Module 1.2 Flashcards
How do Earth’s warming and cooling cycles affect evolution?
Non-uniform temperature shifts (12°C–22°C averages) drove evolutionary changes, with warm periods favoring diversification and cool periods leading to extinctions or adaptations.
What are the two main eons of Earth’s history?
Precambrian (4600–545 mya): Earliest life (microbes → shelled animals). Phanerozoic (545 mya–present): Complex life dominates.
How did temperature shifts shape the Mesozoic?
Triassic (245 mya): Warm temps → first mammals & dinosaurs. Jurassic (208–144 mya): First birds. Cretaceous (end): Warm cycle → asteroid impact (66 mya; uranium evidence) kills dinosaurs.
Why did mammals dominate the Cenozoic?
Post-dinosaur extinction (Palaeocene epoch), mammals diversified in cooler climates, leading to modern ecosystems (Holocene).
When did Earth have the highest oxygen levels?
Ordovician period—enabled animals with inefficient lungs to survive.
How did Pangea affect climate?
Pangea, the supercontinent, significantly impacted global climate patterns, particularly through the opening and closing of its surrounding oceans and the subsequent changes in ocean currents and atmospheric circulation.
Formed in Permian (286 mya); contributed to extreme cooling.
Where are we in Earth’s temperature cycles today?
Nearing the end of a cool cycle (Holocene epoch).
What major evolutionary milestone occurred in the Cambrian period?
First fish appeared.
545 mya
What key development happened ~505 million years ago?
First land plants evolved.
Why was the Ordovician period unique for animal life?
Highest oxygen levels in Earth’s history—allowed animals with weak lungs to thrive.
When did amphibians first emerge?
408 million years ago (Devonian period).
When did reptiles evolve?
360 million years ago (Carboniferous period).
What characterized the Permian period?
Extreme cold + formation of Pangea.
How did Earth’s climate change during the Paleozoic?
Started warm (Cambrian) → peaked oxygen (Ordovician) → ended very cold (Permian).
