A population showing variation in colour.

Continuous or discontinuous?

There is lots of food so your population survives and reproduces. Add 5.

The bright yellow of some of your offspring attracts predators. All but two of them get eaten.

There’s lots of food and hiding places for the green andblue, but the red ones can’t hide and get eaten.

Plenty of food and its spring so another 10 offspring are born, they are a variety of colours.

Plenty of food and its spring so another 10 offspring are born, they are a variety of colours.

It’s winter and 5 of your population die

Its mating time again, blue and green mate and produce 5 green and 2 blue offspring. A mutation also produces 2 red offspring

Its mating time again, blue and green mate and produce 5 green and 2 blue offspring. A mutation also produces 2 red offspring

There is lots of food, and all reproduce 2 offspring, but the white are better at finding water and hiding from predators so they produce 5 offspring

There is lots of food, and all reproduce 2 offspring, but the white are better at finding water and hiding from predators so they produce 5 offspring

The bright red colour attracts mosquitoes carrying a deadly disease. They all die.

The bright red colour attracts mosquitoes carrying a deadly disease. They all die.

It is a particularly hot summer, blue and green are poor temperature regulators; white and yellow, which reflect heat, are more likely to survive.

It is a particularly hot summer, blue and green are poor temperature regulators; white and yellow, which reflect heat, are more likely to survive.

When food is plentiful again the remainder mate and produce 5 offspring some white and some yellow.

When food is plentiful again the remainder mate and produce 5 offspring some white and some yellow.

A scientist finds this population and reports that this species occurs in two colours. He says they have adapted to their habitat. What does he mean?

What is the population?Has it changed?

In outline, Darwin stated the following:

Many more individuals are born than can possibly survive.

Individuals within a population vary slightly from one another.

There is a frequent recurring struggle for existence.

Some individuals will have a better chance of surviving than others (they will be naturally selected).

Any selected variety will tend to propagate its form.

Q.What did the individuals in our population compete for in the struggle to survive?

Q.Which individuals were naturally selected?

Lamarck (a french biologist) proposed:During a life, structures or characteristics may be used or not used.Extensive use would lead to increased size and/or efficiency.

Characteristics acquired during a lifetime could be inherited and so passed on to any offspring.

Q.Does our population show any evidence to contradict or support Lamark?

To test Lamarck’s theory, Weismann cut off the tails of mice for successive generations. Q.What should have happened if Lamarck’s ideas were to be supported?Q.What do you think did happen?

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