1. RISE AND FALL
UNIT 5 EVOLUTION

2. Rise and Fall
The rise and fall of major groups of organisms have shaped the history of life
Rise and fall rates are often related to speciation and extinction rates
There can be a rise in a new group of species when the amount of births are greater than those lost to extinction

3. Rise and Fall Factors
There are many factors that can affect the rise and fall of organisms…
Plate Tectonics
Mass Extinctions
Adaptive Radiations

4. Plate Tectonics
Plate Tectonics – the theory that Earth’s continents are part of big plates on Earth’s crust that float on the upper part of the mantle
The outer layer of these plates is known as the “lithosphere”
The movement of these plates can result in earthquakes and volcanoes
Continental Drift – when movements in the mantle cause tectonic plates to move over time
Mountains and islands are located at plate boundaries

5. Patterns of Continental Drift
Plates can move away from each other
Example – North American and Eurasian plate
Plates can slide past each other
Forming regions where earthquakes are common
Example – The San Andreas Fault in California
Plates can collide into each other
Can cause the formation of mountains along plate boundaries
Example – The Indian plate colliding into the Eurasian plate (forming the Himalayan Mountains)

6. Consequences of Continental Draft
Can alter the habitat in which an organism lives in
Can alter the physical environment and climate
This can result in extinctions as well as new opportunities
Can promote allopatric speciation
When continents break apart, connected regions start to become isolated
Can explain the geographic distribution of extinct and present-day organisms

7. Mass Extinctions
Fossils show how majority of species have become extinct
A species can become extinct for many reasons
Destroyed Habitat
Change in environment
Temperature change
The origin of one species can be the death of another species
Mass Extinction – when large numbers of species become extinct worldwide

8. Mass Extinction Events
In the past 500 million years, there have been 5 major mass extinctions
There are two mass extinctions that have caused the most change in history
Permian Mass Extinction
Cretaceous Mass Extinction

9. Permian Mass Extinction
Severely affected both aquatic and terrestrial life
Affected 96% of marine animal species
8 out of 27 land insects were removed
Occurred during extreme episodes of volcanic eruptions
Volcanic eruptions produced enough carbon dioxide to warm the global climate and cause ocean acidification

10. Cretaceous Mass Extinction
Occurred more than 65 million years ago
Removed more than 50% of all marine species
Known for causing the extinction of “dinosaurs”
Researchers believe this extinction was caused because of a thin piece of clay made of “Iridium”
Iridium is very rare on Earth, but very common in objects that fly towards Earth (meteorites, large comets, clouds, asteroids)
Researchers believe that this “clay” is debris of a large comet or asteroid that collided into the Earth, causing this mass extinction

11. Consequences of Mass Extinctions
Can cause an ecological community to disappear
Takes 5-10 million years to recover the diversity of life
Took 100 million years for marine families to recover after Permian mass extinction
Can affect the organisms living in ecological communities
Mass extinctions can result in adaptive radiation

12. Adaptive Radiation
Adaptive Radiation – a period of evolutionary change in which organisms form new species whose adaptations allow them to fill different ecological roles
Occurred on a large scale after the 5 mass extinctions
Survivors of the mass extinction would adapt to the remaining ecological niches
Common among organisms that face little competition from other species

13. Adaptive Radiations
Worldwide Adaptive Radiation – adaptive radiations that occur on broad geographic areas around the world
Example – the extinction of dinosaurs resulted in the expansion of mammals (both in diversity and size) to fill ecological roles occupied by dinosaurs
Regional Adaptive Radiations – adaptive radiations that occur over limited geographic areas
Occurs when organisms move to a location with little competition