Cambrian explosion
Ancient life's eruption
The Cambrian explosion was a period roughly 540 million years ago when most major animal groups first appear in the fossil record, seemingly all at once in geological terms.
The "explosion" spans perhaps 20 million years—a blink in deep time.
Before this, life was mostly simple and single-celled; after, the seas teemed with complex creatures: trilobites, early arthropods, primitive chordates.
The term now applies figuratively to any rapid diversification: a Cambrian explosion of smartphone apps, the Cambrian explosion of internet startups in the 1990s.
Cambrian lagerstätte in Canada
- fossilsPreserved ancient organism traces
- PrecambrianEarliest geological eon
- stratigraphyStudy of rock layers
- sedimentary layersAccumulated geological deposits
fossilization · radiometric dating · paleobiology · geological time
Extinct marine arthropods
- brachiopodsStalked marine filter feeders
- arthropodsJointed-limb invertebrates
- mollusksSoft-bodied invertebrates, often shelled
- spongesPorous absorbent masses
corals · chordates · echinoderms · phyla · invertebrates · bilateral symmetry · segmentation · hard shells
Formation of distinct species
- natural selectionDifferential reproductive success
- common ancestorOrigin point of descendants
- divergenceSeparation from common origin
- phylogenyEvolutionary relationships among organisms
Hox genes · bilateral symmetry · ecological niches · cladistics · phenotype · genotype · macroevolution · tree of life
Rapid increase in quantity
- diversificationExpanding into varied areas
- multicellularHaving multiple cells
Burgess Shale
Cambrian lagerstätte in Canada
- fossilsPreserved ancient organism traces
- PrecambrianEarliest geological eon
- stratigraphyStudy of rock layers
sedimentary layers · fossilization · radiometric dating · paleobiology · geological time
trilobites
Extinct marine arthropods
- brachiopodsStalked marine filter feeders
- arthropodsJointed-limb invertebrates
- mollusksSoft-bodied invertebrates, often shelled
sponges · corals · chordates · echinoderms · phyla · invertebrates · bilateral symmetry · segmentation · hard shells · exoskeletons
speciation
Formation of distinct species
- natural selectionDifferential reproductive success
- common ancestorOrigin point of descendants
- divergenceSeparation from common origin
phylogeny · Hox genes · bilateral symmetry · ecological niches · cladistics · phenotype · genotype · macroevolution · tree of life
proliferation
Rapid increase in quantity
- diversificationExpanding into varied areas
- multicellularHaving multiple cells
- evolutionevolution, natural selection, mutation, adaptation, speciation
- Earth history eventsice age, volcanic eruption, mass extinction, asteroid impact, continental drift
- origins debatecreationism, evolution, intelligent design, creation science, Darwinism
- creationismcreation, creator, young earth, creation science, creation story
- macroevolutionmacroevolution, speciation, extinction, fossil record, common descent
- vertebrate originsnotochord, gill slits, lancelet, hagfish, lamprey