Macroevolution Biology 1-2

Macroevolution  Macroevolution-evolutionary changes on a grand scale. Including appearance of new groups, adaptive radiation and mass extinction. Including appearance of new groups, adaptive radiation and mass extinction. The evolution of diversity through speciation and the development of new traits. The evolution of diversity through speciation and the development of new traits. The history of the major changes in life on Earth.The history of the major changes in life on Earth.

Fossil Record  Fossil record-record of evolution over millions of years based on the order fossils appear in the Earth. Fossil-preserved remnant or impression of an organism that lived in the past. Fossil-preserved remnant or impression of an organism that lived in the past.

Fossil Record cont’d  The fossil record shows the changes that have occurred in Earth’s history. It shows the major changes in the surface of the planet as well as the appearance and disappearance of different groups of organisms. It shows the major changes in the surface of the planet as well as the appearance and disappearance of different groups of organisms.

Radiometric Dating  Radiometric dating-use of radioactive isotopes to determine the age of a fossil or rock. Isotope-version of an element with a different number of neutrons. Isotope-version of an element with a different number of neutrons.

Radiometric Dating cont’d  Over time, a radioactive isotope changes into a nonradioactive form. Half life-the amount of time it takes for 50% of a radioactive sample to decay. Half life-the amount of time it takes for 50% of a radioactive sample to decay. Different elements have different half lives.Different elements have different half lives.

Radiometric Dating cont’d  For each half life that has passed, 50% of the radioactive isotope decays. E.g., if only one half of the radioactive isotope remains, one half life has passed. E.g., if only one half of the radioactive isotope remains, one half life has passed. 1/4 is two half lives, 1/8 is three half lives, etc.1/4 is two half lives, 1/8 is three half lives, etc. How many half lives have passed gives the age of the fossil. How many half lives have passed gives the age of the fossil.

Continental Drift  The surface of the Earth is constantly changing, producing change in the organisms. The surface of the earth is made of plates that move. The surface of the earth is made of plates that move.

Continental Drift cont’d Continental drift-change in the position of the continents caused by the movement of the Earth’s crust. Continental drift-change in the position of the continents caused by the movement of the Earth’s crust. Explains both the presence of fossils of the same species on different continents as well as each developing its own families.Explains both the presence of fossils of the same species on different continents as well as each developing its own families.

Extinction and Radiation  Changes due to continental drift have resulted in both mass extinctions and explosions. There have been about 12 episodes of mass extinction. There have been about 12 episodes of mass extinction. 6 in the last 600 million years.6 in the last 600 million years. Each was followed by an explosion in number of species. Each was followed by an explosion in number of species.

Extinction/Radiation cont’d  The surviving species have traits that become the basis of adaptations to the changed environment. K-T extinction event (65 mya). K-T extinction event (65 mya). The ancestors of the mammals and birds, along with some of the reptiles, fishes and other groups survive.The ancestors of the mammals and birds, along with some of the reptiles, fishes and other groups survive. Adaptive radiation happens as they take advantage of the lack of competition.Adaptive radiation happens as they take advantage of the lack of competition.

Evolution of New Groups  The fossil record also shows the development of new traits that lead to the appearance of new groups of animals and plants. Natural selection only edits existing traits. Natural selection only edits existing traits. Enough changes produces brand new traits.Enough changes produces brand new traits.

Evolution cont’d  Traits appear with a use in one environment but may have another use in a different environment. Allows the organism to survive in a new or different environment. Allows the organism to survive in a new or different environment. An accumulation of new traits leads to the appearance of new groups different from the others. An accumulation of new traits leads to the appearance of new groups different from the others.