Download natural selection

MACROEVOLUTION AND EARTH'S HISTORY
Macroevolution is the main event in the
evolutionary history of life on Earth
•Documented in the fossil record
•The geologic record is based on the
sequence of fossils
•Earth's history divided into three eons
•Within the most recent eon, eras and
periods marked by mass or lesser
extinctions
•Some major events in the history of life
•Precambrian period: oldest known fossilsprokaryotes from 3.5 billion years ago
•Paleozoic era: lineages that gave rise to
modern life forms
•Mesozoic era: age of reptiles, including
dinosaurs
•Cenozoic era: Explosive evolution of
mammals, birds, and flowering plants
Radiometric dating can gauge the
actual ages of fossils and the rocks in
which they are found
•Based on the decay time of radioactive
isotopes relative to other isotopes
•Carbon-14 for relatively young fossils
•Isotopes with longer half-lives for older
fossils
Continental drift has played a major role in macroevolution
• Continental drift is the slow, incessant movement of Earth's crustal plates on the
hot mantle
• World geography changes constantly
LE 15-03a
Eurasian Plate
North
American
Plate
Arabian
Plate
Pacific
Plate
African
Plate
Nazca
Plate
South
American
Plate
Indian
Plate
Split
developing
Australian
Plate
Antarctic Plate
Edge of one plate being pushed over edge of
neighboring plate (zones of violent geologic events)
• Continental movements have greatly influenced the
distribution of organisms around the world
• Formation of Pangaea 250 million years ago altered
habitats and triggered extinctions
• Breakup of Pangea beginning 180 million years ago
created a number of separate evolutionary arenas
• Explains the geographical distribution of diverse
life forms
• Examples: marsupials, lungfishes
LE 15-03b
0
Eurasia
65
Africa
South
America
India
Antarctica
Laurasia
135
251
LE 15-03d
North
America
Asia
Europe
Africa
South
America
Australia
= Living lungfishes
= Fossilized lungfishes
CONNECTION
Plate tectonics are the forces involved in movements of Earth's crustal plates
• The geologic processes that result include volcanoes and earthquakes
• Can create devastation or opportunities for
organisms
• The boundaries of plates are hot spots of such geologic activity
LE 15-04a
San Andreas Fault
North
American
Plate
San Francisco
Santa Cruz
Pacific
Plate
Los Angeles
California
15.5 Mass extinctions were followed by diversification of life-forms
• Extinctions occur all the time, but extinction rates have not been steady
• Over the last 600 million years, at least six periods of mass extinctions have occurred,
including
• Permian extinction (250 million years ago); claimed 96% of aquatic life
• Cretaceous extinction (65 million years ago); eliminated dinosaurs
• Cause of mass extinctions is unclear
• Permian extinction occurred at a time of enormous volcanic explosions
• Cretaceous extinction may have been caused by an asteroid
• Mass extinctions have been followed by an explosive increase in diversity
• Provide surviving organisms with new environmental opportunities
• Example: rise of mammals after extinction of dinosaurs
LE 15-05
North
America

Yucatan
Peninsula
Chicxulub
crater

Yucatan
Peninsula
BINOMIAL NOMENCLATURE
-Naming system used today
-Formed by Linnaeus
-Name an organism using the Genus and species
*Homo sapiens
-WHY??
-Aristotle was the first to classify
*classified as either plant or animal
*divided further into: land, water, or air dwellers
*plant classification was based on their stems
WHY Bionomial Nomenclature?
-Early scientists used common names which caused confusion
Ex: robin, pine tree
-Everyday names may not accurately describe the organism
Ex: Jellyfish is not a fish, not made of jelly
-Can name many species with one name
Ex: Maple tree
…..Sugar Maple, Red Maple, Silver Maple
Using Genus & species if known as the SCIENTIFIC NAME
*Describes organism
*Ex: Trifolium agrarium
-3-leaved and found in fields
KINGDOMS
1.MONERA
-prokaryotic
-Asexual reproduction
-Includes greatest number of living things on Earth
EX: bacteria
2.PROTISTA
-eukaryotic without specialized tissue systems
-ingest food
-aquatic, moist habitats
EX: Algae
3.FUNGI
-heterotrophic organisms
-absorb nutrients
-most are terrestrial
-EX: Yeast, mushrooms
KINGDOMS (cont.)
4. PLANTAE
-all plants
-eukaryotic/muticellular
-photosynthetic
EX: mosses, tress, flowers, shrubs
5. ANIMALIA
-Eukaryotic, multicelluar
-Ingest food
-Sexual reproduction, few asexually
EX: spiders, elephants, humans
Clown, Fool, or Simply Well Adapted?
• The blue-footed booby has many specialized characteristics that are very functional in
water but less useful on land
• Such evolutionary adaptations are inherited traits that enhance an organism's ability to
survive and reproduce in its particular environment
• Evolution is the changes in organisms over time
DARWIN'S THEORY OF
EVOLUTION
A sea voyage helped Darwin frame his theory of evolution
• Pre-Darwinian ideas about the origin of species
• Early Greek philosophers: Simpler life forms preceded more
complex ones
• Aristotle: Species are fixed and do not evolve; had a great
impact on Western thinking
• Judeo-Christian biblical view: All species were individually
designed by a divine creator
• In the century prior to Darwin, only a few scientists questioned the
belief that species are fixed
• Buffon: The study of fossils suggested that Earth is older than
6,000 years, and fossil forms might be early versions of modern
forms
• Lamarck: Fossils are related to modern forms because life
evolves; acquired characteristics are inherited
• Charles Darwin made a round-the-world sea voyage as a
naturalist on HMS Beagle in the 1830s
• Darwin observed similarities between living and fossil
organisms and the diversity of life on the Galápagos
Islands
• Darwin's experiences during the voyage helped him frame
his ideas about evolution
Marine Iguana …..Galapagos Islands
LE 13-1b
Great
Britain
Europe
Asia
North
America
PACIFIC
OCEAN
The
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Marchena
Pinzón
Isabela
0
0
40 km
Equator
Daphne
Islands
Santa Santa
Cruz Fe
Florenza
40 miles
Africa
San
Cristobal
Española
PACIFIC
OCEAN
Equator
South
America
Genovesa
Santiago
Fernandina
ATLANTIC
OCEAN
Australia
Cape of
Good Hope
Cape Horn
Tierra del Fuego
Tasmania
New
Zealand
• After his return, Darwin began to document his observations
and his new theory of evolution
• Darwin's On the Origin of Species by Means of Natural
Selection was published in 1859
• "Descent
with modification" summarizes Darwin's view of life
• All organisms are related through descent from a remote
common ancestor
• Descendants spread into diverse habitats over millions of
years and acquired adaptations to their environments
• The history of life resembles a tree with multiple branchings
from a common trunk
• Species that are closely related share characteristics
Darwin proposed natural selection as the mechanism of
evolution
• The essence of Darwin's theory of natural selection is
differential success in reproduction
• Organisms produce more offspring than the environment
can support
• Organisms vary in many characteristics that can be
inherited
• Excessive numbers of organisms lead to a struggle for
survival
• Individuals whose characteristics are best adapted
to their environment are more likely to survive and
reproduce
• The unequal ability of individuals to survive and
reproduce leads to a gradual change in the
characteristics of a population over generations
• Natural selection is supported by evidence from
artificial selection
Vegetables are all
derived from wild
mustard plant
LE 13-2c
African wild dog
Coyote
Wolf
Thousands to
millions of years
of natural selection
Ancestral canine
Fox
Jackal
The study of fossils provides strong evidence for
evolution
• Fossils are the hard parts of organisms that remain
after organic materials decay
• Rarely, an entire organism is fossilized
• The fossil record strongly supports the theory of
evolution
• Changes in sea level and drying and refilling of
lakes over time result in rock strata that trap
organisms
• Fossils appear in an ordered array within layers of
sedimentary rocks
• The fossil record reveals that organisms have evolved in a
historical sequence
• Many fossils link early extinct species with species living
today
13.4 A mass of other evidence reinforces the evolutionary view of life
• Biogeography
• The geographic distribution of species suggested to Darwin that organisms evolve from
common ancestors
• Isolated organisms resemble each other more than organisms in similar but distant
places
• Comparative anatomy
• Homologous structures are features that often have different functions but are
structurally similar because of common ancestry
• Vestigial structures are remnants of structures that served important functions in an
organism's ancestors
LE 13-4a
Human
Cat
Whale
Bat
• Comparative embryology
• Common embryonic structures in all vertebrates are evidence for common descent
LE 13-4b
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo
• Molecular biology
• Comparisons of DNA and amino acid sequences between different organisms reveal
evolutionary relationships
• Molecular biology provides strong evidence that all life forms are related
CONNECTION
13.5 Scientists can observe natural selection in action
• Examples of evolutionary adaptation observed over a short time
• Different camouflage adaptations in different environments
• Development of pesticide resistance in insects
Video: Seahorse Camouflage
LE 13-5b
Chromosome with gene
conferring resistance
to pesticide
Additional
applications of the
same pesticide will
be less effective, and
the frequency of
resistant insects in
the population
will grow
Pesticide application
Survivor
• Examples of evolutionary adaptation reveal three key points about natural selection
• Natural selection is more of an editing process than a creative mechanism
• Natural selection is contingent on time and place
• Significant evolutionary change can occur in a short time
POPULATION GENETICS AND THE
MODERN SYNTHESIS
• 13.6 Populations are the units of evolution
• Population
• A group of individuals of the same species living in the same place at the same time
• May be isolated from other groups or concentrated
• The smallest unit that can evolve
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Population genetics
• Combines Darwin's and Mendel's ideas in studying how populations change genetically
over time
• The modern synthesis
• Connects population genetics with other sciences
• Focuses on population as the unit of evolution and central role of natural selection
• Studying evolution at the population level
• Evolution: change in the prevalence of certain heritable characteristics in a population
over a span of generations
• Gene pool: the total collection of genes in a population at any one time
• Microevolution: a change in the relative frequencies of alleles in a gene pool
• Species: a group of populations capable of interbreeding and producing fertile offspring
13.7 The gene pool of a nonevolving population remains constant over the
generations
• In a nonevolving population, the shuffling of alleles that accompanies sexual reproduction
does not alter the genetic makeup of the population
• In Hardy-Weinberg equilibrium, the frequency of each allele in the gene pool will remain
constant unless acted upon by other agents
• For a population to be in Hardy-Weinberg equilibrium, it must satisfy five main conditions
• The population is very large
• The population is isolated
• Mutations do not alter the gene pool
• Mating is random
• All individuals are equal in reproductive success
• The Hardy-Weinberg conditions are rarely met in nature
• We can follow alleles in a population to observe if Hardy-Weinberg equilibrium exists
• Hardy-Weinberg equilibrium provides a basis for understanding how populations evolve
LE 13-7a
Webbing
No webbing
LE 13-7b
Phenotypes
Genotypes
WW
Ww
ww
Number of animals
(total = 500)
320
160
20
Genotype frequencies
320
500
160
500
= 0.64
Number of alleles
in gene pool
(total = 1,000)
640 W
Allele frequencies
800
1,000
= 0.32
160 W + 160 w
= 0.8 W
200
1,000
20
500
40 w
= 0.2 w
= 0.04
LE 13-7c
Recombination
of alleles from
parent generation
Sperm
W sperm
p = 0.8
w sperm
q = 0.2
WW
= 0.64
Ww
pq = 0.16
p2
W egg
p = 0.8
Eggs
w egg
q = 0.2
wW
qp = 0.16
q2
ww
= 0.04
Next generation:
Genotype frequencies
Allele frequencies
0.64 WW
0.8 W
0.32 Ww
0.04 ww
0.2 w
CONNECTION
13.8 The Hardy-Weinberg equation is useful in public health science
• Public health scientists use the Hardy-Weinberg equation to estimate frequencies of
disease-causing alleles in the human population
• Example: phenylketonuria (PKU)
13.9 In addition to natural selection, genetic drift and gene flow can contribute
to evolution
• Genetic drift: change in the gene pool of a population due to chance
• Can alter allele frequencies in a population
• The smaller the population, the greater the impact
• Bottleneck effect: an event that drastically reduces population size
• Founder effect: colonization of a new location by a small number of individuals
LE 13-9a
Original
population
Bottlenecking
event
Surviving
population
• Gene flow: the movement of individuals or gametes between populations
• Can alter allele frequencies in a population
• Tends to reduce differences between populations
• Natural selection
• Best-adapted individuals have the most reproductive success
• Results in accumulation of traits that adapt a population to its environment
CONNECTION
13.10 Endangered species often have reduced variation
• Loss of genetic variability due to bottlenecking may reduce a population's ability to adapt to
environmental change
• Particularly threatening to endangered species such as the cheetah
VARIATION AND NATURAL
13.11 Variation is extensive in most populations
SELECTION
• Individual variation exists in all sexually reproducing populations
• Heritable variation results from a combination of genotype and environmental influences
• Polymorphism: two or more forms of phenotypic characteristics
• Geographic variation: variation of an inherited characteristic from place to place
• May occur along a geographic continuum (a cline)
13.12 Mutation and sexual recombination generate variation
• Mutations-changes in the nucleotide sequence of DNA-can create new alleles
• Only mutations in cells that produce gametes can affect a population's gene pool
• A mutation may rarely improve adaptation to the environment and thus contribute to
evolution
• Sexual recombination generates variation by shuffling alleles during meiosis
LE 13-12a
A1
Parents
A2
A1
A3

Meiosis
A1
Gametes
A2
A3
LE 13-12b
A1
A2
A3
Gametes
Fertilization
Offspring,
with new
combinations
of alleles
A1
A1
A2
and
A3
CONNECTION
13.13 The evolution of antibiotic resistance in bacteria is a serious public health
concern
• Natural selection has led to the evolution of antibiotic-resistant bacteria
• Overuse and misuse of antibiotics has contributed to the proliferation of antibiotic-resistant
strains
• Example: tuberculosis
13.14 Diploidy and balancing selection preserve variation
• Diploidy (two sets of chromosomes) helps to prevent populations from becoming
genetically uniform
• Recessive alleles are "hidden" from natural selection and remain in the population
• Balancing selection allows two or more phenotypic forms in a population
• Balanced polymorphism may result from
• Heterozygote advantage; example: sickle-cell disease
• Frequency-dependent selection
• Neutral variation provides no apparent advantage or disadvantage
• Example: fingerprints
13.15 The perpetuation of genes defines evolutionary fitness
• Evolutionary fitness is the relative contribution an individual makes to the gene pool of the
next generation
• Survival of genes depends on production of fertile offspring
• Selection indirectly adapts a population to its environment by acting on phenotype
13.16 Natural selection can alter variation in a population in three ways
• Stabilizing selection: favors intermediate phenotypes
• Directional selection: acts against individuals at one of the phenotypic extremes
• Disruptive selection: favors individuals at both extremes of the phenotypic range
Frequency of individuals
LE 13-16
Original
population
Phenotypes (fur color)
Original
population
Evolved
population
Stabilizing selection
Directional selection
Disruptive selection
13.17 Sexual selection may produce sexual dimorphism
• Sexual dimorphism
• The distinction in appearance between males and females of a species
• Sexual selection
• The determining of "who mates with whom"
• Leads to the evolution of secondary sexual characteristics that may give individuals an
advantage in mating
13.18 Natural selection cannot fashion perfect organisms
• There are at least four reasons why natural selection cannot produce perfection
• Organisms are limited by historical constraints
• Adaptations are often compromises
• Chance and natural selection interact
• Selection can only edit existing variations