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Evolution
• Evolution- change in allele frequency in a population over time (decent with
modification)
• Population- Group of individuals of a single species that occupy the same
general area
• Allele- an alternative version of a gene
• Gene- a discrete unit of hereditary information consisting of a specific
nucleotide sequence in DNA, codes for a protein that leads to a physical
characteristic
Types of Evolution
• Microevolution- evolution within a species
• Macroevolution- evolution that produces a
new species
• Origins of life according to evolution
Lamarckian Evolution
Lamarck’s theory
is incorrect
3 concepts
•Theory of need
•Theory of use and disuse
•Theory of inheritance of
acquired characteristics
Charles Darwin
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Naturalist on the HMS Beagle
Surveying ship
5 year voyage beginning in 1831
Made observations and collected specimens
along the way, many from the Galapagos Islands
• Returned to England and began to develop his
theory of Evolution
•Galapagos finches that Darwin observed have different beaks
based on the food that they eat
•Darwin believed the differences in their beaks were due to
evolution
•He believed the different species of finches adapted to
different environments at different times, so they could get
the food that was available there
•Darwin believed they evolved from a common ancestor
Artificial Selection
Species definitely have the ability to
change over time to become very
different than what they once were
Charles Darwin
• Published “On the Origin of Species by Means of Natural
Selection” in 1859
• Published “The Descent of Man” in 1871
Evolution by Natural Selection
• Mechanism of evolution- evolution is what
happens, natural selection is how it happens
• Individuals whose inherited traits give them a
higher probability of surviving and reproducing in a
given environment tend to have more offspring
than other individuals which leads to the
accumulation of favorable traits in a population
over generations
Evolution by Natural Selection
• Traits must be genetically based
• Genes must lead to a reproductive advantage
• Causes the allele frequency in the population
to change
• Takes many generations
• Remember: favorable traits are based on the
environment
Survival of the fittest
• Somewhat misleading
• Does not necessarily mean physical strength
• It means better adapted to the current
environment
What leads to natural selection?
• Environmental change- an allele that was once not
an advantage becomes an advantage because the
environment is different.
• Immigration (gene flow)- individuals with more
advantageous genes join a population.
• Genetic drift- random selection of a gene because
of an event that significantly decreases population
size and eliminates all or most individuals with a
particular gene.
• Mutation- altering of the nucleotide sequence can
make a gene more advantageous.
Microevolution
• Pests and pesticides
• Bacterial resistance to
antibiotics
• Selection to avoid
predation
Microevolution- evolution within
a species