The History of Life Chapter 17

17-1 The Fossil Record What is the name for a scientist who studies fossils? Fossil Record provides evidence of the history life on Earth. Infer structure of organisms What they ate Environments they lived in Fossils are found in specific layers of rock. Able to date the age of ancient organisms.

Fossil Evidence Identify and compare anatomical structures between fossils and living organisms. Age of a fossil is determined by two techniques. 1. Relative Dating 2. Radioactive Dating

Relative Dating Compares fossils with others found in various layers of rock. Oldest layers on bottom Index fossils Used for comparison Found in specific layers of rock in different locations.

Radioactive Dating Radioactive decay to determine age of fossils. Decay is measured as HALF-LIFE the time for half of the radioactive atoms in a sample to decay

Radioactive Dating Different radioactive elements have different half-lives. Carbon 12  most common and does not decay Carbon 14  radioactive Has half-life of 5730 Years More C-12 compared to C-14 = older fossil

Carbon-14 Decay

Geologic Time Scale Precambrian Time  Eras  Periods Represents evolutionary time. Precambrian Time  Eras  Periods Cenozoic – Age of Mammals 65 mya to present

17-2 Earth’s Early History Birth of planet took place over 100 million years Collisions with other large objects Produced tremendous amount of heat How did the first organic molecules form? Miller and Urey Experiment

Origins of Earth and Early Life https://www.youtube.com/watch?v=mF9U5x6Nxnw http://www.bing.com/videos/search?q=Miller+and+Urey+Ex periment+Animation&Form=VQFRVP#view=detail&mid=CDF2 71175991A1838660CDF271175991A1838660

Question of the DAY Radioactive Uranium-232 has a half-life of approximately 70 years. The Chernobyl Nuclear Power Plant Disaster in 1986 released high levels of radiation into nearby surrounding areas including the town of Pripyat. What year would see a reduction in radiation to 25% of the original level of uranium-232?

17-3 Evolution of Multicellular Life Precambrian Time- 90% of Earth’s history Life only existed in the seas Simple anaerobic life  photosynthetic life  aerobic life Prokaryotes  Eukaryotes  Multicellular organisms Do not write anything down from the next slides! Key points will be highlighted for you!

Paleozoic Era Carboniferous Period – reptiles and giant insects Cambrian Period – Cambrian Explosion Invertebrates, brachiopods, arthropods (trilobites) Devonian Period – Plants adapt to drier areas Insects Age of Fishes – jaws, bony skeletons, scaled bodies SHARKS!!! First land animals – amphibians Carboniferous Period – reptiles and giant insects plant remains  coal Mass Extinction – 95% of life extinct

Mesozoic Era Dominance of dinosaurs and flowering plants Triassic Period – Age of Reptiles 225 mya  first dinosaurs First mammals very small Jurassic Period – Dinosaurs ruled Earth Archaeopteryx appeared – first birds Fossils show skulls/teeth of dinos but body and feathers of birds Cretaceous Period – T. rex and flying reptiles Flowering plants produced seeds enclosed in fruit EXTINCTION EVENT

Cenozoic Era Quaternary Period – Ice Ages Ocean levels drop 100 meters Age of Mammals Mammals evolve to live in different environments Tertiary Period – Earth warm and mild Whales and dolphins evolve Grasses provide food source for grazing mammals Quaternary Period – Ice Ages Ocean levels drop 100 meters 20,000 years ago – climate warms Mammals such as bats, cattle, mammoths common 200,000 years ago – first fossils of Homo sapiens in Africa

NOVA The Missing Link http://www.youtube.com/watch?v=GOKW_7KajCU How does information presented to you in the video clip provide evidence of evolution?

17-4 Patterns of Evolution What is macroevolution? 1. Extinction Most researchers look for a single massive event – Asteroid striking Earth at Chicxulub Crater, Mexico Extinction of dinosaurs Ecosystems collapse due to natural factors (earthquakes, volcanoes) Organisms still able to compete Food webs destroyed Disrupts energy flow

Adaptive Radiation adaptive radiation: multiple species evolve from a single species also known as divergent evolution Darwin’s Finches

Convergent Evolution convergent evolution: different species evolve to have similar appearances and behaviors

Coevolution Process in which two species evolve in response to changes in each other over time Plant adaptation = animal adaptation

Punctuated Equilibrium vs Gradualism punctuated equilibrium: involves long periods of stability that are interrupted by episodes of rapid change gradualism: evolution occurs slow and steady over a long period of time