Food Chains

Question 1

What are producers?

Answer 1

•Organisms at the first level of the food chain e.g. green plants or algae
•they make glucose by photosynthesis
•glucose is used to make other biological molecules in a plant which make up the biomass

Question 2

What are primary consumers?

Answer 2

•organisms at the second level of the food chain
•these are herbivores that only eat plants

Question 3

What are secondary consumers?

Answer 3

•Organisms at the third level of the food chain
•these are carnivores that eat herbivores

Question 4

What are tertiary consumers?

Answer 4

•Organisms at the fourth level of the food chain
•these are carnivores that eat other carnivores
•they have no predators and are at the top of the food chain (apex predators)

Question 5

What are decomposers?

Answer 5

Fungi and bacteria that break down dead plant or animal matter

Question 6

How do decomposers break down matter?

Answer 6

•they secrete enzymes
•the matter is broken down into small soluble food molecules and they move into microorganisms by diffusion

Question 7

What is biomass?

Answer 7

•The mass of living material (the “energy stored in a plant”)
•energy is transferred through living organisms in an ecosystem when they eat other organisms

Question 8

Why is only around 10% of biomass transferred to the next levels of the food chain?

Answer 8

•not all biomass can be eaten e.g. carnivores cannot eat bone, claws and teeth
•not all biomass eaten is converted into biomass of the animal eating it e.g. it lost can be lost as faeces, urea or in plants lost due to respiration as carbon dioxide
•herbivores do not have all the enzymes to digest all the material they eat so it is egested instead

Question 9

What are predators?

Answer 9

Consumers that hunt and kill other animals

Question 10

What are prey?

Answer 10

Organisms that predators eat

Question 11

In a stable community, what determines the population size of any species?

Answer 11

The population of any species is usually limited by the amount of food available

Question 12

In a stable community what happens if the amount of prey increases?

Answer 12

The population of the predators increase

Question 13

In a stable community what happens if the population of predators increases?

Answer 13

The number of prey decrease

Question 14

Why are predator-prey cycles are always out of phase with each other?

Answer 14

It takes a while for one population to respond to changes in the other population e.g. in a community where foxes eat rabbits, when the number of rabbits increase, the number of foxes doesn’t increase immediately as it takes time for them to reproduce