biology of humans 2/e - napa valley collegenapavalley.edu/people/briddell/documents/bio 105/human...

© 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


Evolution and Our Heritage

OUTLINE:

Evolution of Life on Earth

Scale of Evolutionary Change

Evidence of Evolution

Human Evolution



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


Figure 22.1 Representation of the early 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


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


Figure 22.2 Apparatus used by Miller and Urey.


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


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


Figure 22.3 Possible steps in the origin of life on Earth.


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


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


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


Microevolution

Some processes that lead to microevolution

Genetic drift

Gene flow

Mutation

Natural selection


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


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


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


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


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


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


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


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


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


Natural Selection

Web Activity: Agents of Change


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


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


Figure 22.5 Categories in the classification of living organisms.


Phylogenetic Trees

Branching diagrams that depict hypotheses about

evolutionary relationships among species or groups

of species

Begin by constructing a character matrix


Figure 22.6 A phylogenetic tree depicts hypotheses about

evolutionary relationships among organisms.



Comes from several sources

Fossil record

Biogeography

Comparison of anatomical and embryological

structures

Molecular biology


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


Figure 22.7 A sampling of past life in fossils.


Figure 22.8 A typical sequence for fossilization.


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


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


Figure 22.9 The evolution of whales as revealed by transitional

fossils.


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


Geographic Distributions and Comparative

Molecular Biology

Web Activity: Biogeography and Continental Movement


Figure 22.10 The story of marsupials and Australia.


Figure 22.11 Homologous structures.



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


Figure 22.12 Resemblance early in development indicates

common descent.


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



Web Activity: Principles of Evolution


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


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


Figure 22.13 A tree shrew.


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)


Figure 22.14 Examples of modern primates.


Figure 22.15 Monkeys and apes are placed with humans in

another suborder.


Figure 22.16 Hypothesized relationships among living primates.


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


Figure 22.17 Some major differences in skeletal anatomy and

teeth between chimpanzees and humans.


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)


Figure 22.18 Hominin footprints from Laetoli, Tanzania.


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


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


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


Figure 22.19 Fossilized remains and reconstruction of Lucy.


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


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


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


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


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


Homo neanderthalensis

Cro-Magnons (form of H. sapiens)

Accomplished hunters and artists

Lived in groups


Figure 22.20 Relatively recent representatives of the genus Homo.


Table 22.1 Review of Some Milestones in Human Evolution


Figure 22.21 The major hominin species.


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


Human Evolution

| Evolution and Faith

culture_wars_evolution.mov

culture_wars_evolution.mov


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

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