Unit 5 : Evolution Chapter 15 - Darwin’s Theory of Evolution.
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Unit 5 : Evolution
Chapter 15 - Darwin’s Theory of Evolution
Charles Darwin
• English
• Born 1809
• HMS Beagle - 1831
• Naturalist
• Very Religious
Darwin’s Observations
• Animals and plants were well adapted
• Diverse reproductive strategies
• Puzzled by location of animals– Rabbits in Argentina, not in Australia
• Fossils– similar, dissimilar, Extinction
The Beagle’s Journey
Pinta IslandIntermediate shell
Pinta
Isabela IslandDome-shaped shell
Hood IslandSaddle-backed shellHoodFloreana
Santa Fe
Santa Cruz
James
Marchena
Fernandina
Isabela
Tower
Giant Tortoises of the Galápagos Islands
Section 15-1
The Galapagos Islands
DesertLarge rainfall
Intermediate Shell
Domed Shell
Saddle backed Shell
Climate variation throughout
Tortoises of the Galapagos
Saddleback• long neck, curved
shell, found on Hood Island, desert like
Dome Shaped• shorter neck, domed
shell, lush vegetation, covers the ground, Isabela island
Many different varieties in different locations
Finches
Journey Home
• Animals and plants varied a great deal from island to island
• Did the organisms on different islands belong to the same species?
• Was the ancestor from S. America?
Influences on Darwin
• Fossil Record
James Hutton - 1785
• Earth - millions of years old, not 5700
Charles Lyell - 1833• Past events are explained by the processes
that scientists can see today.
Jean-Baptiste Lamarck - 1809
• Proposes 1st theory of evolution– use vs. disuse– acquired traits are passed on– leads to changes in species
Figure 15–7 Lamarck’s Theory of EvolutionSection 15-2
Thomas Malthus - 1798
• Economist - unchecked population growth leads to a lack of space and food
Frog Eggs - What detemines survival?
Artificial Selection
• Farmers and breeders– Selective Breeding
Darwin’s View - On the Origin of the Species - 1859
Darwin: Reluctant Rebel
Natural Variation passed on to future generations
Struggle for Existence
Fitness
• Ability to survive and reproduce successfully
Adaptations - physical characteristics or behaviors
Camouflage
Survival of the Fittest - (Natural Selection)
• Individuals that are best suited for their environment have high levels of fitness and therefore survive and reproduce
Descent with Modification
• Species change overtime
• All organisms share a common ancestor (common descent)
Darwin’s Evidence of Evolution
• Fossil Record
• Distribution of Living Species
• Homologous Body Structures
• Embryo Development
Fossil Record
• Evidence of change over time
• Age of the Earth
Distribution of Living Species - I
Unrelated organisms look similar because of common ecological conditions - Convergent Evolution
Beaver
NORTH AMERICA
Muskrat
Capybara SOUTH AMERICA
Coypu
Figure 15–14 Geographic Distribution of Living Species
Beaver
Muskrat
Beaver andMuskrat
Coypu
Capybara
Coypu andCapybara
Distribution of Living Species - II
Finches - all share a common mainland ancestor, differences are due to the environment
Homologous Structures - same basic design, modifications
Vestigial Organs - traces of homologous structures
Embryo Development
Embryonic Cells develop in the same group and similar patterns
Reviewing Darwin’s Theory• Variation
• Large amounts of offspring
• Competition
• Struggle for Existence
• Survival of the Fittest
• Descent with Modification via Natural Selection
• Common Descent
How does evolution really work?
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