History of Organisms
Evolution is a theory based on real evidence.
Timeline of Organisms
- Earth is 4.6 billion years old.
- Origin of life is 3.8 billion years ago.
- Oldest fossils are 3.5 billion years ago.
- Photosynthesis evolved 2.4 billion years ago.
- Eukaryotes evolved 1.8 billion years ago.
- Multicellular organisms evolved 800 million years ago.
- Humans evolved 500,000 years ago.
- Fossils
- Must be >10,000 years old to count.
- Petrified remains of living organisms.
- Stratigraphy Strata
- Layers of sedimentary rock.
- Top strata is the youngest layer and includes younger fossils.
- Bottom strata is the oldest layer and includes older fossils.
- Extinct
- Species no longer exist.
- Extant
- Species still in existence.
- Radiometric Dating Carbon dating is a type
- The amount of radioactive atoms remaining in a fossil or rocks, tells age.
- Atmosphere has constant level of the ratio between carbon-12 (stable) and carbon-14 (radioactive).
- Carbon accumulates in body tissue as living beings grow, at the same ratio in the atmosphere.
- When they die, carbon-14 slowly decays over time. The amount of carbon-12 stays stable.
- Using the ratio between the two, we can tell how long something was dead.
-
- Other molecules besides carbon that have long radioactive half-lives are used for dating.
- Paleometric Dating
- Rock layers preserve a record of magnetic field at time they form (say iron from magma from volcanic eruption).
- Mass Extinctions
- Occur when sea levels dip (not always b/c of the dip, but always associated with a dip.).
- Time Scales
-
- Eons
- Largest duration.
- Era
- Medium duration.
- Periods
- Smallest duration.
Scientific Method
- Observations
- Hypothesis
- Best guess, based on ideas, observations, and data.
- Devise a test of hypothesis and experiment
- Predict the data expected from that experiment (prediction)
- What data do you expect from experiment?
- Run the experiment to gather data (testing)
- Reject or fail-to-reject that hypothesis.
- Go to step 2 and revise hypothesis.