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

extinction is forever
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.
mass extinction
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…..
factors that contribute to extinction
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.

On a clean sheet of paper (to be kept with notes). Set up the entire page as shown below.

Natural factors

Man-Made factors

natural factors
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.
natural factors of extinction
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.
natural factors of extinction1
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.
natural factors of extinction2
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.
natural factors of extinction3
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.
chalk talk
Chalk Talk
  • Review of natural factors of extinction.
man made factors of extinction
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.
man made factors of extinction1
Man-made Factors of Extinction
  • Cutting of rainforests
    • Destroys habitats and food sources of many different animals.
    • Trees are logged for human needs.
man made factors of extinction2
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.
man made factors of extinction3
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 1920’s from hunting.
man made factors of extinction4
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.
chalk talk1
Chalk Talk
  • Review of man-made factors of extinction.


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?