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Why Evolution Is True
Chapter 1: What Is Evolution
Life on earth evolved gradually beginning with one primitive species that then branched out
over time, throwing off many new and diverse species. The mechanism for most but not all
of evolutionary change is natural selection.
6 parts to this:
1)Evolution – species undergoes genetic change over time. Differences based on change
2)Gradualism – takes many generations to make a substantial change
3)Common Ancestry – recent ancestor—similar trait, which creates “natural”
classification this is strong proof for evolution. If we were created = no “natural”
agreed upon classification
4)Speciation (splitting) ---starts with 2 populations of the same species that cannot
interbreed—exponential rise on the number of possible future species
5)Natural Selection –requires individuals of species to vary genetically in ability to
survive and reproduce causes species to look specifically “designed” for
environment – not perfect
a.Mutations MOSTLY change in pre-existing trait. Rarely creates new ones.
Descendants entirely dependent on ancestor’s pre-existing design.
b.Natural selection produces the “fitter” species--- not the fittest
6)Non-selective mechanisms of evolutionary change – simple random change in
proportion of genetics caused by the fact that families have different numbers of
offspring (not adaptive)
Theory of Evolution ---documented set of principles that explains how and why evolution
happens. Testable and can make verifiable predictions. Tests: fossil evidence of lineage;
species show genetic variation, which accounts for speciation. Also, retrodictions: fact and
data not necessarily predicted by evolution, but only make sense in the light of evolution.
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