EvolutionEvolution

• is change in the inherited traits of a population of organisms from one generation to the next (over VAST amounts of time). These changes are caused by a combination of three main processes: variation, reproduction, and selection.

The Fossil Record

• Fossils are usually found in sedimentary rocks

• The simplest dating method is called Relative dating, where the rocks closer to the surface are considered younger and the deeper layers are older.

A

B

Radioactive Dating •Radiometric dating involves using radioactive isotopes to detect the amount of decay. Ex: C14 dating

Geologic Time Scale• A scale which is a kind of calendar that communicates all the events of the Earth since its formation is known as the Geologic Time Scale.

Earth’s Early HistoryEarth is believed to be about 4.6 billion years old

• This age was determined from meteorites and moon rocks• The earliest atmosphere contained H2 (hydrogen), CH4 (methane), NH3 (ammonia) and H2O (water vapor)• A fossil is any evidence of previous life

Ex: amber, trace fossils, molds & casts, imprints, tracks

• Biogenesis – living organisms come only from other living organisms.

• The beginning of life is thought to have originated in the oceans from protocells. All the ingredients for life were present in the atmosphere and oceans.

• Primitive life forms are considered to most closely resemble Archaebacteria (most primitive kind)

• Cyanobacteria – type of photosynthetic bacteria believed to have been the earliest group of organisms to evolve.

cyanobacteriastromatolites

Important MilestonesImportant Milestones1. Photosynthesis releases O2 into the

atmospherea. Kills all anaerobic organisms exposed to O2

b. Leads to aerobic processes being selected for (precursor to cellular respiration)

Important MilestonesImportant Milestones2. Prokaryotic → EukaryoticEndosymbiotic Theory – eukaryotic cells arose from

living communities formed by prokaryotic organisms

1. Mitochondria and chloroplasts contain DNA similar to bacterial DNA

2. Mitochondria and chloroplasts have ribosomes similar to bacterial ribosomes

3. Mitochondria, chloroplasts, and bacteria all divide by binary fission

Important MilestonesImportant Milestones

3. Sexual Reproductiona. Leads to more genetic diversity in a

population, increases long-term survival of a species

4. Multicellular organismsa. Bigger organisms

b. Cell differentiation

c. Not constrained to limits of simple diffusion

Patterns of Evolution

Macroevolution – large-scale evolutionary patterns and processes that occur over long periods of time

Extinction • Natural selection, climate changes, and Natural selection, climate changes, and

catastrophic events have caused 99 percent of catastrophic events have caused 99 percent of all species that have ever lived to become all species that have ever lived to become extinct.extinct.

• Mass extinctionsMass extinctions – caused by continents – caused by continents moving, sea level changing, volcano eruptions, moving, sea level changing, volcano eruptions, large meteorslarge meteors

• Mass extinctions leave habitats open and Mass extinctions leave habitats open and provide ecological opportunities for remaining provide ecological opportunities for remaining organisms, which frequently results in a burst of organisms, which frequently results in a burst of evolution. (Extinction of dinosaurs made room evolution. (Extinction of dinosaurs made room for adaptive radiation of mammals.)for adaptive radiation of mammals.)

Adaptive Radiation (also called Divergent Evolution)

• A single species evolves into diverse forms that A single species evolves into diverse forms that live in diverse ways.live in diverse ways.

• Produces homologous structuresProduces homologous structures