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Chapter Chapters 1-9

BIO120H1 Chapter Chapters 1-9: Why Evolution is True


Department
Biology
Course Code
BIO120H1
Professor
Doug Thomson
Chapter
Chapters 1-9

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WHY EVOLUTION IS TRUE
CHAPTER 1 What is Eolutio
- 6 tenets to the evolutionary process
- common ancestry
- phylogeny
- disusses te sietifi theo ust e testale + ake eifiale peditios)
- evolutionary predictions from the 6 tenets
- Pale’s aguet: God eated atue ad eethig i it
- Dai’s aguet: adaptatios ae eehee, e eoled
- suggested evolution + natural selection
- first to use evidence to convince ppl evolution was true
- wrote: on the Origin of Species
-Darwinism: theory of evolution by natural selection
- life on earth evolved gradually from one primitive species, branched out over time, threw off many new +
diverse species, & the mechanism for almost all evolutionary change is natural selection
The 6 tenets to the evolutionary process:
1. Evolution
2. Gradualism
3. Speciation
4. Common ancestry
5. Natural selection
6. Nonselective mechanisms of evolutionary change
1. Evolution
= a species undergoes change over time
- mutations in DNA cause species to evolve over generations
- species descended from earlier species
- all species evolve, but at different rates
- The theo of eolutio does ot pedit that speies ill ostatl e eolig, o ho fast the’ll hage he the
do. That depends on the evolutioa pessues the epeiee. 
2. Gradualism
- it takes many generations to produce a substantial evolutionary change
- a single species evolves faster/slower as evolutionary pressures vary
- strong natural selection = fast evolutionary change
- well adapted species in stable environment = slower evolutionary change
3. Speciation (splitting)
- all species share some fundamental traits
- DNA code: fundamental pathway used to produce energy, read + translated into proteins
- speciation = diversity
- there is a single ancestral species, common ancestor, missing link
- speiatio is the eolutio of diffeet goups that a’t iteeed/ehage gees
- diff speies ould’t e attated to eah othe as ates
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- offspring could be sterile
- cross-fertilization prevented bc diff species use diff pollinators/flower at diff times
- speies do’t hae to split
- >99% go extinct
- speciation is slow
- node = common ancestor
4. Common Ancestry
- flip side of speciation
- using DNA sequences or fossils to look back in time & find descendant lineages fusing at ancestors
- form a nested hierarchy: hierarchy in which groups of species whose members share a few traits are subdivided into
smaller groups of species sharing more traits
**phylogeny: evolutionary tree
- Darwin showed that the nested arrangement of life is exactly what evolution predicts
- can reconstruct evolutionary relationships by sequencing the DNA of various species and measuring how similar they
are
- physical traits & DNA sequences = valid info about evolutionary relationships
5. Natural Selection
- explains apparent design in nature by a purely materialistic process
- produces organisms that are well adapted to their habitats and way of life
- requires only that individuals of a species vary genetically in their ability to survive and reproduce in their environment
- must work with the design of organism as a whole, which can compromise adaptations
- mutations are changed in traits that already exist, means evolution must build new species starting w design of
ancestors
- yields only improvements, not perfection (fitter not fittest)
- the only process tht can produce adaptation
6. Nonselective Mechanisms of Evolutionary Change
- random changes in proportions of genes
- failies hae diff #’s of offspig
Old Beliefs about Evolution
- Mutationism predicts that new groups should arise instantly from old ones, without transitions in the fossil record (not
true)
- evolution may occur but not gradually
- evolution may be true but natural selection not its cause; there was believed to be a teleological force
Scientific Theory
-a scientific theo is a stateet of hat ae held to e the geeal las, piiples, o auses of soethig ko o
observed.
-it is a well-thought-out group of propositions meant to explain facts about the real world
-For a theory to be considered scientific, it must be testable and make verifiable predictions
- must be able to make observations tht support or disprove it
- there is no one moment when a scientific theory suddenly becomes a scientific fact; evidence has to accumulate in its
favour
- scientific theories are usually tested against alternative theories
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Evolutionary Predictions from the 6 Tenets
- we should be able to find evidence for evolutionary change in the fossil record
- older fossils = primitive organism
- younger fossils = more complex organisms
- should be able to see lineages + descent w modification
- should be able to find cases of speciation in the fossil record, + new species forming in the wild
- should e ale to fid e’s of speies tht lik together major groups suspected to have common ancestry (missing
links/transitional forms)
- expect that species show genetic variation for many traits
- be able to find cases of imperfect adaptation
- be able to see natural selection acting in the wild
- retrodictions: fats ad data that ae’t eessail pedited  the theo of eolutio, ut make sense only in light of
the theory of evolution
CHAPTER 2 Witte i the Roks
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