Food chains

food chains and cycles

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Pyramids of biomass

Show the mass of living material at each stage of the chain.

The amount of energy decreases from one stage to the next in a food chain. Food production is more efficient if the food chains were shorter of if the energy loss was less in each animal.

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The sun is the ultimate source of energy for most communities of living things.

Green plants absorb some of the suns energy to make their own food by photosynthesis.

The other organisms in the food chain are consumers, because they all get their energy and biomass by consuming (eating) other organisms.

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PRODUCERS --- GREEN PLANTS. THEY MAKE FOOD BY PHOTOSYNTHESIS

PRIMARY CONSUMERS --- USUALLY EAT PLANT MATERIAL. HERBIVORES (RABBITS, COWS, CATTERPILLERS ETC)

SECONDARY CONSUMERS --- USUALLY EAT ANIMAL MATERIAL. CARNIVORES (CATS, DOGS, LIONS ETC)

PREDATORS --- KILL FOR FOOD, SECONDARY OR TERTIARY CONSUMERS.

PREY --- THE ANIMALS THAT PREDATORS FEED ON

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Some of the available energy goes into growth and the production of the off spring. This energy does not become available in the next stage.

Most of the available energy is used up in:

  • energy released in respiration is used for movement and other life processes, and is eventually lost as heat to the surroundings and..
  • energy is lost in waste such as faeces.

all the energy used up in these ways is returned to the environment.

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Pyramids of biomass

 

Biomass means the mass of living material at a stage in a food chain. The biomass at each stage decreases as you go from one stage to the next, just like the amount of energy.

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calculating efficiency

 This bullock has eaten 100 kJ of stored energy in the form of grass, and excreted 63 kJ in the form of faeces, urine and gas. The energy stored in its body tissues is 4 kJ. So how much has been used up in respiration?  

 The energy released by respiration = 100 - 63 - 4 = 33 kJ

efficiency = 4/100 x 100 = 4%

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