POPULATIONS Population size A population is the number

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 survive ANIMALS 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 § Traps heat to keep warm § Large body size to surface area ratio § Reduces heat loss by radiation § A large amount of body fat § Acts as a food store and to keep warm § Camouflage § 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 eyelashes 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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