Evolution and Biodiversity

1
Evolution and Biodiversity

• Chapter 4

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Key Concepts

• Origins of life
• Evolution and evolutionary processes
• Ecological niches
• Species formation
• Species extinction

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How Did We Become Such a Powerful Species So
Quickly?

• Strong opposable thumbs
• Walk upright
• Intelligence

4
Origin Evolution of Life

• Chemical evolution - 1st billion yrsorganic
  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.

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Animation- Chemical Evolution
Stanley Miller's experiment animation
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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 (3.63.8 billion years ago)
Fig. 4-3, p. 66
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How Do We Know Which Organisms Lived in the Past?

• Fossil record
• Radiometric dating
• Ice cores
• DNA studies

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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)

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Natural Selection

• Definition Process where particular beneficial
  trait is reproduced in succeeding generations
  more than other traits
• Three Conditions1. Genetic Variability2. Trait
  must be inherited3. Differential Reproduction -
  individuals w/ trait have more offspring

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Adaptations

• Structural- coloration, mimicry, protective,
  gripping
• Physiological - hibernate, chemical
• Behavioral - ability to fly, migrate

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Animation
Change in moth population animation
Genes mutate, individuals are selected, and
populations evolve.
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Animation
Adaptive trait interaction
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Ecological Niches and Adaptation

• Ecological niche occupation (role)
• Habitats address
• Fundamental niche no competition
• Realized niche with competition

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Broad and Narrow Niches and Limits of Adaptation

• Generalist species - broad niche
• Specialist species - narrow niche, more
  extinction-prone under changing environmental
  conditions. Which is better?
• Limits of adaptation- gene pool reproductive
  capacity

Refer to Spotlight, p. 72- cockroaches
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Niches of Specialist and Generalist Species
Specialist species with a narrow niche
Generalist species with a broad niche
Niche separation
Number of individuals
Niche breadth
Region of niche overlap
Resource use
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Animation
Stabilizing selection animation.
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Animation
Disruptive selection animation.
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Specialized Feeding Niches for Birds
Herring gull is a tireless scavenger
Brown pelican dives for fish, which it locates
from the air
Black skimmer seizes small fish at water surface
Ruddy turnstone searches under shells and pebbles
for small invertebrates
Dowitcher probes deeply into mud in search
of snails, marine worms, and small crustaceans
Avocet sweeps bill through mud and surface water
in search of small crustaceans, insects, and
seeds
Scaup and other diving ducks feed on mollusks,
crustaceans, and aquatic vegetation
Knot (a sandpiper) picks up worms and small
crustaceans left by receding tide
Flamingo feeds on minute organisms in mud
Oystercatcher feeds on clams, mussels, and other
shellfish into which it pries its narrow beak
Piping plover feeds on insects and
tiny crustaceans on sandy beaches
Louisiana heron wades into water to seize small
fish
Fig. 4-10, p. 72
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Cockroaches Natures Ultimate Survivors
Fig. 4-11, p. 72
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Evolutionary Divergence of Honeycreepers
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Misconceptions of Evolution

• Survival of the fittestFitness reproductive
  success ? strongest
• Progress to perfection

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Speciation

• What is speciation?
• Geographic isolation
• Reproduction isolationmutation natural
  selection operate independently in gene pools of
  geographically isolated populationsoriginal
  populations become genetically distinct- unable
  to produce live, fertile offspring

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Geographic Isolation can Lead to Speciation
Adapted to cold through heavier fur, short ears,
short legs, short nose. White fur matches snow
for camouflage.
Arctic Fox
Northern population
Spreads northward and southward and separates
Early fox population
Different environmental conditions lead to
different selective pressures and evolution into
two different species.
Gray Fox
Adapted to heat through lightweight fur and long
ears, legs, and nose, which give off more heat.
Southern population
Fig. 4-8, p. 68
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Animation
Speciation on archipelago animation
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Factors Leading to Extinction

• Plate tectonics
• Climatic changes over time
• Natural catastrophes
• Human impacts

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Extinctions

• Background extinctions 1-5 species per million
• Mass extinctions- five previous mass extinctions
  25 - 75 species go
• Mass depletions- gt background, but lt mass
• Human impacts - 6th major mass extinction???

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Continental Drift (Plate Tectonics) The
Breakup of Pangaea
Fig. 4-6, p. 66
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Mass Extinctions of the Earths Past
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Changes in Biodiversity over Geologic Time
1600
Terrestrialorganisms
Silurian
Triassic
Jurassic
Permian
Devonian
Cambrian
Ordovician
1200
Cretaceous
Marineorganisms
Pre-cambrain
Carboniferous
Number of families
800
Tertiary
Quaternary
400
0
1.8
0
65
145
205
250
290
355
410
440
500
545
3500
Millions of years ago
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Genetically Engineered Mouse
Mouse on right has human growth hormone gene-
grows 3x faster and 2x larger
Fig. 4-B, p. 69