Aquatic ecology and Biodiversity

Unit 2- Ecosystem ecology

2.1.7. Biotic components
Biotic components
Organisms that make up the biotic component of an ecosystem are classified as autotrophic organisms and heterotrophic organisms based on how they get their nutrition, food or organic nutrients for their growth, development and survival. Autotrophs are primary producers. Green plants incorporate the sun’s energy by photosynthesis. This energy stored in the form of chemical bonds. Heterotrophs are secondary producers or consumers. All animals are consumers.
Autotrophs (Producers)
Autotrophs are the organisms that can manufacture the organic compounds from simple inorganic compounds in the environment. In aquatic ecosystems, most of the producers are of various species of floating and drifting forms of phytoplankton and bacteria. In addition, macrophytes also serve as producer in aquatic ecosystems.
Most producers make their organic nutrients they need through photosynthesis. The overall net chemical change can be summarized as follows:
6 CO2 + 6 H2O + solar energy -----> C6H12O6 + 6 O2
Heterotrophs (Consumers)
These are the organisms which cannot synthesize the organic nutrients they need and get their organic nutrients by feeding on the tissues of producers or other consumers. There are several classes of consumers, depending on their food source.

• Primary consumers (herbivores): Feed directly on plants or other producers. e.g. - zooplankton (copepods, cladocerans etc.)
• Secondary consumers (primary carnivores) feed on primary consumers. e.g. Aquatic insects, crustaceans etc.
• Tertiary consumers (secondary carnivores) feed only on secondary consumers. e.g. small fishes.
• Tertiary carnivores :Feed only on animal-eating animals. They are predators. e.g. large fishes like tuna, seer fish, sharks etc.