This is a presentation for the topic "Food Chains and Food Web"

1. FOODCHAINS
AND
FOODWEBS

2. WhatformsaFood Chain?
Theseries of organisms taking partatvarious biotic levels form a food chain.
(a)– Food Chain in nature in forests.
(b)-Food Chain in nature in grasslands.
(c)-Food Chain in nature in ponds.

3. Levels ofaFood Chain
Each step or a levelofa food chain forms a trophic level.
TERTIARY CONSUMERS
CONSUMERS
SECONDARY
CONSUMERS
PRIMARY CONSUMERS
CONSUMERS
PRODUCERS (PLANTS)

4. Flowofenergy!!
Interactions among various components of our environment involves flow of energy from one component of system
tothe another.
• Autotrophs capture the energy present in sunlight andconvert itintochemical energy.
• This energy supports allactivities ofthe living world.
• This energy fromautotrophs flow toheterotrophs anddecomposers.
• We know that duringflowof energy some amount ofenergy islost in environment.
SUNLIGHT PRODUCERS
PRIMARY
CONSUMERS
SECONDARY
CONSUMERS
TERTIARY
CONSUMERS
Fact:- Flow of energyis unidirectional.

5. Theflow of energybetween the various componentsof the system has been extensively studied and it has
been found that:
1. The plants capture about 1% ofthe total sunlight that falls on their leaves, and further they convert this
energy intochemical energy.
2. When plants areeaten by primaryconsumer only 10% ofthe energy produced by the plants is available
forthe consumer.
3. In this manner at every level only 10% ofthe energy is made available for the next trophiclevel.
4. There aregenerally greater number ofindividuals at lower levels offoodchain.
BONUSQUESTION:-Whydo food chainsgenerallyconsist of only 3-4steps?
Answer:
Since verylittle amountof energyis available for the next level of consumersfood chains aregenerallyof
3-4 steps.

6. FoodWeb
• Each organism iseaten by twoormore type oforganismswhich in turn areeaten by several other organisms.
• Soinstead ofastraight foodchain ,relationship can be shown by series of branching lines known as foodweb.

7. Biological Magnification
• Unknowingly many harmful chemicals enter ourbodies through foodchain.
• Several pesticides get absorbed bythe plants through soil, water.
• These chemicals arenot degradable andtherefore get accumulated at each trophic level.
• As humans areat topofthe food chain maximum concentration ofsuch chemicals accumulate in our
body. This phenomenon is know as biological magnification.