1. Pathways of Evolution

2. Divergent & Convergent Pathways
Divergent Evolution
Two or more species evolve increasingly different traits.
Disruptive selection may be the precursor.
Adaptive radiation – More than two species resulting from one original species – a la Darwin’s finches.
Convergent Evolution
Two or more species become increasingly similar.
Homoplasies – similar traits in different species of uncommon descent.
The marsupials of Australia and placental mammals demonstrate this. Page 603 – Figure 2
The shark and the dolphin converge as well.

3. Divergent Evolution

4. Convergent Evolution

5. Coevolution – Working Together
Coevolution occurs when one species evolves in response to the evolution of another species.
The fig and the fig wasp – the flower depends on the fig wasp for pollination while the wasp requires the flower to reproduce.
Leaf-cutter ants and fungus – the ants bring leaf pieces to feed the fungus which is eaten by the ants. Only home for fungus and sole food source of ants.

6. Coevolution – Working Together

7. FIN

8. Phylogenetic Relationships

9. Phylogeny – What it is…
Phylogeny is the theoretical evolutionary history of a species – your ancestry.
Monophyletic group or clade - Organisms that belong to the same group (descendants from a common ancestor).
These evolutionary relationships can be illustrated using a phylogenetic tree or cladogram. These are constructed using a system of classification based on shared derived traits called cladistics.

10. What does “cladistics” do?
Cladistics uses synapomorphies to construct cladograms or phylogenetic trees.
Synapomorphies are shared traits that evolved only once and have been inherited by two or more related species.
The greater number of shared derived traits two species have, the more closely related they are in terms of evolutionary history.

11. Applying Cladistics
When using cladistics to separate a number of organisms into separate clades, you must establish an “outgroup” based on the organisms being studied.
The “outgroup” is the first group to have diverged from the other groups of a clade.
See the next slide in this presentation…
Lets go over the construction of this cladogram together – it uses a variety of members of the Kingdom Animalia.

12. Applying Cladistics Hair Lungs Bony Shell Grasping Hands Jaws Lamprey-
Turtle +
Gorilla
Lungfish
Pike
Wolf
Human

13. Another Fine Cladogram Example

14. Applying Genetic Evidence
Genetic sequences or protein (amino acid) sequences can also be used to indicate the evolutionary relationship between two species.
Why?
Follow this thought…
Evolution based on characteristic changes.
Characteristics based on DNA sequences
DNA  RNA  Pn
Therefore, the less differences there are in amino acid and DNA sequences, the more closely related two species will be.

15. The Phylogenetic Wrap-Up
DNA mutates over time – the sequence of nucleotides changes and the protein’s amino acid sequence may change (not always due to codon overlaps).
The further back in time you have diverged, the more mutations have occurred – this means you will have more differences in your codes & sequences.
Few differences means you have just recently split and there has not been a lot of time for your codes & sequences to become all that different from one another yet.
The greater the number of differences = the further back in time your divergence occurred.

16. FIN