Question

which of the following is the primary consumer in the maize field ecosystem?
A.Wolf
B.Phytoplankton
C.Lion
D.Grasshopper

Answer 1

An ecosystem has two sets of mutually dependent and regularly interacting components, ie, abiotic and biotic. Biotic components include the living organisms, from microbes to highly evolved plants and animals. Abiotic components are the non-living physico-chemical factors of the environment.

Complete answer:
Ecosystem is a complex and self-supporting dynamic system of mutually dependent and regularly interacting abiotic and biotic components. It is also known as biogeocoenosis. The sum total of organisms of an ecosystem is known as the biota. The area occupied by the biota is known as the biotype. Basic unit of biota is population.
Biotic components in an ecosystem include the living organisms and their biotic interactions and interrelations. Functionally biotic components fall under four main categories, autotrophs or producers, heterotrophs or consumers, decomposers or reducers and transformers or converters. Producers are the organisms which can synthesize organic food all by themselves from inorganic constituents such as H2O, CO2 and salts. Examples for producers are green plants.
Heterotrophs or consumers are the organisms which feed upon other organisms. They have no powers for synthesizing organic food from inorganic constituents. They can synthesize organic food only from organic constituents. Examples are animals, some fungi and some plants. Decomposers are a group of micro-consumers which bring about the decomposition or degradation of the complex compounds of dead matter and waste into simple organic and inorganic constituents by enzymatic action. Examples are bacteria, some yeasts and many fungi. Transformers convert the breakdown products of decomposition into still simpler inorganic and organic substances which can be utilized by the producers. They include some bacteria.
In an ecosystem, organisms depend successively upon one another for food energy. As a result, there is a regular repetition of the ‘eating others and being eaten by others’ process. Such a chain of organisms through which food energy is transferred from primary producers to decomposers through the successive levels of consumers is known as a food chain. It is an energy sequence of several nutritional (trophic) levels. Usually there are 4 or 5 trophic levels in a food chain. They are producers, primary consumers or herbivores, primary carnivores or secondary consumers, secondary carnivores or tertiary consumers, tertiary carnivores or quaternary consumers and decomposers.
Here the maize plant is a producer, which can synthesize food. Lion and wolf are secondary carnivores or tertiary consumers, which feed on primary consumers or primary carnivores. Phytoplankton is a producer in the marine ecosystem. Grasshopper is the primary consumer which can feed maize plant leaves.

Figure: Trophic levels

Hence the correct answer is option(D)

Note: In some cases, adjacent ecosystems overlap or merge together in a narrow zone in between them. Such narrow intermediate zones where two or more ecosystems merge together are ecotones. An ecotone may be very narrow, just a few meters wide, or several km wide. It may gradually become more and more similar to the nearest recognizable ecosystem.