Extinction= couldn

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Extinction couldnt adapt to environmental
changesnatural selection and variation produce
adaptations, new sets of adaptations can lead to
a new spcecies
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Speciation
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Speciation

• Species group of organisms that breed with one
  another and produce fertile offspring in nature
  (share a common gene pool)
• Speciation formation of new species (small
  changes in adaptations/variations can lead to
  change in species over time

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Speciation can happen in two modes

• Modes of speciation
• Sympatric new species develop in same geographic
  region
• Sym same
• Allopatric new species develop in separate
  regions
• allo other

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Isolation isnt always bad

• As new species evolve, populations become
  reproductively isolated from each other When 2
  populations can not breed and produce fertile
  offspring, resulting in separate gene pools
• Behavioral isolation Capable of breeding, but
  have different courtship rituals or behaviors
  (sympatric or allopatric)
• Geographic isolation Separate by geographic
  barriers (allopatric)
• Temporal isolation Reproduce at different times
  (sympatric or allopatric)

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Geographic Isolation (allopatric)

• Two populations are separated by geographic
  barriers. Over time different pressures result in
  distinct species
• Rivers, mountains, bodies of water, glaciers,
  deserts

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Behavioral Isolation

• Differences in the behavior of two populations
  prevent mating
• Because there is no gene exchange between
  populations, evolution occurs
• Behaviors
• Mating rituals
• Mate preference
• Mate calling

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Behavioral Isolation (sympatric)
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Temporal Isolation (sympatric)

• Two or more populations are separated by the time
  of year/day that reproduction occurs
• Nocturnal vs Diurnal mating
• Seasonal mating differences

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Speciation can happen at two different rates

• Gradualism Evolution occurs slowly, gradually
  and continuously
• Punctuated Equilibrium Species remain unchanged
  for long periods of time. During certain events,
  species undergo rapid evolution.
• After mass extinctions
• Both of the processes above have likely happened

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Trilobytes Punctuated Equilibrium
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Speciation of Darwins Finches

• Speciation in the Galapagos finches occurred by
• Founding a new population A small population of
  finches migrates to a different island
• Geographic isolation Finches dont usually fly
  over open water, so stayed on own island
  (separate gene pool)
• Changes in the new populations gene pool
  Adapted to new environment (directional
  selection) to be more fit
• Reproductive isolation Differences in phenotypes
  and mating rituals may turn different finches off
  to one another
• Ecological competition Similar finches compete,
  so individuals that are most different from each
  other have the highest fitness, because less
  competition.
• Continued Evolution Process repeats and over
  many generations, it produced the 13 different
  finch species

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What is extinction?

• Extinctions occur when the last individual of a
  species dies out.
• Functional Extinctions occur when individuals
  remain but the odds of sustainable reproduction
  are low
• i.e. the species is effectively extinct even
  though individuals remain.

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When do extinctions occur?

• Extinctions occur when the environment of a
  species changes faster than the species can
  adapt.
• In other words, a species adaptations are no
  longer sufficient in allowing that species to
  acquire and compete for resources.
• Extinctions can be local, widespread, or global.
• For example, the timber wolf was until recently
  extinct in Wisconsin but not in Minnesota
• Wild elk and woodland caribou are now extinct in
  Wisconsin but may be found on game farms.

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Extinctions are natural.

• Extinctions occur naturally.
• Nearly all of the species that have existed on
  earth have gone extinct.
• There have been 5 major mass extinctions in
  geological history.
• Recovery from these events took millions of
  years.

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Mass Extinction Diagram
Source http//www.uwec.edu/jolhm/EH4/Extinction/E
xtinction.ppt
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Mass Extinction

• Sudden extinctions (confined to a few million
  years or less) which sweep away a large variety
  of living creatures.
• Geologic time is marked by these events.
• Paleozoic era ended theoretically because of a
  major climate shift.
• Mesozoic era ended theoretically because an
  object from space struck Earth.
• Cenozoic era continues today..

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Natural Factors of Extinction

• Volcanic Activity
• Huge lava flows that produced enormous amounts of
  ash.
• The ash in the air altered the global climate and
  ocean chemistry.
• Global Warming
• Animals could not survive the extreme change in
  temperatures and climate.
• Global Cooling (Ice Ages)
• Cooling events caused Glaciation events
• Ocean water would freeze and therefore lower the
  sea level.

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Natural Factors of Extinction

• Oxygen Depletion
• As water cools, it causes dramatic shifts in
  limiting factors such as oxygen.
• As oxygen levels in sea water were depleted, many
  species died out.
• Asteroid or comet impact
• The impact from a huge asteroid would have sent
  tidal waves across the earth and caused many
  fires.
• Clouds of dust and ash would block the sunlight.
• The planet would cool and plants and animals
  would die due to lack of sunlight.
• The impact that killed the Dinosaurs was thought
  to have occurred in somewhere near Mexico.

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Human Causes of Extinctions

• Major current causes of extinctions include
• Habitat Loss fragmentation, degradation, and
  outright destruction of ecosystems that support
  native ecosystems (leading cause).
• Invasive Species the introduction or
  overpopulation of species that over-consume
  natural resources and are uncontrolled by
  predators (second leading cause).
• Over-harvesting the removal of species at rates
  that exceed reproduction
• Pollution introduction of harmful agents that
  reduce the effectiveness of a species adaptations