Paleobiology and MacroevolutionCh. 22.1-22.5

Geological Timeline

PrecambrianPaleozoic MesozoicCenozoic

Mapping Out The Past• Several Methods:1) Carbon-14 Dating

(living material)2) K-40 Dating (Certain

soil types)3) Relative dating

through strata layers4) Trace fossils foot

tracks show migration; poop shows available food

5) Casts, molds, and petrified fossils

The Ever Changing Earth• Gradual Factors:1) Continental Drift tectonic plates

constantly shift and collide2) Climate change heating and

cooling cycles influenced by atmosphere changes/sun spots

3) Glaciers and Sea Levels change geography and marine habitats

• Sudden Factors:1) Earthquakes caused by shifts in

plates2) Volcanos change geography and

lower global temps.3) Celestial Impacts Meteors and

asteroids; change geography and lower global temps.

Global Distribution• Shifting continents explain distribution

patterns of similar species• Continuous Distribution live any

where there is a suitable environment; seagulls live along all northern hemisphere coastlines

• Disjunct Distribution similar species spread all over the Earth• Dispersal movement from original

environment• Vicariance fragmentation by

geographic factors• Southern Beech trees

• only found on southern continents• Appear on Gondwana (early super

continent) and spread before it fell apart too

Biogeographical Realms• Formation of continents allowed for

the creation of biogeographical realms where in biotas formed (all organism in a region)

• Endemic species found only in one specific realm– Mammals of Australia mostly endemic

marsupials– Unique because most other continents

were connected by land bridges • Sometimes species on different

continents with no common ancestor have identical phenotypes. How?– Convergent evolution species in similar

environments evolve the same adaptations

– Cactus morphology is the same everywhere

Biodiversity • The amount of variation for

all living things on Earth1) Adaptive Radiation rapid

speciation of related populations living in different environments; Darwin’s Finches– Adaptive zones new areas

for the species to expand into

– Major adaptations often lead to excess to new areas• Eggs shells reptiles have full

land life cycle• Thicker fur allows mammals

to move to colder areas

Biodiversity • The amount of variation for all living

things on Earth2) Extinctions death of all members of one species • Lower diversity by removing species• Raise diversity by allowing new top

species the resources to expand– Dinosaurs dying out allowed mammals to

take over the Earth• Background Extinction Rate normal

lose of species that do not adapt to gradual environmental changes

• Mass Extinctions many species die out in a short about of time– Often caused by fast climate changes– 5 have occurred and 6th may be happening

now with Greenhouse Gases

The Big Five 1) Ordovician extinction:

– 60% of life gone2) Devonian Extinction:

– Hostile environmental changes 3) Permian extinction:

– Worst; 85% of life gone– Volcanic activity caused “runaway

greenhouse” effect; rapid temp. change

4) Triassic extinction:– 50% of marine life and 80% of

terrestrial quadrupeds gone5) Cretaceous extinction:

– 50% of life gone; dinosaurs– 10km diameter asteroid impact; dust

clouded covered and cooled the Earth

Changes in Fossils • As species adapt and speciation

occurs, changes in fossils can tell us about the environment they are adapting too

• Horses bodies grew in size; better structures for running; better teeth for tougher plant life…what could these tell us?– Body size smaller size is not

favored; perhaps increase in predator size or numbers

– Legs environment is more open; change in predator’s ability to run as well

– Teeth change in climate/environment made smaller tougher plants selected

Types of Evolution • The 100s of extinct species of

horses all of the world support a slow shift in characteristics as they evolved

• Phyletic gradualism hypothesis small gradual changes over long stretches of time

• Most fossil records are too incomplete to support this

• Punctuated equilibrium hypothesis changes come quickly as isolated populations adapt to their environments, then long periods of steady growth till another shift occurs

Problems with Time• The vast amount of time life has

existed on Earth is plenty to support the gradual hypothesis

• Fossils are “snapshots” of a species separated by thousands of years, where generations of small changes could have occurred

• Alternating periods of directional selection would make a species seem unchanged– Small body size is favorable over 500

generations, but then a change favors larger body sizes for the next 500 generations

– Fossils of body before the small selection and after the large selection would be the same

Homework• Suggested

Homework:– Test Your

Knowledge– Do not do #6 and

#10• Actual Homework:– Discuss the

Concepts #1– Design the

Experiment– Interpret the Data