Ecosystem: Trophic Levels

AIPMT Biology - Trophic Levels in an Ecosystem

AIPMT Biology Aspirants, read out the next AIPMT Biology Study material/ Notes of Ecosystem: Trophic Levels, useful for AIPMT Biology.

In an Ecosystem, every organism is assigned a place according to their feeding relationship with other organisms. Based on source of their nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level or feeding level. Organisms at each trophic level transfer energy and nutrients from one trophic level to another in an ecosystem.

  • Organisms in ecosystem’s trophic levels can be broadly classified as Producers and Consumers.
  1. Producers/ Primary producers/ Autotrophs: make the First Trophic Level. Able to make their own food.Energy enters ecosystem through autotrophs. Most autotrophs are photosynthetic organisms that use solar energy to synthesize organic compounds for food, cellular respiration and as building material for growth.Most common autotrophs are plants, algae, phytoplanktons (in aquatic ecosystem) and photosynthetic prokaryotes, along with few chemosynthetic prokaryotes.
  1. Consumers/ Heterotrophs: Depend on plants (directly or indirectly) for their food needs. There are several types of consumers in a ecosystem:
  • Primary Consumers or Herbivores: make the Second Trophic Level. Eat plants and other primary producer. Animals such as cow, rabbits, grasshoppers, goat, deer, and zooplankton (feed on phytoplankton) etc. are primary consumers.
  • Secondary Consumers or Primary Carnivores: make the Third Trophic Level. Eat on primary consumers. Carnivores that eat on herbivores are secondary consumers. Animals such as spiders, birds, fishes, frogs, wolf and some zooplankton-eating fish are secondary consumers.
AIPMT Biology - Trophic Levels in an Ecosystem

Trophic Levels in an Ecosystem

  • Tertiary Consumers or Top Carnivores: make the Fourth Trophic Level. Feed on secondary consumers.Carnivores that eat other carnivores are tertiary consumers. Animals such as tiger, lion, man, hawk, and killer whales. Also known as Secondary Carnivore.
  • Decomposers / Detritus feeders or Detritivores: Heterotrophs that feed on detritus. Detritus is dead organic material, such as the dead remains of organisms, feces, fallen leaves, and wood. Mites and earthworms, some insects, catfish, and larger scavenger organisms such as vultures are other detritus feeders. Detritivores are in turn eaten by secondary and tertiary consumers.

Decomposers is a subcategory of Detritivores. Mainly fungi and bacteria are decomposers. Decomposers help in break-down of dead organic matter of plants and animals.. They do so by secreting digestive enzymes that increase degradation of dead organisms into simple organic and inorganic compounds, water, minerals and nutrients like carbon. These simple forms are thus returned by decomposers to the soil, water, and air for reuse by producers.

Decomposers are also known as Saprotrophs. Decomposers as name suggests help in decomposing dead matter.

Omnivores such as pig, crow, fox, cockroach, and humans, feed on both plants and animals. So omnivores feed on multiple trophic levels.

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