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 • 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)
History of Evolution • 1809 – Jean Baptiste Lamarck • Believed all organisms were constantly acquiring traits that helped them live more successfully (reproduce more)
Believed in “use it or lose it” • Ex: by trying to use their front limbs to fly, birds could transform those limbs into wings; birds that don’t use their wings would eventually lose them
Believed that creatures developed traits during their lifetime and could give those traits to their offspring • EX: In reaching higher leaves giraffes stretch their necks
Lamarck’s ideas were wrong, but he was one of the first to propose an evolutionary theory
1831 – Charles Darwin • sailed on the H.M.S. Beagle • noticed that the characteristics of animals (finches) varied among the Galapagos Islands
developed the theory of evolution based on natural selection • published his theory in On the Origin of Species (1859)
Evolution 101 • Explains how GROUPS/populations of organisms change over time • Individuals do NOT evolve (Ex. you cannot “evolve” yourself to become 5 feet taller by next week)
Occurs when there is a change in gene frequency within a population over time • Can occur in by two different processes 1. Natural Selection 2. Genetic Drift
Evolution by Natural Selection There are two parts of natural selection 1. Struggle for existence (competing for resources) 2. Survival of the fittest (or fit enough)
Fitness • How likely it is an organism can survive and reproduce • Result of adaptations (STRUCTUAL changes due to variation) Coral Snake –No Poison King Snake
Individuals vary • Have distinct advantages & disadvantages • Some variations (not all!) give individuals a slight advantage to survive and reproduce
Variations arise from: • Mutations • Gene shuffling (Meiosis, crossing over) • Variation can give rise to ADAPTATIONS which natural selection acts on
Over time, natural selection results in changes in the inherited characteristics of a population. • These changes increase a species’ fitness in its environment.
BBC Galapagos • http://www.youtube.com/watch?v=-FT3FU2XOgo&list=PLDD8AFC17D8735E65
Why is it called Natural selection? • Darwin saw how similar it was to artificial selection • Artificial Selection – humans “select” which individuals to reproduce (selective breeding) ex: different breeds of dogs
Natural selection – Most fit individuals reproduce the most successfully • Selection – results in a change in the inherited characteristics of a population