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Evolution: It's a Thing - Crash Course Biology #20

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This chapter's topics can be applied to the world around us because people use this stuff to date fossils and dead organisms. By doing this, we can learn what their ancestors were and around what time period they were alive. Along with this, scientists also find out how organisms and the Earth has evolved over time.

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1. When do fossils form in sedimentary rock? They usually form when small particles of sand, silt, clay, or lime muds settle to the bottom of a body of water.
2. What three things make a good index fossil? Three things are that it is easily recognized, occurs in only a few rock layers (lived for a short amount of time), and if they are widely distributed.
3. What are the three major divisions on a geologic time scale? The three major divisions are eons, eras, and periods.
4. What two things have to equal each other in order for a clade to survive? The birth rate of the new species and death rate have to equal each other.

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Fossils are the most important source of information about extinct species

Lower layers are generally older than upper layers

Carbon 14 has a short half-life

An example of a index fossil would be trilobites

Rapid evolution may occur after a small population becomes isolated, or migrates to a new environment

In coevolution, relationships become so specific that neither can survive without the
other

During adaptive radiation, a small group or species evolves over a short period of time, into several different forms that live in different ways.

With convergent evolution, organisms face similar natural selection pressures

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Fossil- Preserved remains or traces of ancient life
Paleontologist- Researchers who study fossils to learn about ancient life
Relative Dating- places rock layers and their fossils into a temporal sequence
Index Fossils- Distinctive fossils used to establish and compare the relative ages of rock layers and their fossils.
Half-Life- The time required for half of the radioactive atoms in a sample to decay
Plate tectonics- theory that explains how solid continental plates move slowly above Earth’s molten core “continental drift”
Background Extinction- some species become extinct because of the slow but steady process of natural selection
Mass Extinction- affects many species over a relatively short period of time
Gradualism- involves a slow, steady change in a particular line of descent
Punctuated Equilibrium-equilibrium that is interrupted by brief periods of more rapid change