Evolution

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Evolution

• General Science
• Chapter 9

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Chapter Learning Objectives

• Identify two important processes of evolutionary
  change
• Explain the difference between natural selection
  and mutation
• Name three things that scientists study to learn
  about evolution

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Words to Know

• Evolution changes in a species over time
• Evolve change over time
• Extinct no longer living on Earth referring to
  a species that has died out
• Fossils Remains of organisms that lived long ago

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• Natural Selection the way that those organisms
  best suited to their environment survive and pass
  their helpful traits along to offspring
• Paleontology scientific study of fossils
• Theory group of ideas or principals that
  explain why something happens

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Evolution of Life

• Life started on Earth about 4 billion years ago
• Protists
• All plants and animals evolved from these simple
  organisms
• Even humans who have been around for 5 million
  years
• Earth is 4.6 billion years old
• Evolution is the change in a species over time

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I. Evolution is Change Over Time

• Species change over time
• Woolly Mammoth no longer exists
• Mammoth changed into modern day elephant
• Dinosaurs are extinct
• Many scientists believe that birds evolved from
  dinosaurs
• Evolution takes time
• Thousands or millions of years

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• Extinct means to no longer live on Earth
• Wooly mammoth was discovered in Siberia frozen in
  a block of ice totally preserved for 25,000 years
• Bones and teeth of dinosaurs have been found all
  over the world
• Extinct insects found in hardened tree sap
• This evidence helps to construct pass life on
  Earth and evolution

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• Fossils are the remains of organisms from the
  past
• Fossils show that life on Earth was very
  different than what we see today
• Fossils also show todays organism evolved from
  those species

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• Paleontology is the scientific study of fossils
• They are like detectives putting together a story
• Fossils allow scientists to read the story
• For example the first horses were the size of
  dogs
• Had four toes instead of one
• Shorter teeth

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Cutting Edge

• Most scientists believe dinosaurs disappeared
  from Earth quickly
• Most commonly thought reason is because of a
  meteorite that hit the Earth
• Caused a great cloud of dust
• This blocked the Sun
• Caused sudden change of Earths Weather
• 1991 found a crater 112 miles wide in Mexico

The Chicxulub crater
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II. DNA and Evolution

• DNA also helps in the theory of evolution
• DNA holds the life code
• Allowed to find that pigs and mice of some of
  same genes
• Human DNA is 98 the same as chimpanzees
• Means that at some point in history we had the
  same ancestor

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• Scientists also study structures of living
  animals for clues
• Lions foreleg, a bats wing, and a dolphins
  flipper are very similar
• Must have come from same ancestor
• Their bone structure is also similar to our arms

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III. Charles Darwin

• 1831 he sailed around the world at age 22
• Recorded all the different plants and animals he
  found
• His findings led to his theory of evolution
• His theory is the basis of the modern study of
  evolution

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IV. Natural Selection

• Remember that offspring are a combination of both
  parents
• They get half their genes from their mom and half
  from their dad
• Each offspring have a new combination of genes
• Some gene combinations lead to survival and
  reproduction
• Some gene combinations lead to death of an
  organism

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• There are four main ideas to explain natural
  selection
• Most organisms have more offspring than can
  survive
• Insects lay thousands of eggs, but only a few
  will become full grown insects
• Offspring compete for food and space
• Many or most offspring do not survive and
  reproduce
• There is only so much food
• There is only so much living space
• Organisms that survive have traits best suited to
  the environment
• Organisms that can get food and space and
  protection from enemy will survive
• Natural selection passes along helpful traits to
  offspring

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Science Practice

• How do you think each organism listed may have
  adapted to its environment?
• Polar bears living in arctic region
• Cacti live in deserts
• Rats live in cities
• Ferns live in rain forests

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V. Mutations Causes Evolutionary Changes

• Mutations can cause a species to change
• This is different than natural selection
• Natural selection occurs through new combinations
  of existing genes
• Mutation occurs when a WHOLE NEW gene is formed
• A kind of genetic mistake

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Barbara McClintock

• Studied corn to learn about genes
• Discovered that genes were not fixed on a
  chromosome and they could move around
• Helped to explain how new species arise
• Explains how some cells like cancer go crazy and
  spread
• At 81 she won the Nobel Prize