Ecology - Trophic Levels and Biomass 221-224

Question 1

what are trophic levels
2 points

Answer 1

1) different stages of a food chain, they consist of one or more organisms that perform a specific role in the food
2) they’re named after their location in the food chain

Question 2

what is trophic level 1
2 points

Answer 2

1) contains producers which are the organisms at the start of the food chain
2) called producers because they make there own food by photosynthesis

Question 2

what is trophic level 4
3 points

Answer 2

1) contains tertiary consumers
2) eat other carnivores - secondary consumers
3) they have no predators and are at the top of the food chain - known as apex predators

Question 2

what is trophic level 2
2 points

Answer 2

1) contains primary consumers
2) herbivores that only eat plants and algae

Question 2

what is trophic level 3
2 points

Answer 2

1) contains secondary consumers
2) carnivores that eat primary consumers

Question 3

what happens to energy and biomass levels as you go up a food chain

Answer 3

there’s less energy and biomass every time you move up a trophic level

Question 3

what are decomposers
2 points

Answer 3

1) can be bacteria or fungi, they decompose any dead plant or animal material left in an environment
2) they do this by secreting enzymes that break the dead stuff down into small soluble food molecules which then diffuse into the microorganisms

Question 3

what is a pyramid of biomass
2 points

Answer 3

1) they represent a food chain, each bar on the pyramid shows the relative mass of a living animal at a trophic level
2) there’s a bar for each trophic level, at the bottom is level 1 and the next bar up is level 2

Question 3

how can you draw pyramids of biomass
3 points

Answer 3

1) if you’re given actual number you can use them to draw bars of the correct scale
2) the order of organisms in the pyramid must follow the order of the food chain
3) each bar must also be labelled

Question 4

how can you calculate the efficiency of biomass transfer
3 points

Answer 4

1) if you know the amount of biomass available at each trophic level you can work out how much has been lost each time
2) do this by taking away the biomass that’s available at that level from the biomass that was available at the previous level
3) you can then calculate the efficiency by using - efficiency=(biomass transferred to next level/biomass available at the previous level)x100

Question 4

what happens to biomass between each trophic level
4 points

Answer 4

1) producers use energy from the sun to make food during photosynthesis of the energy that hits these producers only about 1% is transferred for photosynthesis
2) some of the glucose is used by producers to make biological molecules which make up their biomass
3) biomass is transferred through a food chain in an ecosystem when organisms eat other organisms
4) but only about 10% of the biomass is passed onto the next level

Question 4

why is biomass lost between each trophic level
4 points

Answer 4

1) organisms don’t always eat all the organisms they’re eating - some of it is inedible like the bone
2) organisms don’t absorb all the stuff in the food they ingest and it’s released as faeces
3) some of the biomass taken in is converted into other substances that are lost as waste - e.g. organisms use a lot of glucose in respiration to provide energy for moving and keeping warm this produces lots of CO2 and water as by-products
4) urea is another waste product released in urine with water when the proteins in the biomass are broken down

Question 5

how can you calculate the efficiency of biomass
3 points

Answer 5

1) if you know the amount of biomass available at each trophic level you can work out how much is lost between each level
2) do this by taking away the biomass available at that level from the biomass that was available at the previous level
3) then you can calculate the efficiency of biomass transfer using: efficiency=(biomass transferred to the next level/biomass available at previous level)x100