8-2.7 Summarize the factors, both natural and man-made, that can contribute to the extinction of a species.

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8-2.7 Summarize the factors, both natural and
man-made, that can contribute to the extinction
of a species.
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Extinctionis forever!!

• When is a species considered extinct?

• If no members of that species are still alive.
• Most organisms that have ever lived on Earth are
  now extinct.

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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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Factors that contribute to extinction

• Natural factors
• Have caused extinctions throughout history.
• Man-made factors
• Have caused extinction in more recent times.
• Brainstorm potential examples of each type.

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On a clean sheet of paper (to be kept with
notes). Set up the entire page as shown below.
Natural factors
Man-Made factors
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Natural Factors

• Organisms could not survive changes due to
  various natural events.
• Natural extinctions have occurred throughout
  geologic history.
• Not all extinctions have a negative impact.
• They clear the way for new kinds of life.

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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.

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Natural Factors of Extinction

• 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.

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Natural Factors of Extinction

• 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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Chalk Talk

• Review of natural factors of extinction.

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Man-made Factors of Extinction

• Many plants and animals are likely to become
  extinct in the near future.
• Humans remove survival needs of many organisms.
• We are also threatening our own biological
  resources.
• Man-made factors are damaging the Earth.

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Man-made Factors of Extinction

• Cutting of rainforests
• Destroys habitats and food sources of many
  different animals.
• Trees are logged for human needs.

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Man-made Factors of Extinction

• Removing of Natural Habitats
• Cutting down rainforests, agricultural activities
  and houses for humans.
• Animals have no where to live, breed and hunt.

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Man-made Factors of Extinction

• Over-harvesting or Hunting
• Many animals have been hunted to extinction by
  humans.
• Example, the Carolina Parakeet.
• Lived in the southeastern United States.
• Appeared 5 million years ago and became extinct
  in the early 1920s from hunting.

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Man-made Factors of Extinction

• Pollution
• Industrial activities have polluted rivers and
  oceans with toxic chemicals.
• Introduction of foreign species
• Sailors would bring domesticated animals to
  remote areas. (dogs, rats)
• These animals would kill native animals and
  compete for food sources.

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Chalk Talk

• Review of man-made factors of extinction.

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KEY QUESTIONS
1. What is extinction?
2. What are some man-made factors that
contribute to the extinction of plants and
animals?
3. What are some natural phenomena that
contributes to the extinction of plants and
animals?
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