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Chapter 17, 18 and 19
Evolution Unit
Earth: The Just-Right, Adaptable Planet
• During the 3.7
billion years since life
arose on Earth, the
average surface
temperature of the
earth has remained
within the range of
10-20oC
Figure 4-1
The consistent
temperature range
has allowed life to
Evolve, Flourish and
create the Diversify
on Planet Earth
Our Home
Evolution of Life On Earth
Chemical Evolution Biological Evolution
(1 billion years) (3.7 billion years)
Formation Large Variety of
First Single-cell Single-cell
of the Small organic multicellular
protocells prokaryotes eukaryotes
earth’s organic molecules organisms
form in the form in form in
early molecules (biopolymers) form, first
seas the seas the seas
crust and form in form in in the seas
atmosphere the seas the seas and later
on land
Fig. 4-2, p. 84
Stanley Miller’s Experiment
Or- How we figured our how life
evolved from non-living components
http://highered.mcgraw-
hill.com/sites/9834092339/student_view0/chapter26/an
imation_-_miller-urey_experiment.html
Stanley Miller’s Experiment
Vial of Material from Original Experiments Found
(youtube) 1.5 mins
Bill Nye Explains Stanley Miller’s Experiments
Creating the Potential for Life (united streaming) 8
mins
Time Line -1953 Miller’s Experiments
1977 Undersea vent discovery
Time Frame of Human Evolution
• Time Scales Demonstration-string
Modern humans (Homo
sapiens sapiens) appear
about 2 seconds before
midnight
Age of Recorded human history
mammals begins about 1/4 second
Age of
reptiles before midnight
Insects and
amphibians
invade the Origin of life
land
(3.6-3.8 billion
years ago)
First fossil
record of
animals
Plants
begin
invading
land Evolution and
expansion of life
Fig. 4-3, p. 84
• If the diagram of
Evolution were a
clock, at what time
would Fish have
evolved?
• What time are
flowering plants
present?
• What time do humans
evolve?
Evolution and Geological Time
• Over the last billion years, the
location of the continents has
changed. This has led to the
evolution of similar species on
different continents…
225 million years ago 135 million years ago
65 million years ago Present
Fig. 4-5, p. 88
http://contintental drift theory pangae
Changes in climate throughout the earth’s
history have shifted where plants and
animals can live
Figure 4-6
Asteroids and meteorites hitting the
earth have wiped out large numbers
of species and created evolutionary
opportunities for Natural Selection of
new species
Ex: KT Meteorite killed off dinosaurs
and gave rise to the “age of
mammals”
Our knowledge about past life comes from
fossils, chemical analysis, cores drilled out
of buried ice, and DNA analysis
NATURAL SELECTION
• Evolution by natural selection involves
the change in a population’s genetic
makeup through successive generations
• Through either:
–genetic variability
–Mutations: random changes in DNA
that can be inherited by offspring
Natural Selection and Adaptation:
3 conditions are necessary for
evolution:
1. Genetic variability
2. Traits must be heritable
3. Trait must lead to differential
reproduction
Types of Natural Selection
• Stabilizing: occurs when the most common
phenotype is selected for.
• Disruptive: occurs when changes favor
individuals at both extremes of the distribution,
individuals at the extremes contribute more
offspring than those in the center, producing two
peaks.
• Directional: occurs when natural selection favors
a single phenotype and therefore allele frequency
continuously shifts in one direction.
http://wps.pearsoncustom.com/wps/media/obje
cts/3014/3087289/Web_Tutorials/17_A02.swf
Directional Selection
Microevolution occurs when allele frequencies
change from one generation to the next
Ex. Industrial melanism
Moth Populations: Directional
Selection
PLAY
ANIMATION
Wrap Up of Natural Selection Types
Adaptive Trait Game
PLAY
ANIMATION
Limits on Adaptation through
Natural Selection
• A population’s ability to adapt to
new environmental conditions
through natural selection is limited
by its gene pool and how fast it can
reproduce.
Coevolution
• Interacting species can engage
in a back and forth genetic
contest in which each gains a
temporary genetic advantage
over the other. This often
happens between predators and
prey species
Example: Toxic Newts
Every species in an ecosystem has a specific
role or Niche
1. Fundamental niche: the potential
range conditions and resources a species
could theoretically use
2. Realized niche: to survive and avoid
competition, a species usually occupies
only part of its fundamental niche
2 Species of Barnacles- 2 niche
In the previous diagram the two species of
barnacles grow on different parts of the rocks.
When the lighter coloured (Balanus sp.) were
removed from the rocks the darker coloured
(Chthamatus sp.) was able to move down onto the
unoccupied surface. But when the Chthamatus
sp. was removed from the upper areas of the rock
Balanus sp. was not able to move up and occupy
these upper areas, because Balanus sp. can't
stand to be exposed to the air for a long time,
which is the case with rocks close to the high tide
mark. Balanus can only occupy the lower niche.
Generalist and Specialist
Generalist
species
Specialist
tolerate a
species can
wide range
only
of
tolerate a
conditions.
narrow
range of
conditions.
Figure 4-7
Cockroaches: Nature’s Ultimate
Survivors
• 350 million years old
• 3,500 different species
• Ultimate generalist
– Can eat almost anything.
– Can live and breed
almost anywhere.
– Can tolerate radiation. 4-A
Figure
Specialized Feeding Niches
• Resource partitioning reduces competition
and allows sharing of limited resources.
Figure 4-8
Avocet sweeps bill through
mud and surface water in
search of small crustaceans,
Ruddy
insects, and seeds
Herring gull is a turnstone
tireless scavenger searches
Brown pelican under shells
dives for fish, and pebbles
which it locates Dowitcher probes deeply for small
Black skimmer
from the air into mud in search of invertebrates
seizes small fish
at water surface snails, marine worms,
and small crustaceans
Louisiana heron wades into
water to seize small fish
Piping plover feeds
Flamingo Scaup and other Oystercatcher feeds on
on insects and tiny
feeds on diving ducks feed clams, mussels, and
crustaceans on
minute on mollusks, other shellfish into which
sandy beaches
organisms crustaceans,and it pries its narrow beak
in mud aquatic vegetation Knot (a sandpiper)
picks up worms and
small crustaceans left
by receding tide
(Birds not drawn to scale) Fig. 4-8, pp. 90-91
SPECIATION
• Speciation: A new species can
arise when member of a
population become isolated for
a long period of time
Pre-zygotic Barriers
Mechanical isolation:
Structural differences prevent gamete
exchange.
Gametic isolation:
Gametes die before uniting with gametes of
other species, or gametes fail to unite.
Post-zygotic Barriers
Hybrid inviability:
Hybrid zygotes fail to develop or fail to
reach sexual maturity.
Hybrid sterility:
Hybrid fails to produce functional gametes.
Hybrid breakdown:
Offspring of hybrids are weak or infertile.
Allopatric Speciation
• Induced when the ancestral population becomes
separated by a geographical barrier.
• Example:
Grand Canyon and ground squirrels
Adaptive Radiation
• Emergence of numerous species from a common
ancestor introduced to new and diverse environments.
• Example:
Darwin’s Finches
Sympatric Speciation
• Result of a radical change in the genome that produces
a reproductively isolated sub-population within the
parent population (rare).
• Example: Plant evolution - polyploid
A species doubles it’s chromosome # to
become tetraploid.
Parent population
reproductive sub-
population
Evolutionary Divergence
• Each of the
finches
evolved into a
new species,
from a
common
ancestor, to fill
a niche
Figure 4-9
Animation: Evolutionary Tree
Diagrams
PLAY
ANIMATION
Geographic Isolation
• …can lead to reproductive isolation, divergence
of gene pools and speciation.
Figure 4-10
Extinction:
• Extinction occurs
when the
population cannot
adapt to changing
environmental
conditions.
The golden toad of Costa Rica’s
Monteverde cloud forest became extinct
because of climate change.
Figure 4-11
Bar width represents relative Species and families
Era Period Millions of experiencing
years ago number of living species
Cenozoic mass extinction
Quaternary Today Extinction Current extinction crisis caused
by human activities.
Tertiary
Extinction
65
Cretaceous: up to 80% of
Cretaceous reptiles (dinosaurs)
Mesozoic
Jurassic Extinction Triassic: 35% of animal families
180
Triassic
250 Extinction Permian: 90% of animal families
Permian
Carboniferous
345 Extinction
Devonian: 30% of animal
Paleozoic
families
Devonian
Silurian
Ordovician Extinction
500 Ordovician: 50% of animal
Cambrian families
Fig. 4-12, p. 93
II. Mass Extinctions
A. Paleozoic Era between Ordovician/ Silurian 438 mya
(million years ago): First Ice Age=75% of all species
extinct
Paleozoic Era between Devonian/ Carboniferous 360 mya:
Sea levels rising=70% of all species extinct
Paleozoic Era between Permian/Triassic 245 mya: all land
masses colliding together to form Pangaea and single
world ocean=90% of all species extinct
Mesozoic Era between Triassic/ Jurassic 214 mya: comets
hitting the Earth (theory)
60% of all species extinct-first extinction of some
dinosaurs
Mesozoic/Cenozoic Era: Cretaceous/Tertiary 65 mya:
Volcanic lava, maybe an asteroid hitting the earth.
2nd and final extinction of most dinosaurs
GREATEST EXTINCTIONS THROUGHOUT HISTORY
Current Day
Cretaceous
Ordovician
Devonian
Permian
Jurassic
Dinosaurs go extinct
Terrestrial
Number of families
Marine
Millions of years ago
Fig. 4-13, p. 94
Effects of Humans on
Biodiversity
• The scientific consensus is
that human activities are
decreasing the earth’s
biodiversity.
Figure 4-13
GENETIC ENGINEERING
• We have used artificial selection to change the
genetic characteristics of populations with
similar genes through selective breeding.
(Cows are an example of this)
• We have used
genetic
engineering to
transfer genes from The mouse on the right has been
one species to engineered to be obese.
another.
Figure 4-15
Genetic Engineering:
Genetically Modified Organisms (GMO)
recombinant
DNA: genes
from
different
organisms
are
combined.
Figure 4-14
How Did We Become Such a Powerful
Species so Quickly?
• We lack:
– strength, speed, agility.
– weapons (claws, fangs), protection (shell).
– poor hearing and vision.
• We have thrived as a species because of
our:
-opposable thumbs, ability to walk upright, and
complex brains (problem solving).
