BIO 1220 - Lecture 8

what is the fossil record and fossils?

• fossil record - total collection of fossils that have been found throughout the world, provides direct evidence about organisms from the past

• fossil - physical evidence from an organism that lived in the past

when do fossils form?

when parts of organisms are buried under sediment

what are the different fossil types?

• intact - little to no change

• compression - flattened from weight above

• cast - hollow mold fills with sediment

• permineralized - groundwater flows through

• trace - biological record rather than phyiscal

what are the limitations of the fossil record and what do they mean?

1. habitat bias:

• organisms living where sediment is actively being deposited are more likely to fossilize

2. taxonomic and tissue bias:

• organisms with hard parts are more likely to leave fossil evidence

3. temporal bias:

• recent fossils more common than ancient fossils

4. abundance bias:

• abundant/present organisms leave evidence much more than species that are rare/local

how is earth history divided?

• eons

• eras

• periods

• epochs

what is radiometric dating?

used to assign absolute dates to events and species in fossil record

what do evolutionary firsts indicate

the appearance of important new lineages/innovations

what conditions do fossils form under?

buried rapidly and decompose slowly

(fossilization is a rare event)