chapter 13 how populations evolve · fossils are the imprints or remains of organisms ... –...
Post on 25-Mar-2020
9 Views
Preview:
TRANSCRIPT
© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
Chapter 13 How Populations Evolve
The blue-footed booby has adaptations that make it
suited to its environment. These include
– webbed feet,
– streamlined shape that minimizes friction when it dives,
and
– a large tail that serves as a brake.
Introduction
© 2012 Pearson Education, Inc.
Figure 13.0_2
Chapter 13: Big Ideas
Darwin’s Theory
of Evolution
The Evolution of
Populations
Mechanisms of
Microevolution
A five-year voyage around the world helped Darwin
make observations that would lead to his theory of
evolution, the idea that Earth’s many species are
descendants of ancestral species that were
different from those living today.
13.1 A sea voyage helped Darwin frame his theory of evolution
© 2012 Pearson Education, Inc.
Some early Greek philosophers suggested that life
might change gradually over time.
– However, the Greek philosopher Aristotle viewed
species as perfect and unchanging.
– Judeo-Christian culture reinforced this idea with a literal
interpretation of the biblical book of Genesis.
Fossils are the imprints or remains of organisms
that lived in the past.
In the century prior to Darwin, fossils suggested
that species had indeed changed over time.
13.1 A sea voyage helped Darwin frame his theory of evolution
© 2012 Pearson Education, Inc.
13.1 A sea voyage helped Darwin frame his theory of evolution
In the early 1800s, Jean Baptiste Lamarck suggested that life on Earth evolves, but by a different mechanism than that proposed by Darwin.
Lamarck proposed that
– organisms evolve by the use and disuse of body parts and
– these acquired characteristics are passed on to offspring.
© 2012 Pearson Education, Inc.
Video: Galápagos Marine Iguana
Video: Galápagos Island Overview
Video: Albatross Courtship Ritual
Video: Soaring Hawk
Video: Galápagos Tortoise
Video: Galápagos Sea Lion
Video: Blue-footed Boobies Courtship Ritual
During Darwin’s round-the-world voyage he was
influenced by Lyell’s Principles of Geology,
suggesting that natural forces
– gradually changed Earth and
– are still operating today.
Darwin came to realize that
– the Earth was very old and
– over time, present day species have arisen from
ancestral species by natural processes.
13.1 A sea voyage helped Darwin frame his theory of evolution
© 2012 Pearson Education, Inc.
During his voyage, Darwin
– collected thousands of plants and animals and
– noted their characteristics that made them well suited to
diverse environments.
13.1 A sea voyage helped Darwin frame his theory of evolution
© 2012 Pearson Education, Inc.
Figure 13.1C
Darwin in 1840
NorthAmerica
Pinta
GenovesaMarchena
Santiago Equator
Daphne Islands
SantaFe
SantaCruz
PinzónFernandina
Isabela
Florenza Española0
0 40 miles
40 km
SanCristobal
PACIFICOCEAN
GalápagosIslands
GreatBritain Europe
Asia
HMS Beagle in port
Equator
Africa
PACIFICOCEAN
ATLANTICOCEAN
SouthAmerica
Cape ofGood HopePACIFIC
OCEAN
Cape Horn
Tierra del Fuego
Australia
Tasmania
NewZealand
Figure 13.1C_1
NorthAmerica
GreatBritain Europe Asia
Equator
AfricaPACIFICOCEAN
ATLANTICOCEAN
SouthAmerica
Cape ofGood HopePACIFIC
OCEAN
Cape Horn
Tierra del Fuego
Australia
Tasmania
NewZealand
In 1859, Darwin published On the Origin of Species by Means of Natural Selection,
– presenting a strong, logical explanation of descent with modification, evolution by the mechanism of natural selection, and
– noting that as organisms spread into various habitats over millions of years, they accumulated diverse adaptations that fit them to specific ways of life in these new environments.
13.1 A sea voyage helped Darwin frame his theory of evolution
© 2012 Pearson Education, Inc.
Darwin devoted much of The Origin of Species to
exploring adaptations of organisms to their
environment.
Darwin discussed many examples of artificial
selection, in which humans have modified species
through selection and breeding.
13.2 Darwin proposed natural selection as the mechanism of evolution
© 2012 Pearson Education, Inc.
Figure 13.2
Brussels sprouts
Lateralbuds Terminal bud
Flowersand stems
Cabbage
Broccoli
Stem
KohlrabiWild mustard
Leaves
Kale
Darwin recognized the connection between
– natural selection and
– the capacity of organisms to overreproduce.
Darwin had read an essay written in 1798 by the economist Thomas Malthus, who argued that human suffering was the consequence of human populations increasing faster than essential resources.
13.2 Darwin proposed natural selection as the mechanism of evolution
© 2012 Pearson Education, Inc.
Darwin observed that organisms
– vary in many traits and
– produce more offspring than the environment can
support.
13.2 Darwin proposed natural selection as the mechanism of evolution
© 2012 Pearson Education, Inc.
Darwin reasoned that
– organisms with traits that increase their chance of
surviving and reproducing in their environment tend to
leave more offspring than others and
– this unequal reproduction will lead to the accumulation
of favorable traits in a population over generations.
13.2 Darwin proposed natural selection as the mechanism of evolution
© 2012 Pearson Education, Inc.
There are three key points about evolution by
natural selection that clarify this process.
1. Individuals do not evolve: populations evolve.
2. Natural selection can amplify or diminish only heritable
traits. Acquired characteristics cannot be passed on to
offspring.
3. Evolution is not goal directed and does not lead to
perfection. Favorable traits vary as environments
change.
13.2 Darwin proposed natural selection as the mechanism of evolution
© 2012 Pearson Education, Inc.
Camouflage adaptations in insects that evolved in
different environments are examples of the results
of natural selection.
13.3 Scientists can observe natural selection in action
© 2012 Pearson Education, Inc.
Video: Seahorse Camouflage
Biologists have documented natural selection in action in
thousands of scientific studies.
Rosemary and Peter Grant have worked on Darwin’s
finches in the Galápagos for over 30 years. They found that
– in wet years, small seeds are more abundant and small beaks are
favored, but
– in dry years, large strong beaks are favored because all seeds are
in short supply and birds must eat more larger seeds.
13.3 Scientists can observe natural selection in action
© 2012 Pearson Education, Inc.
Another example of natural selection in action is the
evolution of pesticide resistance in insects.
– A relatively small amount of a new pesticide may kill 99%
of the insect pests, but subsequent sprayings are less
effective.
– Those insects that initially survived were fortunate
enough to carry alleles that somehow enable them to
resist the pesticide.
– When these resistant insects reproduce, the percentage
of the population resistant to the pesticide increases.
13.3 Scientists can observe natural selection in action
© 2012 Pearson Education, Inc.
Figure 13.3B
Pesticideapplication
Chromosome withallele conferringresistance to pesticide
Additional applications of thesame pesticide will be less effective,and the frequency of resistantinsects in the population will grow.
Survivors
These examples of evolutionary adaptation highlight two important points about natural selection.
1. Natural selection is more of an editing process than a creative mechanism.
2. Natural selection is contingent on time and place, favoring those characteristics in a population that fit the current, local environment.
13.3 Scientists can observe natural selection in action
© 2012 Pearson Education, Inc.
Darwin’s ideas about evolution also relied on the fossil record, the sequence in which fossils appear within strata (layers) of sedimentary rocks.
Paleontologists, scientists who study fossils, have found many types of fossils.
13.4 The study of fossils provides strong evidence for evolution
© 2012 Pearson Education, Inc.
The fossil record shows that organisms have evolved in a historical sequence.
– The oldest known fossils, extending back about 3.5 billion years ago, are prokaryotes.
– The oldest eukaryotic fossils are about a billion years younger.
– Another billion years passed before we find fossils of multicellular eukaryotic life.
13.4 The study of fossils provides strong evidence for evolution
© 2012 Pearson Education, Inc.
Video: Grand Canyon
Many fossils link early extinct species with species
living today.
– A series of fossils traces the gradual modification of
jaws and teeth in the evolution of mammals from a
reptilian ancestor.
– A series of fossils documents the evolution of whales
from a group of land mammals.
13.4 The study of fossils provides strong evidence for evolution
© 2012 Pearson Education, Inc.
Figure 13.4H
Pakicetus (terrestrial)
Rodhocetus (predominantly aquatic)
Dorudon (fully aquatic)
Pelvis andhind limb
Pelvis andhind limb
Balaena (recent whale ancestor)
13.5 Many types of scientific evidence support the evolutionary view of life
Biogeography, the geographic distribution of
species, suggested to Darwin that organisms
evolve from common ancestors.
Darwin noted that Galápagos animals resembled
species on the South American mainland more
than they resembled animals on islands that were
similar but much more distant.
© 2012 Pearson Education, Inc.
13.5 Many types of scientific evidence support the evolutionary view of life
Comparative anatomy
– is the comparison of body structures in different species,
– was extensively cited by Darwin, and
– illustrates that evolution is a remodeling process.
– Homology is the similarity in characteristics that result
from common ancestry.
– Homologous structures have different functions but
are structurally similar because of common ancestry.
© 2012 Pearson Education, Inc.
Comparative embryology
– is the comparison of early stages of development among
different organisms and
– reveals homologies not visible in adult organisms.
– For example, all vertebrate embryos have, at some point
in their development,
– a tail posterior to the anus and
– pharyngeal throat pouches.
– Vestigial structures are remnants of features that
served important functions in an organism’s ancestors.
13.5 Many types of scientific evidence support the evolutionary view of life
© 2012 Pearson Education, Inc.
Advances in molecular biology reveal evolutionary
relationships by comparing DNA and amino acid
sequences between different organisms. These
studies indicate that
– all life-forms are related,
– all life shares a common DNA code for the proteins found
in living cells, and
– humans and bacteria share homologous genes that have
been inherited from a very distant common ancestor.
13.5 Many types of scientific evidence support the evolutionary view of life
© 2012 Pearson Education, Inc.
Darwin was the first to represent the history of life as a tree,
– with multiple branchings from a common ancestral trunk
– to the descendant species at the tips of the twigs.
Today, biologists
– represent these patterns of descent with an evolutionary tree, but
– often turn the trees sideways.
13.6 Homologies indicate patterns of descent that can be shown on an evolutionary tree
© 2012 Pearson Education, Inc.
Homologous structures can be used to determine the branching sequence of an evolutionary tree. These homologies can include
– anatomical structure and/or
– molecular structure.
– Figure 13.6 illustrates an example of an evolutionary tree.
13.6 Homologies indicate patterns of descent that can be shown on an evolutionary tree
© 2012 Pearson Education, Inc.
Figure 13.6
Tetrapodlimbs
Amnion
Lungfishes
Amphibians
Mammals
Lizardsand snakes
Crocodiles
Ostriches
Hawks andother birds
Feathers
Tetra
po
ds
Am
nio
tes
Bird
s
1
2
3
4
5
6
13.7 Evolution occurs within populations
A population is
– a group of individuals of the same species and
– living in the same place at the same time.
Populations may be isolated from one another (with little interbreeding).
Individuals within populations may interbreed.
We can measure evolution as a change in heritable traits in a population over generations.
© 2012 Pearson Education, Inc.
A gene pool is the total collection of genes in a
population at any one time.
Microevolution is a change in the relative
frequencies of alleles in a gene pool over time.
13.7 Evolution occurs within populations
© 2012 Pearson Education, Inc.
Population genetics studies how populations
change genetically over time.
The modern synthesis connects Darwin’s theory
with population genetics.
13.7 Evolution occurs within populations
© 2012 Pearson Education, Inc.
Organisms typically show individual variation.
However, in The Origin of Species, Darwin could
not explain
– the cause of variation among individuals or
– how variations were passed from parents to offspring.
13.8 Mutation and sexual reproduction produce the genetic variation that makes evolution possible
© 2012 Pearson Education, Inc.
Mutations are
– changes in the nucleotide sequence of DNA and
– the ultimate source of new alleles.
13.8 Mutation and sexual reproduction produce the genetic variation that makes evolution possible
© 2012 Pearson Education, Inc.
On rare occasions, mutant alleles improve the
adaptation of an individual to its environment.
– This kind of effect is more likely when the environment is
changing such that mutations that were once
disadvantageous are favorable under new conditions.
– The evolution of DDT-resistant houseflies is such an
example.
13.8 Mutation and sexual reproduction produce the genetic variation that makes evolution possible
© 2012 Pearson Education, Inc.
Chromosomal duplication is an important source of
genetic variation.
– If a gene is duplicated, the new copy can undergo
mutation without affecting the function of the original
copy.
– For example, an early ancestor of mammals had a
single gene for an olfactory receptor. That gene has
been duplicated many times, and mice now have 1,300
different olfactory receptor genes.
13.8 Mutation and sexual reproduction produce the genetic variation that makes evolution possible
© 2012 Pearson Education, Inc.
Sexual reproduction shuffles alleles to produce
new combinations in three ways.
1. Homologous chromosomes sort independently as they
separate during anaphase I of meiosis.
2. During prophase I of meiosis, pairs of homologous
chromosomes cross over and exchange genes.
3. Further variation arises when sperm randomly unite with
eggs in fertilization.
13.8 Mutation and sexual reproduction produce the genetic variation that makes evolution possible
© 2012 Pearson Education, Inc.
Animation: Genetic Variation from Sexual Recombination
13.9 The Hardy-Weinberg equation can test whether a population is evolving
Sexual reproduction alone does not lead to
evolutionary change in a population.
– Although alleles are shuffled, the frequency of alleles
and genotypes in the population does not change.
– Similarly, if you shuffle a deck of cards, you will deal out
different hands, but the cards and suits in the deck do
not change.
© 2012 Pearson Education, Inc.
The Hardy-Weinberg principle states that
– within a sexually reproducing, diploid population,
– allele and genotype frequencies will remain in equilibrium,
– unless outside forces act to change those frequencies.
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
For a population to remain in Hardy-Weinberg
equilibrium for a specific trait, it must satisfy five
conditions. There must be
1. a very large population,
2. no gene flow between populations,
3. no mutations,
4. random mating, and
5. no natural selection.
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
Imagine that there are two alleles in a blue-footed
booby population, W and w.
– Uppercase W is a dominant allele for a nonwebbed
booby foot.
– Lowercase w is a recessive allele for a webbed booby
foot.
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
Consider the gene pool of a population of 500
boobies.
– 320 (64%) are homozygous dominant (WW).
– 160 (32%) are heterozygous (Ww).
– 20 (4%) are homozygous recessive (ww).
– p = 80% of alleles in the booby population are W.
– q = 20% of alleles in the booby population are w.
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
Figure 13.9B
Phenotypes
Genotypes
Number of animals
(total 500)
Genotype frequencies
Allele frequencies
Number of alleles
in gene pool
(total 1,000)
0.8 W 0.2 w
40 w640 W 160 W 160 w
WwWW ww
20160320
0.64 0.32 0.04
320500 500
160 20500
800 2001,0001,000
The frequency of all three genotypes must be
100% or 1.0.
– p2 + 2pq + q2 = 100% = 1.0
– homozygous dominant (p2) + heterozygous (2pq) +
homozygous recessive (q2) = 100%
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
What about the next generation of boobies?
– The probability that a booby sperm or egg carries W = 0.8 or 80%.
– The probability that a sperm or egg carries w = 0.2 or 20%.
– The genotype frequencies will remain constant generation after generation unless something acts to change the gene pool.
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
Figure 13.9C
Gametes reflect allelefrequencies of parentalgene pool.
Sperm
Eggs
WW Ww
wwwW
W
W w
w
Next generation:
Genotype frequencies
Allele frequencies 0.2 w0.8 W
0.64 WW 0.32 Ww 0.04 ww
q 0.2
p 0.8
p2 0.64 pq 0.16
qp 0.16 q2 0.04
p 0.8 q 0.2
How could the Hardy-Weinberg equilibrium be
disrupted?
– Small populations could increase the chances that allele
frequencies will fluctuate by chance.
– Individuals moving in or out of populations add or remove
alleles.
– Mutations can change or delete alleles.
– Preferential mating can change the frequencies of
homozygous and heterozygous genotypes.
– Unequal survival and reproductive success of individuals
(natural selection) can alter allele frequencies.
13.9 The Hardy-Weinberg equation can test whether a population is evolving
© 2012 Pearson Education, Inc.
Public health scientists use the Hardy-Weinberg
equation to estimate frequencies of disease-
causing alleles in the human population.
One out of 10,000 babies born in the United States
has phenylketonuria (PKU), an inherited inability to
break down the amino acid phenylalanine.
Individuals with PKU must strictly limit the intake of
foods with phenylalanine.
13.10 CONNECTION: The Hardy-Weinberg equation is useful in public health science
© 2012 Pearson Education, Inc.
Figure 13.10
INGREDIENTS: SORBITOL,
MAGNESIUM STEARATE,
ARTIFICIAL FLAVOR,
ASPARTAME† (SWEETENER),
ARTIFICIAL COLOR
(YELLOW 5 LAKE, BLUE 1
LAKE), ZINC GLUCONATE.
†PHENYLKETONURICS:
CONTAINS PHENYLALANINE
PKU is a recessive allele.
The frequency of individuals born with PKU
corresponds to the q2 term in the Hardy-Weinberg
equation and would equal 0.0001.
– The value of q is 0.01.
– The frequency of the dominant allele would equal 1 – q,
or 0.99.
– The frequency of carriers
= 2pq
= 2 0.99 0.01 = 0.0198 = 1.98% of the U.S. population.
13.10 CONNECTION: The Hardy-Weinberg equation is useful in public health science
© 2012 Pearson Education, Inc.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
If the five conditions for the Hardy-Weinberg
equilibrium are not met in a population, the
population’s gene pool may change. However,
– mutations are rare and random and have little effect on
the gene pool, and
– nonrandom mating may change genotype frequencies
but usually has little impact on allele frequencies.
© 2012 Pearson Education, Inc.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
The three main causes of evolutionary change are
1. natural selection,
2. genetic drift, and
3. gene flow.
© 2012 Pearson Education, Inc.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
1. Natural selection
– If individuals differ in their survival and reproductive
success, natural selection will alter allele frequencies.
– Consider the imaginary booby population. Webbed
boobies (ww) might
– be more successful at swimming,
– capture more fish,
– produce more offspring, and
– increase the frequency of the w allele in the gene pool.
© 2012 Pearson Education, Inc.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
2. Genetic drift
– Genetic drift is a change in the gene pool of a
population due to chance.
– In a small population, chance events may lead to the
loss of genetic diversity.
© 2012 Pearson Education, Inc.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
2. Genetic drift, continued
– The bottleneck effect leads to a loss of genetic diversity
when a population is greatly reduced.
– For example, the greater prairie chicken once numbered in the
millions, but was reduced to about 50 birds in Illinois by 1993.
– A survey comparing the DNA of the surviving chickens with
DNA extracted from museum specimens dating back to the
1930s showed a loss of 30% of the alleles.
© 2012 Pearson Education, Inc.
Animation: Causes of Evolutionary Change
2. Genetic drift, continued
– Genetic drift also results from the founder effect, when
a few individuals colonize a new habitat.
– A small group cannot adequately represent the genetic
diversity in the ancestral population.
– The frequency of alleles will therefore be different between the
old and new populations.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
© 2012 Pearson Education, Inc.
3. Gene flow
– is the movement of individuals or gametes/spores
between populations and
– can alter allele frequencies in a population.
– To counteract the lack of genetic diversity in the
remaining Illinois greater prairie chickens,
– researchers added 271 birds from neighboring states to the
Illinois populations, which
– successfully introduced new alleles.
13.11 Natural selection, genetic drift, and gene flow can cause microevolution
© 2012 Pearson Education, Inc.
13.12 Natural selection is the only mechanism that consistently leads to adaptive evolution
Genetic drift, gene flow, and mutations could each result in microevolution, but only by chance could these events improve a population’s fit to its environment.
Natural selection is a blend of
– chance and
– sorting.
Because of this sorting, only natural selection consistently leads to adaptive evolution.
© 2012 Pearson Education, Inc.
13.12 Natural selection is the only mechanism that consistently leads to adaptive evolution
An individual’s relative fitness is the contribution it
makes to the gene pool of the next generation
relative to the contribution of other individuals.
The fittest individuals are those that
– produce the largest number of viable, fertile offspring and
– pass on the most genes to the next generation.
© 2012 Pearson Education, Inc.
Natural selection can affect the distribution of
phenotypes in a population.
– Stabilizing selection favors intermediate phenotypes,
acting against extreme phenotypes.
– Directional selection acts against individuals at one of
the phenotypic extremes.
– Disruptive selection favors individuals at both extremes
of the phenotypic range.
13.13 Natural selection can alter variation in a population in three ways
© 2012 Pearson Education, Inc.
Figure 13.13
Originalpopulation
Evolvedpopulation
Phenotypes(fur color)
Fre
qu
en
cy o
fin
div
idu
als
Originalpopulation
Stabilizing selection Directional selection Disruptive selection
13.14 Sexual selection may lead to phenotypic differences between males and females
Sexual selection
– is a form of natural selection
– in which individuals with certain characteristics are more
likely than other individuals to obtain mates.
In many animal species, males and females show
distinctly different appearances, called sexual
dimorphism.
Intrasexual selection (within the same sex) involves
competition for mates, usually by males.
© 2012 Pearson Education, Inc.
13.14 Sexual selection may lead to phenotypic differences between males and females
In intersexual selection (between sexes) or mate
choice, individuals of one sex (usually females)
– are choosy in picking their mates and
– often select flashy or colorful mates.
© 2012 Pearson Education, Inc.
The excessive use of antibiotics is leading to the
evolution of antibiotic-resistant bacteria.
As a result, natural selection is favoring bacteria
that are naturally resistant to antibiotics.
– Natural selection for antibiotic resistance is particularly
strong in hospitals.
– Methicillin-resistant (MRSA) bacteria can cause “flesh-
eating disease” and potentially fatal infections.
13.15 EVOLUTION CONNECTION: The evolution of antibiotic resistance in bacteria is a serious public health concern
© 2012 Pearson Education, Inc.
What prevents natural selection from eliminating
unfavorable genotypes?
– In diploid organisms, recessive alleles are usually not
subject to natural selection in heterozygotes.
– Balancing selection maintains stable frequencies of
two or more phenotypes in a population.
– In heterozygote advantage, heterozygotes have greater
reproductive success than homozygotes.
– Frequency-dependent selection is a type of balancing
selection that maintains two different phenotypes in a
population.
13.16 Diploidy and balancing selection preserve genetic variation
© 2012 Pearson Education, Inc.
Figure 13.16
“Left-mouthed”
“Right-mouthed”
Fre
qu
en
cy o
f
“le
ft-m
ou
thed”
ind
ivid
uals
Sample year
1981 ʼ82 ʼ83 ʼ84 ʼ85 ʼ86 ʼ87 ʼ88 ʼ89 ʼ900
0.5
1.0
The evolution of organisms is constrained.
1. Selection can act only on existing variations. New,
advantageous alleles do not arise on demand.
2. Evolution is limited by historical constraints. Evolution
co-opts existing structures and adapts them to new
situations.
3. Adaptations are often compromises. The same
structure often performs many functions.
4. Chance, natural selection, and the environment interact.
Environments often change unpredictably.
13.17 Natural selection cannot fashion perfect organisms
© 2012 Pearson Education, Inc.
Figure 13.UN04
change in allelefrequencies in a
population
Microevolution
may result from
is the
randomfluctuations
more likely in a
due tomovement
ofdueto
leadsto
(c)(b)(a)
ofindividuals
may beresult of
(d) (g)
(f)(e)
individualsor gametes
adaptiveevolution
best adaptedto environment
Concept Check
The similarity in bone structure and arrangement between cats and bats
suggests that
– bats originated from bird-like ancestors.
– bats originated from four-legged ancestors, such as cats.
– modern bats fly much faster than ancient bat species.
© 2012 Pearson Education, Inc.
Answer
The similarity in bone structure and arrangement between
cats and bats suggests that
b) bats originated from four-legged ancestors, such as cats.
© 2012 Pearson Education, Inc.
Concept Check
Darwin proposed the theory of natural selection as the mechanism of
evolution based on three observations about nature. Which of the
following were part of Darwin’s observations?
– Populations have the potential to produce more individuals than the
environment can support.
– Individuals in some populations have varied characteristics.
– Variation in individuals appears to be inherited.
– All of the above.
© 2012 Pearson Education, Inc.
Answer
Darwin proposed the theory of natural selection as the mechanism of
evolution based on three observations about nature. Which of the
following were part of Darwin’s observations?
d) All of the above.
© 2012 Pearson Education, Inc.
Concept Check
Natural selection acts on genetic
variation. The ultimate source of
genetic variation is mutation in the DNA
(or RNA is some organisms). However
in sexually reproducing organisms with
long generation time what process(es)
account(s) for individual variation?
– random fertilization
– crossing over
– independent assortment
– all of the above
© 2012 Pearson Education, Inc.
Answer
Natural selection acts on genetic
variation. The ultimate source of
genetic variation is mutation in the DNA
(or RNA is some organisms). However
in sexually reproducing organisms with
long generation time what process(es)
account(s) for individual variation?
d) all of the above
© 2012 Pearson Education, Inc.
Concept Check
Evolutionary fitness is an often misunderstood concept. Which of the
following imaginary individuals would have the greatest evolutionary fitness?
– Sparrow A
– Sparrow B
– Sparrow C
– Sparrow D
© 2012 Pearson Education, Inc.
Sparrow A Sparrow B Sparrow C Sparrow D
Beak size (mm) 13 15 17 16
Lifespan (years) 2.5 2 3 3
Offspring that
survive to
adulthood
10 16 12 14
Answer
Evolutionary fitness is an often misunderstood concept. Which of the
following imaginary individuals would have the greatest evolutionary fitness?
b) Sparrow B
© 2012 Pearson Education, Inc.
Sparrow A Sparrow B Sparrow C Sparrow D
Beak size (mm) 13 15 17 16
Lifespan (years) 2.5 2 3 3
Offspring that
survive to
adulthood
10 16 12 14
Interpreting Data
The figure above shows the frequency of foot phenotypes in a
population of blue-footed boobies. What is the frequency of the W allele
in this population?
– 0.2
– 0.4
– 0.5
– 0.6
© 2012 Pearson Education, Inc.
Answer
The figure above shows the frequency of foot phenotypes in a
population of blue-footed boobies. What is the frequency of the W allele
in this population?
c) 0.5
© 2012 Pearson Education, Inc.
Interpreting Data
The figure above shows the frequency of foot phenotypes in a population of blue-footed boobies. What is the frequency of the w allele in this population?
– 0.2
– 0.4
– 0.5
– 0.6
© 2012 Pearson Education, Inc.
Answer
The figure above shows the frequency of foot phenotypes in a population of blue-footed boobies. What is the frequency of the w allele in this population?
c) 0.5
© 2012 Pearson Education, Inc.
Interpreting Data
The figure above shows the frequency of foot phenotypes in a population of blue-footed boobies. What is the expected frequency of the WW genotype in this population assuming the population is in Hardy-Weinberg equilibrium (Hint: The frequency of W is 0.5 and the frequency of w is 0.5.)?
– 0.20
– 0.25
– 0.40
– 0.50
© 2012 Pearson Education, Inc.
Answer
The figure above shows the frequency of foot phenotypes in a population of blue-footed boobies. What is the expected frequency of the WW genotype in this population assuming the population is in Hardy-Weinberg equilibrium (Hint: The frequency of W is 0.5 and the frequency of w is 0.5.)?
b) 0.25
© 2012 Pearson Education, Inc.
Interpreting Data
The figure above shows the frequency of foot phenotypes in a
population of blue-footed boobies. Is this population in Hardy-Weinberg
equilibrium?
– Yes
– No
© 2012 Pearson Education, Inc.
Answer
The figure above shows the frequency of foot phenotypes in a
population of blue-footed boobies. Is this population in Hardy-Weinberg
equilibrium?
b) No
© 2012 Pearson Education, Inc.
Biology and Society
One concept of conservation biology is known as minimum viable population. Some species’ populations are so fragmented and small that they may have very little genetic variability left. With minimal genetic variation in the population there is little likelihood that a population can adapt to an environmental threat, such as a new disease. Florida panthers are at or below the minimum viable population level (estimated population less than 80).
Do you think that it is practical to use limited resources to conserve a population like the Florida panther?
© 2012 Pearson Education, Inc.
Disagree Agree
Strongly A B C D E Strongly
Biology and Society
During the anthrax crisis of 2001, public health officials urged citizens to not take the antibiotic ciprofloxacin as a preventative measure. Public health officials were concerned that over use of ciprofloxacin would lead to resistant varieties of anthrax and other bacterial pathogens. Ciprofloxacin is one of the few readily available effective antibiotics that can treat anthrax.
Do you think that public health officials should more directly regulate the availability of ciprofloxacin to assure its proper use?
© 2012 Pearson Education, Inc.
Disagree Agree
Strongly A B C D E Strongly
Biology and Society
For some, science and religion seem to be at odds—especially with
regard to the topic of evolution. Many evolutionary scientists hold
devout religious beliefs. Like many devoutly religious people these
scientists are able to reconcile their religion and their science. Others
find the two ways of knowing to be in conflict. There is little doubt that a
literate citizen should explore the interface between science and
religion. There is a social controversy but there is not a scientific
controversy.
Do you think that this issue should be a part of a science class?
© 2012 Pearson Education, Inc.
Disagree Agree
Strongly A B C D E Strongly
Concept Review
The Mammals that Conquered the Seas
• Fossil evidence indicates that vertebrates originated in
aquatic environments and later adapted to land.
• Mammals originated on land. But some mammals, such
as whales, later adapted to marine environments,
reversing the trend.
Concept Review
The Mammals that Conquered the Seas
• Whales may live in water, but they are not fish.
• They are clearly warm-blooded mammals, breathing air
and nursing their young. Along with dolphins and porpoises,
they belong to an order of mammals called cetacea.
• The whales’ return to water was poorly understood until
fossil discoveries over the last two decades helped trace their
transition.
Concept Review
The Mammals that Conquered the Seas
• This shift occurred during the Eocene era, about 55
to 34 million years ago.
• Archaic whales, or archaeocetes, may have been drawn
back to aquatic life by ancient seas teeming with food.
Concept Review
The Mammals that Conquered the Seas
• Whales’ transitional ancestors had characteristics of both
land and sea creatures – legs and hooves for walking, tails
for swimming.
Concept Review
The Mammals that Conquered the Seas
• But later fossil and molecular studies suggest closer ties
to artiodactyls, even-toed hoofed mammals such as
camels and pigs.
• The hippopotamus may be an especially close whale
relative.
• Scientists once thought whales might be descended from
extinct wolf-like hoofed mammals called mesonychids.
Testing Your Comprehension
The Mammals that Conquered the Seas
Distant ancestors of whales had what characteristics?
a) fur
b) milk-producing glands
c) legs and feet
d) all of the above
Testing Your Comprehension
The Mammals that Conquered the Seas
Distant ancestors of whales had what characteristics?
d) all of the above
Testing Your Comprehension
The Mammals that Conquered the Seas
Whales are most closely related to which terrestrial mammals?
a) artiodactyls such as camels, pigs, and cows
b) carnivores such as bears, raccoons, and otters
c) perissodactyls such as horses, donkeys, and zebras
d) all of the above
Testing Your Comprehension
The Mammals that Conquered the Seas
Whales are most closely related to which terrestrial mammals?
a) artiodactyls such as camels, pigs, and cows
Testing Your Comprehension
The Mammals that Conquered the Seas
Which of the following do not help explain how modern whales
fit into the mammalian family tree?
a) DNA analysis
b) the fossil record
c) modern whale anatomy
d) antibody-antigen physiology
Testing Your Comprehension
The Mammals that Conquered the Seas
Which of the following do not help explain how modern whales
fit into the mammalian family tree?
c) modern whale anatomy
Testing Your Comprehension
The Mammals that Conquered the Seas
Which of these is not thought to be an ancestor of modern
whales?
a) Basilosaurus
b) Ambulocetus
c) Orca
d) Dorudon
Testing Your Comprehension
The Mammals that Conquered the Seas
Which of these is not thought to be an ancestor of modern
whales?
c) Orca
Biology and Society
The Mammals that Conquered the Seas
Selective pressures in the Eocene environment caused whales
to adapt and return to water. Environmental pressures
are also driving natural selection in the present-day world.
Strongly
Agree
Strongly
DisagreeA. E.C.B. D.
Biology and Society
The Mammals that Conquered the Seas
During the Eocene era, ancient oceans covered much of what
is now the Indian subcontinent, including Pakistan. Important
whale ancestor fossils have been found there, but such work
has also been interrupted by modern-day conflict. Scientists
should receive special protection to conduct research globally,
despite political or social problems.
Strongly
Agree
Strongly
DisagreeA. E.C.B. D.
Thinking About Science
The Mammals that Conquered the Seas
Most mammals cannot live without fresh water. But
cetaceans obtain their water, in part, from sips of the salty
ocean. To investigate when the ancestors of whales
became able to ingest seawater, scientists applied a
technique to measure the ratio of certain oxygen isotopes
in fossilized teeth. The ratio of these isotopes is different in
fresh and salt water.
Describe how this difference helped shape the hypothesis
of the scientists conducting the research.
Interpreting Data and Graphs
The Mammals that Conquered the Seas
These drawings illustrate how
various hypotheses of whale
ancestry have changed as new
findings come to light.
According to each of the four
drawings, which category of
creature is the whale’s closest
relative?
1. Explain how Darwin’s voyage on the Beagleinfluenced his thinking.
2. Explain how the work of Thomas Malthus and the process of artificial selection influenced Darwin’s development of the idea of natural selection.
3. Describe Darwin’s observations and inferences in developing the concept of natural selection.
4. Explain why individuals cannot evolve and why evolution does not lead to perfectly adapted organisms.
You should now be able to
© 2012 Pearson Education, Inc.
5. Describe two examples of natural selection known to occur in nature.
6. Explain how fossils form, noting examples of each process.
7. Explain how the fossil record, biogeography, comparative anatomy, and molecular biology support evolution.
8. Explain how evolutionary trees are constructed and used to represent ancestral relationships.
9. Define the gene pool, a population, and microevolution.
You should now be able to
© 2012 Pearson Education, Inc.
10. Explain how mutation and sexual reproduction produce genetic variation.
11. Explain why prokaryotes can evolve more quickly than eukaryotes.
12. Describe the five conditions required for the Hardy-Weinberg equilibrium.
13. Explain why the Hardy-Weinberg equilibrium is significant to understanding the evolution of natural populations and to public health science.
You should now be able to
© 2012 Pearson Education, Inc.
14. Define genetic drift and gene flow. Explain how the bottleneck effect and the founder effect influence microevolution.
15. Distinguish between stabilizing selection, directional selection, and disruptive selection. Describe an example of each.
16. Define and compare intrasexual selection and intersexual selection.
17. Explain how antibiotic resistance has evolved.
18. Explain why natural selection cannot produce perfection.
You should now be able to
© 2012 Pearson Education, Inc.
Concept Review
Founder Mutations
• A founder mutation is a mutation shared by many
individuals because they share a common ancestor.
• Founder mutations associated with disease are often
recessive and spare individuals who carry only one
copy of the mutant gene.
• This makes it possible for the mutation to spread from
the founder to his or her descendants instead of being
eliminated.
• Founder mutations provide a window to human
migrations.
Concept Review
Founder Mutations
• Mutations arise by random changes to DNA
sequences.
• Genes can be mutated to cause inherited disease in
two general ways:
1) Different individuals may carry different mutations in
the gene associated with the disease.
2) Precisely the same mutation may be seen again and
again in a disease-associated gene.
Concept Review
Founder Mutations
• A repeatedly observed disease-causing mutation can
occur if
- A hotspot for mutation is mutated independently in
different individuals.
or
- A mutation occurs in one individual, the founder, and is
transmitted to the founder’s descendants.
Concept Review
Founder Mutations
• Everyone who carries the founder mutation also
shares nearby sequences of DNA.
• This shared DNA region is a haplotype.
• Over time, haplotypes
become progressively shorter
because of recombination
between homologous
chromosomes.
• Therefore, the length of the
haplotype provides an estimate
of how long ago the founder
mutation occurred.
Concept Review
Founder Mutations
Concept Review
Founder Mutations
• Founder mutations are hundreds to thousands of
times more common than typical mutations that cause
disease.
• Founder mutations reach high frequencies through
natural selection because they provide an advantage to
individuals who carry only one copy of the mutated
gene.
• For example, carrying a single copy of the founder
mutation that causes hereditary hemochromatosis
enhances iron absorption, an advantage when diets are
poor in iron.
Concept Review
Founder Mutations
• The frequency of a founder mutation represents a
balance between two competing forces – the harm
caused by carrying two copies of the mutation weighted
against the benefit provided by carrying one copy of the
mutation.
• This is balancing selection.
Concept Review
Founder Mutations
PTC Taste Perception and the Out of Africa Hypothesis
• About 75% of people worldwide perceive the chemical
PTC as extremely bitter; the rest cannot taste it at all.
• The inability to taste PTC is due to a founder mutation.
• In African populations, there are seven different forms
of the gene associated with PTC perception.
• Outside of Africa, there is only one major taster and
one nontaster form of the gene.
Concept Review
Founder Mutations
• The nontaster mutation is in a very short haplotype,
indicating an ancient origin for this mutation.
• Two conclusions can be drawn:
Concept Review
Founder Mutations
• The existence of a single nontaster haplotype is
consistent with the tenet of the Out of Africa hypothesis
that ancestors of modern non-African populations
migrated from Africa about 75,000 years ago. These
migrants carried one major taster and one nontaster
form of the gene.
• The single PTC nontaster mutation suggests that
migrants from Africa did not interbreed with local
populations that almost certainly would have carried
their own unique mutations of this gene.
Concept Review
Founder Mutations
The Hemochromatosis Founder Mutation as a Window
to European Migrations
• The hemochromatosis founder mutation is found at
highest frequencies in Celtic peoples of northwestern
Europe and at lower frequencies in other regions of
Europe.
• The Celts were a dominant group in central Europe
2,000 years ago but were largely displaced north and
west by the expanding Roman Empire.
Concept Review
Founder Mutations
• Did the hemochromatosis founder mutation arise in
central Europe before Celtic migrations? Or did it
originate in today’s Celtic lands and spread
southeastward?
Concept Review
Founder Mutations
• The large size of the haplotype that contains the
hemochromatosis mutation indicates that it originated
recently: 60 to 70 generations ago, or about A.D. 800.
• Because this was long after the displacement of the
Celts from central Europe, the mutation must have
arisen in northwestern Europe and spread
southeastward through the founder’s descendants.
• Analysis of founder mutations offers insight into where
we came from and how we came to inhabit modern
homelands.
Founder Mutations
Testing Your Comprehension
How many copies of a founder mutation are required to
cause disease?
a) 1
b) 2
c) 4
d) 8
Founder Mutations
Testing Your Comprehension
How many copies of a founder mutation are required to
cause disease?
b) 2
Founder Mutations
Testing Your Comprehension
If two people have the same genetic disease caused by
a mutation other than a founder mutation, they usually
will have
a) exactly the same mutation in the same gene
b) different mutations in the same gene
c) hotspot mutations in different genes
d) markedly different symptoms
Founder Mutations
Testing Your Comprehension
If two people have the same genetic disease caused by
a mutation other than a founder mutation, they usually
will have
b) different mutations in the same gene
Founder Mutations
Testing Your Comprehension
Over time, haplotypes become
a) shorter
b) longer
c) more harmful
d) less harmful
Founder Mutations
Testing Your Comprehension
Balancing selection leads to
a) elimination of founder mutations
b) a continual increase in the frequency of founder
mutations
c) a stable frequency of a founder mutation
d) a fluctuating frequency of a founder mutation
Founder Mutations
Testing Your Comprehension
Balancing selection leads to
c) a stable frequency of a founder mutation
Founder Mutations
Biology and Society
The investigation of founder mutations and other
markers of human origins shows that human
populations are very closely related. If people could be
educated about their close degree of kinship, this would
help prevent conflicts across the world.
Strongly
Agree
Strongly
DisagreeA. E.C.B. D.
Founder Mutations
Thinking About Science
The figure shows two sets of DNA sequences obtained
from 8 different people. The A shown in red is a disease-
causing mutation. Letters in the blue-bordered columns
are DNA sequences that may vary, but do not cause the
disease. Which set comes from people carrying a
founder mutation?
a) The top set
b) The bottom set
Founder Mutations
Thinking About Science
The figure shows two sets of DNA sequences obtained
from 8 different people. The A shown in red is a disease-
causing mutation. Letters in the blue-bordered columns
are DNA sequences that may vary, but do not cause the
disease. Which set comes from people carrying a
founder mutation?
b) The bottom set
Interpreting Data and Graphs
Founder Mutations
• DNA sequences of a small part of one gene from a
healthy individual and three individuals with genetic
disease caused by mutations of this gene are shown in
the following table.
Which mutation is likely to cause this disease?
Is this a founder mutation?
Healthy ACCGTAC
Diseased 1 ACTCTAC
Diseased 2 TCCCTAC
Diseased 3 ACCCTAG
top related