Evolution

Learning Outcomes

State that competition which arises from variation leads to differential survival of, and reproduction by, those organisms best fitted to the environment.
Give examples of environmental factors that act as forces of natural selection.
Assess the importance of natural selection as a possible mechanism for evolution.
Give examples of artificial selection such as in the production of economically important plants and animals.

🕜Estimated Time: 1 hour

Watch the video below to gain an understanding of what evolution is and how the theory came about.

Selection pressure determines which individual gets a higher chance to survive and reproduce.
If the selection pressure is from the organism's natural environment, the process is termed as natural selection (e.g. being hunted by predators).
If the selection pressure is exerted by humans, the process is termed as artificial selection (e.g. selective breeding by man).

Artificial selection is where human ‘selects’ the variety of organism that suits their needs.
E.g.
- - Cows that produce plenty of milk and good meat are selected by humans and used for reproduction.
  - After many generations, such selective breeding results in good meat-producing and milk-producing cows.

Evolution is the process by which the present complex forms of living organisms arises from simple ancestral forms.
Natural selection is a possible mechanism for evolution.
Natural selection is the process which results in the best adapted organisms in a population surviving to reproduce.
Evolution takes place over millions of years, so in order to gather evidence to prove that natural selection is the cause of evolution, we have to look at examples that occurred.
- - Case study on the Finches on the Galapagos Islands

In the 1800s, Charles Darwin travelled to the Galapagos Islands to understand how life first arise in the new islands.
- - The Galapagos Islands are an archipelago of 13 major islands and more than a hundred smaller islands.
On his visit to the Galapagos Islands, Charles Darwin discovered several species of finches that varied from island to island, which helped him to develop his theory of natural selection.

Geographical location of South America and the Galapagos Islands

On the South American mainland, finches have short and straight beaks.
- - However, in the nearby Galapagos Islands, there are 6 major types of beaks found.
  - There were variations in the characteristics of the finches, such as the beak sizes, across the different islands.

The different varieties of finches on the Galapagos Islands and their respective diet

Therefore, within each island,

The finches with beaks suited to the particular diet survived and reproduced, passing on the alleles with favourable traits to their offsprings. Finches with such beaks increase in number.
On the other hand, finches with beaks that are not suited to the diet will die and decrease in number.

Biology Resources Main Page

Fill out the form below to test your understanding on the topic of Evolution. Remember to click 'View responses' to see the correct answers.

Page updated

Google Sites

Report abuse