and sedimentary components.

The first statement is correct as carbon from the atmosphere moves to green plants by the process of photosynthesis, and then to animals. During photosynthesis, plants absorb carbon dioxide from the atmosphere and convert it into organic compounds. Animals then consume these organic compounds, incorporating carbon into their own bodies.

The second statement is also correct as carbon returns to the atmosphere through the process of respiration and decomposition of dead organic matter. During respiration, both plants and animals release carbon dioxide into the atmosphere. Dead organic matter is decomposed by microorganisms, which also release carbon dioxide.

The third statement is also correct as the carbon cycle is a relatively short-term cycle compared to other biogeochemical cycles such as the nitrogen cycle or the phosphorus cycle. The carbon cycle operates on a timescale of decades to centuries, whereas the nitrogen and phosphorus cycles can operate over thousands to millions of years.

Therefore, all the given statements about the Carbon Cycle are correct.

The second statement is correct, but the first statement is incorrect.

Explanation:

The sulphur cycle involves the biogeochemical cycling of sulfur through various stages in the ecosystem. The cycle includes both sedimentary and atmospheric components.

Atmospheric sulphur dioxide is released through natural processes such as volcanic eruptions and through human activities such as the burning of fossil fuels. The sulphur dioxide reacts with water in the atmosphere to form sulphuric acid, which falls to the earth's surface as acid rain. The acid rain then reacts with minerals in the soil to release sulphate ions, which are taken up by plants and microorganisms.

The sedimentary part of the sulphur cycle involves the weathering of rocks and minerals containing sulphur, which releases sulphate ions into the soil and water. These sulphate ions are then taken up by plants and microorganisms, and are eventually returned to the soil and water through the decay of organic matter.

Therefore, statement 1 is incorrect as the sulphur cycle is not completely sedimentary. Statement 2 is correct as atmospheric sulphur dioxide is carried back to the earth after being dissolved in rainwater as weak sulphuric acid.