1. Natural Selection

2. —Charles Darwin from "The Origin of Species"
Used by permission of Darwin Day
Celebration (at DarwinDay.org), 2006
I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.
  —Charles Darwin from "The Origin of Species"
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

3. CHARLES DARWIN – 1809-1882 English
Traveled around the world on the Beagle (ship)
Most of trip was among the Galapagos Islands
Believed that the earth was 6000 years old and that all plants and animals were unchangeable over time
During his travels, he observed many live species, as well as fossils
He did not understand why some species survived while others were going extinct
These ideas went directly against his beliefs

4. Darwin’s Observations
From island to island, he noticed that the species of mockingbird, finches, and other animals varied.
Many of the species Darwin collected had not yet been discovered or classified
Darwin took his collections and drawings home and after reading essays and studies by many other scientists (Gould & Mathus), he developed the idea of natural selection

5. 5 Principles of Natural Selection
Individuals in a population show variation.
Variations can be inherited.
Organisms have more offspring that can survive under normal circumstances.
Variations that increase reproductive success will have a greater chance of being passed on from generation to generation.
A population will slowly change over time in response to the environment.

6. Darwin… By 1840, Darwin had developed the theory of natural selection.
He then published “On the Origin of Species by Means of Natural Selection”
On the last page of this book, he called his theory “evolution”
Evolution is what the process is called ~ natural selection is HOW evolution happens
Another researcher, Wallace, also wrote a similar book at the same time and both books were published and presented to the scientific community.

7. Evolution Overview: Evidence for Evolution, Types of Natural Selection, & Speciation
Biology 1
Dr. Butts

8. How and why does evolution occur?
Individuals are born with random traits inherited from parents
Some of these traits might be advantageous
Individuals who have more advantage in their environment will survive and reproduce with greater success
The advantageous traits will be passed down to offspring

9. Evidence of Evolution The Fossil Record
Provides records of species that lived long ago
Shows evolutionary relationships among ancient and current living things

10. Evidence of Evolution Comparative Anatomy:
Homologous Structures: anatomically similar structures that occur in species that come from a common ancestor

11. Evidence of Evolution Comparative Anatomy
Vestigial Structures: structures that are present, but no longer needed

12. Evidence of Evolution Comparative Anatomy
Analogous Structures: structures that are similar in function, but are not in living things that share ancestry

13. Evidence of Evolution Comparative Embryology
Studying of the growth and development of various organisms
The more similar the embryonic development of organisms, the more closely related they are

14. Evidence of Evolution
Comparative Biochemistry: comparing DNA and other molecules
The more closely related, the more similar the DNA sequences

15. Evidence of Evolution Geographic Distribution & Biogeography
Similar climates and biomes have similar living things because living things evolve to be successful in their environment

16. CoEvolution
Some species evolve in close relationship with other species. The relationship may sometimes become so close that the evolution of one species may affect the other.

17. Examples of Evidence: Coevolution

18. Examples of Evidence: Camouflage: blending in with environment
Mimicry: nonpoisonous organisms mimicking poisonous ones in order to avoid predators

19. Camouflage

20. Mimicry

21. Evidence of Evolution Antibiotic and Pesticide Resistance
Antibiotic: bacteria become resistant to antibiotics over time due to over and misuse
Pesticide: Insects and other pests become resistant to pesticides due to overuse

22. Adaptation & Natural Selection
Camouflage: blending in with environment
Mimicry: nonpoisonous organisms mimicking poisonous ones in order to avoid predators

23. Adaptation & Natural Selection
Genetic Drift
Founder Effect: Pioneer species leaves original colony and begins a new one
Bottleneck: a once large population is dramatically decreased due to some bottleneck event (ex. Drought, flood, disease, etc)

24. Adaptation & Natural Selection
Stabilizing Selection
most common
eliminates extremes, which gets rid of negative traits
ex. Birth weights of human babies does not show variation

25. Adaptation & Natural Selection
Directional Selection
one extreme selected for
ex. Peppered moth (p.435, fig )

26. Adaptation & Natural Selection
Disruptive Selection
splits a population into 2 groups
removes average individuals and selects for extremes
Ex. Selection based on habitat (snakes in grasslands vs. rocky mountains)

27. Adaptation & Natural Selection
Sexual Selection
mate selection based on physical characteristics
Nonrandom Mating
mating based on nonrandom factors (proximity, sexual selection, etc)

28. Speciation What is a species?
Groups of organisms that can successfully reproduce with one-another.
What is speciation?
Process by which new species are formed
Populations diverge to the point they can no longer reproduce together (reproductive isolation)

29. Speciation Allopatric Speciation Physical barrier causes speciation
Sympatric Speciation
Speciation without a physical barrier

30. Speciation Adaptive Radiation
Rapid evolution due to environmental factor(s) that cause a change in what is advantageous vs. disadvantageous

31. Speciation Coevolution Species evolve in response to one another
Convergent Evolution
Similar traits evolve in different parts of the world due to similar climates and geography

32. Hardy Weinberg
Theory that states that if gene frequencies remain stable, the population is said to be in equilibrium (or homeostasis) and thus, not evolving.
5 things must be true:
1. Population is large.
2. No immigration nor emigration
3. Mating is always random.
4. Mutations never occur
5. Natural selection does not occur.

33. Hardy Weinberg Is it true for humans? You decide…
Assumes 5 things to be true:
1. Population is large?
2. No immigration nor emigration?
3. Mating is always random?
4. Mutations never occur?
5. Natural selection does not occur?
Are populations ever really NOT evolving then?