Transcript Macroevolution and Mass Extinction powerpoin

Lecture: Macroevolution and Mass Extinction
Macroevolution
 Macroevolution- large-scale evolutionary
changes that take place over long periods of
time
 6 Themes:
– Adaptive radiation (divergent evolution),
convergent evolution, coevolution, punctuated
equilibrium (gradualism), changes in
developmental genes and mass extinction
Adaptive Radiation
 Single species evolves into several different forms
that live in different ways
– New niches are always filled!
– Darwin’s finches
– Banobos and Chimps
 Divergent Evolution- isolated populations of a
species evolve independently
– Geographic barriers separate members of a population, or
a small group leaves
– Example: Brown bear and Polar bear
Convergent Evolution
 Unrelated organisms come to resemble each
other
– Species with different ancestors develop similar
characteristics because natural selection has made
similar adaptations in response to similar
environments
– Example: African serval cat and South American
maned wolf
Coevolution
 Two species evolve in response to changes in
each other over time
– Organisms with close ecological interactions
– Many flowering plants depend on certain pollinators
to reproduce and their flowers must attract them
– Example: Hummingbirds and fuschia flowers
Gradualism vs. Punctuated Equilibrium
 Gradualism- new species evolve as genomes of two
populations differentiate over lots of time
– Small genetic changes occur slowly
– Darwin’s theory
– Some evidence in fossil record, but big gaps suggest…
 Punctuated equilibrium- populations remain
genetically stable for long periods of time,
interrupted by brief periods of rapid genetic
change
– This could be caused by a big environmental change,
increase in mutation rates, or isolation of a small
population
Major Time Periods- Precambrian and Paleozic
 Precambrian Time- 90% of Earth’s History
– All life in sea
– Simple Anaerobic  photosynthetic  Oxygen 
Aerobic and Eukaryotes  Multicellular
 Paleozoic Era- lots of marine life
– Cambrian Period- 1st hard bodies and 1st
representatives of most animal phyla
– Ordovician and Silurian Periods- Larger animals,
first vertebrates, insect, terrestrial plants
– Devonian Period- More fish, first sharks, more
plants, land invasion (amphibians)
– Carboniferous and Permian Periods- More
vertebrates, more insects, mass extinction
Major Time Periods- Mesozoic and Cenozoic Eras
 Mesozoic Era- 180million years- dinosaurs
and flowering plants
– Triassic Period- First mammals
– Jurassic Period- Dinosaurs, first birds
– Cretaceous- reptiles, meat-eaters, mass
extinction
 Cenozoic Era- mammals on land, water and air
– Tertiary Period- marine mammals, flowering
plants and grasses, grazers, insects
– Quaternary Period- ice ages, our early ancestors
Mass Extinction
 Mass Extinction- periods where most of the
species were eliminated
– 99% of life that has existed on this planet is
extinct
– Scientists have identified 5 mass extinctions– Permian extinction- 250 million years ago- more
than 90% of the ocean animals were eliminated
 Happened around same time Pangaea formed, so maybe
it was from the loss of water habitats when the supercontinent formed
– Cretaceous extinction- 65 million years agomost famous extinction- wiped out the dinosaurs
 Most likely explanation- a meteor
Cladograms
 Diagrams showing the evolutionary
relationships among a group of organisms
 We can show appearance of new traits and
relationships of organisms