Ch. 23.2 Broad Pattern of Evolution

Question 1

Theory of Plate Tectonics

Answer 1

States that the continents are art of great plates of Earth’s crust that essentially float on the hot, underlying portion of the mantle. Movements in the mantle cause the plates to move over time in a process call continental drift.

Question 2

Pangea

Answer 2

“Super Continent” plate movements brought previously separated landmasses together. Pangea’s interior was cold and dry, and greatly altered the physical environment and climate, which drove some species to extinction and provided new opportunities for groups of organisms that survived the crisis.

Question 3

Consequences of Continental Drift

Answer 3

• Alters habitats in which organisms live (Pangea); climate change, and physical environment changes.
• Promotes allopatric speciation on a grand scale
• Mass extinctions

Question 4

Mass Extinctions

Answer 4

Occurs when disruptive changes to the global environment have cause the rate of extinction to increase dramatically, large numbers of species become extinct worldwide.

5 mass extinctions are documented in the fossil record over the past 500 million years. In each mass extinction, 50% or more of marine species became extinct.

Question 5

Permian Mass Extinction

Answer 5

Occurred during the most extreme episode of volcanism in the past 500 million years. 1.6 million km^2 in Siberia was covered with lava hundreds of meters thick. The eruptions are thought to have produced enough carbon dioxide to warm the global climate causing ocean acidification thereby reducing the availability of calcium carbonate which is required for reef building corals and many shell building species. Added nutrients such as phosphorus to marine ecosystems would have stimulated the growth of microorganisms. Upon their deaths, bacterial decomposers would feed on them which requires the use of oxygen and thus reducing the amount of oxygen. This would give rise to anaerobic bacteria that emit a poisonous metabolic by product, hydrogen sulfide gas.

Question 6

Cretaceous Mass Extinction

Answer 6

66 million years ago, marked the boundary between the Mesozoic and Cenozoic eras. This event extinguished more than half of all marine species and eliminated many families of terrestrial plant and animals, including all dinosaurs, except birds which are members of the same group. Iridium is an element that is very rare on Earth but common in many of the meteorites and other extraterrestrial object that occasionally fall on Earth. Researchers propose that this clay is fallout from a huge cloud of debris that billowed into the atmosphere when an asteroid collided with Earth. This cloud could have blocked sunlight and severely disturbed the global climate for several months.

Question 7

Consequences of Mass Extinction

Answer 7

• Eliminates a large number of species, reducing a thriving and complex ecological community in pale to its former self. Once an evolutionary lineage disappears, it cannot reappear.
• Takes millions of years for life on Earth to recover
• Changes the types of animals that reside in different ecological communities, giving rise to a number of predators that compete for food, and put prey animals at greater risk
• Can curtail lineages with novel abilities
• Mass extinction can pave the way for adaptive radiations in which new groups or organisms proliferate

Question 8

Adaptive Radiations

Answer 8

Periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological niches, or roles, in their communities.

• Adapting to vacant ecological niches
• Adaptive radiations have also occurred in groups of organisms that possessed major evolutionary innovations, such as seeds or armored body coverings, or that colonized regions in which they faced little competition from other species. ( rise of photosynthetic prokaryotes, the evolution of large predators in the early Cambrian, and the radiations following the colonization of land plants, insects, and tetrapods.)