Transcript Ch 14.1 The record of life - Cincinnati Public Schools

Ch 14.1
The record of life
You will …
1. examine how rocks and fossils provide evidence of
changes in Earth’s organisms
2. correlate the geographic time scale with biological
events
3. Sequence the steps by which small molecules
may have produced living cells.
Early History of Earth
• A. No life could possibly exist:
1. Temperature: colliding meteorites; decay of
radioactive materials, compression of minerals,
volcanic eruptions.
2. Early Atmosphere: Small amounts of O2, CO2, and
nitrogen.
3. Oceans: Approx. 4 billion years ago the Earth
began to cool. Water in the atmosphere condensed
causing rainstorms and lightening to occur for a
few million years. Oceans formed and introduced
the first organisms.
History in Rocks
• a. No direct evidence: Theories, physical process of
reforming rocks.
• b. Fossils: We study fossils to make predictions. 99%
of species are extinct. (Look at fig 14.1 Types of fossils)
* c.
Paleontologist: Scientist who study ancient life.
Fossil bones and teeth can help determine size,
movement, and type of organism. Climate and
geography can also be determined.
• d. Fossil are found where? Sedimentary rock, bottoms
of lakes, streams, and oceans.
The Age of a Fossil
• Layers of sedimentary rock can help determine age.
• a. Relative dating: Law of Super Position. The layers at the
surface must be younger that the layers below it. Scientist
can discover the order of appearance and extinction.
• b. Radiometric dating: Radioactive isotopes in rocks help
determine exact age because unstable nuclei break down
over time. The decay rate is called the half-life.
• c. Chemical Analysis helps Scientist: (Potassium-40,
Carbon-14) More sampling and different methods help with
consistency in results
A trip Through Geological Time:
The calendar of Earth.
a. The Geological Time Scale: Divided into 4 era
(Precambrian, Paleozoic, Mesozoic, Cenozoic) Each era
is subdivided into periods. Fig 14.4
b. Precambrian: Oldest fossils found in the deserts of
Australia. Resembles modern species of bacteria called
cyanobacteria. Accounts for 87% of Earth’s history.
Prokaryotes only forms of life until the end of period
when eukaryotic organisms emerged. (544 million years
ago)
c.
Paleozoic: Ended 245 million years ago. Cambrian
period first showed an enormous increase in life.
Oceans became filled with animals such as worms,
sea stars, anthropods, fishes …. Then came
amphibians, reptiles. A mass extinction occurred at the
end of the period. ( 90% ocean and 70% land).
d.
Mesozoic: Began 245 million years ago. Drastic
changes in organisms and geology. Divided into 3
periods: Triassic period: oldest, small mammals like
mice were found. Jurassic period: (middle) became
known as the age of the dinosaur. Cretaceous period:
(last) marked the end of the dinosaur approx. 66
million years ago. Theories include a meteorite hitting
the earth to cause extinction.
e.
Changes during the Mesozoic period: Geological
events changed the way species lived. The theory
of the continental drift, plate tectonics, changed the
way organisms lived.
f.
Cenozoic: 66 million years ago. We lived here now.
Mammals flourish, primates appeared 30 million
years ago. Humans 200,000 years ago