INTERDEPENDENCE of LIVING ORGANISMS

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© Hans pfletschinger

The picture shows a bee visiting a sage flower

It provides an example of interdependence

The bee is dependent on the flower for its nectar

The flower is dependent on the bee for pollination

(You will need to have an understanding of respiration and photosynthesis to follow this slide show)

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A food chain

(1) The caterpillar eats the leaf….

(2)....the blue tit eats thecaterpillar...

(3)....the kestrel eats theblue tit.

This is an example ofa food chain

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1

2

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Animals depend on plants for foodThe food chain

Cabbage

Snail

Thrush

Sparrow hawk

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The sparrow hawk does not depend directly on plants but it does depend on thrushes, which eat snails, which eat cabbages.

So the sparrow hawk is indirectly dependent on plants

Food chains are never so simple as the ones in slides 3 and 4

Sparrow hawks do not feed exclusively on thrushes; thrushes eat worms as well as snails; snails eat many plants, not just cabbages

A more accurate picture is given by a food web

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fox owl stoat

rabbit

rat

beetle

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QuestionWhat is the most likely outcome of a severe fall in the numbers of foxes?

(a) Increase in rabbits, decrease in rats, increase in owls

(b) Increase in rabbits,increase in stoats, increase in vegetation

(c) Decrease in rabbits, increase in beetles, increase in vegetation

(d) Increase in rabbits, increase in owls, decrease in vegetation.

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All organisms depend on sunlight

SUNLIGHT

Wheat grains

Flour

Bread

Cow

Milk

Cheese

Nectar

Bees

Honey

Photosynthesis in wheat

Photosynthesis in grass

Photosynthesis in flowering plants

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Pyramid of numbers

Example of a food pyramidThe width of each band represents the

number of organisms

Plant leaves

Caterpillars

Blue tits

Owl

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But wait!

• Pyramids may be inverted, particularly if the producer is very large (e.g. an oak tree).

So…

PYRAMIDS OF BIOMASS, which represent the biomass (n° of individuals x mass of each

individual), should solve the scale and invertion problems of the pyramid of numbers.

Dependence on oxygen and carbon dioxide

Animals need oxygen for respiration

Plants produce oxygen in photosynthesis

Animals produce carbon dioxide in respiration

Plants use up carbon dioxide in photosynthesis

The process of decay uses up oxygen and produces carbon dioxide

This interdependence is represented by the Carbon Cycle

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Atmospheric carbon dioxide

Production of carbon

dioxide

Uptake of carbon

dioxide

Burning of fuel: wood, coal, oil and gas.

Respiration in allorganisms

Decay of organic matter

Photosynthesis inplants

Absorption by the oceans

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12The carbon cycle

Dependence on bacteria

-Most bacteria are beneficial

-They break down dead organisms into simpler substances

-Soil bacteria make mineral salts available to plants

-Bacteria and fungi are called decomposers

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Recycling and the role of decomposers

PRODUCERS green plants

CONSUMERS animals

DECOMPOSERSbacteria and fungi

SOILminerals and humus

sunlight

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Decomposers

• If it were not for bacterial and fungal decomposition, we would be knee deep in dead leaves after a few years

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Conclusion

The inter-relationships between all living organisms are so complex that

any disturbance in the patterns of interdependence can have far-

reaching consequences

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Question 1Which of the following might be genuine food chains?

(a) zebra - lion - giraffe - leopard - antelope

(b) grass - grasshopper - lizard - snake - eagle

(c) aquatic vegetation - hippopotamus - tick - oxpecker bird - tawny eagle

(d) stickleback - pondweed - minnow - pike - kingfisher

Question 2

Which of these organisms might be classed as ‘producers’?

(a) mosses

(b) fungi

(c) trees

(d) earthworms

Question 3Which of these statements is most accurate?

In bright sunlight a green plant will be...

(a) photosynthesising only

(b) respiring only

(c) photosynthesising and respiring

(d) taking in oxygen and giving out CO2

Question 4

Which of these increase the concentration of carbon dioxide in the atmosphere?

(a) respiration

(b) photosynthesis

(c) combustion

(d) decay