Evolution & Natural Selection

First thoughts on the idea… “Acquired Traits” –If you want it you can make yourself have it Once a structure is modified it is passed onto offspring Lamark

Next to hypothesize….Charles Darwin “Natural Selection” Organisms best suited to their environment reproduce more successfully than other organisms, increasing favorable traits.

Evolution… is a gradual change in a species over time that is caused by natural selection.

Why change? Environment causes species to change Species with traits that help it adapt to its environment have more offspring and pass those traits to them These species have greater “FITNESS”

So what EVIDENCE do we have? 1 - Homological Structures Same embryonic structures that have been modified

2 – Analogous Structures Structures that look similar and have the same function, but they are not embryologically similar – they are not from a common ancestor

3 – Vestigial Structures Structures that are no longer useful, but were useful for our ancestors.

4 – Similarities in Embryology Early stages of different vertebrate are VERY SIMILAR!

5 – Similarities in Macromolecules Amino acid sequence – the more difference there is between the sequences the longer it has been since there was a common ancestor

Co-evolution The change of two or more species in close association with each other

Convergent Evolution When the environment selects for similar features, even though ancestors are very different

Divergent Evolution Two or more related species become more and more dissimilar, due to changing habitats. Can eventually result in new species. Artificial Selection

Adaptive Radiation When many different species evolve from one species