B7 Food Chains (page 86) Flashcards
What are food chains?
They show what’s eaten by what in an Ecosystem.
Food chains always start with what?
A producer
(Producers make (produce) their own food using energy from the sun).
Producers are usually what?
they are usually green plants or algae - they make glucose by photosynthesis (see page 50).
When a green plant produces glucose, some of it is used to make other what?
other biological molecules in the plant.
What are the biological molecules in a plant?
These biological molecules are the plant’s biomass - the mass of living material.
Biomass can be thought of as what in a plant?
as energy stored.
How is Energy transferred through living organisms in an ecosystem?
when organisims eat other organisms.
Producers are eaten by what consumers?
by primary consumers. (first consumers)
Primary consumers are then eaten by what consumers?
by secondary consumers. (second consumers)
Secondary consumers are eaten by what consumers?
tertiary consumers (third consumers).
Look at the diagram on page 86, and explain the food chain example?
Producers: - 5000 dandelions…
feed
Primary consumers - 100 rabbits….
which then feed
Secondary consumer - 1 Fox.
Populations of Prey and Predators go in Cycles.
Consumers that hunt and kill other animals are called what?
Predators.
What do Predators eat?
their prey (their prey is what they eat).
(this is in a stable community containing prey and predators) - more on stable community see page 83.
The population of any species is usually limited by what?
by the amount of food available.
If the population of the prey increases, then what will happen?
the population of the predators will also increase.
If the population of the predators increases, what will happen with the number of prey?
the number of prey will decrease.
Look at Diagram 2 on page 86, explain the diagram?
more grass means more rabbits. more rabbits means more foxes. But more foxes means fewer rabbits. Eventually fewer rabbits will mean fewer foxes again. This up and down pattern continues. see diagram 2 on page 86
Predator-prey cycles are always out of phase with each other why?
This is because it takes a while for one population to respond to changes in the other population. E.g. when the number of rabbits goes up, the number of foxes doesn’t increase immediately because it takes time for them to reproduce.
You might think that the start of a food chain always has to be a plant, in most cases it is, but sometimes organisms like Algae too explain why?
because they photosynthesise.
Look at the following food chain for a particular area:
grass»_space;> grasshopper»_space;> rat»_space;> snake.
a) Name the producer in the food chain (1 mark)
b) How many consumers are there in the food chain (1 mark)
c) Name the primary consumer in the food chain? (1 mark).
d) All the rats in the area are killed. Explain two effects that this could have on the food chain. (4 marks)
a) grass (1 mark)
b) three (1 mark)
c) grasshopper
d) The population of grasshoppers could increase (1 mark) as there’s nothing to eat them (1 mark). The population of snakes could decrease (1 mark) as there’s nothing for them to eat (1 mark).
