1. Evolution: How Population Evolve
PreAP Biology

2. Figure 1.14

3. Lamarck’s Theory of Acquired Inheritance (early 1800s)
Jean Baptiste Lamarck
Observed fossil records and the current diversity of life
Suggested that organisms evolved by the process of adaptation
Traits gained during a lifetime could then be passed on to the next generation

4. Lamarck’s Theory of Acquired Inheritance
Suggested giraffes acquired long necks because ancestors stretched higher and higher into the trees to reach leaves at a time when there was drought in the African prairies
Lengthened neck was passed to offspring

5. Charles Darwin
Observed organisms and their distributions on Galápagos Islands
Saw similarities b/w Galápagos organisms and those in South America.

6. Figure 13.5

7. Darwin’s Theory of Natural Selection
Observations:
Overproduction of offspring leads to competition of limited resources (food, space, breeding partners)
Individuals of a population vary in characteristics, and many such traits are passed on to offspring
Conclusions:
Individuals with inherited characteristics make them best adapted to survive in their environment and reproduce and leave more offspring than less fit individuals

8. The theory of natural selection is comprised of several logical steps, based on observation and inference:
There is competition among individuals in a population.
There is variation among individuals in a population.
This variation is, at least in part, heritable.
This variation contributes to fitness; fitter individuals will leave a larger contribution of offspring in the next generation.
The succeeding generation will have an increased proportion of the traits that confer the higher fitness.

9. Hundreds to thousands of years of breeding (artificial selection)
Natural Selection
Prominent force in nature
Support in the results of artificial selection—selective breeding of domesticated plants/animals
Populations tend to evolve in response to environmental conditions
Hundreds to thousands of years of breeding (artificial selection)
Ancestral dog (wolf)
Figure 13.2B

13. Evidence of Evolution Fossil Record Biogeography Comparative anatomy
Comparative embryology
Molecular Biology

14. Evidence: Fossil Record
Fossils
Are preserved remnants or impressions left by organisms that lived in the past.
Are often found in sedimentary rocks.

15. Fossil Formation Dead animal sinks. Tissue begins to decay
Carcass covered with sediment. Lower layers turn to rock.
Rock is folded.
Fossil is exposed at the surface.

16. The fossil record
Is the ordered sequence of fossils as they appear in rock layers.
Reveals the appearance of organisms in a historical sequence.
Fits with other evidence of evolution.

17. Fossil Record reveals that organisms have evolved in a historical sequence

20. Evidence: Biogeography
Biogeography, the geographic distribution of species
Suggested to Darwin that organisms evolve from common ancestors
Darwin noted that Galápagos animals
Resembled species of the South American mainland more than animals on similar but distant islands

22. Evidence: Comparative Anatomy
Comparison of body structures between different species
Similarities give signs of common descent
Homologous structures—features that have similar structure but have different functions

24. Evidence: Comparative Anatomy
Vestigial structures—Small body structures that may have been functional in the ancestors of a species, but has no real function at the present time (appendix, tail bone)

25. Evidence: Comparative embryology
Different organisms go through similar embryonic stages
All vertebrates have an embryonic stage in which gill pouches appear in the throat region—evidence of a common ancestor

27. Molecular Biology
Study of molecular basis of genes and gene expression
Universality of genetic code
Conservation of amino acid sequences in proteins such as hemoglobin

28. Figure 13.13

30. Populations are the Units of Evolution
A population
Is a group of individuals of the same species living in the same place at the same time
A species is a group of populations
Whose individuals can interbreed and produce fertile offspring

31. Populations are the Units of Evolution
Population genetics
Focuses on populations as the evolutionary units.
Tracks the genetic makeup of populations over time.
The modern synthesis
Connects Darwin’s theory with population genetics

32. Populations are the Units of Evolution
A gene pool
Is the total collection of genes in a population at any one time
Microevolution
Is a change in the relative frequencies of alleles in a gene pool

33. Genetic Variation in Populations
Individual variation abounds in populations.
Not all of this variation is heritable.
Only the genetic component of variation is relevant to natural selection.
A population is said to be polymorphic for a characteristic if two or more morphs, or forms, are present in noticeable numbers.

34. Sources of Genetic Variation
Mutations and sexual recombination
Produce genetic variation.
Are changes in the DNA of an organism.
Sexual recombination
Shuffles alleles during meiosis.

35. Analyzing Gene Pools The gene pool Alleles in a gene pool
Consists of all alleles of all individuals making up a population.
Alleles in a gene pool
Occur in certain frequencies.

36. Analyzing Gene Pools In a nonevolving population
In a nonevolving population
The shuffling of alleles that accompanies sexual reproduction does not alter the genetic makeup of the population
Hardy-Weinberg equilibrium
States that the shuffling of genes during sexual reproduction does not alter the proportions of different alleles in a gene pool
Webbing
No webbing
Figure 13.7A

37. Hardy-Weinberg Equilibrium
The population is very large
The population is isolated
Mutations do not alter the gene pool
Mating is random
All individuals are equal in reproductive success

38. One or More of these Conditions will lead to Evolution
Population is small
Population is not isolated; migration in/out
Mutations (changes in genes) alter gene pool
Mating is non-random
Individuals are not equal in reproductive success; natural selection does happen

39. Causes of Microevolution
Genetic drift—change in gene pool of a small population due to chance
Loss/gain of individuals

40. Genetic Drift
Bottleneck effect—results from an event/disaster that drastically reduces population size (elephant seals after being hunted in 1890s)
Figure 13.9A
Figure 13.9B

41. CONNECTION Endangered species often have reduced variation
CONNECTION
Endangered species often have reduced variation
Low genetic variability
May reduce the capacity of endangered species to survive as humans continue to alter the environment
Figure 13.10

42. Causes of Microevolution
Genetic drift
Founder effect—random change in gene pool that occurs in a small colony
A few individuals start a new population

43. Causes of Microevolution
Gene flow—gain/loss of allele from a population
Is the movement of individuals or gametes between populations
Can alter allele frequencies in a population
Tends to reduce genetic differences between populations

44. Causes of Microevolution
Mutation—random change in organism’s nucleotide sequence
Can create a new allele
Rare events
Ultimate source of the genetic variation that initiates evolution

45. Causes of Microevolution
Nonrandom mating
males and females with similar phenotypic traits tend to mate
In species that stay in one place, individuals tend to mate with neighbors rather than more distant members of the population

46. Nonrandom Mating Sexual selection may produce sexual dimorphism
Sexual selection may produce sexual dimorphism
Sexual selection leads to the evolution of secondary sexual characteristics
Which may give individuals an advantage in mating
Figure 13.17B
Figure 13.17A

47. Natural selection can alter variation in a population in three ways
Stabilizing selection
Favors intermediate phenotypes
Directional selection
Acts against individuals at one of the phenotypic extremes
Disruptive selection
Favors individuals at both extremes of the phenotypic range

48. Modes of Natural Selection

49. Insecticide-resistant Populations

50. Acknowledgements
BIOLOGY: CONCEPTS AND CONNECTIONS 5th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2006. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
Unless otherwise noted, illustrations are credited to Pearson Education which have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONS 3rd Edition, by Campbell, Reece, Mitchell, and Taylor, ©2000. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.