Transcript ES Chapter 4 modified

Chapter 4
4-1 origins of life.
Key Concepts
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Origins of life- Life started about 3.7 billion years
ago.
Evolution and evolutionary processes: Micro
(small genetic changes) and Macro (long-term,
species wide changes)
Ecological niches: Species adapting to a specific
role in their ecosystem.
Species formation: Unique adaptations of small
populations.
Species extinction: a failure to adapt.
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
Biological Evolution
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Evolution: Change in the genetic make-up
of a population over time.
Theory of evolution: Life comes from life.
All species descended from ancestral
species.
Microevolution: occurs on a genetic level.
Mutations are either advantageous or
deleterious.
Macroevolution: Successive changes over
generations of a population.
Microevolution
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Gene pool: All the genes in an individual.
Genetic variability: Genetic diversity amongst a
population. Allows for adaptation, key to
population survival.
Mutations: Random changes in the structure of
DNA. Can be advantageous or deleterious.
Mutagens: capable of changing DNA. Radiation,
certain chemicals. Cigarettes…
Natural selection: Certain populations having
traits that allow them to be more successful than
others.
Natural Selection
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Differential reproduction: Some species
reproduce better than others (competitive).
Adaptation (adaptive trait): Heritable trait
that allows an organism to survive and
reproduce.
Coevolution: Biological Arms Race. Species
gaining a temporary genetic advantage over
competitors.
Ecological Niches and Adaptation
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Ecological niche: Species way of life or
functional role in an ecosystem.
Habitats: Physical location of a species.
Fundamental niche: Potential range of a
species. Resources it could use.
Realized niche: What it does use.
Broad and Narrow Niches and
Limits of Adaptation
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Generalist species: broad niches. Variety of
potential foods and habitats. Rats, roaches,
coyotes, catfish.
Specialist species: Very adapted. Limited
foods and niches. Pandas, red cockaded
woodpeckers…
Limits of adaptation: Gene pool, and
reproduction speed.
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
Fig. 4-4, p. 68
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. 4-5, p. 68-69
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
Fig. 4-6, p. 70
Misconceptions of Evolution
 “Survival
of the fittest”:
Reproductive strength, not
individual health.
 “Progress to perfection” More
evolved does not mean better,
in fact, the loss of traits often
leads to extinction.
Speciation
What is speciation?
 -A new species arises when members
of one population are isolated.
 Geographic isolation: members of one
population become physically isolated
from the other.
 Reproduction isolation: Members of
the separated population can no longer
interbreed with the original population.
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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. 4-7, p. 71
Factors Leading to Extinction
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Plate tectonics
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Climatic changes over time
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Ice ages.
Droughts
Natural catastrophes
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Sinking/uplifting
Volcanos
Meteors
Human impacts
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Habitat degradation
Invasive species
Extinctions
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Background extinctions
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Species disappearing a low rate, mainly by “Natural
Causes”. 99.9% of all species.
Mass extinctions: Rise in extinction rates above the
background level.
Mass depletions: High rates, but not that high.
Human impacts: During the 20th century, extinction
rates increased 100-1,000 times. Humans change the
environment faster than species can adapt.
Biodiversity = Speciation – Extinction. Biodiversity
represents the planets raw genetic material for future
evolution. Lack in biodiversity = inability to adapt.
“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. 4-8, p. 72
Top 5 best mass extinctions of all
time!
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Ordovician: 500 million years ago. 50% of
animal families wiped out.
Devonian: 30% of agnathan and placoderm
fishes.
Permian: 90% of all animal species. 95% of
marine species. All trilobites.
Triassic: 35% of animal families, lots of reptiles.
Cretaceous: up to 80% of all animal species.
Mass Extinctions of the Earth’s Past
Fig. 4-9, p. 73
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
145
65
1.8 0
Millions of years ago
Fig. 4-10, p. 74