Transcript PPT 2 revised - Bibb County Schools

Natural Selection
http://evolution.berkeley.edu/evolibrary/home.php
http://evolution.berkeley.edu/evolibrary/home.php
www.darwinday.org/englishL/life/beagle.html
www.darwinday.org/englishL/life/beagle.ht
Used by permission of Darwin Day
Celebration (at DarwinDay.org), 2006
I have called this principle, by which
each slight variation, if useful, is preserved,
by the term Natural Selection.
—Charles Darwin from "The Origin of Species"
http://evolution.berkeley.edu/evolibrary/home.php
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
CHARLES DARWIN – 1809-1882
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English
Traveled around the world on the Beagle (ship)
Most of trip was among the Galapagos Islands
Believed that the earth was 6000 years old and
that all plants and animals were unchangeable
over time
During his travels, he observed many live species,
as well as fossils
He did not understand why some species survived
while others were going extinct
These ideas went directly against his beliefs
Darwin’s Observations
• From island to island, he noticed that the
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species of mockingbird, finches, and other
animals varied.
Many of the species Darwin collected had not
yet been discovered or classified
Darwin took his collections and drawings home
and after reading essays and studies by many
other scientists (Gould & Mathus), he developed
the idea of natural selection
5 Principles of Natural Selection
1. Individuals in a population show variation.
2. Variations can be inherited.
3. Organisms have more offspring that can
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survive under normal circumstances.
Variations that increase reproductive
success will have a greater chance of being
passed on from generation to generation.
A population will slowly change over time in
response to the environment.
Darwin…
• By 1840, Darwin had developed the theory of
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natural selection.
He then published “On the Origin of Species by
Means of Natural Selection”
• On the last page of this book, he called his theory
“evolution”
– Evolution is what the process is called ~ natural
selection is HOW evolution happens
• Another researcher, Wallace, also wrote a similar
book at the same time and both books were
published and presented to the scientific
community.
Evolution Overview:
Evidence for Evolution,
Types of Natural Selection,
& Speciation
Biology 1
Dr. Butts
How and why does evolution
occur?
• Individuals are born with random traits
inherited from parents
• Some of these traits might be
advantageous
• Individuals who have more advantage in
their environment will survive and
reproduce with greater success
• The advantageous traits will be passed
down to offspring
Evidence of Evolution
• The Fossil Record
– Provides records of
species that lived long
ago
– Shows evolutionary
relationships among
ancient and current
living things
Evidence of Evolution
Comparative Anatomy:
– Homologous Structures: anatomically similar
structures that occur in species that come
from a common ancestor
Evidence of Evolution
Comparative
Anatomy
– Vestigial Structures:
structures that are
present, but no
longer needed
Evidence of Evolution
Comparative
Anatomy
– Analogous
Structures:
structures that are
similar in function,
but are not in
living things that
share ancestry
Evidence of Evolution
Comparative
Embryology
– Studying of the
growth and
development of
various organisms
– The more similar the
embryonic
development of
organisms, the more
closely related they
are
Evidence of Evolution
• Comparative Biochemistry: comparing
DNA and other molecules
• The more closely related, the more similar
the DNA sequences
Evidence of Evolution
• Geographic
Distribution &
Biogeography
• Similar climates and
biomes have similar
living things because
living things evolve to
be successful in their
environment
CoEvolution
Some species evolve in close relationship
with other species. The relationship may
sometimes become so close that the
evolution of one species may affect the
other.
Examples of Evidence: Coevolution
Examples of Evidence:
• Camouflage:
blending in with
environment
• Mimicry:
nonpoisonous
organisms
mimicking
poisonous ones in
order to avoid
predators
Camouflage
Mimicry
Evidence of Evolution
• Antibiotic and
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Pesticide
Resistance
Antibiotic:
bacteria become
resistant to
antibiotics over
time due to over
and misuse
Pesticide: Insects
and other pests
become resistant
to pesticides due
to overuse
Adaptation & Natural Selection
• Camouflage:
blending in with
environment
• Mimicry:
nonpoisonous
organisms mimicking
poisonous ones in
order to avoid
predators
Adaptation & Natural Selection
• Genetic Drift
– Founder Effect:
Pioneer species
leaves original colony
and begins a new
one
– Bottleneck: a once
large population is
dramatically
decreased due to
some bottleneck
event (ex. Drought,
flood, disease, etc)
Adaptation & Natural Selection
• Stabilizing
Selection
• most common
• eliminates
extremes, which
gets rid of negative
traits
• ex. Birth weights of
human babies does
not show variation
Adaptation & Natural Selection
• Directional
Selection
• one extreme
selected for
• ex. Peppered moth
(p.435, fig. 15.17)
Adaptation & Natural Selection
• Disruptive Selection
• splits a population into
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2 groups
removes average
individuals and selects
for extremes
Ex. Selection based on
habitat (snakes in
grasslands vs. rocky
mountains)
Adaptation & Natural Selection
• Sexual Selection
• mate selection
based on physical
characteristics
• Nonrandom
Mating
• mating based on
nonrandom factors
(proximity, sexual
selection, etc)
Speciation
• What is a species?
• Groups of organisms that
can successfully reproduce
with one-another.
• What is speciation?
• Process by which new
species are formed
• Populations diverge to the
point they can no longer
reproduce together
(reproductive isolation)
Speciation
• Allopatric
Speciation
• Physical barrier
causes speciation
• Sympatric
Speciation
• Speciation without a
physical barrier
• Adaptive
Speciation
Radiation
• Rapid evolution
due to
environmental
factor(s) that
cause a change in
what is
advantageous vs.
disadvantageous
Speciation
• Coevolution
• Species evolve in
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response to one
another
Convergent
Evolution
Similar traits
evolve in different
parts of the world
due to similar
climates and
geography
Hardy Weinberg
• Theory that states that if gene frequencies
remain stable, the population is said to be
in equilibrium (or homeostasis) and thus,
not evolving.
• 5 things must be true:
1. Population is large.
2. No immigration nor emigration
3. Mating is always random.
4. Mutations never occur
5. Natural selection does not occur.
Hardy Weinberg
• Is it true for humans? You decide…
• Assumes 5 things to be true:
1. Population is large?
2. No immigration nor emigration?
3. Mating is always random?
4. Mutations never occur?
5. Natural selection does not occur?
• Are populations ever really NOT evolving
then?