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What’s It All About Essential Question:
Can relative dating and relative frequency be a trusted thing?
Objectives: Describe the fossil
record Sate the information
that relative dating and radioactive dating provide about fossils
Identify the divisions of the geological time scales
Fossil Formation Provides evidence about the history of life
on Earth Shows how different groups of organisms,
including species have changed over time The fossil record is incomplete because just
the right conditions must occur.
How Fossils Form
Water carries small rock particles to lakes and seas.
Dead organisms are buried by layers of sediment, which forms new rock.
The preserved remains may later be discovered and studied.
See page 418!
Interpreting Fossil Evidence Relative Dating—Age of a fossil is
determined by comparing its placement with that of fossils in other layers of rock Estimate of the age
Radioactive Dating—Calculate the age of a sample based on the amount of remaining radioactive isotopes it contains Accurate Age
Geologic Time Scale Used by paleontologists Represents evolutionary time Mark major changes in fossils
Division of Time Era—One of several subdivions of time
between the Precambrian and present Period—Unit of time in which eras are
subdivided
Draw a big table that looks like this:
Glaciations; mammals increased; humans
Mammals diversified; grasses
Aquatic reptiles diversified; flowering plants; mass extinction
Dinosaurs diversified; birds
Dinosaurs; small mammals; cone-bearing plants
Reptiles diversified; seed plants; mass extinction
Reptiles; winged insects diversified; coal swamps
Fishes diversified; land vertebrates (primitive amphibians)
Land plants; land animals (arthropods)
Aquatic arthropods; mollusks; vertebrates (jawless fishes)
Marine invertebrates diversified; most animal phyla evolvedAnaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life
Cenozoic
Mesozoic
Paleozoic
PrecambrianTime
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
1.8–present
65–1.8
145–65
208–145
245–208
290–245
363–290
410–363
440–410
505–440
544–505
650–544
Key EventsEra Period Time(millions of years ago)
Cen
ozoi
c E
ra Quaternary Period 1.8-present Glaciations, mammals increased, humans
Tertiary Period 65-1.8 Mammals diversified, grasses
Mes
ozoi
c E
ra Cretaceous Period
145-65 Aquatic reptiles diversified, flowering plants,
mass extinction Jurassic Period
208-145 Dinosaurs diversified, birds
Triassic Period 245-208 Dinosaurs, small mammals, cone-bearing
plants
Pal
eozo
ic E
ra Permian Period
290-245 Reptiles diversified; seed plants; mass extinction
Carboniferous Period 360-290 Reptiles; winged insects diversified; coal swamps
Devonian Period 410-360 Fishes diversified; land vertebrates (prim amphibs)
Silurian Period 440-410 Land plants; land animals (arthropods)
Ordovician Period 505-440 Aquatic arthropods; mollusks; vertebrates (jawless
Cambrian Period fishes) 544-505 Marine inverts diversified; most animal phyla
evolved