How Traits Change Over Time

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How Traits Change Over Time
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How man has changed the traits of organisms
through Selective Breeding.
Cats which are small and not aggressive
and can play the piano?

• Dogs have been breed to be
  friendly

Gold-colored fish
Cows to produce more milk
Horses for speed
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If you wished to breed the prettiest guppies, how
would you do it?

• By only selecting the most colorful guppies
  and those with the longest tails, then breeding
  them generation after generation.

Guppy which has been selectively bred.
Wild guppies
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Dog breeders have been selectively breeding for
desirable traits for centuries.
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• Farmers have cultivated many popular
  vegetables from wild mustard,
• by artificially selecting for certain
  attributes.

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Selective Breeding

• nature provides variation, humans select
  variations of genes that are useful.
• Example - a farmer breeds only his best livestock

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• In essence, when humans selectively breed
  organisms for certain traits, they are selecting
  for certain genes.

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Charles Darwin (1809-1882) Sailed around the
world 1831-1836
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What did Darwins Travels reveal

• The diversity of living species was far greater
  than anyone had previously known!!

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How did tortoises and birds differ among the
islands of the Galapagos?

• Each island had its own type of tortoises and
  birds that were clearly different from other
  islands

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Galapagos Turtles
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Natural Selection

• The traits that help an organism survive in a
  particular environment are selected in natural
  selection

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He wondered if nature could select for certain
traits in the same way that man selects for
certain traits.

• Can you find the animals in the pictures below?

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• Observations
• Organisms produce many more offspring than can
  possibly survive in nature.
• Example- salmon typically lay 10,000 eggs
• Only a few will survive to adulthood and
  reproduce.

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Natural Selection

• Organisms vary and
• these variations (genes) are inherited by
  their
• offspring.

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• As resources become scarce, individuals must
  compete with each other to survive.
• Most organisms will not make it to adulthood
• Very few will breed and pass on their genes.

• Thousands of frog eggs are laid in clumps in a
  fresh water pond. Each clump is laid by one
  female. Few will survive to adulthood.

• Apple trees produce far more seeds than could
  possibly survive to become full grown trees.

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• Putting these facts together, Darwin
  discovered one of the most important ideas in
  biology--
• Natural Selection.

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• Offspring that do survive are best adapted to
  their environment
• They will pass their genes on to their offspring.
  
• Over time, populations of organisms become better
  adapted to their environment by this process of
  natural selection.

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For example, this species of insect is well
adapted (carries the right genes) to blend into
its environment.

• Do you see the walking stick insect?
• It received those genes from its parents, whose
  genes were successful enough to allow them to
  survive
• long enough to breed.

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Another example of natural selection at work
(click below to watch video clip)
Note Turn caption on while viewing
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Populations are constantly changing (The
Eternal Arms Race)

• Click on the video below to see an interesting
  case of an evolving arms race.

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Evolution means change over time.

• Cars have changed over time.
• Computers have changed over time.
• Video games have changed over time.

pong
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Primate Brain Capacity
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Vestigial Organs

• Traces of homologous organs in other species
• Organ that serves no useful function
• e.g. Appendix , wisdom teeth

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Natural Selection (in summary)

• 1. Organisms vary and these variations (genes)
  are inherited by their offspring.
• 2. Organisms produce more offspring than can
  possibly survive in nature.
• Those offspring that do survive are best adapted
  to their environment and will pass their genes on
  to their offspring.
• The result is, over time, populations of
  organisms become better adapted to their
  environment by this process of natural selection
  which increases their survival rate .