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Class 10, Science, Chapter-13, Lecture-2, Food Chain (Notes)

Types of Biotic community of an Ecosystem:

  • Producers:
    The organisms which can make organic compounds like sugar and starch from inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll.
    Examples: Green plants and blue-green algae
  • Consumers:
    The organisms which consume the food prepared either directly from producer or indirectly by feeding on other consumers for their sustenance.
    Three Types:
  1. Herbivores:
    The animals which eat only plants are called herbivores. Examples- Horse, deer, cow, rabbit, squirrel etc. The animals which get their food by eating the producers directly are called primary consumers.
  2. Carnivores:
    The animals which depend or eat the flesh of other animals for food are called carnivores.
    Examples- Lion, tiger, snake, hawk etc.
    The small carnivores which feed on primary consumers are called secondary consumers
    The top carnivores which feed upon the secondary consumers are called tertiary consumers
  3. Omnivores:
    The animals which eat both plants and animals are called omnivores.
    Examples- Human beings, dog, crow
  • Decomposers:
    The microorganisms, comprising bacteria and fungi which break down the complex organic substances present in dead plants and animals and their wastes into simple inorganic substances are called decomposers.

Food Chain:

A sequence of the living organisms in a community, through which food energy is transferred from one organism to another organism by consuming, is called a food chain.
Examples of food chain:

GRASS $ \to $ GRASSHOPPER $ \to $ FROG $ \to $ SNAKE $ \to $ VULTURE
(Producer)    (Herbivore)    (Carnivore)  (Carnivore)  (Top carnivore)


ALGAE(Phytoplankton) $ \to $ PROTOZOA(Zooplankton) $ \to $ SMALL FISH $ \to $ BIG FISH
     (Producer)                               (Herbivore)                        (Carnivore)      (Top carnivore)

Food Web:

The network of a large number of interconnected food chains existing in an ecosystem which contains many under crosses and linkages among the various species present in it is called a food web.

Trophic levels:

The various steps or levels in the food chain where the transfer of food energy takes place are called trophic levels.

  1. The producers or autotrophs constitute the first trophic level.
  2. The herbivores or primary consumers constitute the second trophic level.
  3. The carnivores or secondary consumers constitute the third trophic level.
  4. The top carnivores or tertiary consumers constitute the fourth trophic level.

THE TEN PERCENT LAW:

The ten per cent law states that only 10 per cent of the energy entering a particular trophic level is transferred to the next higher trophic level.

The amount of energy available to a trophic level is only 10% of the energy available at the previous level.

Reason:
When the organisms (predator) of a trophic level eat the organisms (prey) of the previous trophic level, some of the energy is lost to the environment as heat and some of the energy is consumed for metabolic activities.
Only 10 percent of the energy is converted to biomass and is available for the next trophic level.

Flow of Energy in Food Chain is Unidirectional.

In a food chain, organisms (prey) of lower trophic level are consumed by the organisms (predator) of higher trophic level.
The biomass of prey gets converted to biomass and energy of the predator.
The process continues for higher trophic levels.
Since, predators cannot be consumed by prey, the flow of biomass and energy is unidirectional.

Food chains generally consist of only three or four steps.

Reason:
The amount of energy and biomass available to the organisms of a trophic level is only 10 percent of that available to the previous trophic level.
So, the number of individuals present in a trophic level goes on decreasing towards the top.
After fourth trophic level, very little usable energy remains for the organisms and the food chain becomes unsustainable.

A large number of individuals (producers) are present at the lower trophic levels of an ecosystem.

The amount of energy and biomass available to the organisms of a trophic level is only 10 percent of that available to the previous trophic level.
So, the number of individuals present in a trophic level goes on decreasing towards the top.

Bio- magnification

The increase in the concentration of non-biodegradable chemicals in the organisms of a trophic level due to accumulation of the chemicals from previous trophic level is termed as biomagnifications.

Effective management and ways of solid waste disposal:

  1. Recovery and recycling
  2. Source reduction
  3. Incineration
  4. Dumping (Land filling)
  5. Treatment of sewage