Lecture 5

Hadean

The geological eon representing the time from Earth's formation to the beginning of the Archean, characterized by a molten surface gradually cooling.

Continental Crust

The part of Earth's crust that primarily comprises sial and is generally more buoyant and thicker than oceanic crust.

Oceanic Crust

The part of Earth's crust that is primarily composed of mafic rocks like basalt and is denser and thinner than continental crust.

Geologic Timescale

A system of chronological dating that relates geological strata to time, based on the presence and absence of fossils.

Magnetic Reversals

Changes in Earth's magnetic field that are used to date geological formations and events.

Isotopic Evidence

Data derived from the ratios of isotopes within elements, often used to support theories of planetary formation such as the giant impact hypothesis.

LUCA

Last Universal Common Ancestor; the most recent organism from which all organisms now living on Earth descended.

Biomarkers

Molecules produced by life that can serve as indicators of past biological activity in geological records.

Nucleic Acids

Biomolecules essential for life, composed of nucleotide sequences, including DNA and RNA.

Molecular Clocks

A method that uses the mutation rates of biomolecules to estimate the time of divergence between species.

Hydrothermal Vents

Underwater fissures that emit heated mineral-rich water and may provide energy and chemical ingredients for early life.

Panspermia

The hypothesis that life exists throughout the Universe, distributed by meteoroids, asteroids, comets, and planetoids.

Redfield Ratio

The atomic ratio of carbon, nitrogen, and phosphorus in marine organisms; often cited as 106:16:1.

Biology's Central Dogma

A framework that describes the flow of genetic information within a biological system from DNA to RNA to protein.

RNA World Hypothesis

The theory that RNA was the first self-replicating molecule, leading to the development of life.

Transcription

The process by which the information in DNA is copied into messenger RNA.

Translation

The process in which cellular ribosomes create proteins from messenger RNA.

Mutation

A change in the nucleotide sequence of an organism's DNA, which can lead to variability in traits.

Biosignatures

Physical or chemical markers in rocks that indicate past biological activity.

Fossils

Preserved remains or traces of ancient organisms, providing insights into the history of life on Earth.