What is Evolution?

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What is Evolution?
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EVOLUTION the process of change over time

• Evolution is the idea that new species develop
  from earlier species by accumulated changes. This
  is also referred to as descent with
  modification.

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Evolution is NOT

• It is NOT a fact...it's a theory
• a well supported testable explanation of
  something that occurred in the natural world.

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Lamarck's Hypothesis Inheritance of Acquired
Characteristics

• 1. Acquired Characteristics Through use and/or
  non-use, those features needed for survival are
  developed in each individual.
• 2. Inheritance Those characteristics
  developed (acquired) by individuals are
• passed on to their offspring, who can
  continue that development.
• 3. New Species Eventually, over many
  generations, enough differences have developed
  that we can say we have a new species.

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Darwin's Hypothesis Natural Selection

• Overproduction There are more offspring produced
  than will survive and reproduce
• 2. Survival of the fittest (not necessarily the
  strongest) Those with more adaptive traits tend
  to survive longer and/or produce the most
  offspring these are the naturally selected.

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Natural selection is based on 4 facts

• 1.Organisms produce more offspring
  than can survive.
• 2.There is variation among offspring.
• 3.There are limited resources
• (not enough food, water, space,
• etc. for everyone).
• 4.The organisms best fit to their environment
  will survive and the others will not.

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Organisms produce more offspring than can survive.

• Example A frog can lay 200 eggs, yet not all
  eggs will survive to become
  adult frogs.

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Results of Evolution -- Speciation!!

• Speciation is the process that creates new
  species!
• A species is a group of organisms that can
  naturally interbreed and produce fertile
  offspring.
• The Liger--the offspring of a tiger and a lion.
• Tigers and lions are still considered separate
  species, because although they can produce
• offspring, the offspring
• is not fertile.

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Evidence of Evolution -- Fossils!!

• Fossils are preserved remnants or impressions
  left by an organism that lived in the past.
• Usually, the deeper down
  the fossil is, the older it is.

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Evidence of Evolution -- Embryology!

• It is believed that all vertebrates evolved from
  a common ancestor. The genetic
  information that guides their
  development is nearly the same.
• That's why scientists can learn about human
  development by studying other organisms--including
  zebrafish.

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Evidence of Evolution --Anatomical/Physiological
Similarities

• Notice how there are similar bones and similar
  structures in humans, birds and whales!
• Can you tell which is the bird and
  which is the whale?

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Vestigial Organsorgan that serves no useful
functionover generations, they reduce in size
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Adaptations!Inherited characteristic that
increase an organisms chance of survival

• Why are most animals in the artic white?
• So they blend in with the snow and avoid being
  seen!
• Why do sharks have such sharp
• teeth?
• It allows them to catch their prey!
• Why do elephants have such big ears?
• To let heat escape their bodies so they can
• stay cool!

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Extinction!

• Extinction occurs when there
  are no members of a species
  left alive.

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Want a ticket?

• What do these pictures represent?

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• What is a vestigial structure?
• How do vestigial structures support the theory of
  evolution?
• Give an example of a vestigial structure.

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• How do fossils serve as evidence of evolution?
• What can we learn about evolution by looking at
  amino acid sequences (DNA)?

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Ticket Out

• Copy the table below and fill in.

Definition Examples
Homologous structures
Analogous structures
Vestigial structures