History of Life

HISTORY OF LIFECh. 14

History of Life Fossil Evidence of Change Paleontologist - a scientist who studies fossils Fossil - preserved evidence of an organism

Trace fossils - indirect evidence of organism. ex footprints, burrows, feces

Molds and Casts - impression of an organism Replacement - original organism is replaced with

mineral crystals Petrified - Empty pore spaces are filled by minerals Amber - Preserved tree sap hardened Original Material - Mummification or freezing

Fossils Fossil Formation - formed in sedimentary

rocks

Dating Fossils Relative Dating - determine the age of rocks by

comparing them to those in layers around it

Law of superposition - younger layers are deposited on top of older layers, similar to stacking the daily paper on top of each other

Radiometric dating - uses the decay of radioactive isotopes of measure the age of a rock

Half-life - amount of time it takes for half of the original isotope to decay, typically use carbon 14 for dating

Law of Superpostion

Time Geologic Time Scale - model that

expresses the major geological and biological events in Earth's history, divided into precabrian and phanerozoic

Earth formed roughly 4.6 billion years ago Era - Paleozoic, Mesozoic, and Cenozoic

times Period - smaller division of time (see

diagram)

Earth History in a Day If the entire history of the earth was

broken down into 1 Day: No Life from 12:01 am - 1:00 pm Microscopic bacteria from 1:00 pm - 8:00

pm Dinosaurs came at 10:34 pm Humans at 11:56 pm

Time

Historic Periods Precambrian - 90% of the earth's history, goes from the

beginning of Earth's formation until 542 million years ago

Stromatolites - bacteria that produced oxygen and released it into the atmosphere, because of this Oxygen became plentiful and allowed other organisms to emerge

Paleozoic - Cambrian explosion, most major animal groups diversified, marine species moved to the land. There was a mass extinction that ended this period, 90% of the organisms disappeared

Historic Periods Mesozoic - The time of the Dinosaurs, birds, and

flowering plants. A meteorite struck the earth possibly causing another mass extinction

K-T boundary - the layer of rock that proves of a meteorite impact

Plate Tectonics - the movement of the plates that make up the Earth's surface

Cenozoic - The time of the Mammals, this is when humans as well as most other mammals roamed the Earth

Stromatolites

Dinosaurs How did the dinosaurs die?

The Origin of Life Spontaneous generation - idea that life arises from

nonlife ex. it was once believed that worms, insects, and fish came

from mud

Theory of Biogenesis - states that only living organisms can produce other living organisms

If life can only exist from pre-existing life, then how did the first life-form appear? Which came first the chicken or the egg? Can we even figure this out? Discuss this with your partner and come write your ideas down

Origin of Life Simple organic molecules - UV light from

the sun, electricity from lighting, and the gases present in the atmosphere and early oceans were created through chemical reactions which produced Amino Acids, sugars, and nucleotides

Deep Sea Vents - hydro thermal vents produced sulfur, and other elements which supported a food chain for early organisms

Origin of Life Meteorites - some believe that this could be the

source of life

Clay - Some believe that clay was used by the Amino Acids to hold the chains of AA's together

Genetic code - RNA was life's first coding system, they can also behave like enzymes

There are still holes in this mystery, it remains unresolved

Origin of Life

Cell Theory archea - prokaryotic cells that are restricted to

volcanic and other extreme environments, get there nutrients from inorganic molecules like sulfur, they do not need or produce oxygen

Oxygen - was not present in the atmosphere until after 1.8 billion years ago

Cyanobacteria - photosynthesizing prokaryotes, formed the ozone layer, which ultimately made conditions on earth more habitable

Cell Theory Endosymbiont Theory - prokaryotes lived

inside of eukaryotic cells and performed cell functions just as a mitochondria or chloroplast would

These cells evolved into the modern day Eukaryotic cells

Cell Theory

Pangea

Review Ch. 14 Review p 411 - 4-8, 10 p 412 - 14,15,19 p 413 - 35-40 p 414-415 - 4,5,8,13,17