Unit1-5 Flashcards
(21 cards)
What are the four eons of geologic time?
Hadean, Archean, Proterozoic, Phanerozoic
What event marks the beginning of Earth’s history 4.6 BYA?
A massive meteor impact that led to moon formation and extreme heating of Earth.
Why is there no rock record from the Hadean eon?
Hadean Earth was heavily bombarded by asteroids, which likely vaporized early rock and oceans.
What was the Miller-Urey experiment?
It simulated early Earth conditions and produced organic molecules like amino acids from simple gases.
What gases were used in the Miller-Urey experiment?
Methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor (H₂O) — no oxygen.
What are some hypotheses for the origin of organic molecules?
From meteorites, deep-sea vents, or reactions in a reducing atmosphere.
What are microfossils?
Fossilized microscopic life, possibly 3.5 BYA, resembling prokaryotes.
What are stromatolites?
Mats of cyanobacteria that trap minerals; oldest known are 2.7 BYA.
What is isotopic evidence of early life?
Preference for carbon-12 by living organisms indicates carbon fixation by 3.8 BYA.
What are biomarkers?
Organic molecules (e.g., lipids) indicating biological activity in ancient rocks.
What environmental factors caused mass extinctions?
Climate shifts, volcanic eruptions, glaciations, meteors, and continental drift.
How did plate tectonics affect evolution?
By isolating or mixing populations, influencing speciation and extinction.
What is ‘Snowball Earth’?
A period when the Earth was nearly entirely covered in ice.
How did early photosynthesis change Earth?
Oxygen accumulated in the atmosphere, forming the ozone layer and altering ecosystems.
What are the three domains of life?
Bacteria, Archaea, Eukarya
What are the five supergroups of eukaryotes?
Excavata, SAR, Archaeplastida, Amoebozoa, Opisthokonta
What is the Endosymbiotic Theory?
Mitochondria and chloroplasts originated as engulfed prokaryotes.
Why is compartmentalization important in eukaryotes?
It allows for specialized functions and greater complexity.
What did sexual reproduction lead to?
Increased genetic diversity through meiosis and crossing over.
What was the Cambrian explosion?
A rapid diversification of animal life ~542–488 MYA.
What adaptations were necessary for life on land?
UV protection (ozone), prevention of desiccation, and water acquisition strategies.
