1. Natural Selection
4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation.

2. Evidence? (for or against)
What is evolution?
What does it mean to you?
Do you think it happens?
Evidence? (for or against)

3. DEFINITIONS:
Evolution are the changes in the gene pool of a population over time. Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully. Adaptation is an inherited characteristic that increases an organism’s chance of survival.

4. Darwin and Evolution

5. Sailed around world 1831-1836 Galåpagos Islands Darwin Wolf Pinta
Isabela
Darwin
Wolf
Pinta
Marchena
Genovesa
Fernandia
Santiago
Bartolomé
Råbida
Pin zon
Seymour
Baltra
Santa Cruz
Santa Fe
Tortuga
Española
San Cristobal
Floreana
EQUATOR
Galåpagos
Islands

6. Each island had its own type of tortoises and birds
Through his travels he found that species diversity was much greater than previously known.

7. Marine Iguana
Land Iguana

8. His observations led to the development of the theory of evolution.

9. What is a Theory? Supported by multiple sources of evidence
A well tested idea that explains an observed phenomena
Supported by multiple sources of evidence

10. Darwin’s Postulates Populations have natural Variation
Overproduction of offspring.
Struggle for existence.
Unequal survival and reproduction rates. (Those with traits more likely to help them survive will pass traits to their offspring)

11. What is a species?
A group of individual organisms that are capable of reproducing and produce viable offspring.
When organisms can no longer reproduce or do not produce viable offspring then they are no longer the same species.

12. insect and nectar eaters
FOUNDER SPECIES
insect and nectar eaters
fruit and seed eaters
KAUAI AKIALAOA
AMAKIHI
IIWI
APAPANE
KONA FINCH extinct
LAYSAN FINCH
AKIAPOLAAU
MAUI PARROTBILL

13. Based on his observations, Darwin proposed that EVOLUTION occurs by NATURAL SELECTION.

14. Population of organisms
Mutations & Sexual reproduction produces variations among offspring.
Overproduction of offspring
Limited resources leads to a struggle for survival between offspring.
Survivors reproduce more successfully.
Population changes over time.

15. The Genetic Makeup of a Population Can Change
Populations evolve by becoming genetically different
Genetic variations
First step in biological evolution
Occurs through mutations in reproductive cells
Mutations in other cells can happen , but only reproductive cell mutations are passed on
Sometimes a mutation can result in a new genetic trait that gives it a better chance to survive, sometimes not.

16. Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring
Natural selection: acts on individuals
Second step in biological evolution
Adaptation may lead to differential reproduction
Genetic resistance in bacteria, cockroaches
When environmental conditions change, populations
Adapt
Migrate
Become extinct

17. A group of bacteria, including genetically resistant ones, are
exposed to an antibiotic
Normal bacterium
Resistant bacterium
Eventually the resistant strain
replaces the strain affected by
the antibiotic
The genetically resistant bacteria
start multiplying
Most of the normal bacteria die

19. Evidence Supporting Evolution
Fossil Record

20. Evidence Supporting Evolution
Homologous Structures

21. Evidence Supporting Evolution
Vestigial Structures

22. Evidence Supporting Evolution
Embryo Development

23. Opposing Theory at the Time Lamark: Theory of Acquired Traits
Lamark believed that organisms acquired traits by using their bodies in new ways
These new characteristics were passed to offspring
Why was Lamark’s theory refuted???

24. Can a fish species willfully grow limbs and fingers if they are needed to crawl out of the water onto dry land?

25. Origin of Species
Darwin published his book The Origin of Species in 1859
His findings are still supported today by further evidence and the scientific community.

26. Activity: Choose two online natural selection simulations.
Work through the simulation and discuss the strengths and weaknesses of the simulation with regard to modeling natural selection.
Which simulation do you believe does a better job modeling natural selection? Justify your answer.
In your own words, explain how a new species forms.
(requires shockwave)
(requires flash)