1. Chapter 15.1
Natural Selection and the Evidence for Evolution

2. Section 15.1 Summary – pages 393-403
Charles Darwin
Studied to become a clergyman and a doctor before becoming a naturalist.
5-year voyage around the world on HMS Beagle ( ).
Published The Origin of Species in 1859.
Not the first person to propose that species evolve.
Section 15.1 Summary – pages

3. Section 15.1 Summary – pages 393-403
Darwin’s Influences
From Thomas Malthus – not all offspring survive to reproduce. Some are better at competing for limited resources and are therefore more likely to reproduce and pass on their traits to offspring.
From Charles Lyell – the earth is very old and geologic change occurs very slowly.
Section 15.1 Summary – pages

4. Section 15.1 Summary – pages 393-403
Darwin’s Influences
Darwin bred pigeons so he was familiar with the principle of artificial selection.
Artificial selection – selection of specific traits in domestic animals by breeders.
Section 15.1 Summary – pages

5. Section 15.1 Summary – pages 393-403
Selection and Evolution
Natural selection – not all members of a population are equally likely to survive and reproduce. Why?
Evolution – heritable change in organisms over time.
Section 15.1 Summary – pages

6. Section 15.1 Summary – pages 393-403
Evidence: structural adaptations
Mimicry – one species resembles another species.
A harmless species imitates a harmful one. What do you think the ratio of harmful to harmless species must be and why?
2. Two or more harmful species look like each other. How does this benefit both species?
Section 15.1 Summary – pages

7. Section 15.1 Summary – pages 393-403
Structural adaptations
Warning coloration - bold, distinctive pattern of color characteristic of a poisonous or unpalatable organism,
Yellow jacket hornets, honeybees, and many other species of wasps all have harmful stings and similar coloration and behavior.
Section 15.1 Summary – pages

8. Section 15.1 Summary – pages 393-403
Structural adaptations
Camouflage – adaptation that allows species to blend with their surroundings.
Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.
Section 15.1 Summary – pages

9. English peppered moth, Biston betularia
The peppered moth
English peppered moth, Biston betularia

10. Section 15.1 Summary – pages 393-403
Direct evidence of evolutionary change
Non-resistant
bacterium
Antibiotic
Resistant
bacterium
The bacteria in a population vary in their ability to resist antibiotics.
When the population is exposed to an antibiotic, only the resistant bacteria survive.
The resistant bacteria live and produce more resistant bacteria.
Section 15.1 Summary – pages

11. Section 15.1 Summary – pages 393-403
Indirect Evidence for Evolution
Fossils
Comparative anatomy
Comparative biochemistry
Comparative embryology
Section 15.1 Summary – pages

12. Section 15.1 Summary – pages 393-403
Anatomy
Homologous structures - features with a common evolutionary history.
Crocodile
forelimb
Whale
forelimb
Bird
wing
Section 15.1 Summary – pages

13. Section 15.1 Summary – pages 393-403
Anatomy
Analogous structures do not have a common evolutionary origin but are similar in function.
Analogous structures don’t shed light on evolutionary relationships, but they do provide evidence of evolution. How?
Section 15.1 Summary – pages

14. Section 15.1 Summary – pages 393-403
Anatomy
Vestigial structure –no longer serves its original purpose in present-day organism.
Was probably useful to an ancestor.
Vestigial structures, such as pelvic bones in the baleen whale, are evidence of evolution because they show structural change over time.
Section 15.1 Summary – pages

15. Section 15.1 Summary – pages 393-403
Biochemistry
Nearly all organisms share DNA, ATP, and many enzymes, such as cytochrome c.
Biochemical Similarities of Organisms
Percent Substitutions
of Amino Acids in
Cytochrome c Residues
Comparison of Organisms
Two orders of mammals
5 and 10
Birds vs. mammals
8-12
Amphibians vs. birds
14-18
Fish vs. land vertebrates
18-22
Insects vs. vertebrates
27-34
Algae vs. animals 57
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16. Section 15.1 Summary – pages 393-403
Darwin’s Theory in a Nutshell
More offspring are produced than will survive to adulthood.
There is phenotypic variation among offspring (due in large part to differences in genotypes)
“Fittest” individuals will be more likely to reach adulthood and reproduce (pass on genes to offspring).
Section 15.1 Summary – pages