Chapter 3 | Geology & Paleontology

Chronology

The arrangement of events or dates in the order of their occurrence

Lord Kelvin

Studied temperatures of solid states as they cooled, assuming the plant’s interior is solid — the planet has a molten core

Isotopic dating

Measuring the amount of remaining isotope allows for the measurement of the age of the rock

• Higher rate of decay is better for newer rocks

• Lower rate of decay is better for older rocks

Carbon dating

Highest probability of decay (C-14 → N-14)

Radiometric dating

• Allows for dating of geological periods

• End/new decided by shifts in the fossil record

Fossil record

• An incomplete record

• Favors hard-bodied organisms, abundance & widespread organisms that existed for a long time

Trace fossils

Indirect evidence of life

Mold

An impression of an organism

Cast

A mold filled with sediment

Replacement

The material of an organism replaced with mineral crystals that leave detailed replicas of hard or soft parts

Petrified or permineralized

Empty pore spaces filled in by minerals

Amber

Preserved tree sap traps an entire organism. The sap hardens and preserves the trapped organism

Extinct species

Found by studying fossils; morphology, behavior, development, nutrition etc.

Biomarkers

Distinctive molecules detected in rock; signals for different types of life

Early Earth (4.6 BYA)

• Seas formed from a hostile environment

  • Rocks and ice vaporized water

• Little oxygen in the atmosphere

• Species evolve to favor the lighter carbon isotopes

• Abiotic synthesis of organic molecules (clay)

Zircon crystals

Form a cage around isotopes, notably carbon

Characteristics of Life

• Metabolism

• Reproduction

• Respond to environment through regulation

• Evolve over time

Protocells

Nonliving cells created to study how abiotic material formed life

RNA World Hypothesis

• Catalyzes through ribozymes

• First genetic material

• First chains to replicate

• RNA strands develop mutations

History of Earth Thought

• Reducing environment

• Replicate early atmospheric conditions

• Deep sea hydrothermal vents formed early life

• Volcanic activity formed early life

• Life formed in space (panspermia)