Page 59 - Science Coursebook

3.8 Charles Darwin

In 1859, another book containing new ideas was published. The
author was Thomas Malthus. Malthus suggested that the population
of humans on Earth could not grow for ever. Eventually, he wrote,
there would not be enough food for us all.
This was another important piece in the puzzle. Now Darwin
thought that he could see the steps that could lead to the evolution of
a new species. In 1859, he published his most famous book, The Origin
of Species.
These were the main points in his theory:
• The organisms in a species are not all exactly the same as each
other. They show variation.
• Many organisms will not survive until adulthood. They may be
killed by predators, die of disease, or not be able to get enough to
eat.
• The individuals that have variations that make them best adapted
to their habitat are the ones that have the best chance of surviving. This poster, printed in 1891, shows
• The best-adapted organisms are therefore the ones that are most some of the many pigeon breeds
likely to breed and have offspring. that existed in Darwin's time.

• The offspring will inherit some of the features of their parents.
• If this continues, generation after generation, then there could be
a change in the species over time. Eventually, it could change so
much that it would be a different species.

Darwin called his theory natural selection. This is the term that
we still use today.
Activity 3.8

Darwin’s big idea

SE In your group, look at each of the steps in Darwin’s theory. For each step, discuss
what you think helped him to think out his theory.
Some people in the group could research some more information about this,
using the library or the internet.
Now plan how you can present your ideas to the rest of the class. For example,
you could draw a big mind map, or write your ideas down in words.

Summary
• Darwin was the first person to suggest a way in which one species

could change into another species.
• Darwin put forward (proposed) the theory of natural selection.
• The theory of natural selection states that the individuals that are best
adapted to their environment are the ones that are most likely to pass
on their features to the next generation.

3 Variation and inheritance 57