© Boardworks Ltd 20063 of 25
A population is the number of individuals of the same species living in a certain habitat.
What is the difference between a population and a community?
What is a population?
A community includes all the different species living in a certain area.
© Boardworks Ltd 20064 of 25
What is a population?
The size of the population within a community can change over time. What factors will affect population size?
competition predators
disease migration
© Boardworks Ltd 20065 of 25
Competition occurs between different species…
Competition is one of the factors that affects population sizes. What type of organisms compete for resources?
What is competition?
© Boardworks Ltd 20066 of 25
Why do living things need to compete, and for what do they compete?
Members of the same species also compete for resources.
Why do animals compete?
© Boardworks Ltd 20067 of 25
What four things do animals have to compete for?
What do organisms compete for?
food
mates
water
space
© Boardworks Ltd 20068 of 25
What four things do plants have to compete for?
What do organisms compete for?
light
minerals
water
space
© Boardworks Ltd 20069 of 25
What happens if animals within a community have overlapping niches?
A niche is the position that an organism occupies in a community.
Niche competition
Animals with overlapping niches compete. The greater the overlap between niches, the greater the amount of competition between the species.
A niche organism has a specialized type of lifestyle.
© Boardworks Ltd 200610 of 25
What three things might happen to the less competitive species?
If species compete for all aspects of their niches, one species will better the other.
become extinct in that area.
move to another area
adopt new survival strategies
Competition losers
Competition results in winners and losers.
© Boardworks Ltd 200613 of 25
A predator is an animal that hunts and kills other animals for food.
A prey animal is one that is attacked and eaten by a predator.
Predators can be either:
Animals that eat other animals
carnivorous (eat meat only) e.g. wolves
omnivorous (eat meat and vegetation) e.g. humans.
© Boardworks Ltd 200614 of 25
Predators are adapted to hunting, catching and eating prey.
Prey are adapted to detecting and fleeing predators.
Predator and prey adaptations
© Boardworks Ltd 200615 of 25
The snowshoe hare lives in northern parts of North America. How is it adapted to avoid predators such as lynxes?
large furry feet act as snow shoes and protect the soles from cold
large ears help in detecting predators
greyish-brown fur turns white in winter for camouflage
strong teeth for chewing bark and twigs
Prey adaptations
© Boardworks Ltd 200616 of 25
How are lynxes adapted for catching snowshoe hares?
very strong hind leg muscles capable of pouncing 6.5 metres! extra large paws
act as snow shoes
excellent eyesight and hearing, and very sharp teeth!
warm thick furry coat protects from the cold
Predator adaptations
sharp claws for puncturing flesh
© Boardworks Ltd 200617 of 25
This population data comes from fur trapping records. How are the populations linked?
Predator-prey populations
0
50
esti
mat
ed p
op
ula
tio
n s
ize
(th
ou
san
ds)
1800 1820 1840 1860 1880 1900
100
150
year
lynx
snowshoe hare
© Boardworks Ltd 200618 of 25
How does the lynx population depend on the number of snowshoe hares?
Predator-prey populations
0
50
esti
mat
ed p
op
ula
tio
n s
ize
(th
ou
san
ds)
1800 1820 1840 1860 1880 1900
100
150
year
lynx
snowshoe hare
Take a closer look at this part
of the graph.
© Boardworks Ltd 200619 of 25
1850
Why does the peak for the lynx population always come after the peak for the number of snowshoe hares?
Predator-prey populations
0
50
esti
mat
ed p
op
ula
tio
n s
ize
(th
ou
san
ds)
1845 1855 1860 1865
100
150
year
lynx
snowshoe hare
For the populations to survive, there must always
be more hares than lynxes
© Boardworks Ltd 200620 of 25
Predator and prey population sizes follow a cycle.What happens if the prey population increases?
Predator-prey cycle
normal prey population
prey population increases
prey population decreasesbecause of more predators
prey populationincreases
predator population increases because
of more food
predator population decreases because
of less food
© Boardworks Ltd 200621 of 25
Predator and prey population sizes follow a cycle.What happens if the prey population decreases?
Predator-prey cycle
normal prey population
prey population decreases
prey population increasesbecause of fewer predators
prey populationdecreases
predator population increases because
of more food
predator population decreases because
of less food
© Boardworks Ltd 200623 of 25
Glossary
competition – The struggle for resources between individuals of the same or different species.
community – All the different types of species within a specific area.
niche – The position that an organism occupies in a community.
population – The number of one particular species within a specific area.
predator – An animal that hunts and kills other animals for food.
prey – An animal that is killed and eaten by another animal.