2. Objectives
By the end of this session you will 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?
3. 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
4. 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!
7. 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!
9. 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”
10. 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
11. In Simple Terms…
Only individuals best
adapted to the
environment will survive!
Simples!
12. 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!
