Ecology interactions among organisms part 3 - 30th and 31st July

Food Chain

What is a food chain? 

It is a series of organisms through which energy is transferred in material form. Carbon compounds move through the foodchains.

 

Each feeding level in the food chain is called a trophic level.

Note: Ultimately, all the energy in the ecosystem comes from the SUN.

Food Web

What is a food web?

A food web is interconnected food chains in ecosystem

Example of a food web:

(image taken from: http://chatt.hdsb.ca/~fosterk/FOV1-00097FBE/FOV1-000AD76C/S07453EB5)

Non-cyclical Nature of Energy Flowing Biological Systems

Energy flows in one-direction (non-cyclical). It is either utilised or lost into the surroundings but cannot be recycled.

Unidirectional flow of energy

The amount of available energy in a food web decreases with each trophic level.
 

Food consumed = growth + respiration + heat + egesta+ excreta
 

Only about 10% of the energy is stored as new tissues and is available for transfer to next feeding level. 90% of the energy is lost due to some food may not be eaten, or passes through the body without being digested and a lot of the energy is used in respiration.

Hence, the shorter the food chain, the greater the amount of food energy is available.

Detritivores 

Decomposers are detritivores that recycle organic matter back to inorganic nutrients (carbon, nitrates) in ecosystems. E.g. fungi, bacteria.

Detritus feeder acquire nutrients from dead animals/ plants or animal waste products. E.g.
certain beetles, earthworm, termites, bacteria, fungi.