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Lecture 6

BIOLOGY 1M03 Lecture Notes - Lecture 6: Natural Experiment, Rifampicin, Allele FrequencyPremium

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Jon Stone

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BIOLOGY 1M03 - Lecture 6 - Evolution by Natural Selection (Continued)
Expansion on Homologies:
Developmental homology is known as similarities in embryonic traits.
An example of this type of homology is the gill pouches found during
embryonic development in chicks, humans, and cats.
Structural homology refers to similarities in adult morphologies (appearances of
An example of this type of homology is the common structural plan found
in the bones of the limbs in vertebrates (animals with a backbone).
Many traits are similar in species because of the theory of having a common
ancestor. If species were created independently of one another, these similarities
might not have occurred.
The homology of structural homology is assessed on the basis of three critea:
○ Topological
○ Ontogenetic
○ Compositional
Evidence for Evolution:
The prediction that species are not static, but dynamic is supported by the
following evidence:
Most species have gone extinct
Fossil (extinct) species frequently resemble living species found in the
same area
Transitional features document change in traits through time
Vestigial traits are common
The characteristics of populations can be observed changing today
The prediction that species are related, not independent, is supported by the
following evidence:
Closely related species often live in the same geographic area.
Homologous traits are common and are recognized at three levels:
Genetic (gene structure and the genetic code)
Developmental (embryonic structures and processes)
Structural (morphological traits in adults)
The formation of new species from pre-existing species can be observed
Evolution’s Internal Consistency - The Importance of Independent Data Sets:
The most powerful evidence for any scientific theory, including evolution by
natural selection, is called internal consistency. This term refers to observation
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