AQA alevel biology - energy transfers in and between organisms (unit 5) A2

Energy and
ecosystems

,Organisms are divided into 3 group
due to how they obtain energy:
1. PRODUCERS – organisms (autotrophs) that photosynthesis to
produce oxygen, glucose and energy
• EXAMPLE - PLANTS
2. CONSUMERS – organisms (heterotrophs) that receive energy by
eating consumers. Animals (consumers) eat plants (producers).
They are called primary consumers. Animals that eat the primary
consumers are called secondary consumers.
• EXAMPLE – ANIMALS

,Consumers
• HERBIVORES – an animal that eats a plant (primary consumer)
• CARNIVORES – an animal that eats animals (secondary/tertiary
consumer)
• OMNIVORES – an animal that eats both plants and animals
(primary/secondary/tertiary consumer)
• DETRIVORES – eats waste, dead consumers and producers

,Organisms are divided into 3 group
due to how they obtain energy:
3. SAPROBIONTS (decomposers) – organisms that break down
complex materials in dead organisms into simpler ones. They
release minerals that can be absorbed by plants.
• EXAMPLE – FUNGI AND BACTERIA

,Energy flow

,Trophic level diagrams
• TROPHIC LEVEL DIAGRAM – shows an organisms trophic level and
their position in the sequence of energy flow
• 1st trophic level = producers
• 2nd trophic level = primary consumers/herbivores
• 3rd trophic level = secondary consumers/carnivores

,
,Energy pyramids
• ENERGY PYRAMID – shows how much energy is passed from one
trophic level to the next
• Most energy consumed contributes to homeostasis, respiration,
growth and reproduction

,
, Food chain
• FOOD CHAIN – a feeding relationship in which the producers are
eaten by the primary consumers (which are then eaten by seconda
consumers which is eaten by a tertiary consumer which is eaten by
quaternary consumer)
• Each stage in the chain is called a TROPHIC LEVEL
• The arrows in the food chain represent energy flow