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Age of Earth
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Natural Selection
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What if the environment
changes?
The organisms that are most suited
will survive, the others will die.
This is a very slow process….does not
occur over night…many generations
must past before any change in the
population can be seen.
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Example: Peppered Moth
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Decent with
modifications
These changes increase
a species’ fitness in their
environment.
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History
• James Hutton -1785-Propsed
that he Earth is millions of
years old.
• Thomas Malthus -1798populations outgrew food
supplies, causing competition
and a struggle for one
species to survive against
another
• Jean-Baptiste Lamark inheritance of acquired
characteristics
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History Continued
•Lylle -1833-plant and animal species had arisen,
developed variations, and then became extinct over
time
•Alfred Russel Wallace -1858-idea of competition
for resources as the main force in natural selection
•Charles Darwin -1859- Publishes “On the Origin of
Species”
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Charles Darwin
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Humans select and breed for certain traits.
Examples: The largest hog, the cow that gives
the most milk, or fastest horse.
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Evidence for Change Over Time
Fossil Record
– Fossils that show
how the same
organism looked
millions of years
ago.
– Use rock layers
– Isotope dating
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Relative Dating
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Stages of
development
from an
embryo
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Vestigial organs
– Organs or
structures
that do not
seem to be
used by the
organism any
longer.
– They are
usually reduced
in size.
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Speciation
• is the evolution of a new species
– occurs when interbreeding happens, or when
the production of fertile offspring is prevented
– natural barriers form and cause the breakup
of populations to form smaller populations
– Examples: Volcanoes, sea-level changes, and
earthquakes
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Speciation Mechanisms
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• Behavioral Isolation
– Populations are capable of interbreeding, but have
different courtship rituals or other type of behavior.
• Geographic Isolation
– Separated by bodies of water or mountains.
• Temporal Isolation
– Reproduction takes place at different times of the year
•Overtime they can change so much that they become
unable to breed as they adapt to their environment.
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Changes in allele frequency within a population
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3 Types of Evolution
1) Divergent
2) Convergent
3) Co-Evolution
Divergent Evolution
Red Fox
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Kit Fox
Convergent Evolution
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Coevolution
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Evolution is the
change in a
species over
time.
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Phylogenetic Trees
•Shows how closely
organisms are related
•Are whales more
closely related to
camels or humans?
•Are snakes more
closely related to birds
or camels?
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Phylogenetic Trees (cont.)
Which are more closely
related, sharks and
amphibians or sharks
and ray-finned fish?
Which 2 species are the
most closely related
because they have hair?
How did you know
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Rates of Evolution
1.Gradualism
2.Punctuated Equilibrium
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Gradualism & Punctuated Equilibrium
• A species can
evolve by
only one of
these, or by
both.
•Species with a shorter
evolution evolved mostly
by punctuated
equilibrium
•Species with a longer
evolution evolved mostly
by gradualism.
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Gradualism
•Very gradually, over a long
time....
•Small variations that fit an
organism slightly better to
its environment are selected
for
•Change is slow, constant,
and consistent.
Punctuated equilibrium
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•change comes in spurts.
•period of very little change, and then one or a few huge
changes occur
•often through mutations in the genes of a few individuals.
Resistance in Bacteria due to Evolution
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Read page p403.
Two main sources of genetic
variation
1.Mutations
2.Genetic Shuffling
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EOCT-
It is important that you are able to
explain how the concepts of genetics provide the basis
for explaining natural selection and evolution. This will
help you answer questions like this:
What is the end result of natural
selection?
A increased number of offspring of a given
phenotype that survive
B changes in the frequency of alleles in a
population
C fossil formation through extinction
D environmental changes of a habitat
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Although the Arctic fox and the kit fox are closely related,
they look very different because the individuals
A acquired traits during their lifetimes that contributed to
survival
B with traits most suited to their environments reproduced most
successfully
C migrated long distances to environments that most suited
their traits
D passed on to their offspring acquired behaviors that were
helpful
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Fossils of Archeopteryx show that this
animal had feathers, like a bird. It also
had a bony tail, teeth, and claws on
its wings, like a reptile. This fossil
is evidence that supports the idea that
A birds and reptiles have a common ancestor
B birds have changed very little over 150 million years
C reptile species are more advanced than bird species
D reptiles are warm-blooded like birds
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Horses and tapirs have a common ancestor, but now look
very different. Horses now are grassland animals adapted for
grazing on grass and shrubs. Tapirs are jungle animals that
live in dense forests and eat fruit, leaves and aquatic
vegetation. Which of the following led to the development of
such differences in the two species?
A selective breeding
B convergent evolution
C DNA hybridization
D natural selection
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