1. Evolution by Natural Selection

2. Scientific Theory
An explanation of natural phenomenon supported by a large body of scientific evidence obtained from many different investigations and observations

3. Evolution
A gradual change in a species (populations) through adaptations over time

5. Charles Darwin “Theory of Evolution by Natural Selection”
Proposed that new species could develop by a process of natural selection.

6. Charles Darwin
Natural selection: When better adapted organisms survive to produce a greater number of viable offspring.
This has the effect of increasing their proportion in the population so they become more common

7. Darwin’s studies
Studied animal species in the Galapagos Islands and found they each had unique adaptations
Galapagos finches demonstrate different adaptations to eat different foods
Galapagos turtles are the largest on earth

9. Natural Selection A mechanism for change in a population
Natural Selection (N.S.) is responsible for most evolutionary change by selectively changing genetic variation through differentiated survival and reproduction
Goal – To be fit “enough” to survive and reproduce

11. How does natural selection produce change in a population
How does natural selection produce change in a population? 3 types of natural selection

12. 1. Stabilizing Selection
Favors average individuals in a population
Those individuals have a “selective advantage”
Reduces variation in a population

13. 2. Directional Selection
Favors one of the extreme variations of a trait
Can lead to rapid evolution of a population

14. 3. Disruptive Selection Favors both extreme variations of a trait
Leads to evolution of two new species

15. Speciation A process of producing two individual species from one
Members of the 2 species no longer interbreed within their natural environment

16. Evidence for Evolution
Structural Adaptations
Methods of protection
Teeth, claws, thorns
Mimicry
Camouflage

17. 2. Physiological Adaptations:
Changes in an organism’s metabolic processes
Resistance to antibiotics or chemicals

18. Fossils:
Provide a record of early life and evolutionary history

19. 4. Anatomy:
Structural features with a common evolutionary origin are called homologous structures.
The body parts of organisms that do not have common evolutionary origins but are similar in function are called analogous structures.
A vestigial structure does not have current function but may have been useful to an ancestor

20. 5. Embryology:
Similarities among the young embryos suggest evolution from a distant, common ancestor

21. 6. Biochemistry:
Comparing DNA and RNA

22. How do we know what happened when?
 1. Radiometric dating relies on half-life decay of radioactive elements to allow scientists to date rocks and materials directly.
 2. Stratigraphy provides a sequence of events from which relative dates can be extrapolated.
 3. Molecular clocks allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates.

23. What’s important from all these notes?
V = variation
I = inheritance (overproduction)
S = selection
T = time