1. The Biosphere
How it Works
Mr G Davidson

2. Parts of an Ecosystem Organisms do not exist in complete isolation.
They interact with each other and their non-living surroundings, to form natural systems called Ecosystems.
An enormous variety of ecosystems exist on the planet.
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G Davidson

3. Pond Ecosystem
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G Davidson

4. Ecosystems
All the organisms (plants and animals) in the diagram live in or around the pond.
The area where organisms live is called their Habitat.
All the organisms of the pond make up the Community.
All the organisms of one kind make up a Population.
The community of organisms and the habitat together make up the Ecosystem.
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G Davidson

5. Producers and Consumers
All organisms within an ecosystem need food to survive.
Depending on how they obtain food, organisms are divided into 2 groups – PRODUCERS & CONSUMERS.
Green plants are called Producers, because they produce their own food.
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G Davidson

6. Producers and Consumers
They use the energy of sunlight to do this (Photosynthesis).
Most other organisms obtain their food by feeding on other organisms.
They are called Consumers.
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G Davidson

7. Consumers
Consumers can be divided into 3 groups depending what they consume.
Consumers that feed on plants are called Herbivores.
Consumers that feed on other animals are called Carnivores.
Consumers that feed on both plants and animals are called Omnivores.
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G Davidson

8. Food Chains
Energy is transferred in the form of chemical energy in food from plants to animals and then to other animals.
A green plant (producer) can be eaten by a herbivore.
The herbivore is called the primary consumer.
The herbivore in turn can be eaten by a carnivore.
The carnivore is called a secondary consumer.
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G Davidson

9. PRIMARY CONSUMER (HERBIVORE)
Food Chain
Rabbit
PRIMARY CONSUMER (HERBIVORE)
Green Plant
PRODUCER
Fox
SECONDARY CONSUMER
(CARNIVORE)
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G Davidson

10. Food Chains
This feeding relationship is called a FOOD CHAIN, and is usually written as:
The arrows in a food chain point from food to feeder and show the direction of energy flow.
Green Plant Rabbit Fox
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G Davidson

11. Food Webs
Feeding relationships are more complicated than food chains suggest.
Food chains interconnect at many points.
This interconnection of food chains is called a food web.
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G Davidson

12. Food Webs FOX SNAIL HEDGEHOG WEASEL FROG VOLE PRIMROSE PLANT OWL
RABBIT
OAK
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G Davidson

13. Energy Flow and Loss
Every time one organism eats another, energy is transferred from the food to the feeder.
E.g.
The arrow indicates the direction of energy flow.
Oak leaf Caterpillar Shrew Badger
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G Davidson

14. Energy Flow and Loss
Not all the energy available at each step in a food chain is passed onto the next step.
Some of the energy is lost.
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G Davidson

15. Energy Flow and Loss Energy not used Energy Used Energy Stored
Some of the energy present in the leaf passes out of the caterpillar in undigested food.
Energy Used
The caterpillar uses some of the energy it gets from the leaf to move, grow, feed and produce heat.
Energy Stored
The rest of the energy the caterpillar gets from the leaf is stored in the body of the caterpillar.
Only this energy is available to the next animal in the chain.
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G Davidson

16. Population Growth
The total number of one kind of organism in an ecosystem is called a population.
Many factors affect the size of a population.
Normally there is a check on the numbers in a population which prevents population explosions.
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G Davidson

17. Growth Limiting Factors
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G Davidson

18. Competition
Competition occurs when 2 or more organisms of the same or different species need the same resource.
Plants compete for light, root space, water and minerals from the soil.
Animals compete mainly for food and a place to live.
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G Davidson

19. Nutrient Cycles
The bodies of organisms contain a number of different chemical elements.
These chemical elements are often in limited supply.
It is important that the chemical elements “locked up” in the bodies of plants and animals are not lost to the ecosystem, but are recycled.
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G Davidson

20. Nutrient Cycles
Some organisms are called decomposers because they help to release the chemical elements from the dead bodies of plants and animals.
These elements, once released into the soil, are available for re-use by organisms.
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G Davidson

21. Nutrient Cycles
Two important chemical elements which are released into the soil by the action of decomposers are CARBON and NITROGEN.
These and other chemical elements circulate in nature; i.e. they move from non-living materials into living things, back to non-living, again into living, and so on, over and over again.
Such circulation is known as a cycle.
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G Davidson

22. Carbon Cycle CARBON DIOXIDE (in air) photosynthesis respiration food
plants
death
Fuels (wood, coal, etc)
burning
humus
decomposers
food
animals
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G Davidson

23. (products are turned to
Nitrogen Cycle
Nitrates in the Soil
Plants
Animals
Death
(products are turned to
ammonium compounds)
Converted
to Nitrites
to Nitrates
Nitrifying bacteria
in plant roots
Nitrogen (in air)
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G Davidson

24. Pyramid of Numbers
A pyramid of numbers is a diagram showing a food chain with the producers at the bottom and the top consumers at the top.
As you go up the pyramid the population numbers decrease.
As you go up the pyramid the size of the organisms increase.
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G Davidson

25. Pyramid of Numbers
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G Davidson

26. Pyramid of Biomass
A more accurate idea of the quantity of animal and plant material at each level of a food chain is obtained by weighing all the organisms at each level, e.g.
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G Davidson