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Evolution and
Biodiversity
Chapter 4
Key Concepts

Origins of life

Evolution and evolutionary processes

Ecological niches

Species formation

Species extinction
How Did We Become Such a
Powerful Species So Quickly?

Strong opposable thumbs

Walk upright

Intelligence
Origin & Evolution of Life

Chemical evolution - 1st billion yrs
organic molecules, biopolymers & chemical rxns needed
for formation of first cells
(Age of Earth = 4.6 billion years)

Biological evolution first life 3.7 bya (prokaryotes)
“Populations - not individuals - evolve by becoming genetically
different.”
Animation- Chemical Evolution
Stanley Miller's experiment animation
Biological Evolution of Life
Modern humans
(Homo sapiens)
appear about
2 seconds
before midnight
Recorded human
history begins
1/4 second
before midnight
Origin of life
(3.6–3.8 billion
years ago)
Fig. 4-3, p. 66
How Do We Know Which
Organisms Lived in the Past?

Fossil record

Radiometric dating

Ice cores

DNA studies
Biological Evolution

Evolution= change in populations genetic makeup over
time
(“Populations - not individuals - evolve by becoming genetically different.”)

“Theory” of evolution= All species descended from earlier,
ancestral species

Microevolution= small genetic changes in a population

Macroevolution= long-term, large scale
evolutionary changes (speciation, extinction)
Natural Selection

Definition: Process where particular beneficial trait is reproduced in
succeeding generations more than other traits

Three Conditions:
1. Genetic Variability
2. Trait must be inherited
3. Differential Reproduction - individuals w/ trait have more offspring
Adaptations

Structural- coloration, mimicry, protective, gripping

Physiological - hibernate, chemical

Behavioral - ability to fly, migrate
Animation
Change in moth population animation
“Genes mutate, individuals are selected, and populations evolve.”
Animation
Adaptive trait interaction
Ecological Niches and
Adaptation

Ecological niche = occupation (role)

Habitats = address

Fundamental niche = no competition

Realized niche = with competition
Broad and Narrow Niches and
Limits of Adaptation

Generalist species - broad niche

Specialist species - narrow niche, more extinctionprone under changing environmental conditions.
Which is better?

Limits of adaptation- gene pool & reproductive
capacity
Refer to Spotlight, p. 72- cockroaches
Number of individuals
Niches of Specialist and
Generalist Species
Specialist species
with a narrow niche
Niche
separation
Generalist species
with a broad niche
Niche
breadth
Region of
niche overlap
Resource use
Animation
Stabilizing selection animation.
Animation
Disruptive selection animation.
Specialized Feeding Niches for
Birds
Black skimmer
seizes small fish
at water surface
Scaup and other
diving ducks feed on
mollusks, crustaceans,
and aquatic vegetation
Flamingo
feeds on
minute
organisms
in mud
Herring gull is a
tireless scavenger
Brown pelican dives for fish,
which it locates from the air
Avocet sweeps bill through
mud and surface water in
search of small crustaceans,
insects, and seeds
Louisiana heron wades into
water to seize small fish
Dowitcher probes deeply
into mud in search of
snails, marine worms,
and small crustaceans
Oystercatcher feeds on
clams, mussels, and
other shellfish into which
it pries its narrow beak
Ruddy turnstone
searches
under shells and
pebbles for small
invertebrates
Knot (a sandpiper) picks up
worms and small crustaceans
left by receding tide
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
Fig. 4-10, p. 72
Cockroaches: Nature’s Ultimate
Survivors
Fig. 4-11, p. 72
Evolutionary Divergence of
Honeycreepers
Fruit and seed eaters
Insect and nectar eaters
Greater Koa-finch
Kuai Akialaoa
Amakihi
Kona Grosbeak
Crested Honeycreeper
Akiapolaau
Maui Parrotbill
Unknown finch ancestor
Apapane
Misconceptions of Evolution

“Survival of the fittest”

“Progress to perfection”
Fitness = reproductive success ≠ strongest
Speciation

What is speciation?

Geographic isolation

Reproduction isolation
mutation & natural selection operate independently
in gene pools of geographically isolated populations
original populations become genetically distinctunable to produce live, fertile offspring
Geographic Isolation can Lead to
Speciation
Arctic Fox
Northern
population
Early fox
population
Spreads northward
and southward
and separates
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Gray Fox
Southern
population
Adapted to heat
through
lightweight fur
and long ears,
legs, and nose,
which give off
more heat.
Fig. 4-8, p. 68
Animation
Speciation on archipelago animation
Factors Leading to Extinction

Plate tectonics

Climatic changes over time

Natural catastrophes

Human impacts
Extinctions

Background extinctions= 1-5 species per million

Mass extinctions- five previous mass extinctions:
25% - 75% species go

Mass depletions- > background, but < mass

Human impacts - 6th major mass extinction???
“Continental Drift” (Plate Tectonics): The
Breakup of Pangaea
LAURASIA
225 million years ago
135 million years ago
EURASIA
AFRICA
65 million years ago
Present
Fig. 4-6, p. 66
Mass Extinctions of the Earth’s Past
Changes in Biodiversity over
Geologic Time
Terrestrial
organisms
Cretaceous
400
Quaternary
Marine
organisms
Tertiary
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
800
Cambrian
1200
Pre-cambrain
Number of families
1600
0
3500
545
500
440 410
355
290
250
205
Millions of years ago
145
65
1.8 0
Genetically Engineered Mouse
Mouse on right has
human growth
hormone genegrows 3x faster and
2x larger
Fig. 4-B, p. 69