EVOLUTION
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Students know and understand the
characteristics and structure of living things,
the processes of life, and how living things
interact with each other and their
environment.
Benchmark 3.18: Organisms change over
time in terms of biological evolution and
genetics.
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Darwin, the Beagle and Finches: 3:59
Darwin’s Discoveries: 10:10
Gene frequency, natural selection, speciation:
29:00
What do you get when you cross a mouse
with a mango? 4:15
Why did the woolly mammoth become
extinct? 2:17
Total time: 49:41 min. (approximately)
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Before Darwin, most
people believed that each
species was created once
and stayed the same
forever.
The modern theory of
evolution began when
Charles Darwin presented
evidence that evolution
happens and offered an
explanation of how
evolution happens.
Darwin, the Beagle
and Finches (3:59)
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Through breeding pigeons,
Darwin gained a new insight.
Through artificial selection,
breeders can produce
individuals that will pass on
desirable traits.
Darwin took a voyage in 1831
from Europe around S.
America, Australia and Africa
with a stop at the Galapagos
Islands off the western coast
of S. America.
It was in the Galapagos
Islands that Darwin noticed
that some species resembled
those found in S. America, but
were slightly different.
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Darwin was influenced by ideas from the
fields of natural history, economics, and
geology.
The ideas of Lamarck, Malthus, Culvier and
Lyell were especially important.
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In 1809, French scientist,
Jean Baptiste Lamarck
proposed that organisms
change over time as they
adapt to their environment.
He also incorrectly
proposed that use or disuse
of a characteristic would be
passed on to future
generations.
If you did not exercise your
right arm all your life and
had wimpy muscles, would
that trait be passed on to
your offspring?
What can you conclude
about Lamarck’s proposal,
and why would it have been
important to Darwin?
Darwin Develops a Non-Random
Theory of Evolution:
Natural Selection and Adaptation (4:41)
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Thomas Malthus was an
English economist who
wrote an essay in 1798
where he observed that
human populations were
growing faster than food
supplies.
While food growth
increased linearly,
populations grew
exponentially.
Darwin observed that all
kinds of organisms tend to
produce more offspring
than can survive, so he
applied this to his theory
that populations are limited
by their environments.
Geologist(s)
Theory
Georges
Cuvier
Species change over time but
not gradually, he thought the
changes were sudden.
James
Hutton and
Charles Lyell
Both Hutton and Lyell thought
that geologic processes work
gradually and constantly. They
showed that Earth’s history was
long enough that it supported
the idea that species changed
gradually over long periods of
time.
Cuvier
Lyell
Hutton
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Darwin formed a key idea: Individuals that
have traits that better suit them to their
environment are more likely to survive.
Individuals that have certain traits tend to
produce offspring with those same traits .
Those differences are part of natural
selection, which Darwin proposed is a cause
of evolution.
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1. Overproduction: Every population is capable
of producing more offspring than can possibly
survive.
2. Variation exists within every population.
Much of this variation is in the form of inherited
traits.
3. Selection: In a given environment, having a
particular trait can make individuals more or less
likely to survive and have successful offspring.
So, some individuals leave more offspring than
others do.
4. Adaptation: Over time, those traits that
improve survival and reproduction will become
more common.
Darwin published “Origin of Species by Means
of Natural Selection” in 1859.
The fossil record reveals a pattern of gradual
change from past to present.
Biogeography shows that environments shape
the evolution of organisms.
Developmental Biology shows that the ancestry
of organisms are similar such as the
development of multicellular organisms from
embryos.
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Anatomy or body structure shows how some
species are the same or different.
There is a hypothesis that all vertebrates
descended from one common ancestor.
When comparing modern vertebrates, the
differences in the size, number and shape of
bone is clear, yet the basic pattern is the
same.
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Strengths:
His theory is
supported by data
and helps explain
that data.
He presented a
logical and testable
theory for the
process of evolution.
He changed the way
scientists think about
the diversity of life.
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Weaknesses:
His theory lacked a
clear mechanism fro
inheritance because
he knew very little
about genetics.
Today, an
understanding of
genetics is integral to
the understanding of
evolution.
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The link between
microevolution and
macroevolution is
speciation.
Speciation is the
formation of a new
species as a process
of genetic change or
as a pattern of
change in the form of
organisms.
What do you get when you cross
a mouse with a mango? (4:15)
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Natural selection
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Migration
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Mate Choice
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Mutation
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Genetic Drift
◦ Causes an increase or decrease in certain alleles in a
population.
◦ The movement of individuals into, out or between
populations. Changes the types of alleles in a population.
◦ Random pairing of mates increases the assortment of traits.
◦ Changes the numbers and types of alleles from generation
to generation.
◦ Random effects of everyday life can affect the survival and
reproduction in populations, thus some alleles can become
more or less prevalent.
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Convergent
evolution is
strongly directed by
environment—
species living in the
same type of
environment should
evolve similar
adaptations.
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Coevolution:
Species that live
close together can
affect one another’s
evolution.
Species that live in
close contact often
have clear
adaptations to one
another’s existence.
Coevolution between the yucca moth
and the yucca plant. A female yucca
moth (Tegeticula yuccasella) pushing
pollen into the stigma tube of the
yucca flower while visiting the flower
to deposit her eggs.
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Over time, species
may split into two
or more lines of
descendants or
lineages. As the
splitting repeats,
one species can
give rise to many
new species.
Darwin’s finches
Adaptive Radiation (13:04)
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If all members of a
lineage die off or
fail to reproduce,
the species is said
to be extinct.
Evolution and
Sexual
Reproduction
Why did the Wooly Mammoth
become extinct? (2:17)
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Gradualism is a model
used to describe the
formation of a new
species through small,
gradual changes as
opposed to large-scale
changes.
Punctuated equilibrium
is where new species
“suddenly” appear in
response to
environmental
changes.
Chapter 16 Lab pg. 387:
Selection Model