T7 trophic levels in an ecosystem Flashcards Preview

aqa gcse biology free > T7 trophic levels in an ecosystem > Flashcards

Flashcards in T7 trophic levels in an ecosystem Deck (19)
Loading flashcards...
1
Q

what does a food chain show

A

describes the feeding relationships between organisms and the resultant stages of biomass transfer

2
Q

what are trophic levels

A

stages in a food chain

3
Q

how are trophic levels represented

A

numbers, starting from 1

after 1, numbered according to how far along the organism is in the food chain

4
Q

what is trophic level 1

A

plants and algae which make their own food through photosynthesis - producers

5
Q

what is trophic level 2

A

herbivores which eat producers - primary consumers

6
Q

what is trophic level 3

A

carnivores that eat herbivores - secondary consumers

7
Q

what is trophic level 4

A

carnivores that eat other carnivores - tertiary consumers

8
Q

what is an apex predator

A

carnivore with no predators

9
Q

how do decomposers break down dead matter

A

release enzymes which catalyse the breakdown of dead material into smaller molecules

soluble small food molecules then diffuse into the microorganisms

10
Q

what is biomass

A

dry mass of all the living organisms in an area

11
Q

why is dry mass used for biomass

A

because wet mass varies as the volume of water in the organism varies

12
Q

equation of efficiency of biomass transfer

A

= (energy transferred/total energy available) x 100

13
Q

what percentage of the incident energy from for photosynthesis do producers transfer

A

1%

14
Q

what percentage of the biomass from one trophic level is transferred to the level above it in feeding

A

approx 10%

15
Q

why are biomass transfers not 100% efficient

A

energy is lost:
egestion (removal of faeces)

excretion (removal of waste products)

respiration (loss of CO2 and water) in which large amounts of glucose are used

production of inedible bones and shells

16
Q

how does the efficiency of biomass transfers affect the number of trophic levels in a biomass pyramid

A

the less efficient the transfers, the fewer trophic levels and the fewer organisms in higher trophic levels

17
Q

what is a biomass pyramid

A

pyramid that shows the total dry mass of organisms at each trophic level

18
Q

what is a pyramid of numbers

A

shows the number of organisms at each trophic level

19
Q

why are some pyramids of numbers not pyramid shaped

A

don’t take size and mass of organisms into account