1. Describe what is this picture showing.
QQ 3/3/11
Describe what is this picture showing.

4. How Populations Evolve
Chapter 13
How Populations Evolve

5. Blue-footed booby mating dance
Evolution
The processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today. A change in the genes!!!
The blue-footed booby is a type of bird living in the Galápagos Islands. This type of bird possesses many specialized characteristics.
evolutionary adaptations- inherited traits that enhance its ability to survive and reproduce in its particular environment
Blue-footed booby mating dance

6. Old Theories of Evolution
Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
That by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.
Example:
A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

7. Conflicting Ideas:
Aristotle and the Judeo-Christian culture believed that species are fixed.
However, in the century prior to Darwin, the study of fossils suggested that life forms change.
Geologists proposed that a very old Earth is changed by many gradual processes, taking thousands to millions of years.

8. DARWIN’S THEORY OF EVOLUTION
On his visit to the Galápagos Islands, Charles Darwin observed many unique organisms.
While on the voyage of the HMS Beagle in the 1830s, Charles Darwin observed similarities between living and fossil organisms and the diversity of life on the Galápagos Islands. He was influenced by Charles Lyell, who published “Principles of Geology”, stating that the earth was millions of years old, not thousands as previously thought. This publication led Darwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.
North America
Europe
Great Britain
Africa
Equator
Asia
Australia
Tasmania
New Zealand
PACIFIC OCEAN
ATLANTIC OCEAN
The Galápagos Islands
South America
Tierra del Fuego
Cape Horn
Cape of Good Hope
Andes
Pinta
Marchena
Genovesa
Santiago
Isabela
Fernandina
Florenza
Española
San Cristobal
Santa Cruz
Santa Fe
Pinzón
Daphne Islands
40 miles
40 km
Figure 13.1B
Figure 13.1A

9. Charles Darwin
Wrote in 1859:“On the Origin of Species by Means of Natural Selection”
Two main points:
1.Species were not created in their present form, but evolved from ancestral species.
2.Proposed a mechanism for evolution: NATURAL SELECTION
Darwin reasoned that natural selection results in favored traits being represented more and more, and unfavored ones less and less in ensuing generations of organisms (Nature “selects” the species that will carry on genetic traits)

10. Thousands to millions of years of natural selection
Darwin found convincing evidence for his ideas in the results of artificial selection, the selective breeding of domesticated plants and animals
Darwin proposed that living species are descended from earlier life forms and that natural selection is the mechanism of evolution.
Thousands to millions of years of natural selection
Ancestral canine
African wild dog
Coyote
Wolf
Fox
Jackal
Figure 13.2C

11. Videos:
Evolution Timeline
Nova Video: Intelligent Design Theory

12. There 5 main Sources of scientific evidence to support natural selection as the means to how different species evolved!

13. Evidence of Evolution: #1 Fossil Records
A Skull of Homo erectus
D Dinosaur tracks
C Ammonite casts
B Petrified tree
E Fossilized organic matter of a leaf
G “Ice Man”
Figure 13.3A–G
F Insect in amber

14. Many fossils link early extinct species, with species living today
The fossil record reveals that organisms have evolved in a historical sequence
Many fossils link early extinct species, with species living today
Figure 13.3I

15. Biogeography- the geographic distribution of species
Evidence of Evolution: #2 Biogeography
Biogeography- the geographic distribution of species
Darwin noted that Galápagos animals resembled species of the South American mainland more than animals on similar but distant islands

16. Evidence of Evolution: #3 Comparative Anatomy
Comparative anatomy- the comparison of body structures in different species
Homology- the similarity in characteristics that result from common ancestry
Homologous structures are features that often have different functions but are structurally similar because of common ancestry
Human
Cat
Whale
Bat
Figure 13.4A

17. Evidence of Evolution: #4 Comparative Embryology
Post-anal tail
Pharyngeal pouches
Chick embryo
Human embryo
Figure 13.4B
Comparative embryology - the comparison of early stages of development among different organisms. Many vertebrates have common embryonic structures.

18. Evidence of Evolution: #5 Molecular Biology (DNA)
Comparisons of DNA and amino acid sequences between different organisms reveals evolutionary relationships
Table 13.4

19. CONNECTION- Natural Selection in Action
Camouflage adaptations that evolved in different environments are examples of the results of natural selection
Development of pesticide resistance in insects another example of natural selection in action
A flower mantid in Malaysia
A leaf mantid in Costa Rica
Pesticide application
Survivor
Chromosome with gene conferring resistance to pesticide
Additional applications of the same pesticide will be less effective, and the frequency of resistant insects in the population will grow

20. POPULATION GENETICS AND THE MODERN SYNTHESIS
Population - a group of individuals of the same species living in the same place at the same time
Species is a group of population whose individuals can interbreed and produce fertile offspring.
Population genetics- studies how populations change genetically over time
Gene pool - the total collection of genes in a population at any one time
Microevolution - a change in the relative frequencies of alleles in a gene pool

21. In a non-evolving population, the shuffling of alleles that accompanies sexual reproduction does not alter the genetic makeup of the population. Therefore, the gene pool would remain constant over the generations.
Webbing
No webbing
Figure 13.7A

22. Hardy-Weinberg equilibrium states that the shuffling of genes during sexual reproduction does not alter the proportions of different alleles in a gene pool.
Phenotypes
Genotypes WW Ww ww
Number of animals (total  500)
320
160 20
500
Genotype frequencies
 0.64
 0.32
 0.04
Number of alleles in gene pool (total  1,000)
Allele frequencies
800
1,000
 0.8 W
 0.2 w
640 W
160 W  160 w
40 w
Figure 13.7B
200

23. We can follow alleles in a population to observe if Hardy-Weinberg equilibrium exists
Recombination of alleles from parent generation
EGGS
Genotype frequencies
Allele frequencies
0.64 WW
0.32 Ww
0.04 ww
0.8 W
0.2 w
Next generation:
W egg p  0.8
w egg q  0.2
W sperm p  0.8
w sperm q  0.2
SPERM
WW p2  0.64
Ww pq  0.16
wW qp  0.16
ww q2  0.04
Figure 13.7C

24. The population is very large The population is isolated
For a population to be in Hardy-Weinberg equilibrium, it must satisfy 5 main conditions:
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
*Public health scientists use the Hardy-Weinberg equation to estimate frequencies of disease-causing alleles in the human population.

25. Hardy-Weinberg Principle
Remember:
If these conditions are met, the population is at equilibrium.
This means “No Change” or “No Evolution”.

26. Other things that can alter allele frequencies in a population
Gene flow is the movement of individuals or gametes between populations and can alter allele frequencies in a population.
Natural selection leads to differential reproductive success in a population.
For example, endangered species often have low genetic variability, which may reduce the capacity of endangered species to survive as humans continue to alter the environment.

27. Other things that can alter allele frequencies in a population
Genetic drift is a change in the gene pool of a population due to chance and can alter allele frequencies (amounts) in a population
Bottleneck effect: type of genetic drift usually results from a disaster that drastically reduces population size. Examples: Earthquakes, Volcano
Founder effect: Genetic drift resulting from the colonization of a new location by a small number of individuals; results in random change of the gene pool. Example: Islands (first Darwin finch)
Original population
Bottlenecking event
Surviving population

28. VARIATION AND NATURAL SELECTION
Variation is extensive in most populations.
Many populations exhibit polymorphism, different forms of phenotypic characteristics
Figure 13.11

29. Mutation and sexual recombination generate variation
Mutation and sexual recombination generate variation
Mutations, or changes in the nucleotide sequence of DNA and can create new alleles. Sexual recombination generates variation by shuffling alleles during meiosis. A1 A2 A3
and X
Parents
Meiosis
Gametes
Fertilization
Offspring, with new combinations of alleles
Figure 13.12
Current example: Antibiotic resistance to bacteria

30. FITNESS
Some variations may be neutral, providing no apparent advantage or disadvantage
An individual’s fitness is the contribution it makes to the gene pool of the next generation
Figure 13.14

31. Natural selection can alter variations in a population in 3 ways:
Natural selection can alter variations in a population in 3 ways:
Stabilizing selection - favors intermediate phenotypes (middle)
Directional selection - Acts against individuals at one of the phenotypic extremes; shifts the population numbers towards one of the extremes.
Disruptive selection - favors individuals at both extremes of the phenotypic range

32. Stabilizing selection Directional selection
Three possible effects to a population of mice due to natural selection
Original population
Stabilizing selection
Evolved population
Frequency of individuals
Phenotypes (fur color)
Directional selection
Disruptive selection
Figure 13.16

33. Natural selection cannot fashion perfect organisms
Organisms are limited by historical constraints
Adaptations are often compromises
Chance (random mutation) and natural selection interact
Selection can only edit existing variations