Transcript Ch15 Bio March 2008 Natural Selection and the Evidence for

Chapter 15.
Natural
Selection an &
The Evidence for
Evolution
 The
theory &
Supporting
Evidence
Chapter 15: Learning Objectives
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Be able to summarize Darwin’s Theory of Evolution
Be able to explain how Structural Adaptations relate to natural selection and use
examples.
How do mimicry and camouflage help species survive?
Be able to explain how Physiological Adaptations relate to natural selection and
use examples.
Distinguish among the types of evidence for evolution; be able to explain how
these demonstrate evolutionary relationships.
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Distinguish between the ways that Natural Selection acts on variations within
populations.
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Fossils, Anatomy, Embryology, Biochemistry
Be able to distinguish between Homologous, Analagous and Vestigal Structures
How do vertebrate embryos indicate common ancestry?
Stabilizing Selection, Directional Selection, Disruptive Selection
Be able to define Species and the basis for speciation.
How do geographic barriers contribute to speciation?
Be able to describe the two theories on the Rate of Speciation, and how they
differ; similar.
Be able to describe Adaptive radiation and Convergent Evolution
Evolution videos
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Evolution Videos for Students Evolving
Ideas.mht (6 evolution video clips)
Assignment: Due Monday, April 7th
Read Chapter 15, and answer do the following. May (encouraged to)
use other sources as well. Be prepared to explain your work in class.
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Directions: Prepare a booklet ( may use a foldable
style such as we used for Biomes) which contains the
following:
Description of Darwin’s Theory Of Evolution and the process of
Natural Selection.
List the steps involved in the process of Natural Selection and
new species formation (see Fig. 15.2)
Define, describe, illustrate the following terms :
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Homologous Structures
Analagous Structures ( 1 plant, 1 animal)
Vestigal Structures
Geographic Isolation –associated with Speciation
( be sure to include …)
*Definition of term
*Pictures (2 for each—hand drawn or copied and colored) to illustrate
the term.
*Explanation of why your pictures demonstrate the terms.
EVOLUTION
Evolution:
Heritable
change in a species over
time.
Theories of Evolutionattempt to explain
diversity of life on earth
 Prior
to 1800’s: :
Creationism
 Beginning
around 1800::
 Scientists attempt to
come to terms with
growing fossil evidence.
1. De
Newer Theories of
Evolution
Buffon(1707-1788): Life and
Earth have a history: Life not fixed
since Creation.(very radical). Life
evolves. Vestigal structures.
2.George S. Cuvier ( 1769-1832):
Theory of Catastrophism: Species
were fixed & unchanging. Mass
extinctions ; other species migrate
to fill in open niche.
Jean Lamarck (1744-1829): Life
evolves
Change through use and disuse.
Evolution due to inheritance of
acquired characteristics.
3.
.
4. Charles Darwin (1809-1882):
 Life evolves.
 Species change over time by way of
Natural Selection
***Charles
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Darwin***
Left Med.School; Degree in
Theology; Avid interest in nature
HMS Beagle to South America &
Galapagos Islands- 5 year charting
voyage- (1831-1836)
Ship’s Naturalist- collect & catalog
flora & fauna
His observations profoundly change
his beliefs
Voyage of the H.M.S. Beagle-
Charles Darwin
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1859 wrote The Origin Of Species by Means of
Natural SelectionControversial:
He suggested:
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Apes apes and humans have common ancestry.
Species change
New Species
Presented evidence that evolution occurred
Proposed mechanism for evolution—Natural
Selection
Darwin’s Observations
Provided The Evidence
and
Mechanism for Evolution
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GALAPAGOS
TOTOISES
Species unique to the
islands, but similar to
those observed on the
s. American mainland.
Marine Iguanas-nowhere else on
Earth-swim, cling to rocks eating
moss
Figure 22.1
Blue-footed boobies-adaptations of
other kinds—attract mates
Galápagos Finches
Insect eaters
Insect eaters
Berry
eater
Seed
eaters Cactus
eaters
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Beak
shape
varies
with diet
His Finch Observations
1.Found on all islands-but
slight variances between
them.
 Different beaks.
2. Similar to those on South
America mainland.
Explaining his observations
1. A few organisms migrated
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From S. America
Populated all 13 islands
2. Variations existed among them.
3.Individuals with useful variations passed
these along to the next generation.
4. Over time offspring with certain
variations make up most of the
population
Conditions varied island to island, so
finches varied by habitat.
5.Many new species formed from these
original ancestors.
The process of Natural
Selection—Steps Darwin
proposes.
1. Organisms produce more
________than can survive
 2. Competition/________ for
Existence-compete for food, living
space;
 3. Only some can ______ and
reproduce.
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4. Those with useful _________
survive in their environment, pass
those traits on to _____________.
5. Over time, their traits become
more __________ in the
population.
Evolution video
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Evolution Videos for Students Evolving
Ideas.mht (hummingbird evolution)
The Mechanism:
How evolution happens…
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Natural selection : Organisms with
_______ (Adaptations) well suited
to an _________ are more likely to
survive and produce more offspring
than organisms without these
favorable traits. Only the fittest
will survive!!!---
To Summarize Darwin
 Species
change over
time and give rise to
new species through the
process of natural
selection (survival of the
___________).
ADAPTATIONS-evidence for
evolution.
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Darwin clearly understood a fundamental principle of
evolution—that ____________, not individuals,
evolve and become adapted to the environments in
which they live.
The term “adaptation” has _____ meanings in evolutionary
biology.
The first meaning refers to the processes by which adaptive
traits are acquired.
The second meaning refers to the traits that enhance the
survival and reproductive success of their bearers.
Adaptations:
Structural or Physiological
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Adaptations : any variation that aids an
organisms chances for ____________ in
its ________________.
Arise over time-many ___________.
Kinds of Adaptations
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1. ________-develop over millions of
years
2. ____________-can occur much more
rapidly.
1. Structural Adaptations
1. Defense: some defense mechanisms
claws, teeth
2. Protective :
a) Mimicry-one organism _____________
another
b) Camouflage-__________ into the surroundings
c) Warning coloration
Coloration
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Conspicuous
colors -- warn
off predators.
poison arrow frogs
Mimicry
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Look alikes
Hawk moth larva
Snake
Mimicry
Cuckoo Bee
Yellow Jacket
mimicry
Camouflage
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A ________ defense where the prey is
camouflaged against its environment.
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peacocks evol video.htm
2. Physiological Adaptations
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Changes in an organism’s _______________
processes.
These can develop rapidly
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Develop by natural selection
Examples:
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Bacteria-resistance to _______________
Weeds—resistance to herbicides
Insects-resistance to ________________
Other evidence for
EvolutionMost evidence for evolution is
___________.
 Fossils
 Comparative Anatomy
 Comparative Development
 Comparative Biochemistry
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1. FOSSILS
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Can help to demonstrate
evolutionary path
Sinornithosaurus
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Feathered Dinosaur: Missing Link
between Birds and dinosaurs
Anatomical Structures
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Homologous Structures
2. Homologous Structures
Structural features that are
similar in arrangement, in
function or both due
to_______ _________
For example: whale forelimb,
crockodile forelimb, bird wing;
Homologous Structures
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VESTIGAL STRUCTURES—A body
structure that no longer serves its
original purpose;
remnants of evolutionary past-whale’s
pelvis
bone
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Vestigial Structures
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Why do dogs have tiny, functionless toes
on their feet (dewclaws)?
 Ancestral
dogs
had five toes on
each foot
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As they evolved they became toe-walkers with only
four toes on the ground
Big toes and thumbs were lost or reduced to their
present state
Remnants of Toes in
Horses
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Normally a horse’s
back foot has only
one functional toe,
the third
Splints are small
remnants of toes 2 and
4 that remain as
vestiges
More vestigal structures
Vestigal structures
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'Whale Evolution' by PBS RichardDawkins_net.mht
Analogous Structures
 Similar
in function, but not
structure.
 Why??
--do not have
common ancestor (wings of
bats and wings of insects)
Analogies: for example, plant adaptations
Adapted to similar _________pressures.
The Process is called ____________evolution.
Analogous Structures
example:
Embryology
 Embryo:
earliest stages of
________ and ________ of both
plants and animals.
 All vertebrate embryos start out
very similarly
Pharyngeal ___________
 Postanal _________
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Organisms evolve by adding stages
to their embryonic development,
DEVELOPMENTAL
PATTERNS
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Comparative Biochemistry
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Compare ______ ______ sequence
Closely related species will show more
similarities in the _____ ______
sequence that makes up the protein.
Example: cytochrome c (table 15.2)
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Identical amino acids in chimpanzee protein
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Chicken protein differs by 18 amino acids
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Yeast protein differs by 56
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Despite its diet and its opposable
thumb, the Giant
. Panda is a bear;
and the Lesser Panda is closer to
raccoons of N. America
The Panda’s Thumb,Is it a bear?
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Panda web pandafix Other Panda
Video.mht
RedPandaClipFilm clip - Red panda
(subspecies styani) feeding on bamboo,
using modified wrist bone as sixth digit Red panda ssp_ - Ailurus fulgens styani ARKive.mht
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.Giant Panda
15.2 Mechanisms of Evolution
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Gene Pool: all of the ________ of the
population’s genes pooled together.
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Allelic Frequency:
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Genetic Equilibrium:
Natural Selection acts on Variation:
Genetic Variation
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Occurs in individuals in populations of all
species
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Frequency can change within a population
3 Modes of Selection
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Directional Selection: Favors
_____ phenotypic extreme.
Can lead to rapid evolution.
 Disruptive Selection:
 Favors
_____phenotypic extremes.
 Stabilizing
Selection: Favors the
______phenotype; overall reducing
variation.
MODES OF SELECTION
DIRECTIONAL SELECTION-only one
selective force on an allele
Unopposed selection.
 This moves the frequency of one
allele in ONE DIRECTION.
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In the US, these are fewer S.C. mutant
alleles than in Africa
Where malaria is a problem, having one
sickle cell allele does not increase life
expectance.
3.Different Types of Natural
Selection
What can change the frequency?
Mutation:_________________
Genetic Drift : ______________
Gene _________ (from immigration or
emigration)
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3. In Disruptive Selection
Individuals at both ________ of the
phenotypic range are ____________ over
intermediate phenotypes.
Fig. 23.12
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Species
 Individuals
that in
nature interbreed and
produce _________
___________.
Physical Barriers
Geographic Isolation
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Whenever a
____________barrier
divides a population.
May cause
reproductive
isolation
Reproductive Isolation
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Occurs when formerly interbreeding
organisms can no longer mate and
produce fertile offspring.
Due to
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Different habitats
Different behaviors
Different mating times
The Debate over the Rate of
Evolution:
Rate of Speciation/Evolution
1.GRADUALISM: Darwin: Evolution
occurs at a slow, steady rate.
Differences accumulate slowly over a
long period of time
2. PUNCTUATED EQUILIBRIUM:
Evolution occurs at an irregular rate—
long steady periods of little or no
change, interrupted by short periods of
rapid evolution
Convergent Evolution
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Convergent
evolution:
unrelated
organisms that
have similar traits
due to adaptation
to similar
environmental
pressures
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Some organisms appear
suddenly in the fossil record.
Few transitional forms found.
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Other show gradual change.
The debate is about the rate
and regularity of evolution—
not about whether evolution
occurs.