1. INTERDEPENDENCE of LIVING ORGANISMS1
INTERDEPENDENCE of LIVING ORGANISMS
© Hans pfletschinger

2. The picture shows a bee visiting a sage flower2
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)

3. A food chain (3)....the kestrel eats the blue tit.
(2)....the blue tit eats the
caterpillar... 2
(1) The caterpillar eats
the leaf….
The kestrel depends on the blue tit as a source of food.
The blue tit depends on the caterpillar. The caterpillar depends on the leaf.
In a food chain such as this, the plants are called the producers and the caterpillar, blue tit and kestrel are the consumers. 1
This is an example of
a food chain

4. Animals depend on plants for food4
Animals depend on plants for food
The food chain
Sparrow hawk
Thrush
Snail
Cabbage

5. The sparrow hawk does not depend directly on plants 5
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

6. 6
owl
stoat
fox
rat
rabbit
beetle

7. Question 7
What 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
A decrease in the fox population would allow beetles, rats and rabbits to increase.
As a result, the vegetation that these animals eat would decrease.
An increase in the numbers of beetles, rats and rabbits would deplete the vegetation but provide more prey for the owl and stoat.
(d) Increase in rabbits, increase in owls, decrease in
vegetation.

8. All organisms depend on sunlight8
SUNLIGHT
Photosynthesis
in wheat
in grass
Photosynthesis in
flowering plants
Wheat grains
Cow
Nectar
The slide shows how three items of the human diet are indirectly dependent on sunlight. The first step in these food chains is the trapping of the sun’s energy by the chlorophyll in green plants.
The green plants, or their products, may be eaten directly or they may pass their energy and raw materials on to the next organism in the food chain.
Flour
Milk
Bees
Bread
Cheese
Honey

9. Pyramid of numbers Owl Blue tits Caterpillars Plant leaves9
Pyramid of numbers
Owl
Blue tits
Caterpillars
Plant leaves
In many food chains, the organisms at the beginning of the chain are very numerous. At each stage in the chain the numbers get fewer.
One barn owl might feed on 10 blue tits; each blue tit might consume dozens of caterpillars.
Example of a food pyramid
The width of each band represents the number of organisms

10. Dependence on oxygen and carbon dioxide10
Animals need oxygen for respiration
Plants produce oxygen in photosynthesis
Animals produce carbon dioxide in respiration
Plants use up carbon dioxide in photosynthesis
In fact, plants and animals both use up oxygen and produce carbon dioxide in the process of respiration but, in sunlight, plants use up all their carbon dioxide for photosynthesis. In darkness, photosynthesis stops but respiration continues, using up oxygen and giving out carbon dioxide.
The process of decay uses up oxygen and produces carbon dioxide
This interdependence is represented by the
Carbon Cycle

11. Atmospheric carbon dioxide11
Atmospheric carbon dioxide
Production of carbon
dioxide
Uptake of carbon
Burning of fuel: wood,
coal, oil and gas.
Photosynthesis in
plants
Respiration in all
organisms
Absorption by the
oceans
When these processes are in balance, the concentration of atmospheric carbon dioxide does not change
When fossil fuels are burned, carbon dioxide production exceeds its uptake by plants and the oceans.
Decay of organic matter

12. The carbon cycle 12
If only plants and animals were involved, the carbon dioxide concentration in the atmosphere would stay in balance. It is the burning of fossil fuels that unbalances the system

13. Dependence on bacteria13
Dependence on bacteria
Most bacteria are beneficial
They break down dead organisms into simpler
substances
Soil bacteria make mineral salts available
to plants
We tend to think only of disease-causing bacteria, but these are in a minority.
Most bacteria are either harmless or directly or indirectly beneficial.
For example, cattle and sheep have a large population of bacteria in their stomachs where these beneficial bacteria help to digest the cellulose cell walls in grass.
Bacteria and fungi are called decomposers

14. Recycling and the role of decomposers14
SOIL
minerals and
humus
sunlight
DECOMPOSERS
bacteria and fungi
PRODUCERS
green plants
Plants depend on soil bacteria for making minerals available from dead remains
Since animals depend on plants, they too depend on soil bacteria
CONSUMERS
animals

15. Decomposers 15
In fact we would be buried more than knee deep in all sorts of dead matter that failed to decompose. Leaves are only one example.
If it were not for bacterial and fungal decomposition, we would be knee deep in dead leaves after a few years

16. 16
Conclusion
The inter-relationships between all living organisms are so complex that any disturbance in the patterns of interdependence can have far-reaching consequences
Example. When, in 1954, myxomatosis nearly wiped out the rabbit population, some grassland became woody scrub because rabbits were not there to nibble off the tree seedlings.
The numbers of buzzards, which fed mainly on rabbits, went into steep decline

17. Question 1 Which 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

18. Question 2 Which of these organisms might be classed as ‘producers’?
(a) mosses
(b) fungi
(c) trees
Fungi are decomposers. Earthworms are consumers.
(d) earthworms

19. Question 3 Which 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

20. Question 4 Which of these increase the concentration of carbon dioxide
in the atmosphere?
(a) respiration
(b) photosynthesis
(c) combustion
(d) decay

21. ANSWER
Incorrect

22. ANSWER
Correct