Natural Selection Notes

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Published on March 11, 2014

Author: charlietheteacher

Source: slideshare.net

Natural Selection Notes

History of Darwin  1831 ___? years ago, Charles Darwin set sail on the HMS Beagle on a 5 year voyage around the world. He served as a naturalist (scientist who studies nature), and kept detailed notes of his findings. On the Galapagos Islands, Darwin noticed that the finches on one island were similar, but not identical to the finches on another island.

History of Darwin  The large ground finch has a heavy, strong beak for cracking large seeds. The cactus finch has a tough beak that is good for eating cactus and nectar. The warbler finch has a small, pointed beak - good for poking into cracks to get small insects.

History of Darwin Why are the finches different on each island? Start with the parent generation of finches. The parents have several baby finches. Some of them have larger beaks, some of them have smaller beaks, just like the pea plants (some are tall, some are short.) Each island has a different food supply. Island #1: only has big, hard seeds. Which babies will do the best on island #1?

History of Darwin Island #2 has no seeds, but has lots of insects who like to hide in cracks in rocks and logs. Which babies do you think would do best on island #2? On island #1, the small beak babies would die, leaving only big-beaked finches. When those big-beaked finches have babies, what kind of babies do you think they will have?

History of Darwin On island #2, the small-beaked babies would thrive, and the big-beaked finches would die. What kind of beaks will the the babies of the small-beaked finches have? On each island, we see a change in the population of finches because of the difference in available food. What happens to the “big-beak” genes on island #2 with the ants?

History of Darwin  What happens to the “small-beak” genes on island #1 where the only food are the large seeds?  On both islands: Nature has selected the best beak.  “Natural Selection:” a process where animals (or plants) with favorable traits survive, and animals without those traits die.  “Survival of the fittest:” those who are the strongest, or best equipped for the environment survive. They pass their genes down to their offspring.

The Dog Example  Before natural selection takes place, dogs have lots of genetic variety. Some of them are big, some are small. Some are faster, some are better diggers, etc…

The Dog Example  Before natural selection takes place, dogs have lots of genetic variety. Some of them are big, some are small. Some are faster, some are better diggers, etc… Some of them are born with thick fur, some are born with short, thin hair.

The Dog Example  Before natural selection takes place, dogs have lots of genetic variety. Some of them are big, some are small. Some are faster, some are better diggers, etc… Some of them are born with thick fur, some are born with short, thin hair. The population of dogs move to a place where it is much colder.

The Dog Example  Before natural selection takes place, dogs have lots of genetic variety. Some of them are big, some are small. Some are faster, some are better diggers, etc… Some of them are born with thick fur, some are born with short, thin hair. The population of dogs moves to a place where it is much colder. What will happen to the dogs with short, thin hair?

The Dog Example  Before natural selection takes place, dogs have lots of genetic variety. Some of them are big, some are small. Some are faster, some are better diggers, etc… Some of them are born with thick fur, some are born with short, thin hair. The population of dogs moves to a place where it is much colder. What will happen to the dogs with short, thin hair? Which dogs are “naturally selected” to carry on their genes to their puppies?

The Dog Example  Before natural selection takes place, dogs have lots of genetic variety. Some of them are big, some are small. Some are faster, some are better diggers, etc… Some of them are born with thick fur, some are born with short, thin hair. The population of dogs moves to a place where it is much colder. What will happen to the dogs with short, thin hair? Which dogs are “naturally selected” to carry on their genes to their puppies? Which gene is passed on, and which gene is lost?

The Dog Example Note: They are now adapted to their environment .

The Dog Example This has occurred through natural selection.

The Dog Example There have been no new genes added. Genes have been lost.

The Dog Example The dogs are less able to adapt to future evironmental changes. If the climate were to become hot, there is no genetic information for short hair, so the dogs would probably overheat.

The Dog Example So we see that natural selection is not an information- gaining process, but an information- losing process. Natural selection is different than large-scale evolution.

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