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Chapter 15

BIO342H5 Chapter Notes - Chapter 15: Genetic Recombination, Allele Frequency, Neo-Darwinism

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Don Mc Kenzie

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Process of change and adaptation developing new life forms and genetic diversity
Theories of Evolution
A. Lamarck
o Formulated the concept of use and disuse
Organs that are used extensively develop, while organs that are not used
o Theorized that complex species arise from older and simpler species through the
accumulation and modification of acquired characteristics
o False now known that characteristics are inherited (not acquired)
B. Darwin
o Organisms produce offspring some survive to reproductive maturity
o Variations between individuals of a given population exist
Those that provide them with a slight advantage are favourable variations
o Those inheriting favourable variations are likely to live longer and produce more
This favourable variations become more common every generation
o Known as natural selection driving force of evolution
o Differentiate organism and slowly into new species
Fitness reproductive success and ability to contribute to the
perpetuation of the species
C. Neo-Darwinism (the modern synthesis)
o Ultimate source of hereditary variation lies in the process of mutation and genetic
recombination some increase chances for survival and reproduction
(favourable genes) while others don’t
This is differential reproduction
After many generations, favourable genes will become prevalent in the
gene pool (all genes in all individuals in a population at a given time)
D. Punctuated Equilibrium
o Evolution is characterized by long periods of stasis ‘punctuated’ by evolutionary
changes occurring in spurts (as shown by fossil records)
o Opposes Darwin’s model which proposes gradual evolutionary changes
Evidence of Evolution drawn from many disciplines
A. Palaeontology
o Study of the fossil record
o Uses radioactive dating techniques to determine the chronological succession of
species in the fossil record
B. Biogeography
o Refers to the distribution of life forms throughout the globe
o Darwin observed that many species found on the Galapagos Islands seemed
more closely related to species of the mainland than to species of the other
Galapagos islands
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