Evolution Theory

From ape to man….

Objectives

By the end of this session you wil l be able to…

• Define the term “evolution”

• Explain the difference between “divergent” and “convergent” evolution.

And maybe even…• Evaluate the concept of evolution – is it fact or theory?

What is Evolution?

“How species adapt over time in order to survive in a specific environment”

Fact of evolution: • Observed changes over time• Known to have occurred

Theory of evolution:• Analysis of observed changes• Why these changes occur

Types of Evolution

Divergent Evolution• Organisms have a common ancestor• Changes in environment cause them to adapt• So they may look/ act differently, but they are still related!

Convergent Evolution• Organisms have similar features• However, they don’t have a common ancestor!• So they may look/ act the same, but they are not related!

Divergent Evolution

Wood Mouse(Apodemus sylvatica)

House Mouse(Mus musculus)

Convergent Evolution

Charles Darwin

• Naturalist• Marine Invertebrates• Influenced by Charles Lyell• 5 year voyage – HMS Beagle• Transmutation of species• Collected species to analyse!

Evolutionary observations mainly based on Galapagos Islands – not all though!

Galapagos Finches

Origin of Species

• Published 24 November 1859

• Introduced the theory that populations evolve through natural selection

• Proved unexpectedly popular(ish!)

• Aroused international interest

• Church of England – mixed response!

• Led to “Darwinism”

Summary of Theory• Species have great fertility. They have more offspring than ever to grow to

adulthood. • Populations remain roughly the same size, with small changes. • Food resources are limited, but are relatively stable over time. • An implicit struggle for survival ensues. • In sexually reproducing species, generally no two individuals are identical. • Some of these variations directly affect the ability of an individual to

survive in a given environment. • Much of this variation is inheritable. • Individuals less suited to the environment are less likely to survive and

less likely to reproduce, while individuals more suited to the environment are more likely to survive and more likely to reproduce.

• The individuals that survive are most likely to leave their inheritable traits to future generations.

• This slowly effected process results in populations that adapt to the environment over time, and ultimately, after interminable generations, these variations accumulate to form new varieties, and ultimately, new species

In Simple Terms…

Only individuals best adapted to the

environment will survive!

Simples!

Public Reaction

What happened then?• Public outcry and mocking• 30th June 1860, Oxford • Subject of massive debate What do we think now?• Generally accepted globally• Only 25% Britons believe it (apparently)• Still criticised in America – some states banned!

The South Park View…