Biology · 25 minutes

Which moths will become more common?

A moth does not choose its colour. But its colour can affect whether a bird finds it. Decide what you think will happen over several generations.

Keep this question in mindIf birds can see one colour more easily, what happens after several generations?

Look before you name the idea

Two colours. One species. One tree.

The pale and dark insects in this photograph are both peppered moths. Look at the trunk. Which one did your eyes find first?

A pale peppered moth and a dark peppered moth resting beside each other on a birch trunk — Two inherited wing colours of the same species. Which moth you notice first depends on the bark behind it.Maarten Sanne · CC BY-SA 3.0 ↗

Three things to know

A population can change even when no moth changes colour.

Keep your eye on what happens between parents and young. That is where the population changes.

Living things differ

Peppered moths of the same species can have different wing colours. A population contains both pale and dark moths.

Colour can be inherited

Young moths can inherit genes that affect wing colour. A moth does not turn dark because it lands on dark bark.

Survivors can have young

A moth that survives can reproduce. Over generations, an inherited colour can become more or less common.

Your prediction

What will happen if birds hunt on pale bark for many generations?

Start with equal numbers of pale and dark moths. Birds will catch the moths they see first. Predict the population after several generations.

APale moths will become more commonDark moths will be easier to see and more likely to be eaten.BDark moths will become more commonPale moths will be easier to see and more likely to be eaten.CThe two colours will stay equalWhich moths are eaten will not change the next generation.DEach dark moth will turn paleThe moths will change their own colour to match the bark.

Why do you think that? One clear sentence is enough.

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