SBI 3U
Date:___________
7.6: The Modern Theory of Evolution
Darwin's Theory could account for how species evolved but could not describe the
________________of variation.
Modern Evolutionary Synthesis:
 The modern theory of evolution that takes into account all branches of biology.
Darwin’s Theory
Modern Theory
Gene Pool:
 complete set of _______________ contained within a species or population
Mutations: The Source of Variation
Recall:
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All species exhibit genetic variation.
Different individuals have different combinations of the many alleles that are already
present in the population.
Sexual reproduction ________________________, or shuffles, these alleles and
produces an almost unlimited number of combinations.
New or altered traits arise when new alleles and genes are produced by _________
and acted upon by __________________ ________________.
Wendy was recently part of a genetics study done in the U.S. on
mutation in the myostatin gene in whippets, which resemble
greyhounds in appearance. The Institute of Health study
reported that whippets with one single defective copy of the gene
have increased muscle mass that can enhance racing performance
in the breed, known for speeds up to 60 kilometres an hour.
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Genetic Mutation = Change in DNA
Bases that make up DNA can be switched, lost, or newly inserted.
Mutations can result in:
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Duplicate copy of genes - Often Viable
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Missing copy of genes - Low chance of survival
The Importance of Gene Duplication
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Source of ___________ genes
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Extra copy of the gene is 'free' to mutate and gain a new function.
Why does this require a duplicate gene?
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If a mutation results in a new protein that no longer performs a vital function it will
die, even if the new protein is beneficial.
Types and Effects of Mutation
1) Beneficial Mutations
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Rare but favored by natural selection (________________ in populations over time)
Produce a change in ____________________ that gives individual an advantage
i.e. - Sickle-cell allele gives carriers a high degree of resistance to _____________
and dramatically ___________________ their chances of survival in regions where
malaria is endemic
i.e. - mutations that have allowed some plants to produce colourful flowers and
attract pollinators have been beneficial to those species, and these new genes have
become widespread
i.e. - development of antibiotic or insecticide resistance
2) Harmful Mutations
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Any mutation that ________________ the reproductive success of an organism
May make an organism less able to resist _______________, or avoid predators, or
less efficient at obtaining ____________
i.e. animals born with extra limbs or other deformities
i.e. genetic disorders such as cystic fibrosis or Huntington's disease
3) Neutral Mutations
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Most _______________, occur in non-coding portions of DNA.
Have ______ immediate influence on the success of an individual
Mutation Rates
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Error rates in chromosome replication = less than 1 mutation / million bases
Genomes can consist of millions or billions of DNA bases
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Individual mutation rates are very difficult to estimate, but recent studies suggest that
species with large genomes are likely to have mutation rates averaging more than
one per individual. Humans with genomes consisting of billions of bases, may
average _______ or more mutations per individual.
Homologous Genes
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Are inherited from a common _________________ but have a _______________
modern purpose.
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Homologous genes _______________ and evolve over time
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Degree of similarity between Homologous genes provides good evidence for degree
of ________________________ between species. (more closely related, more
similar homologous genes)
Pseudogenes
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Genes that have undergone _____________________ and no longer serve useful
______________________
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FYI: Dolphins breathe through their noses like land mammals. However land
mammals have approximately 1000 genes that code for the detection of airborne
chemicals, dolphins have these same 1000 genes but only _______ are functional.
The remaining 800 are ______________________.
Modern Paleontology
Plate Tectonics
Until the 1960's, the locations of some fossils were quite puzzling. Particularly surprising
was the discovery of fossils of the same species in Africa, India and Antarctica - but
nowhere else on Earth. Today the study of biogeography has been complemented by
great advances in the study of plate tectonics and continental drift.
Plate tectonics describes ____________________ of Earth's crust and accounts for
many large surface features such as ____________________, as well as ___________
and ____________________ activity. Figure 7 shows the arrangement of some of
Earth's major land masses about 200 million years ago. Species distribution at that time
were permanently captured in the fossil record.
Activity: Darwinian Challenge - p.567 (Gr 12 Text)
Questions #5, 6, 8 -p.555 (Gr 12 Text)