1. EVOLUTION
“Nothing in Biology Makes Sense Except in the Light of Evolution.”
Theodosius Dobzhansky (Geneticist, )

2. “Lamarckism”
Before Darwin published his theory of evolution, Jean-Baptiste Lamarck’s idea of evolution was widely accepted.
Lamarck proposed that acquired traits could be passed on to offspring. Ex.:
“Giraffes got their long necks by striving to reach the leaves on the tops of trees, so their babies were born with long necks.” (NOT!)
After Darwin published his theory, and after inheritance was explained through genetics, Lamarckism was abandoned.
If you grow big muscles by lifting weights, will you pass this acquired trait on to your offspring?

3. Charles Darwin Charles Darwin was an English naturalist (1800’s).
During the voyage of the Beagle, Darwin observed many species in their natural environments, especially in South America / the Galapagos Islands.
While studying the Galapagos finches, he developed the theory of natural selection.
Darwin published “The Origin of Species” in 1859, containing his theory of evolution by natural selection to explain how the variety of living things existing today developed through time.

4. Darwin was not the only one!
Alfred Russel Wallace also inferred evolution by natural selection.
Darwin had the idea first, but only published his book once he knew Wallace had also arrived at the same conclusion – Darwin had been working on it for over 20 years!! 
Darwin explained his theory more completely and with more supporting evidence, and established his priority.

5. NOT evolved from each other: share a common ancestor 5-6 m.y.a.
Evolution of Species
Evolution = change or development through time
Species = interbreeding population of organisms that can produce healthy, fertile offspring
Adaptation = inherited trait that allows organisms to survive in a particular environment
Species are adapted to their niches.
Speciation = evolution of a new species
NOT evolved from each other: share a common ancestor 5-6 m.y.a.

6. Small size, wings, feathers, beak size
Adaptations are… Shape, size, color, hormones, ability to make eggs, and other genetic traits.
Leaves that capture sunlight, flowers containing gametes for reproduction
Poison to deter predators, enzymes that digest organic matter, coloration
Behavioral traits, including mating behavior that optimizes reproduction and parental care
Small size, wings, feathers, beak size

7. Artificial Selection / Selective Breeding of Cattle
(Videos at pbs.org – 5-6 min.)

8. Artificial Selection of Crop Plants

9. Artificial Selection / Selective Breeding
Domestication and selective breeding by people have generated many breeds/varieties of animals and plants.

10. Why and How do Species Evolve?
Current biodiversity ~ 5-30 million species
99% species that ever lived on the earth are now extinct!
Environments change  advantage for some, disadvantage for others

11. Natural Selection Mechanism of evolution suggested by evidence
Four factors:
Variation within populations  some favorable
Struggle for survival  limited resources, competition
Overproduction of offspring  not all young survive
Differential survival & reproduction  individuals w/ favorable variations survive & reproduce more, traits become more prevalent in each generation 
Cummulative effect over time results in changes in a species (evolution)

12. Variation
Genetic Variation = differences between individuals in a population  fuel for evolution
Environmental changes  variation increases the chances of survival for a species Ex.: new disease  some individuals may survive
Sources of genetic variation:
Recombination of existing alleles (forms of a gene) by sexual reproduction;
Mutation – change in the sequence of a gene; most are neutral or harmful.

13. Selective Pressure
Selective pressure = environmental factor that creates struggle to survive/compete
Individuals have to compete with other individuals of the same species and other species for limited resources:
Space/territory
Food, water, sunlight, soil nutrients
Mates Sexual selection – selection by member of the opposite sex (mate)

14. Evolution is a Compromise Between Different Selective Pressures Illustration: Guppy studies by John Endler at pbs.org

15. Peppered Moths & The Industrial Revolution – A Natural Selection Tale

16. Before factories…

17. After factories… “industrial melanism”
Tell me the story using the words variation, reproduction, genes, and natural selection.

18. After environmental standards improved / pollution control…

19. Species Evolve in Interaction with Other Species
Coevolution = two species evolving interdependently Ex.: predator and prey
Each species is under selective pressure (environmental limitations) for adaptations that are favored in its habitat
A species niche includes interactions with other species
When two species evolve in symbiosis, they become adapted to each other

20. Coevolution Examples Symbiosis: Parasitism Symbiosis: Mutualism
Predator & Prey

21. Reproductive Isolation Results in Speciation
Two populations of the same species may become reproductively isolated  no more gene exchange, evolve separately
Geographic isolation causes reproductive isolation: living in separate places  breeding in separate groups Ex.: islands colonized by mainland species
Different environments next to each other may favor different variations of the same trait ex: forest hummingbirds, grassland hummingbirds

22. Reproductive Isolation
Pre-Zygotic before fertilization/mating; no zygote/embryo forms
Post-Zygotic after fertilization/mating: zygote/embryo not viable or not fertile
Ex.: Drosophilla melanogaster x D. pseudoobscura  hybrids have atrophied testes (infertile)
Hybrid is sterile, inviable, or has low fitness
Ex.: horse x donkey  mule (infertile)

23. Allopatric vs. Sympatric Speciation
Allopatric speciation – populations diverge due to geographic isolation (islands, areas separated by a mountain, river, etc.)
Sympatric speciation - populations diverge without geographic isolation (usually due to reproductive isolation in the same environment)

24. Allopatric or Sympatric Speciation?
Galapagos Finches

25. Allopatric or Sympatric Speciation?

26. Allopatric or Sympatric Speciation?

27. Allopatric or Sympatric Speciation?
The European mosquito Anopheles consists of six morphologically indistinguishable species. They are isolated reproductively as they breed in different areas of the same habitat. Some breed in brackish water, some in running fresh water and some in stagnant fresh water. Therefore, they never meet to breed. If this happens for subpopulations of a species, speciation may follow.

28. How Fast Does Evolution Happen?
Darwin originally proposed evolution happens at a slow, gradual rate  Gradualism
Gould & Eldredge (1972) proposed that populations remain stable through long periods of time, interrupted by rapid genetic changes  Punctuated Equilibrium
 Fossil record lacks many intermediate forms.

29. Common ancestor

30. Relatedness Between Species
Depends on how long ago species shared a common ancestor (diverged from ea. other)
Scientists compare fossils, structures & DNA sequences to establish relatedness
A phylogenetic tree is a diagram showing relationships between different species

31. Analogous or homologous structures?
Phylogenetic Tree of Vertebrate Animals
Analogous or homologous structures?
Divergent
Evolution
Species evolve from same ancestor by differentiating from each other.
Common ancestor of crocs & birds
fishapod-like ancestor of land vertebrates
Common ancestor of all vertebrates (first fish with a backbone)

32. A clade is a group that shares a common ancestor  shared characters
Cladograms
are a type of
Phylogenetic
Tree
A clade is a group that shares a common ancestor  shared characters
Shared characters: quadruped body plan, amniotic eggs, skin that preserves moisture, etc.

33. Analogous or homologous structures?
Convergent Evolution
Analogous or homologous structures?
Unrelated or distantly related species evolve similar adaptations due to similar environment
Selective pressure for sustained rapid swimming in a marine habitat
Divergent Evolution

34. CONVERGENT EVOLUTION

35. Analogous or homologous structures?
CONVERGENT EVOLUTION
Analogous or homologous structures?
Blind spot – nerves & cell layers in front of retina
No blind spot – nerves behind retina

36. Convergent Evolution East African cichlid fishes
Lake Tanganyika cichlids
Lake Malawi cichlids
Convergent evolution of feeding morphology and color among East African cichlid fishes. Species from Lake Tanganyika are in the left column; those from Lake Malawi are to the right. Each of the illustrated fishes from Lake Malawi are more closely related to one another than to any species in Lake Tanganyika.
Similar diets in different lakes have favored similar jaw/mouth shapes.

37. Can Convergent Evolution happen in homologous structures?
Bones are homologous – inherited from a common quadruped ancestor
Evidence suggests that wings evolved separately in mammals and dinosaurs  convergent evolution of flying structures

38. Convergent Evolution: Distantly related species, similar environments
These two succulent plant genera, Euphorbia and Astrophytum, are only distantly related, but have independently converged on a very similar body form.

39. Adaptive
Radiation
Divergent evolution in which several or many species evolve from one ancestor, filling available niches.
Ex.: Marsupials in Australia

40. Adaptive Radiation
Ex.: Archaeoptherix, a transitional form between dinosaur and bird, thought to be the ancestor of modern birds

41. Directional Selection
Trait value
Trait value

42. Stabilizing Selection
Trait value
Trait value

43. Directional vs. Stabilizing Selection

44. Disruptive Selection

45. What type of selection has happened?
Disruptive Selection
Divergent Evolution
Common ancestor

46. Evolution Reminder: Keep your sense of humor… 