Honors Biology Unit 7 Powerpoint #2 2011-2012 Patterns of Evolution Honors Biology Unit 7 Powerpoint #2 2011-2012

Macroevolution Large-scale evolutionary patterns and processes that occur over long periods of time Key Concept: 6 important patterns of macroevolutions

1) Mass Extinction When 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 earth

The Future of Mass Extinction E.O. Wilson of Harvard University predicts that man’s 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 Diameter Equivalent 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 Radiation A single species, or small group, evolves, through natural selection into diverse forms. Example: Darwin’s Galapagos Finches

3) Convergent Evolution When unrelated organisms come to resemble each other due to environmental demands. Example: Placental v. Marsupials

4) Coevolution When two species evolve in response to changes to each other over time Example: Insects and flowers

5) Punctuated Equilibrium Long stable periods interrupted by periods of rapid change. Example: Darwin’s Galapagos Finches

6) Developmental Genes & Body Plans Small changes in the activity of control genes can produce large changes in adult animals Example: HOX genes

Fossil Evidence of Mass Extinction Fossilization 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 Time Based 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 years Index Fossils: distinctive fossil used to compare the relative ages of fossils Radioactive Dating: Calculate the age of a sample based on amount of remaining radioactive isotopes it contains Half-life: length of time required for half of the radioactive atoms in a sample to decay