1. 17.3 Darwin and Natural Selection: What Darwin knew  Darwin understood the fossil record and explained it by combining the two popular ideas of gradualism and catastrophism. Land forms and species change gradually through time. Natural catastrophes can change land forms quickly and eliminate species.

2. 17.3 Darwin and Natural Selection: What Darwin knew  Darwin’s observations of species and patterns in different parts of the world helped him understand a driving force of evolution – natural selection.

3. Patterns in Biogeography: Similar form evolved independently on different continents (why?)

4. Finches in the Galapagos Islands: Similar species with adaptive traits

5. What about Vestigial Body Parts?

6. A Key Insight – Variation in Traits  Darwin’s observations: Populations can produce more individuals than their environment can support (Overproduction). Some versions of a trait might enhance an individual’s ability to survive (or not) and reproduce (or not) in its particular environment (Differential reproductive success).

7. What is Natural Selection?  Natural selection: In a given environment, differential survival and reproduction among individuals of a population that vary in details of shared, inherited traits.  Any trait that enhances an individual’s fitness (ability to survive and reproduce in a particular environment) is called an adaptive trait. Survival of the fittest?

8. Today’s Principles of Natural Selection Darwin explained why there are (and have been) so many different kinds organisms. Modern genetics and evolutionary developmental biology (EvoDevo) explains how it happens. Why + How yields the Natural Selection explanation

9. 18.1 Individuals Don’t Evolve, Populations Do  A population is a group of reproducing individuals of the same species in the same area (same gene pool).  Evolution starts with microevolution: mutations in individuals which are the source of new alleles.  Sexual reproduction can quickly spread a mutation, and the new allele through a population. But, why don’t some variations spread?

10. Variation In Populations  All individuals of a species share certain traits.  Individuals of a population vary in the details (alleles) of their shared traits.

11. Stability and Change in Allele Frequencies: Microevolution  When allele frequencies, relative abundance of alleles of a given gene in a population, change in a population, the population is said to be evolving.  Natural populations are never in genetic equilibrium.  Four processes of microevolution (small-scale changes in a population's allele frequencies) prevent genetic equilibrium: Mutation

12. Stability and Change in Allele Frequencies: Microevolution  Natural populations are never in genetic equilibrium.  Four processes of microevolution (small-scale changes in a population's allele frequencies) prevent genetic equilibrium: Gene Flow (migration of individuals among populations)

13. Stability and Change in Allele Frequencies: Microevolution  Natural populations are never in genetic equilibrium.  Four processes of microevolution (small-scale changes in a population's allele frequencies) prevent genetic equilibrium: Genetic Drift (random change in allele frequency)

14. Stability and Change in Allele Frequencies: Microevolution  Natural populations are never in genetic equilibrium.  Four processes of microevolution (small-scale changes in a population's allele frequencies) prevent genetic equilibrium: Natural Selection

15. What are the four major processes of microevolution that disrupt genetic equilibrium in populations? Stability and Change in Allele Frequencies: Microevolution

16. 18.3-18.5 Natural Selection Revisited  Natural selection is the differential survival and reproduction among individuals of a population that vary in details of their shared traits.  Natural selection is a driving force of evolution.  Natural selection occurs in recognizable patterns depending on the organisms and their environment, especially with polygenic traits.  3 selection patterns: Directional, Stabilizing, and Disruptive.

17.  Directional selection Changing environmental conditions can shift allele frequencies (and their phenotypes) in a consistent direction. Forms of traits at one end of a range of phenotypic variation become more common.

18.  Light color is adaptive in areas of low pollution; dark color is adaptive in areas of high pollution. “Natural” and artificial experiments in Directional Selection: Predation and Peppered Moths (Kettlewell 1955) Low pollution, productive lichen growth High pollution, dead lichen

19. “Natural” and artificial experiments in Directional Selection: Blackcaps

20. Deviation from the mean migratory activity at onset Amount of migratory activity at onset (solid line-parents; dashed line-F 1 offspring)

21. A truly natural experiment in Directional Selection: Predation and Rock-Pocket Mice (Hoekstra et al. 2005)  In rock-pocket mice, two alleles of a single gene control coat color.  Night-flying owls are the selective pressure that directionally shifts the allele frequency.

22. Artificial Selection for Antibiotic Resistant Bacteria (ARB)  A typical two-week course of antibiotics can exert selection pressure on over a thousand generations of bacteria.

23. 18.5 Selection Against or in Favor of Extreme Phenotypes  Stabilizing selection favors an intermediate phenotype and eliminates extreme forms.  Disruptive selection favors extreme forms of a trait and eliminates the intermediate forms.

24. 18.12 Macroevolution  Macroevolution Large-scale patterns of evolutionary change such as one species giving rise to multiple species, the origin of major groups, and major extinction events.  Coevolution Predator and prey Host and parasite Pollinator and flower What explains the presence of ultra-fast pronghorn in North America? (What happens to a group of related individuals over a long period of time)

25. Stasis and Exaptation  Stasis A lineage exists for millions of years with little or no change (e.g. Bdelloid Rotifers).  Exaptation (preadaptation) Some complex traits in modern species held different adaptive value in ancestral lineages (e.g. feathers in birds and dinosaurs).

26. Adaptive Radiation  Adaptive radiation A burst of speciation that occurs when a lineage encounters a new set of niches.  Key innovation A structural or functional adaptation that allows individuals to exploit their habitat in a new way.

27. Extinction  Extinction - the irrevocable loss of a species from Earth.

28. Extinction  Mass extinctions - extinctions of many lineages, followed by adaptive radiations of surviving populations.

29. Adaptive Radiation of Mammals Following the K-T Extinction