POPULATIONS

Population size

•A population is the number of a species living in a particular area

What factors could change a population?

• Competition

• Predation

• Migration

• Disease

• Natural disasters

• War

• For food, water and space

• Predators will eat prey and reduce the population (including the number of offspring)

• Members of the population may leave the area

• A disease could kill some of the population

• Drought, fire, floods, volcanic eruptions etc could alter the habitat and affect the population

• Wars can result in the death of many members of a population

What else can affect the numbers and the distribution of a population?

• How well are individuals adapted?

• This will affect their survival in a habitat.

• What else lives there? This may mean competition for food.

• There may be predators.

What is adaptation?

• Adaptation describes how a plant of animal is able to survive in various environments

• Well adapted organisms can cope with the different aspects of their environment, for example, the temperature

It is always a struggle for plants and animals to

surviveANIMALS STRUGGLE :

• For food• For water• For protection

against weather• Against being

eaten by predators• Against disease• Against accidents

PLANTS STRUGGLE:• For water• For light• For minerals in the

soil• Against weather• Against disease• Against being

eaten

How does adaptation help organisms?

• Well adapted organisms are better at coping with extremes of weather

• They are better at competing for food• They are better at escaping from

predators• They are more likely to survive in

their habitat and produce offspring

An arctic habitat

• This sort of habitat can have extremely low temperatures

• The ground is covered with white snow for most of the year

How are animals adapted to survive in

the Arctic?• Animals like polar bears will have a thick insulating coat

• They usually have a large amount of body fat

• They have a large body size to surface area ratio

• They have a camouflaged coat

How do these adaptations help?

A thick fur coat

Large body size to surface area ratio

A large amount of body fat

Camouflage

Traps heat to keep warm

Reduces heat loss by radiation

Acts as a food store and to keep warm

White fur is good camouflage to hide from prey

A desert environment• A desert can have

very little rainfall• There is a lot of

sunshine during the day

• There is very little shade

• The temperatures can get very hot

• At night it can become very cold

How is a camel adapted to survive in the desert?

• Camels can store large amounts of water in the fat in their humps

• They have feet with a large surface area to allow them to walk on sand

• They also have long eye-lashes to stop sand blowing into their eyes

How do reptiles survive in the desert?

• Most reptiles will find some shade under a rock during the hottest part of the day

• When walking on hot sand a lizard will try to touch the ground with only a small area

• This lizard keeps swopping feet, and only stands on two feet at a time

• This snake keeps a loop of itself off the ground as it moves across the sand sideways

How do plants survive the desert?

• A cactus has a long tap root to reach water deep under the ground

• It has a thick, fleshy stem to store water

• It has needle-shaped leaves to prevent water loss through the stomata

• The needles help to stop animals from eating it

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