EVOLUTION
How populations evolve…
Charles Darwin…
Natural Selection…
Evidences and Mechanisms…
Evolution is merely a change over
time.
• Considered the unifying
theory of biology
• Like a family history only
on a much grander scale
• Without evolution, all of
us would look exactly as
we did the day we were
formed!
• Change over time allows
us to progress from single
cell to infant to adult!!
• Changes can be lifelong
or seasonal.
Charles Darwin is considered to be
the “Father of Evolution”
• Believed animals
arose from
ancestors…called this
“descent with
modification”
• Wrote The Origin of
Species to explain
HOW this happened
• Used voyage on the
“Beagle” to document
evidence
Darwin not the first to propose
evolution…just the first to propose
a cohesive idea.
• Aristotle and Judeo-Christian beliefs were that
species were “fixed” and didn’t change
• Anaximander proposed life arose in water (it
did)
• Buffon challenged that the Earth was young
(fossils helped prove much older)
• Lamark proposed evolution…but…proposed
that by using or not using body parts changes
occur…remembered for this and not evolution
in general…Darwin gets all credit.
Things started to become clear to
Darwin aboard the “Beagle”
• Collected specimens of plants
and animals
• Observed adaptations of
animals in different parts of the
world
• Noticed many things in and
around Galapagos Islands
• Many species found only here
but resemble those found on
SA mainland
• Adaptations included modified
beaks of finches and necks of
tortoise.
Darwin backed up his claim that
living organisms evolve with
several Evidences:
• Fossil Records—historical records of
organisms preserved in rock and
sediment. Erosion of soil exposes the
preserved specimens.
– Younger specimens higher up in
rock layers
– Footprints and other marks also
fossils
– Fishlike fossils are oldest known
– Paleontologist…one who studies
fossils.
Other evidences were biogeography…Animals more
closely resemble those on same continent with different
geography than those on distant continent with same
geography.
• Comparative Anatomy—
certain anatomical similarities
between species bear witness
to evolution. (human, cat,
whale and bat all share same
arm, hand and wrist bones)
• Comparative Embryologycomparison of different stages
of development during
embryonic development. For
instance, all vertebrates have a
stage where gill pouches are
evident…in fish they become
gills…in mammals they
become a voice box.
One new evidence that has become important
since the time of Darwin is Molecular Biology.
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Share similarities in DNA, protein
sequences, genes and gene
products.
Common genetic code (same 4
bases, same 20 amino acids for
all species)
Genetic language passed along
through all branches of evolution
since day one.
Allows us to produce mass
quantities of vaccine, medicine
and other important products
through use of gene similarity
across species. Yeast, viruses
and bacteria all mass produce
important medical products.
These tomatoes, developed by the University
of Arizona, can produce a vaccine that
helps develop immunity towards the HIV
virus that causes aids. You can also eat the
tomatoes to obtain the vaccine.
Darwin’s observations led to his hypothesis that
organisms change due to NATURAL SELECTION
• Most species will
overproduce offspring
leading to a struggle for
existence in obtaining
resources
• Variation within a
population is inherited
• Differential reproductive
success in
population…those with
“best” genes will
produce more offspring.
Relative Importance of Natural
Selection to Evolving Populations
• Struggle for existence helps “weed out” sick,
weak organisms who cannot obtain resources
• Variation allows for some organisms to survive
natural phenomenon because they have a
different gene than those who don’t survive
Weeds with a natural resistance to herbicides
used to control them. Probably developed by
passing genes of plants surviving repeated
applications on to offspring.
Differential reproductive success means that
animals who produce the most offspring are the
most “fit,” meaning they have the “best” genes in
the population to pass on to offspring allowing the
offspring better survival chances.
Result of Natural Selection in
Action
• Adaptation to the environment.
• Organisms who are best suited for survival
and reproduction in the area they live in
• Constant changes in environment mean
constant changes in organisms which
allows for natural selection and adaptation
to take place.
• How have you been forced to adapt since
coming to SWOSU?
When humans interfere with
Natural Selection disaster occurs!!
• Animals or plants selected for desirable traits
but not necessarily those that allow them to
survive in the wild
• Not allowing Mother Nature to do her job in
controlling population numbers
• Larger populations of less desirable organisms
or very “domestic” organisms
• Organisms specialized for only a single reason
or use
Artificial Selection
• "Less than 14,000 years
separates them: the wolf the dog's ancestor- and the
Maltese, one of hundreds of
breeds of today's Canis
familiaris. Humans
transformed wild canines
into the first domesticated
animal -the tamable,
trainable, incredibly variable
dog." -National Geography,
Karen E. Lang