Fossils Flashcards
What is a fossil record?
History of life as documented by fossils, the remains or imprints of the organisms from earlier geological periods preserved in sedimentary rock.
Is the fossil record bias?
Yes, but in a predictable way.
What is the purpose of fossils (and record)?
Hint: 3 purposes
- Can provide important information (e.g relative rock dating).
- Past changes in the environment may be important in predicting and understanding where we are headed.
- Helps us understand what the implications of the current crash in biodiversity might be.
What is a fossil?
A fossil is any trace of an organism that is usually preserved in rocks, including their:
- Body parts
- Tracks and trails
- Chemical signature (scent)
- Excreta
Are all environments capable of preserving fossils well? And where do they typically come from?
No, not all environments are. Fossils dominantly come from marine environments
Therefore, fossil record bias.
How is the fossil record bias? (in a predictable way)
Hint: 3
- Not all environments are capable of preserving fossils. Fossils dominantly come from marine environments
- Not all organisms are capable of being preserved.
Fossils are dominantly hard parts (e.g shells, bones). - There is a low number of individuals/restricted geographic range reduces the likelihood of preservation.
Fossils generally represent the most common form.
Example of how the fossil record is helpful
Whales have a good fossil record, indicating they had legs once but now no longer.
Or humans were once four-legged and now two-legged (bipedal).
Can show the evolution of species
What are three intermediate forms of fossils?
- Fish (gills, scales, fins)
- Tetrapod (rib bones, mobile neck with separate pectoral girdle, lungs).
- Fishapod (half fish + half tetrapod, limbs, bones, joints + functional wrist joint on radiating, fish-like fins instead of toes, half-fish/tetrapod ear region).
How do you preserve an organism?
Normally the remains of a plant or animal are destroyed.
Two special conditions are needed o avoid this:
- Rapid burial
- the possession of hard parts
What are the two special conditions to avoid all the remains of a plant or organism being destroyed?
- Need to harden (geothermal process)
- Rapid burial
When an organism perishes, its soft parts are often quickly eaten by scavengers or decomposed by bacteria. Occasionally, the remains are buried by sediment, when this happens the remains are protected from the environment, where destructive processes take place.
Animals plants have a better chance of being preserved if they have hard parts. Although traces of soft-bodied animals (e.g jellyfish, worms, insects exist) but are not common. Hard parts such as shells, bones, teeth are predominant in the record of the past.
What gives an organism or plant the best chances of being preserved?
Animals and plants have a better chance of being preserved if they have hard parts such as shells, bones or teeth. Although traces of soft-bodied animals (jellyfish, worms, insects exist) but are not common.
Hard parts including shells, bones and teeth are predominant in the record of the past.
If the remains are buried by sediment does it better the chance of the fossils being preserved?
Yes, because they are protected from the environment where destructive processes take place.
What are the three options that can happen when the animal or plant dies/decomposes?
- Disappear
- Nothing could happen
- Dissolve = moulds
- Infill/cast replacement (the rock around it could mould in it/around and replacement and fill happens (common in trees).
- Insects in amber
- Mammals in ice (died 15,000 years ago).
- Carbon film (dark patch around the skeletal bones)
- Encased in tar
What is recrystallisation?
The crystals from the original shell crystalised to other shells around them, resulting in a vague shape (can’t collect very hard).
What does internal mean?
Hint: In the sense of fossils
Go in the organism
