The History of Life on Earth

Flashcards covering key historical events, theories, and concepts related to the history of life on Earth, from chemical evolution to mass extinctions and evolutionary development, based on lecture notes.

Chemical Evolution

The evolution of life by abiogenesis.

Monomers

Small organic molecules, representing the first step in chemical evolution's synthesis process.

Polymers

Macromolecules formed from monomers, representing the second step in chemical evolution.

Protocells

The packaging of macromolecules, representing the third step in chemical evolution.

Reducing Atmosphere

Early Earth's atmosphere characterized by very little oxygen.

Oparin and Haldane

Scientists who, in the 1920s, hypothesized the steps of chemical evolution from primitive Earth conditions.

Miller and Urey Experiment

In 1953, they duplicated conditions of primitive Earth in a lab, providing small molecules to see if organic molecules would form.

Miller and Urey Experiment Results

Identified a variety of common organic molecules, including amino acids, suggesting primitive Earth conditions could produce monomers.

Alkaline Vents

Deep-sea vents that release warm, high-pH water (9-11) and are considered an alternate theory for the origin of life.

Murchison Meteorite

A 4.5 billion-year-old rock that landed in Australia in 1969, containing over 80 amino acids and other organic molecules like lipids, sugars, and nitrogenous bases.

Protocells (pre-life, cell-like structures)

Aggregates of abiotically produced molecules exhibiting properties of life such as osmosis, fission, metabolism, and homeostasis, often forming self-assembled vesicles.

Protobionts

Another term for protocells, which have membrane-like properties and are very similar to primitive cells.

RNA Hypothesis

The theory that RNA was most likely the first genetic information used for heritability, due to its ability to polymerize, replicate, and catalyze reactions.

Ribozymes

RNA catalysts found in modern cells (e.g., ribosomes).

DNA

The molecule that developed much later than RNA and became the dominant form of genetically inheritable information due to its greater stability.

Fossils

Any preserved remain or impression of a past organism, including mineralized, organic matter, trace, or amber forms.

Relative Dating

A fossil dating method that examines a fossil’s position in the strata relative to a fossil index.

Absolute Dating

A fossil dating method that determines the approximate age on a scale of absolute time, using radioactive decay or isomer ratios.

Radioactive Dating

A form of absolute dating where the age is estimated from half-life products in the fossil, using isotopes like Carbon-14 or Potassium-40.

Isomer Ratios (Fossil Dating)

A form of absolute dating that measures the amount of L- and D- form amino acid isomers to estimate age, based on the conversion of L-form to D-form after death.

Prokaryotes

Simple single-celled organisms that reproduced asexually, representing the first forms of life roughly 3.5 billion years ago.

Stromatolites

Layered rocks that form when certain prokaryotes bind thin films of sediment together, providing evidence for the origin of life.

Oxygen Revolution

An event roughly 2.7 billion years ago where oxygen produced by aquatic biological organisms filled the early reducing atmosphere.

Eukaryotes

More complex cells with membrane-bound organelles that developed roughly 1.8 billion years ago.

Endosymbiosis

When a prokaryotic cell engulfed a smaller cell that would eventually evolve into an organelle, a key event in the development of eukaryotes.

Serial Endosymbiosis

A hypothesis explaining the origin of eukaryotes through the infolding of the plasma membrane, followed by the engulfing of aerobic heterotrophic and photosynthetic prokaryotes.

Origin of Multicellularity

Began roughly 1.3 billion years ago during a cold period, leading to a huge explosion of diversity (Ediacaran Period) around 541 million years ago.

Ediacaran Period

A period around 541 million years ago that marked a huge change from small, unicellular/simple multicellular organisms to larger, more diverse multicellular organisms.

Cambrian Explosion

An event roughly 525-535 million years ago characterized by an explosion of new diverse life forms, including large predators and hard-bodied organisms.

Colonization of Land

The event where plants/fungi (420 million years ago) and animals (365 million years ago) moved onto land, overcoming challenges like desiccation and reproduction.

Continental Drift

The movement of the Earth's crustal plates over time, correlated with mass extinctions and adaptive radiations of life.

Mass Extinction Events

The sudden loss of many species in geological time, caused by factors such as natural disasters, asteroid impacts, climate shifts, and human actions.

Permian Extinction

Known as "The Great Dying," roughly 250 million years ago, resulting in the loss of 90-95% of all living organisms, likely caused by rapid global warming from volcanic eruptions.

Cretaceous Extinction

Occurred roughly 65 million years ago, leading to the loss of dinosaurs and many other species, most likely due to an asteroid impact causing a global winter.

The 6th Mass Extinction

The current mass extinction event, driven by human actions, with current extinction rates 100-1000 times higher than historical rates.

Consequences of Mass Extinctions

Areas become open for surviving species to exploit, leading to rapid periods of speciation and worldwide adaptive radiation as many new species form.

Evo-Devo

A field focusing on how rapid speciation after mass extinctions may be due to changes in gene expression that result in new developmental patterns.

Heterochrony

An evolutionary change in the rate or timing of developmental events, such as the slowed growth of the jaw in the human evolutionary lineage.

Homeotic Genes (Hox)

Master regulatory genes that determine basic features like the placement of wings and legs on an animal; slight changes can lead to new body types.

Evolutionary Trends

The observation that evolution is not goal-oriented or striving for perfection, but rather the result of interactions between organisms and their current environments.