BIOL 2112 Chapter Notes - Chapter 13: Heterozygote Advantage, Disruptive Selection, Stabilizing Selection
4 Jun 2018
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1.Explain how Darwin’s voyage on the Beagle influenced his thinking.
Darwin collected thousands of fossils and plants and animals and kept a journal of his
observations. He noticed that organisms had similar characteristics but slightly different from
Island to Island.
He felt that his evidence was better explained by the hypothesis that present day species are the
descendents of ancient ancestors.
His phrase for evolution was “descent with modification” later changed to “genetic changes in a
population from generation to generation.
2.Explain why the concept of evolution is regarded as a theory with great significance.
It is considered a theory because it is still so broad. Evolution still generates new
hypotheses and is supported with large amounts of evidence.
3.Explain how fossils form and why the fossil record is incomplete.
Fossils form by sedimentary rocks layering over the organism called strata. A fossil
record is incomplete because it doesn’t prove where the area was that the organisms lived.Also,
many of Earth’s organisms did not live in areas that favor fossilization. These fossil records also
were destroyed by geologic processes and some fossils are out of reach for paleontologists.
4.Explain how homologies, the fossil record, and molecular biology support evolution.
Homologous structures are anatomical similarities in different organisms. For example,
the human, cat, whale and bat all have the same anatomy but uses are different. The fossils are
shown by the example that ancestors of whales still homologous ankle bones such of a cloven-
hoofed mammal. In terms of Molecular biology is that all forms of life use DNA and RNA and
that all genetic code of RNA triplets being translated into amino acids are the same. Related
species can have characteristics that have an underlying similarity yet function differently.
5.Explain how evolutionary trees are constructed and used to represent ancestral relationships.
Evolutionary trees are constructed by one common ancestral species branching out to a
descendent species because of either DNA or similar characteristics such as Homologous
Structures. Each branch point represents a common ancestor.
6.Describe Darwin’s observations and inferences in developing the concept of natural selection.
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