Transcript The Evolution of Living Things

The Evolution of Living Things
Section 1: Change over Time
Section 2: How does Evolution Happen?
Section 3: Natural Selection in Action
Change Over Time
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Adaptation: a characteristic that helps an
organism survive and reproduce in its
environment
Species: a group of organisms that can
mate with one another to produce fertile
offspring
Population: groups of individuals of the
same species living in the same place
Evolution
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The process in which inherited
characteristics within a population change
over generations such that new species
sometimes arise
Fossils
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The remains or physical evidence of an
organism preserved by geological
processes
Fossil record: a historical sequence of life
indicated by fossils found in layers of the
Earth’s crust
Evidence
of
Ancestry
Adapted from "A Simplified Family
Tree of Life" in The Evidence of
Evolution by Nicholas Hotton III,
Smithsonian, c1968.
Geological
Time Scale
Examining Organisms
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Evidence of Whale Evolution (p. 170, Fig. 7)
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Pakicetus: Scientists think that whales evolved from
land-dwelling mammals that could run on four legs;
one of these ancestors may have been Pakicetus,
which lived about 50 mya
Ambulocetus: This mammal lived in coastal waters
about 49 mya; could swim by kicking its legs and
using its tail for balance
Dorudon: This mammal lived in the oceans about 40
mya; resembled a giant dolphin with tiny hind limbs
that could not be used for swimming or walking
Modern toothed whale: Forelimbs are flippers; no
hind limbs, but do have tiny hip bones; range in size
from 1.4 m porpoises to 33 m blue whales
Comparing Organisms
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Comparing Skeletal Structures: similarities
in arrangement of bones suggests that cats,
dolphins, bats, and humans had a common
ancestor
Comparing DNA: every organisms inherits
the traits determined by DNA; if two
species have similar DNA, the hypothesis
suggesting common ancestry is supported
Charles Darwin (1809-1882)
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Took a five-year voyage around the world on
the HMS Beagle in an effort to study nature
and to explain HOW evolution happens
Studied finches on
the Galapagos islands
Thomas Malthus (1766-1834)
"In October 1838, that is, fifteen months after I had begun my
systematic inquiry, I happened to read for amusement Malthus
on Population, and being well prepared to appreciate the
struggle for existence which everywhere goes on from longcontinued observation of the habits of animals and plants, it at
once struck me that under these circumstances favourable
variations would tend to be preserved, and unfavourable ones
to be destroyed. The results of this would be the formation of a
new species. Here, then I had at last got a theory by which to
work".
Charles Darwin, from his autobiography. (1876)
Charles Darwin –
Theory of Natural Selection
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As random genetic mutations occur within an
organism's genetic code, the beneficial mutations
are preserved because they aid survival -- a
process known as "natural selection." (Descent
with Modification) These beneficial mutations
are passed on to the next generation. Over time,
beneficial mutations accumulate and the result is
an entirely different organism (not just a variation
of the original, but an entirely different creature).
In 1859, Darwin published his famous book, “On
the Origin of Species by Means of Natural
Selection”
Natural Selection in Action
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In 1930, about 99% of the male elephants
in one area had tusks; today, because of
hunting for ivory, only 85% of the male
elephants in that area have tusks
Insecticides – insects developing resistance
Antibiotics – bacteria developing resistance
Peppered moths – industrial melanism
Forming a New Species
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Speciation: the formation of new species
as a result of evolution
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Separation
Adaptation
Division
The Evolution of the Galapagos Finches
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Some finches left the mainland and reached one
of the islands (separation)
The finches reproduced and adapted to the
environment (adaptation)
Some finches flew to a second island (separation)
The finches reproduced and adapted to the
different environment (adaptation)
Some finches flew back to the first island but
could no longer interbreed with the finches there
(division)
This process may have occurred over and over
again as the finches flew to the other islands
Review
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When a single population evolves into two
populations that cannot interbreed
anymore, __________________
has
speciation
occurred.
Review
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Darwin’s theory of
______________explained
the process by
natural
selection
which organisms become well-adapted to
their environment.
Review
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A group of organisms that can mate with
each other to produce offspring is known as
species
a(n) ________________________.
Review
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fossil record
The _____________provides
information
about organisms that have lived in the past.
Review
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selective breeding humans select
In ________________,
organisms with desirable traits that will be
passed from one generation to another.
Review
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A(n) _________________helps
an
adaptation
organism survive better in its environment.
Review
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Populations of insects and bacteria can
evolve quickly because they usually have a
generation time
short ___________________________.