Darwin’s Theory of Evolution by Natural

Selection

25 May 2016

• There was a lot happening in the early 1800s – fossils, strata, etc.

• People believed that the different types of life that were seen through time were links in a 'Great Chain of Being‘

• Jean-Baptiste Lamarck was one of the first scientists to try to explain this chain using natural laws rather than a creator

Backing up a bit…

Lamarckism:

• Lamarck believed that animals became more and more complex, and that animals only kept the characteristics that were useful to them

• He also believed that whatever characteristics an animal developed during their life could be passed on to their offspring

• Lamarck was wrong….but he paved the way for others like Charles Darwin to think about evolution and natural selection

• Charles Darwin published On the Origin of Species in 1859

• Every copy was sold the day it was released • Many were furious, viewing the ideas in the

book as heresy, but most scientists recognized the power of his arguments

• Even today there is controversy in some circles about whether it is appropriate to teach Darwin’s theory in science curriculum

• Thoughts?

Darwin’s theory of evolution by natural selection:

1. More individuals are produced each generation than can survive

2. Variation exists among individuals and that variation can be

passed down from generation to generation

3. Individuals with inherited traits better suited to the environment will survive and pass these traits to their own offspring

SO: the next generation will have a higher proportion of individuals with these favourable traits (adaptations), and the population as a whole will have evolved

Darwin’s finches

• How far can evolution take us? • Humans and chimps come from a

common ancestor that lived about eight million years ago

• We have a common ancestor with whales about 60 million years ago, and with kangaroos over 100 million years ago

• Examples: whale blowholes, Mexican blind cave fish, Pacific salmon, anteater snout

Evolution usually takes millennia, but can sometimes happen much more quickly….

Peppered moths • Spend most of their time on light coloured,

lichen covered tree trunks

• Before 1800, most peppered moths had a light, speckled pattern and the darker variety was very rare

• Then came the Industrial Revolution – soot made light surfaces (e.g. tree trunks) much darker and dark moths became much more common, while the light moths almost disappeared

• Why?

But what about male peacocks?

Questions?