1. Evolution and Speciation
Mechanisms of Evolution

2. Factors that affect Populations
Genetic variation of individuals within a population makes evolution possible.
Each new generation is made up of genetically unique individuals.
Also, new mutations occur randomly new each generation
These lead to creation of new alleles inherited from parents

3. Populations not individuals evolve
Population:A localized group of individuals belonging to the same species.
Species: A group of populations whose individuals have the potential to interbreed and produce viable offspring.
Gene pool: The total collection of genes in a population at any one time.

4. Microevolution
Changing percentages, or frequencies, of alleles within populations are the small events that lead to evolution within a population = microevolution

5. Hardy-Weinberg Principle
The concept that the shuffling of genes that occur during sexual reproduction, by itself, cannot change the overall genetic makeup of a population.

6. Hardy-Weinberg Principle
This principle will be maintained in nature only if all five of the following conditions are met:
1. Very large population
2. Isolation from other populations
3. No net mutations
4. Random mating
5. No natural selection

7. Hardy-Weinberg Principle
Remember:
If these conditions are met, the population is at equilibrium.
This means “No Change” or “No Evolution”.

8. Microevolution
The origin of taxonomic groups higher than the species level.
A change in a population’s gene pool over a secession of generations.
Evolutionary changes in species over relatively brief periods of geological time.

9. Factors that Cause Evolutionary Change
Five Mechanisms of Microevolution
Mutation
Gene flow
Non-random mating
Genetic drift
Natural selection

10. 1. Mutation
Mutation: Change in an organism’s DNA that creates a new allele.
Randomly introduces new alleles into a population and can change allele frequencies in a population

11. 2. Gene flow
Net movement of alleles from one population to another due to the migration of individuals
Occurs between two different interbreeding populations that have different allele frequencies
Hamadryas baboons in Saudi Arabia. At some point in their lives, female Hamadryas baboons leave their birth group and migrate to a different one. This promotes gene flow between different groups, helping all populations maintain healthy and diverse gene pools.

12. 3. Non-random mating Selection of mates other than by chance
Individuals in a population select mates often based on their phenotypes
Increases the population of particular characteristics
Based on:
Preferred Phenotypes
Inbreeding

13. Preferred Phenotypes
Choosing of mates based on their physical and behavioural traits
Prevents individuals with particular phenotypes form breeding
Only the individuals that mate will contribute to the gene pool of the next generation

14. Inbreeding Occurs when closely related individuals breed together
E.g. self-fertilization of flowers
Purebred animals tend to have a higher incidence of deformities and health problems compare with non-purebred animals. (lower fertility rates)
E.g. Shar-pei dog -- hyaluronic acid and mucinosis

15. 4. Genetic Drift
The change in frequencies of alleles due to chance events in a breeding population.
Sample size can greatly affect the gene pool of a population.
The smaller the population, the less likely it is that the parent gene pool will be reflected in the next generation.
In a large population there is a better chance that the parent gene pool will be reflected in future generations.
Occurs by:
Bottleneck Effect -Founder Effect

16. Bottleneck Effect
Changes in gene distribution that result from a rapid decrease in population size
Colonization of a new location by a small number of individuals, results in random change of the gene pool
E.g. Darwin’s finches

17. BOTTLENECK EFFECT
Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000 — but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
Don’t kill me 

18. FOUNDER EFFECT
Genetic drift resulting from the colonization of a new location by a small number of individuals.
Results in random change of the gene pool.
Example:
1. Islands (first Darwin finch)
Darwin’s finches 18

19. FOUNDER EFFECT Founder effect
A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:
a. reduced genetic variation from the original population.
b. a non-random sample of the genes in the original population.
Computer Simulation

20. FOUNDER EFFECT Example: Amish community
Ellis-van Creveld syndrome, involves not only short stature but polydactyly (extra fingers or toes), abnormalities of the nails and teeth, and, in about half of individuals, a hole between the two upper chambers of the heart. The syndrome is common in the Amish because of the founder effect

21. 5. Natural Selection
The result of the environment selecting for individuals in a population with certain traits that make them better suited to survive and reproduce than other in the population
Over many generations, frequencies of alleles of many different genes may change, resulting in significant changes in the characteristics of a population

22. MODES OF ACTION Natural selection has three modes of action:
1. Stabilizing selection
2. Directional selection
3. Diversifying selection
Number of
Individuals
Size of individuals
Small Large 22

23. 1. STABILIZING SELECTION
Acts upon extremes and favors the intermediate
Reduces variation, improves the adaptation of the population to aspects of the environment that remain constant 23

24. 2. DIRECTIONAL SELECTION
Favors variants of one extreme
Common during times of environmental change or during migration to a new habitat
Peppered moths 24

25. 3. DIVERSIFYING SELECTION
Favors variants of opposite extremes
Intermediate phenotypes can be eliminated 25

26. Animations

27. Sexual Selection
Natural selection for mating based, in general, on competition between males and choices made by females
Combat
Visual displays
Sexual dimorphism