THE ORIGIN OF EARTH • The Earth is approximately 4.6 billion years old
Origin of Earth • The early Earth is different than Earth today • The sky was probably pinkish-orange rather than blue • The atmosphere contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen sulfide, and water vapor (this atmosphere would kill us!)
No oxygen • No oceans because the Earth’s surface was too hot • HARSH conditions (volcanic activity, comets, and asteroids)
Fantasia- Rite of Spring (Early Earth) • Around 3.8 billion years ago, the earth finally cooled off enough for water to condense into oceans.
Fossils help us to figure out the Earth’s timeline. • We can tell how old fossils are by dating them. • There are two ways to date fossils.
1. Absolute Dating 2 types of geological dating How old fossils are in specific years Radioactive dating – uses radioactive isotopes that decay. The age is based on how much of the isotope (element) is left in the sample.
Absolute – Radioactive Dating • Different isotopes are used based on the age of the sample. • Carbon 14 is used on organisms that are less than 60,000 years old. • Potassium 40 is used to date organisms that are billions of years old.
2 types of geological dating 2. Relative Dating • Comparing fossils by depth • The deeper the fossil is found, the older the fossil is. • The age of the fossil is relative to what is found below and above it. • May use distinct index fossils to compare ages • Example – magazine stacks
So, again – how old is Earth? If all the time the Earth has been around was a latte . . . Hominids 3 million years0.06% Continental Drift 200 million years4% Abundant plant & animal remains 600 million years13% 4,600,000,000 YEAR OLD LATTE Solar System 4,600 million years
HOW DID LIFE START? FransiscoRedi (1668) • Disproved “Spontaneous Generation Theory” • People previously believed in abiogenesis: life comes from nonliving things
FransiscoRedi (1668) • Showed this with an experiment using maggots and meat (meat without flies did not develop maggots)
Louis Pasteur (1859) • First stated the Law of Biogenesis (all life is from other life) • Conducted an experiment using S-shaped flasks and beef broth
Louis Pasteur (1859) • The S - shape allowed air to enter the flask, but not contaminants • No microbes grew in the flask • When the flask was broken so contaminants could get in, microbes started to grow.
Oparin and Haldane (1920) • Believed a combination of carbon dioxide, ammonia and ultraviolet radiation made organic compounds. • The early sea was “primordial soup” containing large populations of organic monomers and polymers.
Oparin and Haldane (1920) • Haldane believed groups of monomers and polymers evolved lipid membranes, and that these developed into the first cell
Miller and Urey (1950) • Tried to answer how organic molecules could have arisen in early earth • Simulated the conditions of early Earth in a laboratory setting (made primordial soup)
Miller and Urey (1950) • Produced amino acids (organic molecule) by passing electricity through a mixture of hydrogen, methane, ammonia, and water. • Controversy over results • Scientists have been able to reproduce the experiments
FROM PROKARYOTES TO EUKARYOTES (how the cells evolved) • The first cells were prokaryotic (no nucleus) and anaerobic (no oxygen) • By 2.2 bya photosynthetic bacteria (cyanobacteria) were releasing oxygen into the air
FROM PROKARYOTES TO EUKARYOTES • The rise of oxygen in the air caused aerobic prokaryotes to evolve. • About 2 bya eukaryotic cells started to form
The endosymbiotic theory says that eukaryotic cells evolved from prokaryotes that were living symbiotically (today those prokaryotic cells are seen as chloroplasts and mitochondria)