7.4 Ecology (trophic levels in an ecosystem) Flashcards
What does a food chain show?
it describes the feeding relationships between organisms and the resultant stages of biomass transfer
What are trophic levels?
the stages in a food chain
How are trophic levels represented?
Trophic levels are represented by numbers, starting from 1
What is trophic level 1?
Plants and algae which make their own food (through photosynthesis) - called producers
What is trophic level 2?
herbivores which eat producers - called primary consumers
What is trophic level 3?
carnivores that eat herbivores - called secondary consumers
What is trophic level 4?
carnivores that eat other carnivores - called tertiary consumers
What is an apex predator?
A carnivore with no predators
How do decomposers break down dead matter?
- decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules
- soluble small food molecules then diffuse into the microorganism
What is biomass?
the dry mass of all of the livings organisms in an area
Why is dry mass used for biomass?
because the wet mass varies as the volume of the water in the organism varies
How do you calculate the efficiency of biomass transfer?
efficiency = (energy transferred/total energy available) x100
What percentage of the incident energy from light for photosynthesis do producers transfer?
1%
What percentage of the biomass from one trophic level is transferred to the level above it in feeding?
Approximately 10%
Why are biomass transfers not 100% efficient?
energy is lost through:
- egestion (removal of faeces)
- excretion (removal of urine)
- respiration (loss of carbon dioxide and water) in which large amounts of glucose are used
- the production of inedible bones and shells
