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Evidence of Evolution
I. Evolution
Evolution: gradual changes in a species
over time
Jean Baptiste de Lamarck
1. First to propose that living things had
descended from a similar extinct species
a. Acquired traits passed on to
2. Acquired Trait: a trait not
determined by genes. Arises during an
organisms lifetime due to their experience
or behavior
3. Genetic Trait: a trait determined by
Charles Darwin: “Father of Evolution”
1. Studied organisms (finches, tortoises,
iguanas) on the Galapagos islands.
2. Wrote the “Origin of Species”
3. Evolution occurs due to natural selection
Natural Selection: Organisms that are
better adapted to their environment will
have a better chance of survival,
therefore they will reproduce more
E. Steps to Natural Selection
Variation is necessary for natural
a. Within a population there is a
variation in traits (phenotypes)
Living things face a constant struggle for
a. Produce more offspring than there is
room and food for, so they must compete
to survive
Only some individuals survive and
a. Some individuals are more “fit” for the
environment or for life in general
ex. Resistance to disease
4. Each generation consists of individuals
with traits(phenotypes) that made them
more “fit”, so over time, alleles for those
traits will increase in frequency
Species adapt to their environment
a. selection tends to make organisms
better suited to their environment
C. Lethal genes are kept in the gene pool if
in the heterozygous form because those
individuals will not show the lethal
Evidence of evolution: how do we know
it occurs
1. Similarities in Embryology: during
early stages of development, organisms
that descend from common ancestor
look the same
2. Homologous features: similar
features that originated in a shared
ex. Forelimbs of vertebrates
3. Analogous Features(not a piece of
evidence for evolution): serve similar
function and they look similar, but the
organisms don’t share a common ancestor
ex. Wings in insects and birds
4. Vestigial Features: features that are
apparently useless to the modern
organism, but may have been useful to
ex. Tailbone in humans, pelvic bones in whales
5. Similarities in DNA and
macromolecules(proteins, carbs, etc.)
Patterns of Evolution:
1. Coevolution: change of two or more
species in close association with each
ex. Hummingbirds and the flowers they
feed on
2. Convergent Evolution: organisms that
are not closely related evolve to show
similar trait
ex. Sharks and Dolphins
Divergent evolution: two or more
organisms evolve to become more and
more dissimilar
a. Adaptive Radiation: many related
species evolve from a single ancestral
b. Artificial Selection: speeding up of
divergent evolution
ex. Dog breeding