Deep Time and Fossil Record

Deep time (different types and how we measure them)

Chronological time: measurable in seconds, minutes, hours (how we count time presently)

Geological time: measured in millions of years based on rocks (how we understand deep time and is relative)

Dating rocks

Look for radioactive isotopes within the minerals - radiometric dating

Rocks read from bottom to top

Layers made from volcanos

Help determine geological time more precisely

Fossil Record Limitations

We can’t see earlier fossils because they are too deep into the earth

Glacial erratic

When a big rock is carried elsewhere by a glacier millions of years ago - this is how we have access to really old rocks

Where evidence of deep time is gathered form

Fossil record, geological record, phylogenies

Fossil Record

Any traces of organisms over ten thousand years old in rock (footprints, fossil molecules, DNA, feces, etc)

Can give unique info about deep time

Phylogenies in deep time

Shows common ancestors, can estimate how old ancestors are, shows specific features

Geological record giving info of deep time

Record of climate and climate change

Information fossil record gives us

Where organisms lived, who lived alongside who (important so we know who they’re interacting with), how organisms are related to biodiversity, how diversity has changed over time, can look at transition of features

Fossil record now

Is incomplete, preserves large trends and unique insights into what really happened - “The Answer Sheet”

Biodiversity in mass extinctions

Will get really low during the event, and will sky rocket afterwards

Species are very different before and after mass extinction events

Extinct animals and ecosystems

Had major impacts on their ecosystems

Life on earth is a lot less diverse now than it was 10,000-20,000 years ago

What is the geological record

History of large-scale environment changes - amount of carbon in atmosphere, temp, sea level, etc

Shows climate history - can be important in extinction

Shows big events - land formation and mass extinctions

Palaeogeography

How areas were spatially connected to each other

Plate tectonics

Earths plates were in different places billions of years ago (continental drift - some continents were closer)

E.g. South America and Australia have similar biodiversity because their continents used to be closer