patterns in evolution: 17-2, 17-4
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Patterns in evolution: 17-2, 17-4. Endosymbiotic theory. Proposes that complex cells arose from smaller prokaryotes invading the larger eukaryotes. The cells that used oxygen to make ATP became mitochondria . Those that could photosynthesize became chloroplasts. - PowerPoint PPT PresentationTRANSCRIPT
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Patterns in evolution: 17-2, 17-4
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Endosymbiotic theory
• Proposes that complex cells arose from smaller prokaryotes invading the larger eukaryotes.
• The cells that used oxygen to make ATP became mitochondria.
• Those that could photosynthesize became chloroplasts.
• Evidence: both contain DNA different from nuclear DNA
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Sexual reproduction• Eukaryotic cells begin
to reproduce sexually.• The reshuffling of genes
greatly increases gene combinations and variation.
• This increased diversity and the speed of evolutionary change Tetrahymena thermophila
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Multicellularism
• Began a few million years after sexual reproduction.• Life became multicellular, experiencing great diversity
over time.• All developed in the sea.• Because of their soft bodies, few fossils remain.
hydra microfossils
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Big ideas of evolution: Extinction• 99% of all species once
living are now extinct• Most succumb to natural
selection• Mass extinctions have
several causes• Survivors experience a
burst of evolution, producing many new species
Diatrymas: 55-65 MYA stood 2 m tall
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Adaptiveradiation
• A single species or a small group of species evolve into many diverse forms, living in different niches.
Anole lizards of theCaribbean islands
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Convergent evolution
• Unrelated organisms can develop to look similar to others if they adapt to the same environment
• Ex: all species that swim in the water are streamlined, with paddles for locomotion
Shark, dolphin, and penguin representaquatic fish, mammal, and bird species
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Coevolution
• Organisms that are closely connected often evolve together
• Occurs often in flowers and their pollinators• Plants evolve poisons to ward off insects that eat
them, who become immune over time.
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Gradualism• The idea that
evolution happens at a slow, steady pace.
• Exception: horseshoe crabs have changed little from their fossils.
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Punctuated equilibrium
• Evolution can proceed at different rates
• There can be long periods of stability, then brief periods of more rapid change
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Developmental genes and body plans
• Master control genes guide the development of major body parts in animals
• Small changes in the expression of developmental genes can cause large changes in the adult
Antennapedia and wingless fruit flies
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Plant and animal mutations
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The human evolutionary tree