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.
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.
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.
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.
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.
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.
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
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.
Plants depend on soil bacteria for making minerals available from dead remains Since animals depend on plants, they too depend on soil bacteria
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.
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
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) 2
A food chain (1) The caterpillar eats the leaf…. (2)....the blue tit eats the caterpillar... (3)....the kestrel eats the blue tit. This is an example of a food chain 3 1 2 3
Animals depend on plants for food The food chain Cabbage Snail Thrush Sparrow hawk 4
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 5
Question 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 ( d) Increase in rabbits, increase in owls, decrease in vegetation . 7
All organisms depend on sunlight SUNLIGHT Wheat grains Flour Bread Cow Milk Cheese Nectar Bees Honey 8 Photosynthesis in wheat Photosynthesis in grass Photosynthesis in flowering plants
Pyramid of numbers Example of a food pyramid The width of each band represents the number of organisms Plant leaves Caterpillars Blue tits Owl 9
But wait! <ul><li>Pyramids may be inverted, particularly if the producer is very large (e.g. an oak tree). </li></ul><ul><li>So… </li></ul>
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 10
Atmospheric carbon dioxide Burning of fuel: wood, coal, oil and gas. Respiration in all organisms Decay of organic matter Photosynthesis in plants Absorption by the oceans 11 Production of carbon dioxide Uptake of carbon dioxide
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 13
Recycling and the role of decomposers PRODUCERS green plants CONSUMERS animals DECOMPOSERS bacteria and fungi SOIL minerals and humus sunlight 14
Decomposers <ul><li>If it were not for bacterial and fungal decomposition, we would be knee deep in dead leaves after a few years </li></ul>15
Conclusion The inter-relationships between all living organisms are so complex that any disturbance in the patterns of interdependence can have far-reaching consequences 16
Question 2 Which of these organisms might be classed as ‘producers’? (a) mosses (b) fungi (c) trees (d) earthworms
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 CO 2
Question 4 Which of these increase the concentration of carbon dioxide in the atmosphere? (a) respiration (b) photosynthesis (c) combustion (d) decay