Chapter 5 Changes Over Time

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Chapter 5Changes Over Time

• Mrs. Kerstetter
• General Science 7

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Darwins Voyage

• 1831 HMS Beagle sets sail from England
• 22 year old naturalist
• Charles Darwin
• Observed plants and animals he never saw before
• His observations led to.
• THE THEORY OF EVOLUTION BY NATURAL SELECTION

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Darwins Voyage

• Darwin saw great diversity
• great variety of species
• Today we know that there are over 1.7 million
  species of organisms living on Earth
• Species
• A group of similar organisms that can mate and
  produce fertile offspring

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Darwins Voyage

• He found fossils and bones of extinct animals
• In 1835, the Beagle reached the Galapagos Islands
  in the Pacific Ocean
• Group of islands
• Huge diversity between islands

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Darwins Voyage

• Similarities
• With hawks, mockingbirds, finches on mainland
• Differences
• Cormorants on mainland could fly, on island they
  could not fly
• Iguanas
• Tortoises

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Darwins Voyage

• Adaptations (helps organism survive and
  reproduce)
• Noticeable differences from one island to another
• Finches
• Beaks suited to lifestyle
• Sharp, needle-like beak insect eater
• Strong, wide beak ate seeds

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Darwins Voyage

• Evolution
• -Darwin thought species gradually changed over
  many generations and adapted to new conditions
• -called EVOLUTION
• Theory of Evolution
• -can be disproven
• -not a scientific law

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Darwins Voyage

• Natural Selection
• Darwin and Alfred Russel Wallace
• -proposed explanation
• Darwin wrote The Origin of Species
• -explained evolution occurs by means of natural
  selection

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Darwins Voyage

• Natural Selection
• -individuals are better adapted to their
  environment
• more likely to survive and reproduce
• Factors affecting natural selection
• 1. Overproduction
• 2. Competition
• 3. Variations

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Darwins Voyage

• Overproduction
• -more offspring than can possibly survive
• i.e. turtles
• Competition
• -indirect
• -for food and other resources

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Darwins Voyage

• Variations
• -differences between individuals in the same
  species
• Selection
• -helpful traits accumulate, while unfavorable
  ones disappear

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Darwins Voyage

• Role of genes in evolution
• -without variations, all members of species
  would have same traits
• -variations result from mutations in genes or
  shuffling of alleles during meiosis
• Pepperd Moths Natural Selection

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Darwins Voyage

• How do new species form?
• -one of main reasons geological isolation
• -river, volcano, mountain range, ocean waves
• New species form when groups of individuals are
  separate from the rest of the species long enough
  to evolve different traits

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Darwins Voyage

• Continental Drift
• -world-wide scale
• Pangaea
• -one huge continent
• -separated to form our current continents