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

1. Observations
2. Hypothesis
   • Best guess, based on ideas, observations, and data.
3. Devise a test of hypothesis and experiment
4. Predict the data expected from that experiment (prediction)
   • What data do you expect from experiment?
5. Run the experiment to gather data (testing)
6. Reject or fail-to-reject that hypothesis.
7. Go to step 2 and revise hypothesis.

Study Guide

1. What is bya, what is mya?
   • Billions of years ago, millions of years ago.
2. What is the difference between a hypothesis and a prediction?
   • A hypothesis is a best guess based on observations and prior knowledge.
   • A prediction is what you think the results of an experiment will be.
3. When did Earth arise (estimated)?
   • 4.6 billion years ago.
4. When did 1st cells arise? What type of organisms? How do we know?
   • 3.5 billion years ago, we have fossils of them.
5. When did photosynthesis arise? In what type of cells?
   • 2.4 billion years ago, in cyanobacteria.
6. When did eukaryotic single-cells arise? How are eukaryotes different/new?
   • 1.8 billion years ago, they have organelles.
   • Eukaryote multicellular organisms arose 800 million years ago.
7. What are fossils?
   • Petrified remains of living organisms.
8. What is the age of fossils by definition? How do we 'date' them?
   • Greater than 10,000 years old. Using radiometric dating.
9. Coal deposits in rock, are from the remains of what?
   • Organisms from Carboniferous period.
10. Fossil fuels are evidence of what type of event.
    • Mass extinctions.
11. How many mass extinctions occurred in Earth history? How do we know that?
    • Five mass extinction events, by looking at fossils.
12. Do mass extinctions correlate with what ocean trend?
    • Sea levels dropping rapidly.
13. From Activity in Class: how does oxygen affect insect body size?
    • More oxygen allows the body to grow larger.
14. In an experiment and graph, which variable is the one that the scientist purposefully changes, usually represented on the x-axis:
    • Dependent
    • Independent
15. In an experiment and graph, which variable is the one that the scientist measures in response, usually represented on the y-axis?
    • Dependent
    • Independent
16. When did the Dinosaurs go extinct? Which extinction, how long ago?
    • 80 million years ago.
17. When did our related species primates arise?
    • 55 million years ago.
18. When did human species arise? Are humans still evolving?
    • 10 million years ago. Yes.
19. Fun video. but not super accurate, though! Can you spot the inaccuracy?
    • People weren't around when dinosaurs were.
20. In what Period and Epoch did lactose intolerance evolve in humans?
    • 10,000 years ago. Quaternary, holocene.
21. Coal is the fossilized remains of [what] from the Carboniferous period.
    • flowering plants
    • pine trees
    • tree ferns and horsetails
    • ginkgos
    • grasses
22. The ratio of carbon-14 (14C) to its stable isotope, carbon-12 (12C), is relatively constant in living organisms and their environment; however, this changes once an organism dies. In a fossil approximately 40,000 years old, the
    • ratio of 14C to 12C would be higher because the 12C is not replenished after death.
    • ratio of 14C to 12C would be lower because the 14C is not replenished after death.
    • ratio of 14C to 12C would not change because the 14C is replenished after death
23. This graph shows the mean sea level over geologic time. Mass extinctions are denoted by asterisks. What pattern do you see?
    • Mass extinctions are correlated with sea levels dropping.