Origins of Life (Unit 1 Evolution)

Vocabulary-style flashcards covering major terms and concepts from the Origins of Life lecture notes.

Geologic time

The timescale of Earth's history, divided into eons, eras, and periods.

Eon

The largest division of geologic time, containing multiple eras.

Hadean eon

Earliest Earth history; few rocks preserved, heavy meteor bombardment, Moon formation, temperatures extremely high.

Archean eon

Eon when life first emerged; contains the oldest fossils (~3.5 BYA).

Proterozoic eon

Eon preceding the Phanerozoic, marked by “early life” and the formation of Rodinia.

Phanerozoic eon

Current eon with visible, diverse multicellular life; includes the Cambrian.

Rodinia

A, early supercontinent formed during the Proterozoic; broke up before the Phanerozoic.

Gondwana

A southern-hemisphere supercontinent that later contributed to Pangea formation.

Pangea

Supercontinent formed by the union of major landmasses, including Gondwana.

Cambrian period

Period of rapid diversification of multicellular life (the Cambrian explosion).

Snowball Earth

Hypothetical global glaciation with extensive ice cover.

4.6 BYA meteor impact

A massive impact that may have contributed to Moon formation and early Earth conditions.

Miller-Urey experiment

1953 experiment recreating a reducing early atmosphere to synthesize organic molecules like amino acids.

Reducing atmosphere

Early atmospheric condition rich in hydrogen and lacking oxygen, conducive to abiotic synthesis of organics.

Amino acids

Building blocks of proteins; produced abiotically in Miller-Urey-type experiments.

Adenine

A nucleobase formed in early synthesis experiments, a component of DNA/RNA.

Methane (CH4)

A simple organic molecule generated under early atmospheric conditions.

Early organic molecules

Initial simple carbon compounds thought to form on early Earth or arrive via meteorites/comets.

Oxygenic photosynthesis

Photosynthesis that produces O2, a major turning point in Earth's atmosphere.

Carbon fixation

Process converting inorganic CO2 into organic carbon for metabolism.

Nitrogen fixation

Conversion of N2 into usable forms (e.g., ammonia) for biological use.

RNA as first genetic material

Hypothesis that RNA preceded DNA as the original genetic molecule.

Lipid bubbles (protocells)

Membrane-like lipid structures that enclosure reactions and foster primitive cells.

Endomembrane system

Interconnected internal membranes (nucleus, ER, Golgi) in eukaryotes enabling complex processes.

Infolding of the cellular membrane

Process by which internal membranes and the nucleus evolved in eukaryotes.

Nuclear membrane

A membrane surrounding the nucleus, a feature of eukaryotic cells absent in bacteria/archaea.

Golgi apparatus

Organelle involved in modifying, sorting, and trafficking proteins and lipids.

Endoplasmic reticulum (ER)

Membrane network for protein and lipid synthesis and transport.

Mitochondria

Powerful organelles in eukaryotes; descended from ancestral bacteria via endosymbiosis.

Chloroplasts

Photosynthetic organelles in plants/algae; descended from cyanobacteria via endosymbiosis.

Endosymbiosis

Theory that organelles originated as bacteria living inside early eukaryotic cells.

Rickettsia

Ancestral parasite considered the lineage leading to mitochondria.

Cyanobacteria

Photosynthetic bacteria—the ancestor of chloroplasts in plants.

Prokaryotes

Organisms without a nucleus or internal membranes (bacteria/archaea).

Eukaryotes

Organisms with a nucleus and extensive internal membranes.

Stromatolites

Layered structures formed by cyanobacteria; indirect evidence for early life (~2.7 BYA oldest).

Biomarkers

Biochemical signatures (e.g., carbon isotopes) indicating past life in rocks.

Kaapvaal/Pilbara cratons

Ancient rock formations in Africa and Australia that host some of the oldest microfossils.

Cyanobacteria

Autotrophic, oxygen-producing bacteria important in early Earth oxygenation.

Endosymbiotic theory

Idea that mitochondria and chloroplasts originated as free-living bacteria taken inside another cell.

Three domains of life

Eubacteria, Archaea, and Eukaryota; major dividing groups of life.

Five eukaryotic supergroups

Excavata; SAR; Archaeplastida; Amoebozoa; Opisthokonta—the broad eukaryotic lineages.