The theory of natural selectionLESSON # 18: CHARLES DARWIN

Individuals of any population have variations or differences

Overproduction

Each individual produces more offspring than

actually survive.

Heridability

Characteristics are passed down

from one generation to

the next.

Individuals whose variations help survival in a

certain environment are

favoured.

Struggle for existence or competition amongst new

borns.

Survival of the fittest.

Reproductiveadvantage

Surviving individuals

produce the next generation.

The variations which give a reproductive

advantage are transmitted to the offspring.

These characteristics or variants become more frequent in the population.

Gradual accumulation of

variations eventually

originate new species.

NATURAL SELECTION: 5 basic principles

Darwin’s theory of natural selection is not synonymous with evolution; it is a means of explaining how evolutionworks.

On the Origin of Species by Means of Natural SelectionCharles Darwin 1858

Darwin had formulated his theory of natural selection by about 1840.

Soon after, he began writing a multi-volume book compiling evidence for evolution and explaining how natural selection might provide a mechanism for the origin of species.

In 1858, Alfred Russel Wallace, another English naturalist, proposed a theory that was almost identical to Darwin’s theory of natural selection.

One year later, Darwin published On the Origin of Species by Means of Natural Selection. In his book, Darwin used the term evolution only on the last page.

Read the Origin of Species here: http://literature.org/authors/darwin-charles/the-origin-of-species-6th-edition/

Source: Biology. McGraw-Hill 2008 Georgia SW Edition.

Exercise 6 p. 158 The Biston betularia butterfly lives on the trunks of birch trees. There are light-colored and dark-colored butterflies. There are more light-colored ones in rural areas and more dark-colored ones in industrial areas that are polluted by smoke.

Write a paragraph using Darwin’s reasoning to answer the following questions.

a) Can you think of a reason for this difference? What color butterflies would have been more common in the Middle Ages? Why?

Peppered mothMariposa del abedúl

Birch treesAbedúl