Trophic Levels in an Ecosystem Flashcards
All 16 cards in this deck
What is a producer, and which trophic level is it?
An organism that makes its own food, e.g. plants and algae — trophic level 1.
What name is given to organisms at trophic level 2?
Primary consumers — herbivores that eat plants or algae.
What is a secondary consumer?
A carnivore that eats herbivores (primary consumers) — trophic level 3.
What is an apex predator?
A carnivore with no predators, at the top of a food chain.
True or false? A carnivore that eats other carnivores is called a tertiary consumer and is at trophic level 4.
True. Trophic levels are numbered by how far along the food chain the organism is, starting at level 1 with plants and algae.
What are the steps by which a decomposer breaks down dead plant and animal matter?
e.g. a bacterium on a dead leaf- Secretes enzymes out into the environment (onto the dead leaf).
- The enzymes digest the dead matter into small soluble food molecules.
- These molecules diffuse into the microorganism.
What does a pyramid of biomass represent?
The relative amount of biomass in each trophic level of a food chain.
In a pyramid of biomass, which trophic level is drawn at the bottom?
Trophic level 1 — the producers (plants and algae).
True or false? The width of each bar in a pyramid of biomass shows the number of organisms at that trophic level.
False. It shows the biomass (mass of living material) at that level, not the number of organisms.
Why does a pyramid of biomass become narrower towards the top?
Because only about 10 % of the biomass at each level is transferred to the level above; the rest is lost.
About what percentage of the incident light energy do producers transfer for photosynthesis?
About 1 %.
Approximately what percentage of the biomass in one trophic level is transferred to the level above?
About 10 %.
Name the ways biomass is lost between one trophic level and the next.
Not all ingested material is absorbed, so some is egested as faeces; absorbed material is lost as waste — carbon dioxide and water in respiration, and water and urea in urine.
What are the steps to calculate the efficiency of biomass transfer between two trophic levels?
e.g. 500 g of grass eaten gives 50 g of rabbit biomass- Divide the biomass of the higher level by the biomass of the level below: .
- Multiply by 100 for a percentage: .
True or false? All the biomass an animal eats becomes new biomass in its body.
False. Much is egested as faeces or lost as carbon dioxide and water from respiration and urea in urine, so only about 10 % becomes new biomass.
Why are there usually fewer organisms at each higher trophic level, and why are food chains short?
Biomass is lost at every transfer, so there is less biomass available to support organisms at higher levels.