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Period 4

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Mass extinctions are times in Earth's history when abnormally large numbers of species die out simultaneously or within a limited time frame. A series of mass extinctions events have throughout the history of the Earth, some even more devastating than others. These are the 5 Major Extinctions!

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The third largest extinction which affected sea creatures. It had two peak times which were separated by hundreds of thousands of years. Sea creatures such as trilobites, brachiopods and graptolites numbers were drastically reduced. It is estimated 86% of sea creatures were gone.

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3/4 of all species on Earth died out in the Late Devonian mass extinction. Instead of one event, it may have been a series of extinctions. Life in the shallow seas was affected the worst, and reefs were damaged greatly. This is because ocean temperatures dropped drastically.

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96% of species died out in this extinction. All life on Earth today is descended from the 4% of species that survived. It is sometimes called "The Great Dying" because of how many species died off. It was most likely caused by a massive volcanic eruption.

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There were two or three phases of extinction whose combined effects created this extinction. Climate change, flood basalt eruptions and an asteroid impact may have all been the cause. Until this disaster, mammal-like creatures known as therapsids were actually the most numerous. This extinction set the dinosaurs on the path to domination.

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Also known as the KT extinction, is known for the end of the age of the dinosaurs. Theory's suggest that a asteroid or massive volcanic eruptions in India were the cause of this extinction. 76% of species were lost.

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Is a hypothesis that the development of the embryo of an different animals all resemble each other.

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Structures in some organisms that seem to have no use in one species, but are useful in other species

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Differences in similar molecules (usually proteins) . Used to explain patterns in evolution.

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Parts that are similar in structure but have different uses depending on the species

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Certain Genes disappear as individuals die or do not reproduce

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natural selection that come through preference by one sex for certain characteristics in individuals of the other sex.

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Charles Darwin created the idea that nature is the Survival of the Fittest or organism most adapted to the environment.
Darwin's Theory
1) mechanism by which evolution takes place is natural selection
2) diverse groups of animals evolve from one or a few common ancestors

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Divergent, Parallel, and Convergent Evolution

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Divergent, Parallel, and Convergent Evolution

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Migration: population moves over time
Gene Flow: transfer of genetic variation from one population to another

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Change in the structure of a gene resulting in a difference

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Variation: Genetic Mutations that occur
Inheritance:DNA & Sexual Selection determine the traits a species has
Selection:Selection & Genetic Drift determine what traits will die off
Time:Migration allows for movement and diversity