BIOB51H3 Chapter Notes - Chapter 2: Relative Dating, Reverse Transcriptase, Intron
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BGYB51: Chapter 2 (Pages 37 – 49 and 53 – 65)
The Pattern of Evolution
The first scientist to give a definition of species, John Ray, states that “…[O]ne species never
springs from the seed of another.”
The Theory of Special Creation had been the leading explanation in Europe for the origin of
species until a certain point where scholars began to challenge that notion (i.e. when Darwin
started to study biology seriously) and research in biology and geology grew rapidly to disprove
Darwin drew up evidence suggesting that the pattern of life’s history is different than is claimed
by Special Creation. (Read Page 39 for elaboration)
1. Species are not immutable, but change through time
2. Species are derived not independently, but from common ancestors
3. The Earth and life are considerably more than 6 000 years old.
Darwin also introduced a process to explain this pattern called natural selection
2.1 Evidence of Change through Time
Evidence from Living Species
The living evidence for descent with modification comes in two forms:
o By monitoring natural populations, we can directly observe small scale change (i.e.
o If we examine the bodies of living organisms, we can find evidence of dramatic change
Direct Observation of Change Through Time
o Read examples of the change of the Soapberry bug over time on Page 40
o A vestigial structure is a useless or rudimentary vision of a body part that has an
important function in other, closely allied species (e.g. the remnant hind limbs on the
o Humans have muscles attached to the hair follicles that make hair stand up when cold,
intimidated, or needed to seem bigger. These muscles are effective for animals that are
very hairy like chimpanzees. Most of us are not that hairy (except some of you hormone
excessive freaks), and thus the result of these muscles contracting is goose bumps. This
implies that we descended from ancestors who were hairier than us.
o Read page 42 for more examples
o Vestigial traits also occur at a molecular level.
Humans have one on chromosome 6; a DNA sequence that looks like a gene for
the enzyme CMAH
It is actually disabled by a 92-base-pair deletion and humans cannot
Chimpanzees however are able to
This explains that the human race must have descended from a common
ancestor with the chimpanzees
o Read page 43 for more examples
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