biology of humans 2/e - napa valley college 105...lecture presentation anne gasc hawaii pacific...
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© 2014 Pearson Education, Inc.
Lecture Presentation
Anne Gasc
Hawaii Pacific University and
University of Hawaii–Honolulu Community College
BIOLOGY OF HUMANSConcepts, Applications, and Issues
Fifth Edition
Judith Goodenough Betty McGuire
22Evolution and
Our Heritage
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Evolution and Our Heritage
OUTLINE:
Evolution of Life on Earth
Scale of Evolutionary Change
Evidence of Evolution
Human Evolution
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Evolution of Life on Earth
Evolution
Descent with modification from a common ancestor
Earth is estimated to be 4.5 billion years old
Environment of early Earth was very different from
that of today
Hot, volcanic crust
Intense UV radiation
Almost no gaseous oxygen
Physical and chemical evidence suggests that life has
existed for 3.8 billion years
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Figure 22.1 Representation of the early Earth.
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Evolution of Life on Earth
Chemical evolution
Life evolved from chemicals increasing in complexity over
about 300 million years
Possible steps in chemical evolution
Inorganic molecules
Small organic molecules
Macromolecules
Early cells
Prokaryotic
Eukaryotic
Multicellular organisms
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Small Organic Molecules
Inorganic molecules form small organic molecules
Favored by low-oxygen atmosphere
Oxygen attacks chemical bonds
Energy provided by lightning and intense UV radiation
Tested by several groups of scientists
Small organic molecules formed larger molecules
Possibly proteins or nucleic acids
First genetic material could have been RNA or DNA
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Figure 22.2 Apparatus used by Miller and Urey.
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Macromolecules and Early Cells
Organic macromolecules (proteins and genetic
material) aggregated into droplets
Precursors to living cells
Earliest cells
Prokaryotic cells about 3.8 billion years ago
Eukaryotic cells about 1.8 billion years ago
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Macromolecules and Early Cells
Endosymbiont theory
Some organelles within eukaryotic cells were once
free-living prokaryotes
Mitochondria may be descendants of once free-living
bacteria
Multicellularity
Evolved in eukaryotes about 1.5 billion years ago
Eventually led to organisms such as plants, fungi, and
animals
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Figure 22.3 Possible steps in the origin of life on Earth.
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Scale of Evolutionary Change
Microevolution
Changes at the genetic level within a population over
a few generations
Macroevolution
Larger-scale evolutionary change over longer periods
of time
Origin of groups of species
Mass extinctions
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Microevolution
Basic terms in microevolution
Population: group of individuals of the same species
living in a particular area
Gene pool: includes all of the alleles of all of the
genes of all individuals in a population
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Microevolution
Variation in populations: sexual reproduction shuffles
alleles already present in population
Gametes of an individual are variable (crossing over
and independent assortment)
Combination of gametes at fertilization
Mutation: produces new genes and new alleles
Occurs at low rate in any set of genes
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Microevolution
Some processes that lead to microevolution
Genetic drift
Gene flow
Mutation
Natural selection
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Microevolution
Genetic drift
Allele frequencies within a population change
randomly because of chance alone
Usually negligible in large populations
Two mechanisms that facilitate
Bottleneck effect
Founder effect
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Genetic Drift
Bottleneck effect
A change in the gene pool that occurs when there has
been a dramatic reduction in population size
Individuals are killed at random
Alleles in survivors may not be representative of the
original population
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Genetic Drift
Founder effect
Genetic drift in new, small colonies
A few individuals leave their population and establish
themselves in a new, isolated place
Genetic makeup of the colonizing individuals is
probably not representative of the population they left
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Gene Flow
Occurs when individuals move into and out of a
population and interbreed with the resident
population
Cessation of gene flow can be important in formation
of new species
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Gene Flow
Species
A population or group of populations whose members
are capable of successful interbreeding under natural
conditions
Speciation
Formation of a new species
When populations become separated, they may
become genetically distinct and no longer capable of
successful interbreeding
Can result in a new species
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Natural Selection
Charles Darwin
On the Origin of Species (1859)
Species are not specially created, unchanging forms
Modern species are descendants of ancestral species
Evolution occurs by natural selection
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Natural Selection
Individual variation exists within a species, and
some of this variation is inherited
Some individuals leave more surviving offspring than
others because their particular inherited
characteristics make them better suited to their local
environment
Evolutionary change occurs as the traits of
successful individuals become more common in the
population
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Natural Selection
Fitness
Compares the number of reproductively viable
offspring among individuals
Individuals with greater fitness have more of their
genes represented in future generations
Adaptation
Through natural selection, populations become better
suited to their environment
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Natural Selection
Natural selection does not lead to perfect organisms
Can act on available variation only
Can modify existing structures only
Organisms cannot be perfect at everything
Face many competing demands, so adaptations are
often compromises
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Natural Selection
Web Activity: Agents of Change
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Macroevolution
Large-scale evolutionary change over long periods
of time
Linnaeus developed the Latin binomial scheme for
naming organisms
The genus name is followed by the specific epithet;
both are italicized
Example: Homo sapiens
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Macroevolution
Linnaeus also developed a system for classifying organisms
into a series of increasingly broad categories
Species
Genus
Family
Order
Class
Phylum
Kingdom
Domain added later as the most broad category
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Figure 22.5 Categories in the classification of living organisms.
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Phylogenetic Trees
Branching diagrams that depict hypotheses about
evolutionary relationships among species or groups
of species
Begin by constructing a character matrix
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Figure 22.6 A phylogenetic tree depicts hypotheses about
evolutionary relationships among organisms.
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Evidence of Evolution
Comes from several sources
Fossil record
Biogeography
Comparison of anatomical and embryological
structures
Molecular biology
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Fossil Record
Fossils preserved remnants and impressions of
past organisms
Provide strong evidence of evolution
Biased sampling of past life
Fossilization
Occurs as hard body parts such as bones, teeth, and
shells become impregnated with minerals from
surrounding water and sediment
Eventually the sediments may be uplifted by
geological processes, exposing the fossil
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Figure 22.7 A sampling of past life in fossils.
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Figure 22.8 A typical sequence for fossilization.
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Fossil Record
Fossils of extinct organisms show similarities to, and
differences from, living species
Transitional forms link ancient organisms to modern
species
Example: whale evolution
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Fossil Record
Biogeography
Study of the geographic distributions of organisms
Geographic distributions often reflect evolutionary
history and relationships
Related species are more likely to be found in the
same geographic area than are unrelated species
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Figure 22.9 The evolution of whales as revealed by transitional
fossils.
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Geographic Distributions and Comparative
Molecular Biology
New distributions of organisms occur by two basic
mechanisms
Dispersal
Organisms move to new areas
Areas occupied by organisms move or are subdivided
Comparative anatomy
Homologous structures
Structures that are similar and that probably arose from
a common ancestry
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Geographic Distributions and Comparative
Molecular Biology
Web Activity: Biogeography and Continental Movement
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Figure 22.10 The story of marsupials and Australia.
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Figure 22.11 Homologous structures.
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Evidence of Evolution
Comparative molecular biology
Molecular clock hypothesis
Based on the assumption that point mutations in DNA
occur at a constant rate
The more differences in the DNA sequences between
two organisms, the more time has elapsed since the
common ancestor
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Figure 22.12 Resemblance early in development indicates
common descent.
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Comparative Anatomy and Embryology
Convergent evolution
When two organisms evolve similar structures
because of similar ecological roles and selection
pressures
Analogous structures
Structures that are similar because of convergent
evolution
Common embryological origins can be considered
evidence of common descent
Example: all vertebrate embryos look very similar
early in development
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Evidence of Evolution
Web Activity: Principles of Evolution
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Human Evolution
Human roots trace back to the first primates
Primates probably arose from an insect-eating
mammal that lived in trees, like a modern tree shrew
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Human Evolution
Primate characteristics reflect an arboreal lifestyle
specialized for manual capture of insects
Flexible, rotating shoulder joints
Sensitive pads on ends of digits
Nails instead of claws
Grasping feet and hands
Forward-facing eyes
Large brain
Small litter size
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Figure 22.13 A tree shrew.
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Human Evolution
Order Primates
Suborder
Lemurs, lorises, and pottos
Retain ancestral features
Suborder
Monkeys, apes, and humans
Family Hominidae now includes apes and humans
( hominids)
Subfamily Hominidae includes human lineage
( hominins)
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Figure 22.14 Examples of modern primates.
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Figure 22.15 Monkeys and apes are placed with humans in
another suborder.
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Figure 22.16 Hypothesized relationships among living primates.
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Comparisons of Human and Chimp Skeletal
Anatomy
Many aspects of human skeletal anatomy reflect our
terrestrial lifestyle and upright stance while walking
Bipedalism walking on two feet
S-shaped spine
Large patella
Arms shorter than legs
Toes not opposable
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Figure 22.17 Some major differences in skeletal anatomy and
teeth between chimpanzees and humans.
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Misconceptions
Humans descended from chimpanzees
Fact: humans and chimpanzees represent separate
phylogenetic branches that diverged about 6 million
years ago
Modern humans evolved in an orderly stepwise fashion
Fact: more than one species of hominin existed
simultaneously at several points in the past
Different parts of the human body evolved at the same
rate
Fact: different traits evolved at different times and rates
( mosaic evolution)
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Figure 22.18 Hominin footprints from Laetoli, Tanzania.
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Trends in Hominin Evolution
Bipedalism
Shortening of jaw and flattening of face
Reduced sexual dimorphism in body size
Increased brain size along with tool use
Language and behavioral complexity
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Australopithecines
Ardipithecus ramidus
Oldest hominin remains
About 4.4 million years old
Discovered in 1994; descriptions published in 2009
Facultative bipedalism
May have given rise to Australopithecus
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Australopithecines
Species within the genus Australopithecus (from earliest
to most recent)
A. anamensis
About 4 million years old
A. afarensis
“Lucy”
About 3.2 million years old
May have led to Homo
A. africanus
About 3 million years old
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Figure 22.19 Fossilized remains and reconstruction of Lucy.
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Homo habilis
Species within the genus Homo (from earliest to
most recent)
Homo habilis (“handy man”)
About 2.5 million years ago
First member of the modern genus of humans
Differed from A. afarensis in having a larger brain size
May have used stone tools and been capable of
speech
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Homo ergaster, Homo erectus, and Homo
heidelbergensis
Homo ergaster (“working man”)
About 1.9 million years ago
Remains traditionally classified as H. erectus
Homo erectus (“upright man”)
Diverged from H. ergaster about 1.8 million years ago
First hominin to migrate out of Africa
May have used fire
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Homo ergaster, Homo erectus, and Homo
heidelbergensis
Homo heidelbergensis
800,000 to 30,000 years ago
May have given rise to H. sapiens and
H. neanderthalensis
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Homo sapiens
“thinking man”
Oldest fossil evidence for modern humans comes
from Africa about 130,000 years ago
Characteristics
Larger brain
Flat forehead
Absent or small brow ridges
Prominent chin
Very gracile body form
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Homo neanderthalensis
“Neanderthals”
Known from Europe and Asia from about 200,000 to
30,000 years ago
Lived in caves
Features reflect adaptations to cold climates
Had social structure
Now have first version of Neanderthal genome
Modern humans may have bred with Neanderthals in
the Middle East
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Homo neanderthalensis
Cro-Magnons (form of H. sapiens)
Accomplished hunters and artists
Lived in groups
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Figure 22.20 Relatively recent representatives of the genus Homo.
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Table 22.1 Review of Some Milestones in Human Evolution
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Figure 22.21 The major hominin species.
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Human Evolution
Two hypotheses for the evolution of modern humans
Multiregional hypothesis ( multiple origins)
H. sapiens evolved independently in Europe, Asia,
Africa, and Australia from distinctive local populations
of earlier humans
Out of Africa hypothesis ( single origin)
H. sapiens evolved from earlier humans in Africa and
later migrated to Europe, Asia, and Australia
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Human Evolution
| Evolution and Faith
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You Should Now Be Able To:
Describe the evolution of life on Earth
Understand the scale of evolutionary change
Know the evidence of evolution
Understand human evolution