Evolution

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Evolution

• Chapter 4

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How Did We Become Such a Powerful Species So
Quickly?

• 3 Main Adaptive Traits
• Opposable Thumbs
• Ability to Walk Upright
• Intelligence (Complex Brains)

Fig. 4-1, p. 63
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How Do We Know Which Organisms Lived in the Past?

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

Fig. 4-2, p. 65
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Origins of Life
Considerable evidence suggests that life
developed in 2 phases over the past 4.6-4.7
billion years.

• Chemical evolution (1 billion yrs)
• Biological evolution (3.7 billion years)

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Question 1What is biological evolution by
natural selection, and how has it led to the
current diversity of organisms on earth?
Include the importance of variation within the
gene pool and mutation on microevolution and how
this relates to adaptations.
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Biological Evolution

• Biological Evolution
• Theory of Evolution
• Microevolution
• Mutations

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Natural Selection

• Variation exists for a trait
• Traits is heritable can be passed on to
  offspring
• Individuals w/ trait are better able to survive,
  reproduce spread the trait

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In a polluted environment
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Adaptations

• Natural selection works on individuals, Evolution
  occurs in populations!
• Adaptations
• Coevolution

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How microevolution occurs

• Genes mutate,
• Individuals are selected,
• and Populations evolve!

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Question 2How does the formation of new
species (speciation) and extinction of species
affect biodiversity? Explain the mechanism of
speciation and how this increases biodiversity.
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Macroevolution

• Speciation
• Increases biodiversity
• Extinction
• Decreases biodiversity
• Speciation Extinction Current Biodiversity

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Mechanism of Speciation

• Geographic Isolation
• 2 groups from same species become physically
  separated for long time period
• Reproductive Isolation
• Mutation natural selection act on separated
  populations
• Each group adapts to different environmental
  conditions
• Over time, leads to formation of 2 new species

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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. 4-7, p. 71
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Question 3Define ecological niche.
Distinguish between fundamental niche and
realized niche. List the factors that
determine the realized niche.
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Ecological Niches and Adaptation

• Ecological Niche (Occupation)
• Habitats (Address)

Fundamental Niche Realized Niche
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Question 4Distinguish between a specialist
and a generalist. Evaluate the conditions that
favor these two approaches.
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Generalist Species

• Broad Niches
• can live in many places
• can eat a variety of foods
• can tolerate a wide range of environmental
  conditions

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Cockroaches Natures Ultimate Survivors
Fig. 4-A, p. 69
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Specialist Species

• Occupy narrow niches
• (may only have 1 possible habitat)
• use few food types
• can only tolerate a narrow range of environmental
  conditions
• more prone to extinction when environment changes
• reduces competition
• allows for sharing of
• limited resources

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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
If resources are limited, natural selection
favors specialized species.
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Evolutionary Divergence of Honeycreepers
Fig. 4-6, p. 70
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Broad and Narrow Niches

• Generalist species
• Better able to survive rapidly changing
  environmental conditions
• Specialist species
• Benefit under constant environmental conditions
  (reduces competition)

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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
Fig. 4-4, p. 68
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Limits on Adaptation

• A populations ability to adapt is limited by
  its gene pool the speed with which it can
  reproduce
• Natural selection can only work on currently
  existing traits (beneficial adaptations are rare)
• Rapid reproducers are able to adapt much more
  quickly to changes in environment

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Question 5How is survival of the fittest
different from the idea of progress to
perfection?
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Evolution Misconceptions

• Survival of the fittest refers to reproductive
  success not strength!
• Evolution doesnt lead to genetic perfection,
  just works to select for best traits for the
  current environmental conditions.
• Organism best suited to environment, survives
  reproduces. Helpful traits are then passed on!

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Question 6How can genetic engineering affect
our ecosystems?
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Future of Evolution

• Genetic Engineering (gene splicing)
• Genetically Modified Organisms (GMOs)
• Ethical concerns

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Ecological Lesson

• Whenever we intervene in nature, we must pause
  ask What happens next?
• Evaluate possible unintended consequences of
  biotechnology.