1. Charles Darwin and the Theory of Evolution

2. Charles Darwin’s Voyage of the Beagle

3. Galapagos Islands
Even though these islands are close together they varied greatly in their climates
Amount of rainfall, vegetation differences, different species!

4. Darwin’s Observations
The plants and animals were well-suited to their environment
Example: A Cactus is adapted to live in dry areas
Species vary in traits and some traits are better suited for different areas

5. Darwin’s Finches The beaks were different from island to island
Beaks were better suited for feeding depending upon location (islands)

6. Darwin’s Tortoises
Due to differences in plant life; Darwin noticed that tortoises had differences in SHELL shape and NECK lengths

7. 15-2 Jean-Baptiste Lamarck
One of the first scientists to notice living things have changed over time
Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetimes
These traits could then be passed on to their offspring
Do you agree with this theory?

8. Darwin Presents His Case-1859
In this book, Darwin proposed the concept of EVOLUTION by the method of NATURAL SELECTION.
Evolution is?
Natural Selection is?
Speciation is?
Explain how these relate?

9. Evolution by Natural Selection
Struggle for Existence
Each species will compete for food, space, basic needs
Survival of the Fittest/Natural Selection
Fitness=able to survive and reproduce!
Descent with Modification
The “fittest” reproduce thus passing on their GREAT traits!

10. Adaptations
A inherited characteristic that increases an organisms chance of survival.
Examples:
1.Anatomical/stuctural- porcupines sharp quills, camouflage, mimicry
2.Behavioral- mating rituals
3.Physiological-plant performing photosynthesis

11. Evolution occurs in Populations
*not individuals*
But what is a population?
*A group of inter-breeding species

12. Evolution of Populations
Genetic variation is studied in populations (group of same species that interbreed)
Gene pool – all genes that are present in a population
Relative frequency – number of times an allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur

13. How do we know when Evolution has occurred?
A change in the relative frequency of alleles in a population
allele for brown fur
allele for black fur
48% heterozygous black
16% homozygous black
36% homozygous brown
60% or 30/50=brown allele

14. Genetic Variation in Populations
Two main sources of genetic variation
Mutations
Change in a sequence of DNA
Gene shuffling
Independent movement of chromosomes during meiosis and Crossing-Over

15. 3 Causes of Evolution
1. Genetic Drift: change in the gene pool due to chance (small populations will be greatly affected)
A. Bottleneck Effect- over hunting, earthquake, fire etc…
*this can lead to endangered species!
B. Founder Effect- small group leaves the source population to establish their own
Example:Polydactyly in Amish that came
to the United States (they carried the allele)

16. 3 Causes of Evolution con’t
2. Gene Flow:
Fertile immigrants or emigrants bringing or taking alleles from the population
Example: If your 2nd period class has all blue eyed people (bb) and someone comes in that has brown eyes (BB)

17. 3 Causes of Evolution con’t
Natural Selection:
Well suited organisms increase their chance of surviving thus reproducing to pass on their genes (alleles) to the next generation
Example: Peppered Moth example

18. Single-Gene and Polygenic Traits
The number of phenotypes produced for a trait depends on how many genes control the trait
Single-gene trait
Single gene with two alleles
Fewer phenotypes than polygenic traits
Ex: widow’s peak
Polygenic trait
Controlled by two or more genes (each with more than 2 alleles)
Many different genotypes and phenotypes
Ex: height

19. Natural Selection acts on Polygenic Traits 3 ways
Directional Selection
Disruptive Selection
Stabilizing Selection

20. Genetic Equilibrium
If a population was to not evolve, or change, the population would reach equilibrium – when allele frequencies stay the same
Conditions required to reach equilibrium:
Random mating
Large population
No movement in or out of population
No mutations
No natural selection

21. Speciation Isolation prevents interbreeding between populations
Behavioral isolation
Different courtship rituals or reproductive strategies
Geographic isolation
Two populations are separated by geographic barriers (rivers, mountains, oceans, etc..)
Temporal isolation
Species reproduce at different times (winter –vs- spring)