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ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

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ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION. Red Queen Hypothesis (Theory of Natural Selection). The environment is constantly changing Natural selection operates to enable the organisms to maintain their state of adaptation (not to improve it) - PowerPoint PPT Presentation

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Page 1: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

ORIGIN OF SPECIES & MODERN THEORY OF

EVOLUTION

Page 2: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Red Queen Hypothesis (Theory of Natural Selection)

The environment is constantly changing

Natural selection operates to enable the organisms to maintain their state of adaptation (not to improve it)

For a species to remain in existence in a constantly changing environment, it must have enough of the right kind of heritable variation to change along with the environment

If genetic variation is inadequate, the species will go extinct

Page 3: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Selection Pressure

The degree to which the environment plays a role in survival

Low Selection Pressure› Low mortality› Lots of survival, more variability› New combinations can be tested› Includes any new genes and mutations

Page 4: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

High selection pressure› High mortality› Only the most fit survive› Eliminates all but the “best” genes› Population becomes specialized

Page 5: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Environmental Change› Factors that determine our environment are

constantly changing› Change occurs as a result of high selection

pressure Environment change may make all individuals less

fit and extinction possible

› Change occurs as a result of low selection pressure More forms of gene present due to increased

variability Environment change may favour the different gene

Page 6: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

MODERN THEORY OF EVOLUTION

Page 7: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Modern evolutionary synthesis› The modern theory of evolution that

takes into account all branches of biology Biologists today define evolution as

changes in the gene pool of a species over time.

Gene pool: the complete set of alleles contained within a species or population

Page 8: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Mutations: The Source of Variation

All species exhibit genetic variation New or altered traits arise when new

alleles and genes are produced by mutation and acted upon by natural selection

Page 9: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

FACTOR INFLUENCE ON EVOLUTION

Beneficial mutations Relatively rare but are favoured by natural selection and tend to accumulate in populations over time

Harmful mutations More common than beneficial mutations but are selected against and therefore have no influence on populations

Duplication mutations Often neutral and so do not immediately benefit the individual, but provide a source of new genetic material with the potential to evolve into new genes

Mutation rates Relatively low for individuals but can be numerous in populations overall

Page 10: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

http://evolution.berkeley.edu/evolibrary/article/1_0_0/eyes_10

Page 11: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION
Page 12: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Homologous Genes and Pseudogenes

Homologous All mammals have similar numbers and

arrangements of bones because they have inherited this pattern from a common ancestor

Similarly closely related species inherit homologous genes, which mutate and evolve over time

The degree of similarity between homologous genes provides good evidence for the degree of relatedness between species

The more closely related two species are, the more similar we would expect their homolgous genes to be

Page 13: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Chicken 5539

Chimp 16785

Dog 12852

Fly 2208

Human 16735

Mosquito 4019

Mouse 19119

Worm 2445

http://tables.pseudogene.org/collection.py?id=15

Page 14: ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

Pseudogenes pseudogene

› A vestigial gene that no longer codes for a functioning protein; genes that have undergone mutations and no longer serve a useful purpose

Like vestigial anatomical features, a pseudogene is the remaining part of a gene that once serves a useful purpose

These genes are found virtually in all species