1. Evolution- Darwin’s Journey
We just finished looking at how the Earth changed over 4.6 billion years and the mechanisms that came into place that ultimately led to early prokaryotes (simple bacteria) and evolved into eukaryotes (cells with nuclei). How did we get the diversity found today and also present in the fossil record? Evolution – change over time.
Galapagos islands- a unique environmenthttps://

2. Darwin’s journey – “The Mystery of Mysteries”
Darwin sailed from England in 1831 on a 5-year round-the-world journey. Between sea-sickness and rough seas, he was able to stop at various spots and observe life – making notes along the way. When he reached the Galapagos for a 2 month stay – he noticed that many of the plants and animals were similar to organisms he had seen throughout S.America and the world, yet remarkably different. Now the Galapagos are islands formed from volcanic activity 540 miles of coast of S. America – estimated at over 5 million years old (pretty young in the scope of things!)

3. Giant Tortoises
Vice governor of the islands told Darwin that the giant tortoises varied in predictable ways from one island to another. The shape of a tortoise’s shell could be used to identify which island a particular tortoise inhabited, but Darwin did not realize the importance of this statement until

4. Darwin’s Finches 13 Different Species of Finches!
Darwin is known for his finches. However, while collecting them he did not think they were important at all. He thought he was just catching some wrens, warblers, blackbirds until a British scientist identified them all as finches and then Darwin starting to put together all the pieces, but it took him 25 years of research until he published The Origin of the Species
video

5. Theory of Evolution Evolution:
Change in a POPULATION over a period of time
Explains the great diversity of organisms
Theory- well supported testable explanation of natural phenomena
So we can define evolution as a change over time in the genetic composition of a population. Eventually, a population may accumulate enough changes that it constitutes a new species – a new life-form. Thus we can also use the term evolution on a grand scale to mean the gradual appearance of all biological diversity, from the earliest microbes to the enormous variety of organisms alive today.
their origins and relationships, their similarities and differences, their geographic distribution, and their adaptations to the environment

6. Major points of Origin of Species
Descent with Modification
All organisms are related through descent from a common ancestor that lived in the remote past
History of life is a
single tree with
branches representing
life’s diversity

7. Sirenia
(Manatees
and relatives)
Elephas
maximus
(Asia)
Loxodonta
africana
(Africa)
Loxodonta
cyclotis
(Africa)
Hyracoidea
(Hyraxes)
Years ago
10,000 2
5.5
Mammut
Stegodon
Mammuthus
Deinotherium
Platybelodon
Millions of years ago 24
Barytherium
Moeritherium 34

8. Major points of Origin of Species
Natural selection
populations can evolve if individuals that possess certain heritable traits that leave more offspring than other individuals.
WHICH EQUALS…
Unity and diversity – natural selection is the cause of adaptive evolution

9. Evolutionary Adaptation
An accumulation of inherited characteristics that enhance an organisms’ ability to survive and reproduce in specific environments.
So we can define evolution as a change over time in the genetic composition of a population. Eventually, a population may accumulate enough changes that it constitutes a new species – a new life-form. Thus we can also use the term evolution on a grand scale to mean the gradual appearance of all biological diversity, from the earliest microbes to the enormous variety of organisms alive today.

10. Finches

11. How did Darwin’s ideas fit with the times?
KPCOFGS
Use & Disuse
Inheritance of Acquired Characteristics
GRADUALISM
Births outnumbered deaths – war, disease, famine controlled population
Lamarck – use and disuse – idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate (necks of giraffes – stretching to reach leave higher on trees)
Inheritance of acquired characteristics – an organism could pass these modifications to its offspring
Larmarck also believed that evolution happens because organisms have an innate drive to become more complex. Darwin rejected this in favor of natural selection, but he too, thought that variation was introduced into the evolutionary process through inheritance of acquired characteristics.
Cuvier – catastrophes caused extinctions – new forms were organisms that moved in to replace extinct ones
Lyell – same geologic processes happening today also happened in past and at the same rate.
Wallace – developed a similar theory of natural selection – but allowed most credit to be given to Darwin

12. So how does Natural Selection work , anyways?

13. Observation 1 Overproduction of offspring
Population sizes would increase exponentially if all individuals born reproduced successfully

14. Observation #2: Populations tend to be stable in size, except for seasonal fluctuations
Observation #3: Resources are limited
Inference #1: Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving

15. Observation #4 – Natural Variation: Members of a population vary extensively in their characteristics; no two individuals are exactly alike.

16. Observation #5: Much of this variation is heritable
Inference #2: Survival depends in part on inherited traits; individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals

17. Inference #3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations

18. Summary of Natural Selection
In order to occur:
Existing Genetic Variation
Differences in survival and reproduction determined by the environment

20. Artificial Selection

21. Artificial Selection Cross a beagle With a pug… And you get a …
Humans have modified other species over many generations by selecting anf breeding individuals that possess desired traits – a process called artificial selection. As a results of artificial selection, crop plants and animals bred as livestock or pets often bear little resemblance to their wild ancestors.

22. PUGGLE!

23. Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Leaves
Cauliflower
Kale
Flowers
and
stems
Stem
Broccoli
Wild mustard
Kohlrabi

24. Evidence for all of this?

25. 1) Fossil record
The fossil record supports changes over time especially when compared to other anatomies and molecular homologies

26. 2) Vestigial structures
Remnants of organs or structures that served important functions in the organism’s ancestors. The human knee joint and spine derive from ancestral structures that supported 4-legged mammals. Few people reach old age without experiencing some knee or back problems.

27. 3) Homologous structures
The view of evolution as a remodeling process accounts for the findings of comparative anatomy, the comparison of body structures between species. The examples above show similar bone structures, yet the functions are different in each organism. This is an example of a structural theme that was present in a common ancestor.

28. Analogous structures

29. 4) Embryo homology
All vertebrate embryos have a tail and pharyngeal pouches (throat) with very different functions, such as gills in fish and parts of the ears and throat in humans.

30. 5) Homologous proteins (molecular)
All forms of life use the same genetic machinery (DNA and RNA) in essentially a universal code. Because the genetic code is shared by all, it is likely that all species descended from a common ancestor.

31. 6) Biogeography
Geographic distribution of species – closely related species tend to be found in same geographic region.
Sugar
glider
Flying
squirrel

32. Evolution in the 21st century…
Drug resistant pathogens – big problem in bacteria and viruses that reproduce quickly
A) Naturally resistant pathogens not affected by medicine.
B) All those non-resistant are killed.
C) So….the ones with the resistance survive, reproduce, and PASS THAT TRAIT on to their offspring.

33. Part II – A Closer Look at the Evolutionary Process
Natural variation in Cuban tree snails
One common misconception about evolution is that individual organisms evolve, in the Darwinian sense, during their lifetimes. It is true that natural selection acts on individuals; each organism’s combination of traits affects its survival and reproductive success compares to other individuals. But the evolutionary impact of natural selection is only apparent in the changes in a population of organisms over time.
Tree snails – different patterns and colors the result of genetic differences. Suppose predators are less likely to eat snails with a particular color or pattern – those individuals will survive and reproduce and that color or pattern will increase from one generation to the next. Thus, the population, not its individual members, evolves; some traits become more common within the population, while other traits become less common.

34. What Darwin DIDN’T Know:
Darwin found a mechanism for change over time – Natural Selection.
He did not know HOW the heritable variations APPEAR in populations or how organisms actually TRANSMIT these variations to their offspring.

35. MENDEL
Gregor Mendel discovered that traits (we call them GENES) are passed from parent to offspring.
Population genetics – the study of how populations change genetically over time.

36. Sources of Genetic Variation
a) Mutations – any change in the DNA sequence (GGU instead of GCU)
Causes: mistakes during replication
Environment – radiation, chemicals, etc
Mutations are not always a bad thing – sometimes not even noticed in the individual.

37. b) Gene shuffling – result of sexual reproduction
Draw chromosomes and show how they separate and come together.
Individs with traits better suited will survive and reproduce, therefore passing those traits on to next generation.

38. Genetic Drift – traits fluctuate UNPREDICTABLY from one generation to the next.

39. Effects of Genetic Drift
a) The Bottleneck Effect – for some reason the gene pool doesn’t reflect the original pool.
A sudden change in the environment, such as a fire or flood (or hunting!), may drastically reduce the size of a population. In effect, the survivors have passed through a restrictive “bottleneck”, and their gene pool may no long be reflective of the original population’s pool. By chance, certain alleles (traits) may be overrepresented, and others may be underrepresented, and some may disappear altogether.
CA northern elephant seals – 1890’s hunters reduced to 20 individs. Since then they have been protected and are now over 30k. No variation, though, in genes

40. b) The Founder Effect – when a few individuals get isolated from population and establish a new one – gene pool may be different from original.

42. Hardy-Weinberg Principle
Allele (trait) frequencies in a population will remain stable (genetic equilibrium) if:
random mating
large population size
no immigration/emigration
no mutations
no natural selection
The result? No evolution! Does it happen? Sometimes….

43. Part III Speciation – when can we say we have a new species?
It all depends on REPRODUCTIVE ISOLATION – barriers that prevent members of two species from producing viable, fertile hybrids.
Clearly, a fly cannot mate with a frog or a fern, but the reproductive barriers between more closely related species are not so obvious. Sometimes 2 different species can mate and produce offspring.

44. a) Habitat Isolation
– 2 species occupy different habitats within the same area.
2 species of garter snakes – one lives mainly in water, the other on land – they rarely encounter each other, if at all.

45. b) Mechanical Isolation
- Flowers attract different pollinators so cross-pollination doesn’t occur

46. c) Temporal Isolation
Dendrobium orchids – open flowers and release pollen at different times of day – no cross pollination!

47. d) Behavioral Isolation
- Courtship rituals that attract mates and other behaviors unique to a species prevent reproduction
Eastern
Western

48. e) Gametic Isolation
Sperm of one species may not be able to fertilize the egg of another species.

49. What happens if 2 different species DO breed?
a) Reduced hybrid viability – genes from different parents interact and impair development (reduces chances of survival)

50. b) Reduced hybrid fertility – offspring of 2 species are sterile – they cannot produce offspring themselves

51. c) Hybrid breakdown – some first-generation hybrids are viable and fertile, but when they mate with on e another or either parent species, offspring of the next generation are feeble or sterile.

52. Speciation can also occur with or without geographic isolation
a) Allopatric (“other country”) – populations divided into subpopulations with no chance of getting back together.

53. b) Sympatric (“same country”) – speciation takes place in overlapping populations

54. Adaptive Radiation - Beak inheritance-speciation
The evolution of many diversely adapted species from a common ancestor upon introduction to various new environmental opportunities and challenges.

55. Adaptive Radiation in Plants

56. Convergent Evolution
Unrelated organisms resemble one another (maybe live in same environment)

57. Coevolution 2 species evolve in response to changes in each other

58. The Tempo of Speciation
How fast or slow do new species evolve?

59. Punctuated Equilibrium!
Gradualism!
Punctuated Equilibrium!
The fossil record includes many episodes in which new species suddenly appear, persist, and then disappear – punctuated equilibrium

60. Fossil record

61. Importance of Genes
Hox genes – master control genes that control growth of an embryo – certain genes turned on may produce wing, those genes turned off = no wings.
Timing of genes turned on or off may also affect body plans (short versus long legs, for example).