23-history Of Life On Earth

Question 1

Relative dating

Answer 1

• stratigraphy
• Geological strata
• levels of sedimentary rock

Question 2

Radiometric dating

Answer 2

-uses the half-lives (the time for half the atoms in a radioisotope to decay into a different isotope) radioisotopes with predictable decay patterns over long periods of time to calculate the age of objects.

Question 3

Precambrian era (4.6bya-543mya)

Answer 3

~4 B years long
Life was small and aquatic
-Hadean period
         -no life
         -no O2
-Archean period
         -first photosynthetic organisms
         -still no O2
-Proterozoic period
         -prokaryotes diversified
         -first eukaryotes & multicellular organisms 
         -O2 rises to 18%
         - “snowball earth”

Question 4

Paleozoic era (542mya-252mya)

Answer 4

• Cambrian period
  
  • O2 reaches current levels
  • diversification of animals and photosynthetic organisms
• Ordovician period
  
  • glaciation
  • sea levels drop
  • mass extinction at end (~75% species lost)
• Silurian period
  
  • sea levels rise, and Pangea splits (hot, humid)
  • fish diversity
  • plants and animals colonize land
• Devonian period
  
  • continents collide & giant meteor strikes earth
  • fish diversify, first insects and amphibians
  • mass extinction at end (~75% Marine life lost)
• Carboniferous period
  
  • climate cools
  • extensive forests, first reptiles, insect diversity
• Permian period
  
  • swampy
  • O2 levels high at start but drop dramatically at end
  • Pangea forms
  • reptile diversity, massive amphibians and flying insects (O2)
  • Mass extinction at end (~96%)

Question 5

Mesozoic era (251mya-65.6mya)

Answer 5

• Triassic
  
  • Pangea begins to drift, hot/humid
  • first dinosaurs and mammals, marine invertebrates diversify
  • mass extinction (~65%)
• Jurassic
  
  • two large continents, warm climate
  • diverse dinosaurs, radiation of ray-finned fish, flowering plants
• Cretaceous
  
  • continents continue to drift
  • more diverse dinosaurs
  • mass extinction, meteor (~76%)

Question 6

Cenozoic era (65.5mya-present)

Answer 6

Tertiary period
-Paleogene
-climate warms and cools (CO2 levels)
-diverse vertebrate groups, flowering plants, and insects
-Neogene
-continents close to current
-movement of plants and animals
Quaternary
-cold/dry
-humans evolve, many large mammals go extinct

Question 7

Earths physical changes which have effected evolution

Answer 7

• continental drift
• volcanic activity
• climate change (ice ages)
• meteors