chapter 23 lecture outline - napa valley college · 5 origin of life ... – molecules combined to...
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Chapter 23
Lecture Outline
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Human Evolution
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Points to ponder
• What is chemical evolution?
• What is biological evolution?
• What is natural selection, and what three elements are vital for this?
• What was Darwin’s contribution to evolution?
• What have we learned from the fossil record?
• Explain the fossil, biogeographical, anatomical, and biochemical evidence that supports the theory of evolution by common descent.
• What are analogous, homologous, and vestigial structures? Give examples of each.
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Points to ponder
• How are humans classified?
• What characteristics do primates have in common?
• Explain the evolution of hominids.
• Who was Lucy?
• Explain the evolution of humans.
• What is the most widely accepted hypothesis for the evolution of modern humans?
• Compare and contrast Cro-Magnons and Neandertals.
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Origin of life through chemical evolution
• Steps of chemical evolution
– Gases of the primitive atmosphere formed
small organic molecules.
– Molecules combined to form
macromolecules.
– Only RNA might have been needed to form
the first cells; this is supported by the fact
that RNA can act as enzymes called
ribozymes (RNA-first hypothesis).
23.1 Origin of Life
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Origin of life through chemical evolution
– Protocells made of proteins and lipids could
metabolize by using oceanic organic
molecules, but could not reproduce.
– The true cell can reproduce and has DNA as
its genetic material.
23.1 Origin of Life
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Origin of life through chemical evolution
Figure 23.1 Chemical and biological evolution.
23.1 Origin of Life
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cell
Bio
log
ical E
vo
luti
on
C
he
mic
al E
vo
luti
on
protocell
early Earth
plasma
membrane
energy
capture abiotic synthesis
origin of
genetic code
DNA RNA
polymerisation
Stage 3
Stage 4
Stage 1
inorganic chemicals
small organic molecules
Stage 2 polymers
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Biological evolution
• Biological evolution – change in population or species over time
• Two important points
1. Living things descended from a common ancestor and thus have common chemistry.
2. Livings things adapt to their environment.
• Adaptation – a characteristic that enables an organism to survive and reproduce in its environment
23.2 Biological Evolution
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Natural selection
• Natural selection is a theory by Charles
Darwin that describes a mechanism by
which a species becomes adapted to its
environment.
23.2 Biological Evolution
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Natural selection
• Three vital elements • Variation – there must be physical
variations that can be passed from generation to generation
• Competition – there must be competition for limited resources (food, mates, shelter), and those better adapted will survive and reproduce
• Adaptation – subsequent generations will see an increase in individuals with the same adaptations, as long as the environment remains unchanged
23.2 Biological Evolution
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Natural selection Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Originally, giraffes had
short necks.
Giraffes stretched their necks
in order to reach food.
Competition for resources
causes long-necked giraffes
to have the most offspring.
With continual stretching, most
giraffes now have long necks.
Originally, giraffe neck
length varied.
Due to natural selection, most
giraffes now have long necks.
Lamarck’s proposal Darwin’s proposal
Figure 23.3 The two major
mechanisms for evolutionary
change in the nineteenth century.
23.2 Biological Evolution
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Evidence to support the theory
of evolution by common descent
1. Fossil record
2. Biogeographical evidence
3. Anatomical evidence
4. Biochemical evidence
23.2 Biological Evolution
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1. What are fossils?
• Fossils are the traces of past life.
• Fossils allow us to trace the descent of a particular group.
• Charles Darwin, an English naturalist, relied on fossils to formulate the theory of evolution.
• Transitional fossils have characteristics of two different groups.
23.2 Biological Evolution
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Transitional fossils
Figure 23.4 Transitional fossils.
23.2 Biological Evolution
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360
Expanded ribs
Scales
Fish Rounded head,
eyes on sides
377
380
Tiktaalik
roseae
Mil
lio
ns
of
ye
ars
ag
o (
MY
A)
Fins
Neck Flat head,
eyes on top
Early
amphibian
Amphibian
tetrapod
370
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What have we learned from the
fossil record?
• The fossil record tells us that life progressed from simple to more complex.
• Prokaryotes are the first life forms seen in the fossil record, followed by unicellular eukaryotes, and then multicellular eukaryotes.
• Fishes evolved before terrestrial plants and animals.
• Nonflowering plants preceded flowering plants.
• Amphibians preceded reptiles.
• Dinosaurs are directly linked to birds.
23.2 Biological Evolution
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Fossils
Figure 23.5 Archaeopteryx. Figure 23.6 Evolution of the whales.
23.2 Biological Evolution
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feathers
teeth
claws
tail with vertebrae
artist depiction of Archaeopteryx
wing
head
wing
tail
Archaeopteryx fossil
feet
(fossil, left): © Jean-Claude Carton/PhotoShot; (drawing, right): © Joe Tucciarone
a. Ambulocetus
b. Basilosaurus
c. Right whale
modern
40
MYA
50
MYA
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a (fossil Ambulocetus foot): © J.G.M. Thewissen, Northeastern Ohio Universities College of Medicine
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2. Biogeographical evidence
• Biogeography is the study of the distribution of plants and animals throughout the world.
• It supports the hypothesis that organisms originate in one locale and then may spread out.
• Different life forms are expected whenever geography separates them.
• Islands have many unique life forms because of geographic isolation.
23.2 Biological Evolution
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Biogeographical evidence
Figure 23.7 Biogeography.
23.2 Biological Evolution
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sugar glider, Petaurus breviceps,
is a tree-dweller and resembles the placental flying squirrel.
The Australian wombat, Vombatus, is nocturnal and lives in burrows. It
resembles the placental woodchuck.
Kangaroo, Macropus, is an herbivore that inhabits plains and forests. It
resembles the placental Patagonian
cavy of South America. (sugar glider): © ANT Photo Library/Photo Researchers; (wombat): © Photodisc
Blue/Getty RF; (kangaroo): © George Holton/Photo Researchers
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3. Anatomical evidence
• Common descent hypothesis offers plausible
explanation for anatomical similarities among
living organisms.
• Homologous structures – structures
anatomically similar that are inherited by a
common ancestor
• e.g., Vertebrate forelimbs
23.2 Biological Evolution
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3. Anatomical evidence
• Analogous structures – structures that serve the same function but they do not share a common ancestry, and thus are not constructed the same
• e.g., Wings of a bird and wings of an insect
• Vestigial structures – anatomical features fully developed in one group that are reduced and may have no function in another group
• e.g., Whales have a vestigial pelvic girdle and legs
23.2 Biological Evolution
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An example of homologous structures Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
bird
whale human horse cat
bat
humerous
ulna
radius
metacarpals
phalanges
Figure 23.8 Vertebrate
forelimbs are homologous
structures.
23.2 Biological Evolution
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Homologous structures in
vertebrate embryos Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pig embryo
pharyngeal
pouches
postanal
tail
Chick embryo
(both): © Carolina Biological Supply/Phototake
Figure 23.9 Homologous
structures in vertebrate embryos.
23.2 Biological Evolution
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4. Biochemical evidence
• Almost all living things use the same
biochemicals (e.g., DNA and ATP).
• Living things use the same triplet genetic code.
• Living things use the same 20 amino acids in
their proteins.
• Living things share many of the same genes.
23.2 Biological Evolution
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Biochemical evidence describes
evolutionary relationships Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0
2
9
Cytochrome c is a small protein
that plays an important role in
the electron transport chain
within mitochondria of all cells.
Number of Amino Acid Differences Compared to
Human Cytochrome c
Species
human
monkey
pig
duck
turtle
fish
moth
yeast
11
18
20
30
51
Figure 23.10
Biochemical evidence
describes evolutionary
relationships.
23.2 Biological Evolution
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The evolution of humans
22.3 Classification of Humans
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3 domains of life Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
common ancestor
fungi
animals
EUKARYA
protists protists
heterotrophic
bacteria
BACTERIA
ARCHAEA
plants
cyanobacteria
Figure 23.11 The three domains of life.
23.3 Classification of Humans
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Primates
• Characteristics
• Opposable thumb
• Stereoscopic vision (depth perception)
• Well-developed brain
• Reduced number of offspring (usually a
single birth) with an increased period of
parental care
• Emphasis on learned behavior and social
interactions
23.3 Classification of Humans
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• Two major groups (suborders)
• Prosimians – includes lemurs, tarsiers,
and lorises
• Anthropoids – includes monkeys, apes,
and humans
23.3 Classification of Humans
Primates
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Asian and African apes
Figure 23.12 Asian and African apes.
23.3 Classification of Humans
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
white-handed gibbon,
Hylobates lar
Asian Apes
orangutan, Pongo pygmaeus chimpanzee, Pan troglodytes
western lowland gorilla,
Gorilla gorilla
African Apes
(gibbon): © Hans & Judy Beste/ Animals Animals; (orangutan, chimps, gorillas): © Creatas/PunchStock RF
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Comparing the human skeleton
to the chimpanzee Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
b. a.
Human spine exits from the skull’s center;
ape spine exits from rear of skull.
Human spine is S-shaped; ape spine has a
slight curve.
Human pelvis is bowl-shaped; ape pelvis is
longer and more narrow.
Human femurs angle inward to the knees;
ape femurs angle out a bit.
Human knee can support more weight than
ape knee.
Human foot has an arch; ape foot has
no arch.
Figure 23.13 Adaptations in the human skeleton allow upright locomotion.
23.3 Classification of Humans
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Evolution of primates 23.4 Evolution of Hominins
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Pro
sim
ian
s A
nth
rop
oid
s
Ho
min
oid
s
Ho
min
ids
Ho
min
ine
s
Mammalian
ancestor
enters trees.
hominin
common
chimpanzee
western
lowland
gorilla
capuchin
monkey
New World Monkeys
ring-tailed
lemur
70 60 50 40 30 20 10 Million years Ago (MYA)
PRESENT
rhesus
monkey
Humans
Chimpanzees
Gorillas
Orangutans
Bornean
orangutan
Gibbons
white-handed
gibbon
Old World Monkeys
Tarsiers
Philippine
tarsier
Lemurs
Pro
sim
ian
s A
nth
rop
oid
s
Figure 23.14 The evolutionary
tree of the primates.
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Evolution of hominins
• Hominins – All species of the genus
Homo and their close relatives
• Characteristics
• Bipedal
• Flatter face with more pronounced chin
• Brain size
23.4 Evolution of Hominins
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Evolution of hominins
• Suggested fossils of the first hominins (6-7 MYA)
• Central African fossil 7 MYA (Sahelanthropus tchadensis)
• Eastern African fossil 6 MYA (Orrorin tugenensis)
• Eastern African fossil 5.8-5.2 MYA (Ardipithecus kadabba)
• Hominins split from the ape line of descent 7 MYA.
23.4 Evolution of Hominins
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Australopithecines
• A group of hominins that evolved and
diversified in Africa ~3 MYA.
• Some had slight frames and others were
robust with massive jaws for feeding on
plant materials.
• They walked upright.
• Limbs proportions are apelike.
• They had a small brain.
23.4 Evolution of Hominins
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Australopithecines
• Famous skeleton named “Lucy” is from
this group .
• Australopithecus africanus, with a large
brain, is the most likely ancestral
candidate for early Homo.
23.4 Evolution of Hominins
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Australopithecines
Figure 23.15 Australopithecus afarensis.
23.4 Evolution of Hominins
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b. a.
a: © Dan Dreyfus and Associates; b: © John Reader/Photo Researchers
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Characteristics of Homo
1. Brain size is 600 cc or greater.
2. There is evidence of tool use.
3. Jaw and teeth of Homo resemble humans.
Early Homo representatives
• Homo habilis
• Homo erectus
Later Homo representatives
• Neandertals
• Cro-Magnons
23.5 Evolution of Humans
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Human evolution 23.5 Evolution of Humans
Figure 23.16 Human evolution.
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Early Homo: Homo habilis
• Lived 2.0-1.9 MYA
• Large brain with enlarged speech area
• Omnivorous (hunters and gatherers)
• Primitive tools
• May have had culture
23.5 Evolution of Humans
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Early Homo: Homo erectus
• Lived 1.9-0.3 MYA
• Larger brain than H. habilis
• Flat face with the nose projected
• Tall and stood erect
• Striding gait
• May have migrated from Africa to Europe
and Asia
• Advanced tools and fire (systematic hunters)
• May have had language
23.5 Evolution of Humans
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Homo ergaster
Figure 23.17 Homo ergaster.
23.5 Evolution of Humans
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Modern humans: Homo sapiens
• Replacement model, or out-of-Africa
hypothesis, is the most widely accepted
hypothesis.
– It proposes that modern humans evolved
from archaic humans only in Africa.
– Then, modern humans migrated to Asia
and Europe, where they replaced the
archaic species about 100,000 years BP.
23.5 Evolution of Humans
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Hypothesis for modern human evolution
Figure 23.18 Replacement model.
23.5 Evolution of Humans
44
Migration of early Homo from
Africa
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Neandertals
• Discovered in Germany 200,000 years ago
• Massive brow ridges
• Nose, jaws, and teeth protrude forward
• Low and sloping forehead, no chin
23.5 Evolution of Humans
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Cro-Magnons
• Lived about 40,000 to 100,000 years ago
• Oldest fossils to be designated Homo
sapiens
• Modern appearance
• Advanced culture including art, tools, and
maybe language
• Good cooperative hunters
23.5 Evolution of Humans
47 Figure 23.19 The Cro-Magnons.
23.5 Evolution of Humans
Cro-Magnons
48
Human variation
• Human variations between populations are
called ethnicities.
• Variations evolved as adaptation to local
environments.
– Skin color ranges from dark to light.
– Body shape
• Bergmann’s rule – colder regions mean
bulkier build
• Allen’s rule – colder regions mean shorter
limbs, digits, and ears
23.5 Evolution of Humans
49
Human variation
Figure 23.20 Ethnic variations
in modern humans.
23.5 Evolution of Humans
b.
a.
c.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© PhotoDisc/Getty RF; 22.20b: © Sylvia S. Mader; c: © Adam Crowley/Getty Images