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
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.
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
microorganisms.
What is biomass?
The dry mass of all of the living
organisms in an area.
Why is dry mass used for biomass?
Because the wet mass varies as the
volume of water in the organism varies.
How do you calculate the efficiency of
biomass transfer?
efficiency = (energy transferred / total energy available) × 100
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 waste products e.g. urine containing urea and water)
- Respiration (loss of carbon dioxide and water) in which large amounts of glucose are used
- The production of inedible bones and shells
How does the efficiency of biomass
transfers affect the number of trophic
levels in a biomass pyramid?
The less efficient the transfers, the fewer
trophic levels and the fewer organisms in
higher trophic levels.
What is a biomass pyramid?
A pyramid that shows the total dry mass of
organisms at each trophic level
Trophic level 1 is at the bottom of the
pyramid
