The correct option is
D A, B and C
A food chain refers to the chronological series of organisms each depending on other for food. It also explains the feeding pattern or relationship between living organisms, flow of energy and nutrients.
Different organisms occupy different levels in the food chain and each level is referred to as trophic levels. Producers occupying at the bottom of a food chain synthesise the food, followed by primary, secondary and tertiary consumers. Hence statement C is correct.
The sun is the ultimate source of energy. Producers are able to synthesise the food utilising the energy radiating from the sun. Consumers are dependent on plants directly or indirectly for food. It includes herbivores that eat plants, carnivores that eat herbivores and other animals.
Herbivores (rats) are primary consumers that are present at the second trophic level. Carnivores eat herbivores and other animals and come later in the food chain, hence are known as secondary (snake) or tertiary (hawk) consumers depending on their position in the food chain.
A primary carnivore, like a cat, will only eat herbivores, or plant eaters, such as a mouse. Hence statement A is correct.
There are two types of food chain : detritus food chain (DFC) and grazing food chain (GFC).
- The grazing food chain begins with green plants which synthesise the food using sunlight and passes on the energy to herbivores and then to carnivores.
Figure : Grazing food chain
- The Detritus food chain begins with dead organic material. The decaying material acts as a food source for decomposers (bacteria and fungi) and detritivores (earthworms) which are further eaten by other organisms (sparrow). Hence statement B is correct.