Post on 05-Jan-2016
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Chapter 15.1 Natural Selection and the Evidence for
Evolution
• Studied to become a clergyman and a doctor before becoming a naturalist.
• 5-year voyage around the world on HMS Beagle (1831-1836).
• Published The Origin of Species in 1859.
• Not the first person to propose that species evolve.
Charles DarwinCharles Darwin
Darwin’s InfluencesDarwin’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.
Darwin’s InfluencesDarwin’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.
Selection and EvolutionSelection 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.
Evidence: structural adaptations Evidence: structural adaptations • Mimicry – one species
resembles another species.
1. 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?
• 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.
Structural adaptationsStructural adaptations
Structural adaptationsStructural 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.
The peppered moth
English peppered moth, Biston betularia
Non-resistant bacterium
Resistant bacterium
Antibiotic
When the population is exposed to an antibiotic, only the resistant bacteria survive.
The bacteria in a population vary in their ability to resist antibiotics.
The resistant bacteria live and produce more resistant bacteria.
Direct evidence of evolutionary changeDirect evidence of evolutionary change
Indirect Evidence for EvolutionIndirect Evidence for Evolution
• Fossils
• Comparative anatomy
• Comparative biochemistry
• Comparative embryology
AnatomyAnatomy• Homologous structures - features with a
common evolutionary history.
Whale forelimb
Crocodileforelimb
Birdwing
AnatomyAnatomy• 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?
• 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.
AnatomyAnatomy
• Nearly all organisms share DNA, ATP, and many enzymes, such as cytochrome c.
Biochemical Similarities of Organisms
Comparison of OrganismsPercent Substitutions
of Amino Acids in Cytochrome c Residues
Two orders of mammals
Birds vs. mammals
Amphibians vs. birds
Fish vs. land vertebrates
Insects vs. vertebrates
Algae vs. animals
5 and 10
8-12
14-18
18-22
27-34
57
BiochemistryBiochemistry
1. More offspring are produced than will survive to adulthood.
2. There is phenotypic variation among offspring (due in large part to differences in genotypes)
3. “Fittest” individuals will be more likely to reach adulthood and reproduce (pass on genes to offspring).
Darwin’s Theory in a NutshellDarwin’s Theory in a Nutshell