1. Chapter 5 The Forces of Evolution And The Formation of Species

2. How Evolution Works Where Does Variation Come From? Mutations
Point mutation
Chromosomal mutation

3. How Evolution Works (cont’d)
How Natural Selection Works
Phenotypes in environments
Changes in gene frequencies
Directional Selection/ Stabilizing Selection

4. How Evolution Works (cont’d)
Other Ways By Which Evolution Happens
Gene Flow: movement of genes between populations
Genetic Drift: random changes in gene frequency in a population
Founder Effect: genetic bottleneck
Sexual Selection: Differential reproductive success within one sex of any species

5. Classification and Evolution
Taxonomy and Speciation
Systematics: branch of biology that describes organismal variation (what used to be called taxonomy)
Homology: the notion that similar features in two related organisms look alike because of a shared evolutionary history
Analogy: the notion that similar features in two unrelated organisms look alike because of adaptations to similar functions. (Convergent (parallel) evolution)

6. Classification and Evolution (cont’d)
Cladistics
Cladograms
Phenetics: numerical taxonomy
What is a Species?
An interbreeding group of animals or plants that are reproductively isolated through anatomy, ecology, behavior, or geographic distribution from all other such groups (Mayr, 1942)

7. Classification and Evolution (cont’d)
Species Concepts
Biological species concept
Evolutionary species concept
Ecological species concept
Recognition species concept

8. Classification and Evolution (cont’d)
Reproductive Isolating Mechanisms (RIMs)
Any factor that prevents a male and female of two different species from hybridizing
Premating RIMs
Postmating RIMs

9. Classification and Evolution (cont’d)
Premating RIMs
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical incompatibility
Postmating RIMs
Sperm-egg incompatibility
Zygote inviability
Embryonic or fetal inviability
Offspring inviability
Offspring sterility

10. Classification and Evolution (cont’d)
The Origin of Species: how species are formed
Anagenesis (whole group, no branching)
Cladogenesis (splitting events; branching)
Allopatric speciation (geographic isolation)
Parapatric speciation (separate habitats)
Sympatric speciation (form of anagenesis)

11. Classification and Evolution (cont’d)
The Tempo of Speciation
Gradualism
Darwinian
Gaps?
Macroevolution
Punctuated equilibrium

12. Classification and Evolution (cont’d)
Adaptation
(Is everything adaptive?)
Adaptations are evolved phenotypic traits that
increase an organism’s reproductive success

13. Classification and Evolution (cont’d)
Hardy-Weinberg Equilibrium
(p + q)2 = p2 + 2pq + q2 = 1

14. Levels of Selection Group selection Inclusive Fitness
Behavioral ecology
Kin selection
Coefficient of relatedness rb > c
Hamilton’s Rule