Download Ch 17 ppt - College of Science and Mathematics

Hewitt/Lyons/Suchocki/Yeh
Conceptual Integrated
Science
Chapter 17
THE EVOLUTION OF LIFE
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This lecture will help you
understand:
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The Origin of Life
Early Life on Earth
The First Eukaryotic Cells
Charles Darwin and The Origin of Species
How Natural Selection Works
Integrated Science: Animal Adaptations to Heat and Cold
How Species Form
Evidence of Evolution
Does Evolution Occur Gradually or in Spurts?
The Evolution of Humans
Science and Society: Antibiotic-Resistant Bacteria
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The Origin of Life
For thousands of years, people believed that
life was created through spontaneous
generation, the sudden emergence of
living organisms from nonliving material.
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The Origin of Life
Louis Pasteur proved that spontaneous
generation was not the explanation for the
origin of life.
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The Origin of Life
The Miller and Urey experiment modeled the
young Earth’s atmosphere and water.
When Miller and Urey shot electric sparks
through the mixture, complex organic
molecules formed.
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The Origin of Life
Alternate hypotheses for the origin of
organic molecules on Earth:
• Organic molecules came to Earth on
incoming meteorites.
• Organic molecules were synthesized in
deep sea vents.
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The Origin of Life
Scientists now believe that the first genes
were probably made of RNA.
Short strands of RNA can spontaneously
assemble from individual nucleotides. RNA
can even replicate by itself.
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Early Life on Earth
The earliest living organisms were:
• Marine prokaryotes
• Living with no free oxygen
• Heterotrophs (obtaining energy and food
from outside sources)
• Producing energy via anaerobic processes
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Early Life on Earth
Autotrophs—organisms that convert
inorganic materials into food and organic
molecules—evolved later. But this was a
key event in the history of life!
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Early Life on Earth
Cyanobacteria—photosynthetic
bacteria— produced oxygen
as a by-product of
photosynthesis, introducing
oxygen into the Earth’s
atmosphere.
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The First Eukaryotic Cells
Eukaryotes:
• First appeared about 2 billion years ago.
• The nucleus and most organelles probably originated
from inward foldings of the cell membrane.
• According to the endosymbiotic theory, mitochondria
and chloroplasts evolved from prokaryotes living inside
the earliest eukaryotic cells.
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The First Eukaryotic Cells
Mitochondria likely evolved from a group of
oxygen-breathing bacteria.
Chloroplasts probably evolved from
cyanobacteria.
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Charles Darwin and
The Origin of Species
Jean Baptiste Lamarck argued that fossils were
relics of the ancestors of modern species.
Lamarck believed
that organisms
acquired new traits
over their lifetimes
and then passed
them on to their
offspring. He called
this the inheritance
of acquired characteristics.
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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.
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Charles Darwin and
The Origin of Species
Darwin argued that evolution—heritable
changes in organisms over time—
explained the origin of all organisms on
Earth.
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Charles Darwin and
The Origin of Species
Darwin was inspired by:
• His travels on the Beagle.
• The work of geologist Charles Lyell, who
proposed that the Earth’s features developed
gradually over millennia.
• The work of economist Thomas Malthus, who
wrote about famine and the struggle of humans
over resources.
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Charles Darwin and
The Origin of Species
Darwin’s Galápagos Island finches were significant
because they provided what appeared to be an example
of how a single species could evolve into multiple
species, each adapted to a different lifestyle.
The 13 species of finches he found varied in beak size and
shape, depending on their diet.
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How Natural Selection Works
• In any population, individuals have traits, many
of which show variation.
• Traits that are determined by genes are
heritable.
• Advantageous traits benefit an organism and
allow it to leave more offspring—this is natural
selection.
• Advantageous traits become more common in a
population, resulting in adaptation.
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Natural selection - differential survival and reproduction of
phenotypes
Adaptation - heritable modification of the phenotype that increases
ability to survive and reproduce relative to those without the
modification
Fitness – the contribution an individual makes to the gene pool of the
next generation, relative to the contributions of other individuals
Better adapted phenotypes increase in frequency in a population due to
natural selection because they have greater relative fitness
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How Natural Selection Works
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How Natural Selection Works
Adaptations are traits that make an
organism better suited to living in and
reproducing in its environment.
• Many adaptations help organisms survive.
• Some adaptations help organisms attract
mates—this is called sexual selection.
• Other adaptations relate to bearing and
raising offspring.
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The Paradox of Variation:
Evolution requires variation, but natural
selection eliminates variation.
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Integrated Science: Animal
Adaptations to Heat and Cold
Animals thermoregulate:
• Surface-to-volume ratio is an
important factor in heat balance.
• Bergmann’s Rule says that
animals found in cold habitats
are often larger than related forms
in warm habitats.
• Allen’s Rule states that appendages
will be longer/larger in hot-climate
animals and shorter/smaller in
cold-climate animals.
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Integrated Science: Animal
Adaptations to Heat and Cold
Animals also control body temperature with:
• Coloration
• Insulation
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How Natural Selection Works
Natural selection is classified into three
modes:
• Directional selection
• Stabilizing selection
• Diversifying selection
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Directional selection on egg laying in domestic hens
Egg production
1933
1968
125 eggs /yr
245 eggs /yr
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Stabilizing selection on human birth weight
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Diversifying selection on coat color in deer mice
Dark color is favored on
rich soil
Light color is favored on
sandy soil
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Fig. 23. 12
Effects of selection on phenotype distributions
Location of curve = mean
Width of curve = variance
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How Natural Selection Works
The Modern Synthesis incorporates
modern genetics into Darwin’s theory of
evolution.
It focuses on evolution as changes in the
allele frequencies of genes over time.
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How Natural Selection Works
Four different mechanisms produce
evolution:
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Natural selection
Mutation pressure
Genetic drift
Migration
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How Species Form
A species is a group of organisms whose
members can interbreed with each other
but not with members of other species.
The key to speciation—the development of
new species—is the evolution of
reproductive barriers that prevent two
groups of organisms from interbreeding.
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How Species Form
There are two kinds of reproductive barriers:
• Prezygotic reproductive barriers
prevent members of different species from
mating in the first place or prevent
fertilization from occurring.
• Postzygotic reproductive barriers
prevent hybrids from surviving or from
reproducing if they do survive.
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How Species Form
CHECK YOUR NEIGHBOR
Is a mule an example of a prezygotic
reproductive barrier or a postzygotic
reproductive barrier?
Explain your answer to your neighbor.
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How Species Form
CHECK YOUR ANSWER
A mule provides an example of a postzygotic
reproductive barrier. It is the hybrid
offspring of two different species, a horse
and a donkey. Mules are sterile and
cannot reproduce.
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How Species Form
New species may develop as a result of:
• Allopatric speciation (geographic barriers dividing
a population in two)
• Sympatric speciation (speciation without a
geographic barrier).
Examples: hybridization and chromosomal changes,
such as polyploidy.
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
Evidence of Evolution
Evidence for evolution includes:
• Natural selection in action
• Human-imposed artificial selection (e.g.,
domesticated animals and plants)
• Shared anatomy, patterns of development, and
DNA among living creatures
• The fossil record
• Biogeography
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Evidence of Evolution
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Evidence of Evolution
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Does Evolution Occur Gradually or
in Spurts?
Gould and Eldredge proposed the theory of
punctuated equilibrium—species maintain
stability (“equilibrium”) for long periods and
then evolve in rapid bouts (“punctuated”) that
occur during speciation.
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The Evolution of Humans
Humans are:
• Primates—we share an ancestry with
monkeys and apes
• Hominids—the primate group that includes
Homo sapiens and extinct relatives
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The Evolution of Humans
The fossil record has allowed us to
document some aspects of human
evolution.
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Science and Society:
Antibiotic-Resistant Bacteria
Antibiotic resistance is the result of natural
selection.
When a patient takes a course of antibiotics, a few
naturally resistant bacteria may survive the
treatment. These reproduce. Eventually, strains
of bacteria exist that cannot be controlled by the
antibiotic.
All antibiotic use contributes to antibiotic
resistance.
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Science and Society:
Antibiotic-Resistant Bacteria
Ways to slow the development of antibiotic
resistance in bacteria:
• Take antibiotics only when needed
• Take the entire course of antibiotics
• Use antibiotics responsibly in agriculture
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1. A survey of the p eppered moth (Biston betularia ) population of London gives
the following result:
dark (melanic) morphs = 827
light morphs
= 353
Given the M (melanic) is dominant to m (light), and assuming that the population
is in Hardy-Weinberg equilibrium, answer the q uestions below:
(a) What is the frequency of the melanic allele in th e population?
(b) What percentage of the moths will be melanic in the n ext generation?
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
1. A survey of the p eppered moth (Biston betularia ) population of London gives
the following result:
dark (melanic) morphs = 827
light morphs
= 353
Given the M (melanic) is dominant to m (light), and assuming that the population
is in Hardy-Weinberg equilibrium, answer the q uestions below:
(a) What is the frequency of the melanic allele in th e population?
(b) What percentage of the moths will be melanic in the n ext generation?
(a). 827 + 353 = 1180
q 2 = 353/1180 = 0.30
q = sqr root (.30) = 0.55
p = 1 - q = 0.45
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley
1. A survey of the p eppered moth (Biston betularia ) population of London gives
the following result:
dark (melanic) morphs = 827
light morphs
= 353
Given the M (melanic) is dominant to m (light), and assuming that the population
is in Hardy-Weinberg equilibrium, answer the q uestions below:
(a) What is the frequency of the melanic allele in th e population?
(b) What percentage of the moths will be melanic in the n ext generation?
(a). 827 + 353 = 1180
q 2 = 353/1180 = 0.30
(b) p 2 + 2pq = frequency of melanic moths
(0.45)2 + 2 (0.45)(0.55) = 0.70
q = sqr root (.30) = 0.55
p = 1 - q = 0.45
Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley