1. Mader Biology Ch 17 and 18 (and a little of 19)
Evolution
Mader Biology Ch 17 and 18 (and a little of 19)

2. Natural Selection
Obs. 1: Individuals of a population vary phenotypically; no 2 are exactly alike
Obs. 2: Much of this variation is heritable
Inference #1: Those individuals whose heritable traits best fit them for the environment are likely to leave more offspring than less fit individuals
Inference#2: This differential reproductive success will lead to a gradual change in a population

3. Summary of Darwin’s ideas
Natural selection is differential success in reproduction
It occurs through an interaction between the environment and the variability among individuals within a population
The product of natural selection is the adaptation of populations to their environment

4. Natural Selection in Action

5. Natural Selection in Action
Evolution of antibiotic-resistant strains of bacteria
Industrial melanism in the peppered moth

6. Basic Vocabulary
Natural Selection-a population of organisms can change over generations if individuals having certain heritable traits leave more offspring than others
Adaptation- trait shaped by natural selection that increases an organism’s reproductive success (“fitness”). Ex- camouflage, mimicry
Evolution- change in the genetic composition of a population over time

7. History of Evolutionary thought

8. Paleontology & Evolution
Older layers of sedimentary rock (the layers on the bottom) contain fossil species very dissimilar from modern
Each layer (stratum) is characterized by a unique group of fossil species
As you move upward through the layers, you find species more and more similar to modern life

9. Based on paleontology, Lamarck proposed a theory of evolution
Based on 2 mechanisms (1809)
Use and disuse: the idea that parts used the most grow stronger; the parts that don’t get used deterioate
Inheritance of acquired characteristics: the modification that an organism acquires during its lifetime can be passed along to its offspring
Helped set stage for Darwin by proposing that species evolve as a result of interaction with environment

10. Charles Darwin ( )
Born in England, he had a consuming interest in nature that his dad did not like
His dad sent him to medical school (at 16). Charles was bored and left
He then enrolled at Christ College at Cambridge with the intent to become a clergyman
He was invited along on a voyage to chart the South American coastline on board the HMS Beagle that lasted 5 years

11. The Origin of Species (1859) developed 2 main points
Descent with modification
The history of life is like a tree, with multiple branching and re-branching from a common trunk all the way to the tips of it youngest twigs; most branches are dead ends
Natural selection and adaptation
The concept of natural election is based on 5 observations made by Darwin and can be summarized in 3 inferences made from those observations

12. Evidence for evolution

13. Bacterial Resistance
We can see evolution through antibiotic resistance
The population of bacteria can change over time to be resistant to many different drugs

14. The Fossil Record
Older and older fossilized organisms deeper into crust
Found in sedimentary rock
We can determine the age of fossils with carbon dating

15. Biochemistry Similarities in genes and proteins show relatedness
Scientists can determine the evolutionary relatedness based on the DNA sequence

16. Embryology Many animal embryos (in the womb) look similar
This suggests common ancestry

17. Comparative Anatomy Homologous Structures: Analogous Structures:
Structures that are anatomically similar because the organisms share a common ancestor
Analogous Structures:
Structures that are anatomically similar but the organisms do not share a common ancestor
Vestigial Structures:
Physical features that are reduced and unused
Were once used by ancestors but evolved to not need them

18. Mechanisms for Evolution
(aka: how does it occur?)

19. Mechanisms for Evolution
Mutations
Gene Flow
Genetic Drift
Nonrandom Mating
Bottleneck Effect
Founder Effect
Natural Selection

20. Mutation
Changes in DNA introduce variation in a population

21. Natural Selection Stabilizing: Directional: Disruptive:
Middle phenotype favored
Population moves toward norm
Directional:
Extreme phenotype is favored
Population shifts in that direction
Disruptive:
2 or more extreme phenotypes favored
Population splits

22. Reminder: INDIVIDUAL ORGANISMS DO NOT EVOLVE!
Natural selection does not act on individuals, but only in the sense that it affects one individual’s ability to survive and reproduce
The smallest unit that can evolve is a population, a collection of individuals of the same species living in an area together

23. Mechanisms of speciation
How do new species occur?

24. Geographic Isolation Species occur in different areas
Ammospermophilus spp
Species occur in different areas
physical barrier prevents gene flow
Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel

25. Reproductive Isolation