Paleontology and Macroevolution Flashcards
What is a fossil?
A fossil is any trace left by an organism that lived in the past
What are the 4 general categories of fossil formation?
o Compression fossils
o Casts and molds
o Permineralized fossils
o Unaltered/minimally altered remains
What is preserved in compression fossils?
External structures
How do compression fossils form?
Compression and compaction from overlying sediment, leaves behind a carbon film
What do casts and molds preserve?
External and internal structures
How are casts and molds formed?
Originates when buried remains decay. Molds consist of unfilled spaces; casts form when new material infiltrates the spaces and hardens into rock
What do permineralized fossils preserve?
Internal and external structures (e.g., petrified wood)
How do permineralized fossils form?
Dissolved minerals precipitate in the tissues of organisms buried in sediment
What are unaltered remains?
Intact tissue and skeleton
How are unaltered remains preserved?
Organic matter preserved in place not conduce to decay by bacteria and fungi (e.g., peat bogs, resin, ice, etc.) (little oxygen, protective environments)
What are the three components that successful fossilization relies on?
Durability of material
Burial (usually in wet sediment)
Lack of oxygen
Give examples of materials that are particularly durable for fossil formation. (5)
Calcified structures (shells)
Skeleton
Exoskeleton
Wood
Leaves
Why is burial important for fossil formation?
No exposure to oxygen or scavengers
Why is lack of oxygen important for fossilization?
Most bacteria and fungi need oxygen
What is fossilization biased by? (3)
Geography
Taxonomy
Temporal/age
What geographical areas are fossils biased towards?
Lowland marine habitats
Describe the taxonomy bias of the fossil record.
Marine organisms with hard parts
How is fossilization biased with age?
Older fossils are rarer
What area is said to have the best preservation of the earliest life forms?
Burgess Shale
What is a whale?
o Living and extinct whales are all in the Mammalian order Cetacea
o Delimited based on cranial skeletal morphology, especially dentition and ear bones
Are whales artiodactyl or non-artiodactyl ungulates?
Astragalus of Artiodactyl ungulates is a double pully formation
But whales lost astragalus
o Looking back…
Ambulocetus (48-47 MYA)
* Earliest +/- complete whale
* Walked on land but spent time in water
* Swam much like an otter
Artiodactyl Astragulus bones 40-6 MYA
* Pulley form
o Therefore, whales are artiodactyl ungulates, sister to hippos
List the three geological eras.
Paleozoic (ancient life)
Mesozoic (middle life)
Cenozoic (recent life)
What is the timeline of the Paleozoic era?
543-251 mya
What are the periods within the Paleozoic era? (6)
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
What are the 3 periods within the Mesozoic era?
Triassic
Jurassic
Cretaceous
What are the two periods within the Cenozoic era?
Tertiary
Quaternary
What were the major evolutionary events within the Cambrian period? (2)
Arthropod radiation
1st vertebrates
What were the major evolutionary events in the Ordovician period? (3)
1st land plants
1st jawed fish
Ends with mass extinction
What were the major evolutionary events within the Silurian period? (2)
1st bony fish
1st vascular plants
What were the major evolutionary events within the Devonian period? (3)
1st tetrapods
1st insects
Ends with mass extinction
What were the major evolutionary events within the Carboniferous period? (2)
1st winged insects
1st synapsids
What were the major evolutionary events within the Permian period? (1)
Ends with mass extinction
What were the major evolutionary events within the Triassic period? (4)
1st dinosaurs
1st mammals
1st dinosaur radiation
Ends with mass extinction
What were the major evolutionary events within the Jurassic period? (2)
1st eutherian mammals
1st birds
What were the major evolutionary events within the Cretaceous period? (5)
2nd dinosaur radiation
1st flowering plants
Flowering plant radiation
Mass extinction
Mammal radiation
What were the major evolutionary events within the Tertiary period? (1)
1st primates
What were the major evolutionary events within the Quaternary period? (1)
1st humans
During which period did arthropod radiation occur and the first vertebrates were formed?
Cambrian
During which period did land plants and jawed fish emerge?
Ordovician
During which period did vascular plants and bony fish first emerge?
Silurian
During which period did tetrapods and insects first emerge?
Devonian
During which period did winged insects and synapsids first emerge?
Carboniferous
During which period did dinosaurs and mammals first emerge?
Triassic
During which period did eutherian mammals and bird first emerge?
Jurassic
During which period did flowering plants first emerge?
Cretaceous
During which period did primates first emerge?
Tertiary
During which period did humans first emerge?
Quaternary
List the five mass extinctions by period.
Ordovician-Silurian
Devonian-Carboniferous
Permian-Triassic
Triassic-Jurassic
Cretaceous-Tertiary
What is a mass extinction?
events that lead to extinction >60% of species
How many mass extinctions have occurred since the Cambrian era
5
On average, how many species do we lose every million years?
20%
Are we currently experiencing a 6th mass extinction?
Maybe
o In recent times extinction rates do not approach 60% of known taxa
o HOWEVER, in the last 100 years human population growth and habitat loss have accelerated
o Biologists predict 100-1000x normal background rates
