1. Compare and Contrast How is mass extinction different from background extinction

2. Relate Cause and Effect Why would evolution speed up when a small group of organisms migrates to a new environment

3. Relate Cause and Effect Why does adaptive radiation sometimes result in convergent evolution

4. Infer What role does the environment play in convergent evolution

CH 19 HISTORY OF LIFE19.2 Patterns and Processes of Evolution

The fossil record shows a parade of organisms that evolved, survived for a time, and then disappeared

More than 99 percent of all species that have lived on Earth are extinct

How have so many different groups evolved Why are so many now extinct.

Macroevolutionary Patterns

Transformations in anatomy, phylogeny, ecology, and behavior that occur in clades

If more speciation than extinction occurs the clade survives

If more extinction than speciation occurs the clade dies out.

Macroevolution and Cladistics

Fossils are also classified into clades.

Background extinction Slow but steady process of natural selection

Mass extinction Affects many species over a relatively short period of

time Entire ecosystems vanish and whole food webs

collapse.

After mass extinction Survivors produce new species to fill empty niches Biodiversity recovers Takes between 5 and 10 million years.

Gradualism

Slow, steady change in a particular line of descent.

Punctuated Equilibrium

Long lengths of stability that is interrupted by brief periods of more rapid change.

Rapid Evolution

Occurs more often in a small population Occurs more often when migrating to new area Occurs more often after a mass extinction.

Adaptive Radiation

Single species or a small group of species evolves over a relatively short time into several different forms that live in different ways

Occurs when species migrate to a new environment or when extinction clears an environment of a large number of inhabitants.

Convergent Evolution

Different groups develop the same adaptations due to living in similar environments These all eat ants and termites.

Coevolution

Two species evolve in response to changes in each other over time Flowers and pollinators.

1 What is plotted on the y-axis2 Which mass extinction killed of the highest percent

of genera3 Describe the overall pattern of extinction 4 What evidence is the graph probably based on