Patterns of evolution

Honors BiologyUnit 7Powerpoint #22011-2012Patterns of EvolutionMacroevolutionLarge-scale evolutionary patterns and processes that occur over long periods of time

Key Concept: 6 important patterns of macroevolutions1) Mass ExtinctionWhen many different species of organisms go extinct at the same time. End of Paleozoic: 95% of complex life (both plants and animals on the land and in the sea) went extinct. Causes of Mass Extinction Climate Change: rapid changes in yearly weather patterns. Example: Ice Age

Volcanism: the sudden oozing of millions of cubic meters of lava from the earth that release gasses poisoning the atmosphere

Impact Events: Meteors or asteroids impacting the earthThe Future of Mass ExtinctionE.O. Wilson of Harvard University predicts that mans destruction of the biosphere will lead to the extinction of 50% of the species on earth in the next 100 years. 70% of biologists agree Example of Mass Extinction: 65 Million years ago (very recent)50% of all species went extinct including dinosaurs Thought to be caused by the Chicxulub Meteor which hit the Yucatan Peninsula in Mexico.

Chicxulub Crater

Chicxulub Crater Made by a meteor 6 miles in DiameterEquivalent to exploding 190,000 gigatons of TNT

Tsar Bomba: By comparison: The most powerful nuclear bomb ever tested (Russia 1961) was only 0.05 gigatons

2) Adaptive RadiationA single species, or small group, evolves, through natural selection into diverse forms.

Example:Darwins Galapagos Finches3) Convergent EvolutionWhen unrelated organisms come to resemble each other due to environmental demands.Example:Placental v. Marsupials

4) CoevolutionWhen two species evolve in response to changes to each other over timeExample:Insects and flowers

5) Punctuated EquilibriumLong stable periods interrupted by periods of rapid change.Example:Darwins Galapagos Finches

6) Developmental Genes & Body PlansSmall changes in the activity of control genes can produce large changes in adult animalsExample:HOX genes

Fossil Evidence of Mass ExtinctionFossilization does not happen very often. Mass Extinctions also do not occur very often. Scientist believe that there are more fossils to be found around the time of mass extinctions than any other time. Strata Layers of dirt and stone from different time periods on earth. Form bands of rock layers.

Geologic TimeBased Upon major changes in the fossil record in the rock strata

ERAS are longer time divisions than PERIODS

There are four eras:Precambrian (4.6 billion 544 million years ago)Paleozoic (544 - 245 million years ago)Mesozoic (245 65 million years ago)Cenozoic (65 million Present)

Dating of Fossils (p. 419-420)Relative Dating: estimates a fossils age compared with other fossils but no info about age in yearsIndex Fossils: distinctive fossil used to compare the relative ages of fossilsRadioactive Dating: Calculate the age of a sample based on amount of remaining radioactive isotopes it containsHalf-life: length of time required for half of the radioactive atoms in a sample to decay