1. Darwin's Theory of Evolution
Textbook pages

2. Charles Darwin
Charles Darwin, Alfred Wallace and others promoted the idea of evolution as they tried to make sense of the following question:
“How could there be so many different kinds of living things (diversity) and at the same time how can all living things be so similar (unity)?

3. Charles Darwin given credit for the Theory of Evolution
provided evidence for the theory
“On The Origin Of Species By Natural Selection”
made his observations and collected his evidence during a five year trip around the world on the H.M.S. Beagle

5. Galapagos Islands
stop that influenced Darwin the most

6. Galapagos Islands
Of all of the stops Darwin Made the one that influenced him the most was a small group of islands called the Galapagos Islands. He noted that the characteristics of many plants and animals varied considerably from one island to the next.

7. Evolution
change in a gene pool over time

8. The Five Fingers of Evolution

9. The Five Fingers (causes) of Evolution
Small Population
Non-random mating
Mutations
Gene Flow
Natural Selection

10. 1. Small Population
chance can have a large effect on a small population
unlikely events can occur when a gene pool is small

11. 1. Small Population Genetic Drift
In small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time a series of chance occurrences of this type can cause an allele to become common in a population.
Remember genetics is controlled by the laws of probability
Remember with small populations we may not get what is expected (deviation may be high)

12. 1. Small Population Founder effect
Loss of genetic variation when a new population is started by a small number of individuals

13. 2. Non-random Mating
Mating amongst individuals in a population is not always random
Sexual Selection
some features do not have a function that help individuals survive, but help them have more offspring

14. 3. Mutations changes in genetic material
can add new genes to a gene pool

15. 4. Gene Flow
movement of genes due to immigration and emigration

16. 5. Natural Selection
Individuals that have physical or behavioral traits that better suit their environment are more likely to reproduce more successfully than those without those traits.

17. Fitness the ability of an individual to survive and reproduce
an organism’s fitness is the result of adaptations
inherited traits or variations that increase the individuals chances for survival
Darwin said organisms which are best adapted (fit) for the environment are the ones that survive
survival of the fittest

18. Selective pressures
environmental conditions that lead to one allele (trait or gene) being more beneficial to the survival and/or reproduction of members of a species
Ex: moth population turning black
selective pressure =

19. Homozygous Recessive Individual

20. Dominant allele creates a dark phonotype

21. Changing Environment = Selective Pressure

22. Selective pressures
environmental conditions that lead to one allele (trait or gene) being more beneficial to the survival and/or reproduction of members of a species
Ex: black colored individuals become more common within a moth population
selective pressure = soot on trees from pollution

23. Convergent Evolution
Organisms that are not closely related independently evolve similar traits
Ex: sharks and dolphins; insect eaters having long, sticky tongues

24. Convergent Evolution

25. Adaptation Example Darwin’s Finches Adaptations
beak size
Improved Chance for Survival
being able to eat available food sources

26. The Five Fingers of Evolution

27. Darwin’s Theory of Evolution
Inherited variation exists within the genes of every population because of mutations and translation errors.
In a particular environment, some individuals of a population are better suited to survive (because of variation) & have more offspring (natural selection).

28. Darwin’s Theory of Evolution
Over time, the traits that make certain individuals of a population survive & reproduce tend to spread in that population
Overwhelming evidence from fossils that living species evolved from organisms that are extinct.