The History of Life

Chapter 17

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.

17-1 The Fossil Record

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

Fossil Evidence

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.

Relative 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

Radioactive Dating

Carbon-14 Decay

Represents evolutionary time. Precambrian Time Eras Periods

Cenozoic – Age of Mammals 65 mya to present

Geologic Time Scale

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

17-2 Earth’s Early History

https://www.youtube.com/watch?v=mF9U5x6Nxnw

http://www.bing.com/videos/search?q=Miller+and+Urey+Experiment+Animation&Form=VQFRVP#view=detail&mid=CDF271175991A1838660CDF271175991A1838660

Origins of Earth and Early Life

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?

Question of the DAY

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!

17-3 Evolution of Multicellular Life

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

Paleozoic 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

Mesozoic Era

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 AgesOcean levels drop 100 meters20,000 years ago – climate warms

Mammals such as bats, cattle, mammoths common200,000 years ago – first fossils of Homo sapiens in Africa

Cenozoic Era

http://www.youtube.com/watch?v=GOKW_7KajCU

How does information presented to you in the video clip provide evidence of evolution?

NOVA The Missing Link

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

17-4 Patterns of Evolution

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

Adaptive Radiation

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

Convergent Evolution

Process in which two species evolve in response to changes in each other over time

◦ Plant adaptation = animal adaptation

Coevolution

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

Punctuated Equilibrium vs Gradualism