Download natural selection

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Age of Earth
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Natural Selection
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What if the environment
changes?
The organisms must adapt to the
environment. Those that don’t
adapt-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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Descent 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 -1798-proposed
that populations outgrew their
food supplies, causing competition
between organisms and a struggle
for one species to survive against
another
• Jean-Baptiste Lamark -1809believed that all life forms
evolved and that the driving force
of evolution was the inheritance
of acquired characteristics. He
believed that organisms changed
due to the demands of their
environment.
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•Lylle -1833-proposed that plant and animal species
had arisen, developed variations, and then became
extinct over time. He also believed that the Earth’s
physical landscape changed over a long period of time.
•Alfred Russel Wallace -1858-emphasis was based
on the 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.
Evidence for Change Over Time
Fossil Record
– Fossils that show
how the same
organism looked
millions of years
ago.
– Paleontology
– Use rock layers
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Relative Dating
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Homologous
structures
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Stages of
development
p385
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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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Vestigial Organs
c
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• Speciation
•is the evolution of a new species that occurs when
interbreeding happens, or when the production of fertile
offspring is prevented.
In the physical world, natural barriers form and cause the
breakup of populations to form smaller populations.
Volcanoes, sea-level changes, and earthquakes are a few
examples of natural occurrences that affect populations
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Speciation Mechanisms
• 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 with in a population
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Divergent Evolution
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Convergent Evolution
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Coevolution
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Evolution at the species level
is called microevolution.
It results from genetic
variation and natural selection
within a population of
organisms.
Macroevolution is evolution
that occurs between
different species.
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Evolution is the
change in a
species over
time.
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Rates of Evolution
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Gradualism & Punctuated Equilibrium
• Two ways in
which the
evolution of a
species can
occur.
• A species can
evolve by
only one of
these, or by
both.
•Species with a shorter evolution evolved mostly by
punctuated equilibrium, and those with a longer
evolution evolved mostly by gradualism.
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Gradualism
•Very gradually, over a long
time... Over a short period
of time it is hard to notice.
•Small variations that fit an
organism slightly better to
its environment are selected
for: a few more individuals
with more of the helpful trait
survive, and a few more
with less of the helpful trait
die.
•Change is slow, constant,
and consistent.
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Punctuated equilibrium
•change comes in spurts. There is
a 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
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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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Adaptation is the key
concept in natural
selection.
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• Adaptation is a key concept in natural
selection.
• Natural selection can change the inherited
characteristics in a population and
possibly even result in a new species.
The environment affects the
evolution of living things.
House sparrows arrived in North America from Europe
in the nineteenth century. Since then, genetic variation
within the population, and selection in various habitats,
have allowed them to inhabit most of the continent.
House sparrows in the north are larger and darker
colored than those in the south. Darker colors absorb
sunlight better than light colors and larger size allows
less surface area per unit volume, thus reducing heat
loss—both advantages in a cold climate. This is an
example of natural selection acting upon a population,
producing micro-evolution on a continental scale.
• Proposed by Charles Darwin, natural
selection is the process by which
organisms that are best suited to their
environment survive and pass their
genetic traits on to their offspring.