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BIOL 1108
BIOL 1108: Exam 4 -Principles of Biology II
(Latest 2026/ 2027 Update) Review| 100%
Verified Questions & Answer| Grade A.
1.Earth's Geological Time Scale: 4.6 BYA: Earth forms
3.8-3.5 BYA: first life, anaerobic prokaryotes in oceans
2.4 BYA: cyanobacteria release O2, great oxygenation event, ozone layer
forms
1.8 BYA: eukaryotes arise via endosymbiosis, larger, more complex cells
2.~575 Million Years Ago: multicellular animals diversify during the Ediacaran
and Cambrian Explosion (541-485)
3.467-350 Million Years Ago: life colonizes land—plants, arthropods, then
vertebrates adapt to air and gravity
4.65 Million Years Ago: dinosaur extinction mammal radiation’
5.6-7 Million Years Ago: first hominins appear in Africa
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6.200-300 Thousand Years Ago: homo sapiens evolves: large brains, tool use,
culture, global spread
7.First Atmosphere: - a prokaryotic ancestor lived in extreme conditions of
early Earth - little oxygen
- atmosphere is water vapor and volcanic compounds, such as
nitrogen, CO2, methane, and ammonia - life began in the ocean
8. Fossil Stromatolites: first fossil evidence of life, dating back to 3.5 BYA
- form when microbial mats trap and bind sediment particles, creating layered
rock-like structures
- fossils show that: life started in aquatic environment, prokaryotic life
(bacteria) dominated early Earth, photosynthetic cyanobacteria led great
oxygenation event
9. Photosynthetic Bacteria: the rise of photosynthetic bacteria causes oxygen
to be pumped into the atmosphere
- prior to cyanobacteria dominating the planet, the Earth had virtually no
oxygen, prokaryotes were anaerobic - tremendous rise in oxygen drove a
BIOL 1108
, 3
BIOL 1108
mass extinction of most anaerobic bacteria (causing an ice age), and paved
the way for evolution of other organisms
- example: cellular respiration arose as an adaptation to this new
environment
10. Great Oxygenation: among the largest impacts life ever had
11. Prokaryotes to Eukaryotes: eukaryotic cells formed through a series of
endosymbiotic events where one cell engulfed another
- 1st event: an ancestral archaeal cell engulfed an aerobic bacterium,
instead of digesting it, bacterium lived inside the host and eventually became
mitochondrion
- 2nd event: later, heterotrophic eukaryote engulfed photosynthetic
bacteria (cyanobacterium), which evolved into plastids/chloroplasts
12. Ediacaran: - Ediacaran fossils have simple shapes that don't clearly match
modern animals
- macroscopic fossils (Ediacaran) of organisms thought to be animals first
appear in rocks deposited only 565 million years ago
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BIOL 1108
13. Cambrian Explosion: - 541-485 MYA
- rapid diversification of aquatic life (no land animals or land plants yet)
- most modern body plans appear (bilaterians, early deuterostomes including
echinoderm ancestors, arthropods, mollusks)
- hard parts (biomineralization)
- complex eyes/sensory systems
- more elaborate nervous and muscular coordination
- active burrowing ("substract revolution")
- ecological arms race: predation, defenses (spines, shells, behaviors)
14. Cambrian Period: - Cambrian fossils commonly include skeletons made of
silica, calcium carbonate, and calcium phosphate minerals
- Cambrian rocks preserve skeletons that can be related to present-day phyla,
including mollusks and echinoderms
- Cambrian explosion marked a time of rapid diversification
15. Causes of Cambrian Explosion (possible): 1) predator-prey coevolutionary
arms race
2) rising ocean oxygen levels
BIOL 1108
BIOL 1108
BIOL 1108: Exam 4 -Principles of Biology II
(Latest 2026/ 2027 Update) Review| 100%
Verified Questions & Answer| Grade A.
1.Earth's Geological Time Scale: 4.6 BYA: Earth forms
3.8-3.5 BYA: first life, anaerobic prokaryotes in oceans
2.4 BYA: cyanobacteria release O2, great oxygenation event, ozone layer
forms
1.8 BYA: eukaryotes arise via endosymbiosis, larger, more complex cells
2.~575 Million Years Ago: multicellular animals diversify during the Ediacaran
and Cambrian Explosion (541-485)
3.467-350 Million Years Ago: life colonizes land—plants, arthropods, then
vertebrates adapt to air and gravity
4.65 Million Years Ago: dinosaur extinction mammal radiation’
5.6-7 Million Years Ago: first hominins appear in Africa
BIOL 1108
, 2
BIOL 1108
6.200-300 Thousand Years Ago: homo sapiens evolves: large brains, tool use,
culture, global spread
7.First Atmosphere: - a prokaryotic ancestor lived in extreme conditions of
early Earth - little oxygen
- atmosphere is water vapor and volcanic compounds, such as
nitrogen, CO2, methane, and ammonia - life began in the ocean
8. Fossil Stromatolites: first fossil evidence of life, dating back to 3.5 BYA
- form when microbial mats trap and bind sediment particles, creating layered
rock-like structures
- fossils show that: life started in aquatic environment, prokaryotic life
(bacteria) dominated early Earth, photosynthetic cyanobacteria led great
oxygenation event
9. Photosynthetic Bacteria: the rise of photosynthetic bacteria causes oxygen
to be pumped into the atmosphere
- prior to cyanobacteria dominating the planet, the Earth had virtually no
oxygen, prokaryotes were anaerobic - tremendous rise in oxygen drove a
BIOL 1108
, 3
BIOL 1108
mass extinction of most anaerobic bacteria (causing an ice age), and paved
the way for evolution of other organisms
- example: cellular respiration arose as an adaptation to this new
environment
10. Great Oxygenation: among the largest impacts life ever had
11. Prokaryotes to Eukaryotes: eukaryotic cells formed through a series of
endosymbiotic events where one cell engulfed another
- 1st event: an ancestral archaeal cell engulfed an aerobic bacterium,
instead of digesting it, bacterium lived inside the host and eventually became
mitochondrion
- 2nd event: later, heterotrophic eukaryote engulfed photosynthetic
bacteria (cyanobacterium), which evolved into plastids/chloroplasts
12. Ediacaran: - Ediacaran fossils have simple shapes that don't clearly match
modern animals
- macroscopic fossils (Ediacaran) of organisms thought to be animals first
appear in rocks deposited only 565 million years ago
BIOL 1108
, 4
BIOL 1108
13. Cambrian Explosion: - 541-485 MYA
- rapid diversification of aquatic life (no land animals or land plants yet)
- most modern body plans appear (bilaterians, early deuterostomes including
echinoderm ancestors, arthropods, mollusks)
- hard parts (biomineralization)
- complex eyes/sensory systems
- more elaborate nervous and muscular coordination
- active burrowing ("substract revolution")
- ecological arms race: predation, defenses (spines, shells, behaviors)
14. Cambrian Period: - Cambrian fossils commonly include skeletons made of
silica, calcium carbonate, and calcium phosphate minerals
- Cambrian rocks preserve skeletons that can be related to present-day phyla,
including mollusks and echinoderms
- Cambrian explosion marked a time of rapid diversification
15. Causes of Cambrian Explosion (possible): 1) predator-prey coevolutionary
arms race
2) rising ocean oxygen levels
BIOL 1108
