PERIODS

Question 1

Cambrian (541–485 Ma)

Answer 1

Cambrian Explosion — rapid diversification of marine life (trilobites, brachiopods, mollusks, early arthropods, etc.)

Question 2

Ordovician (485–444 Ma)

Answer 2

Known for: Great marine biodiversity; first jawless fishes; first land plants (non-vascular); ended with mass extinction.

Question 3

Silurian (444–419 Ma)

Answer 3

First vascular plants on land; jawed fishes evolve; reef expansion; first terrestrial arthropods.

Question 4

Devonian (419–359 Ma) — “Age of Fishes”

Answer 4

Known for: Explosion of jawed and lobe-finned fishes; first amphibians; extensive forests; early insects; ends with a mass extinction.

Question 5

arboniferous (359–299 Ma) — “Coal Age”

Answer 5

Known for: Huge swamp forests (coal formation); first reptiles; amphibian dominance; high O₂ levels; giant arthropods.

Question 6

Permian (299–252 Ma)

Answer 6

Known for: Diversification of reptiles and synapsids (early mammal ancestors); ends with Great Dying — the largest mass extinction in Earth’s history.

Question 7

Triassic (252–201 Ma)

Answer 7

Known for: First dinosaurs and mammals; reptile radiation post-Permian extinction; ends with another extinction.

Question 8

Jurassic (201–145 Ma)

Answer 8

Known for: Large, iconic dinosaurs; first birds (Archaeopteryx); first flowering plants may begin to appear late.

Question 9

Cretaceous (145–66 Ma)

Answer 9

Known for: Peak dinosaur diversity; flowering plants (angiosperms) diversify; ends with asteroid impact and mass extinction (bye dinosaurs!).

Question 10

Paleogene (66–23 Ma)

Answer 10

Known for: Rapid mammal radiation after dinosaur extinction; appearance of primates; cooler climate begins.

Question 11

Neogene (23–2.6 Ma)

Answer 11

Known for: Expansion of grasslands; diversification of apes and early hominins; continents close to modern positions.

Question 12

Quaternary (2.6 Ma–Present)

Answer 12

Known for: Ice Ages; evolution of Homo sapiens; extinction of megafauna; rise of human civilizations.