1. Evolution

2. Genetic Variation and Evolution
Evolution: changes through time
Species accumulate difference
Descendants differ from their ancestors
New species arise from existing ones
Individuals don’t evolve – populations do

3. A brief history of evolution
Charles Darwin was born on February 12, 1809 in Shrewsbury, England.
From 1831 to 1836 Darwin served as naturalist aboard the H.M.S. Beagle on a British science expedition around the world.
He observed much variation in related or similar species of plants and animals that were geographically isolated from each other.
These observations were the basis for his ideas.

4.
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5. A brief history of evolution
Darwin presumed that populations of individuals changed over time, and, in 1844, he developed the concept of the driving force for evolution. It wasn’t until many years later that he published his idea.
“I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.”
—Charles Darwin from "The Origin of Species“, 1859

6. EVIDENCE OF EVOLUTION STRUCTURAL ADAPTATIONS MIMICRY CAMOUFLAGE
MILLIONS OF YEARS
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7. EVIDENCE OF EVOLUTION STRUCTURAL ADAPTATIONS MIMICRY CAMOUFLAGE
MILLIONS OF YEARS
PHYSIOLOGICAL ADAPTATIONS
CHANGE IN A METABOLIC PROCESS
WHAT DO YOU HEAR ABOUT IN THE NEWS ABOUT SOME BACTERIA?
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9. OTHER EVIDENCE OF EVOLUTION
FOSSILS
ANATOMY
HOMOLOGOUS STRUCTURES - similar structures that evolved from a common ancestor.
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10. OTHER EVIDENCE OF EVOLUTION
FOSSILS
ANATOMY
HOMOLOGOUS STRUCTURES
ANALOGOUS STRUCTURES - various structures in different species having the same appearance, structure or function but have evolved separately, thus do not share common ancestor
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11. OTHER EVIDENCE OF EVOLUTION
FOSSILS
ANATOMY
HOMOLOGOUS STRUCTURES
ANALOGOUS STRUCTURES
VESTIGIAL STRUCTURE - structures or attributes that have apparently lost most or all of their ancestral function in a given species, but have been retained
EMBRYOS
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12. MECHANISMS FOR EVOLUTION
HOW CAN THE GENE POOL CHANGE?
MUTATION - permanent alteration of the nucleotide sequence of the genome
GENETIC DRIFT - the change in the frequency of an allele in a population due to random sampling of organisms
GENE FLOW - the transfer of alleles or genes from one population to another
NONRAMDOM MATING - mating that has not occurred due to chance
SELECTION - survival and reproduction or elimination of individuals with certain genotypes (genetic compositions), by means of natural or artificial controlling factors.
WOULD THESE THINGS EFFECT A LARGE POPULATION OR A SMALL POPULATION MORE?

13. GENETIC DRIFT GENE FLOW - MIGRATION MUTATION
ALL IMAGES:
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14. Five agents of evolutionary change
The Hardy-Weinberg Principle - genetic equilibrium

15. Genetic equilibrium is a basic principle of population genetics.
Hardy–Weinberg principle states that the genotype frequencies in a population remain constant or are in equilibrium from generation to generation unless specific disturbing influences are introduced.
Those disturbing influences include:
non-random mating
new mutations
selection
random genetic drift
gene flow

16. Evolution of species Based on 3 mechanisms 1. Sources of variation
2. Method of selection for those characteristics that would be passed on
3. A mechanism for retaining changes

17. 1. Sources of variation
Genetic diversity thru mutations that are not lethal
Physical or behavioral traits
Sexual reproduction between genetically different individuals

18. 1. Sources of variation

19. 2. Method of selection
Reproductive fitness is the method of selection.
Competition, escaping from and eluding predators
Finding a good mate

20. Selection
Natural selection: environmental conditions determine which individuals in a population produce the most offspring
3 conditions for natural selection to occur
Variation must exist among individuals in a population
Variation among individuals must result in differences in the number of offspring surviving
Variation must be genetically inherited

21. Natural selection: mechanism of evolutionary change
Natural selection: proposed by Darwin as the mechanism of evolution
individuals have specific inherited characteristics
they produce more surviving offspring
the population includes more individuals with these specific characteristics
the population evolves and is better adapted to its present environment

22. Natural Selection Darwin: Evolution is descent with modification
Darwin knew nothing of genes, but what he did have were two observations and a little inference that provided the motive force for evolution.
Darwin: Evolution is descent with modification

23. Natural Selection
Observation 1: Organisms generally have more offspring than can survive to adulthood.
Observation 2: Offspring are not identical. There is variation in their appearance, size, and other characteristics.

24. Natural Selection Survival of the “fittest.”
Inference: Those organisms that are better adapted to their environment have a greater likelihood of surviving to adulthood and passing these characteristics on to their offspring.
Survival of the “fittest.”

25. Survival of the “fittest.”
Darwin’s theory for how long necks evolved in giraffes

26. Selection
Artificial selection: a breeder selects for desired characteristics

27. 3. Maintenance of Variation
Frequency-dependent selection: depends on how frequently or infrequently a phenotype occurs in a population
Negative frequency-dependent selection: rare phenotypes are favored by selection
Positive frequency-dependent selection: common phenotypes are favored; variation is eliminated from the population
Strength of selection changes through time

28. Negative Frequency-Dependent Selection
Side-blotched Lizards
Infectious Diseases
Male common side-blotched lizards come in three throat-color patterns: orange, blue, and yellow. Each of these forms has a different reproductive strategy: orange males are the strongest and can fight other males for access to their females; blue males are medium-sized and form strong pair bonds with their mates; and yellow males are the smallest and look a bit like female, allowing them to sneak copulations. Like a game of rock-paper-scissors, orange beats blue, blue beats yellow, and yellow beats orange in the competition for females.
As a result, populations of side-blotched lizards cycle in the distribution of these phenotypes. In one generation, orange might be predominant and then yellow males will begin to rise in frequency. Once yellow males make up a majority of the population, blue males will be selected for. Finally, when blue males become common, orange males will once again be favored.
As a particular human population is infected by a common strain of microbe, the majority of individuals in the population become immune to it. This then selects for rarer strains of the microbe which can still infect the population because of genome mutations; these strains have greater evolutionary fitness because they are less common.

29. Positive Frequency-Dependent Selection
The scarlet kingsnake, a harmless species, mimics the coloration of the eastern coral snake, a venomous species typically found in the same geographical region. Predators learn to avoid both species of snake due to the similar coloration, and as a result the scarlet kingsnake becomes more common, and its coloration phenotype becomes more variable due to relaxed selection. This phenotype is therefore more "fit" as the population of species that possess it (both dangerous and harmless) becomes more numerous.
Mimicry

30. WHAT IS SPECIATION? GEOGRAPHIC ISOLATION REPRODUCTIVE ISOLATION
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31. Fitness and Its Measurement
Fitness: A phenotype with greater fitness usually increases in frequency
Most fit is given a value of 1
Fitness is a combination of:
Survival: how long does an organism live
Mating success: how often it mates
Number of offspring per mating that survive