Page 4 - 2. Lesson notes-Food chain and Food web

 Producers (T1)

 Primary consumers (herbivores-T2)
 Secondary consumers (primary carnivores -T3)
 Tertiary consumers (Secondary carnivores -T4)
 Quaternary consumers (Tertiary carnivores T5)

Pyramid of trophic levels

 Is a graphical representation.
 Can be the pyramid of numbers, pyramid of biomass or pyramid of energy.

 All the pyramids start with producers.

a) Pyramid of numbers: gives the number of organisms present at each trophic level.
It can be upright or inverted.

b) Pyramid of biomass: gives the biomass of each trophic levels and could be upright or
inverted.

c) Pyramid of energy: is always upright as it shows the flow of energy from one trophic
level to the next trophic level.

Characteristics of Food Chain

1. A food chain involves a nutritive interaction between the living organisms (biotic
components) of an ecosystem. In a food chain, there occurs repeated eating, i.e.,
each group eats the other group and subsequently is eaten by some other group of
organisms.
2. A food chain is always straight and proceeds in a progressive straight line.
3. In a food chain, there is unidirectional flow of energy from Sun to producers and
subsequently to series of different types of consumers.
4. Usually, there are 3 or 4 trophic levels in the food chain. In few chains, there may be
maximum of 5 trophic levels.
5. Some organisms are omnivores. These occupy different trophic positions in different
food chains.
6. At each transfer, generally 80-90 % of energy is lost as heat.

A food chain is the flow of food energy from one organism to the next and to the next and so
on. They usually start with a producer (plants) and end with a carnivore. In a food chain an
organism gets food from one group of organisms.

TERRESTRIAL FOOD CHAINS

1. Two-step Food Chain

Vegetation Elephant
(producer) (herbivore)

2. Three-step Food Chain