IGCSE Ecosystems and Energy Flow Dual Award Notes

For Students studying Dual Award IGCSE Biology with Edexcel- Ecosystems and Energy Flow

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Ecosystems and Energy Flow
Factors Affecting Living Organisms
Climate (i.e. Temperature, oxygen levels, rainfall quantity and light intensity)
Intraspecific Competition (i.e. within the species for food, territory, shelter and mates)
Interspecific Competition (i.e. between species for food, shelter and space)
Soil/Substance (i.e. rock, sand, soil, clay or marsh)
Factors Affecting Population Size
Immigration (moving to)
- For the substance of the ground and the environment
- For food quality, quantity, and what it is
- Space
Emigration (moving away)
- Because predators are in abundance
- Loss of habitat either through human interference or naturally.
- Lack of food
- Lack of space
- Disease
- Predators
- Food
- Disease
- Predators
- Food
Ecosystem a distinct, selfsupporting system of organisms interacting with each other and with
their physical environment.
Population all the organisms of a specific species living in an ecosystem at a particular time.
Community all the populations of living organisms living in an ecosystem at a particular time.
Habitat a place where specific organisms live
Quadrats used to sample a distribution of organisms in their habitats and to estimate the
population size of an organism in different areas.
Substances and energy are transferred along food chains.
Only about 10% of available energy is transferred.
An ecosystem contains many living organisms that interact through feeding relationships. Plants are
producers because they produce their food through photosynthesis. Animals are consumers they eat
other plants or animal to get their energy. Decomposers are organisms such as bacteria and fungi that
breakdown and decompose dead materials and waste products to recycle their nutrients.
Feeding Relationships
There are four main ways to show feeding relationships.
Food Chains
Food webs
Pyramids of number
Pyramids of biomass
Food Chains
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