L2: The nature of the fossil record

Question 1

What is the first step to becoming a fossil?

Answer 1

Die and avoid destruction by biological or physical processes

Question 2

What is taphonomy?

Answer 2

Branch of palaeontology that looks at the fossilisation process

Question 3

What role does transportation play in the fossilisation process?

Answer 3

Need to be transported into an environment in which it can be buried.

Question 4

What are some agents of transport?

Answer 4

Currents, waves, rivers, bioturbation, predation, hermit crabs

Question 5

What can be inferred from a fossil assemblage?

Answer 5

If in their life habitat,, can be used to infer palaeoenvironmental conditions

Question 6

What is sedimentation?

Answer 6

When sediments such as sand, silt and mud are deposited geographically in space and time, via wind, water or volcano etc.

Question 7

What is an accommodation space?

Answer 7

A sediment trap, where sediment will be deposited

Question 8

How does sedimentary rock form?

Answer 8

Formed by the deposition and accumulation of sediments. The weight of overlying sediments causes compaction, squeezing out all the liquid from between the particles. Cementation than occurs a salts crystallise out between the grains

Question 9

What happens to a fossil if it becomes too deeply buried?

Answer 9

Will likely be destroyed due to metamorphosis at high temperatures and pressures

Question 10

What is metamorphosis?

Answer 10

Change that takes place within a body of rock as a result of it being subjected to conditions that are different from those in which it formed e.g. temperature and pressure increases

Question 11

What is diagenesis?

Answer 11

The physical and chemical changes occurring during the conversion of sediment to sedimentary rock.

Question 12

Why is the fossil record incomplete?

Answer 12

Sediments only accumulate over a very small amount of earth surface at a given time
Only a tiny fraction of the organisms that ever lived are fossilised
Many fossils are subsequently destroyed
Only a tiny fraction of fossils will ever be seen

Question 13

Why is the fossil record bias?

Answer 13

Certain organisms/parts are preferentially preserved
Certain environments preferentially preserve sediments and hence fossils
Older rocks are more likely to be damaged
Collector bias

Question 14

How do bacteria leave a fossil record?

Answer 14

Usually preserved by lithification, where their organic matter is replaced by minerals, often bacterial sheaths will be preserved

Question 15

What protists are commonly preserved?

Answer 15

Those that form endotherm/exoskeletons e.g. radiolaria, diatoms, coccoliths

Question 16

Which structures in plants are commonly preserved?

Answer 16

Woody tissues such as lignin, the cuticle and spores, are very hard to breakdown

Question 17

What fungi would be preserved?

Answer 17

Spores and hyphae

Question 18

Which animals are likely to be preserved?

Answer 18

Animals with recalcitrant ego and endo skeletons

Question 19

In what environments do most fossils form?

Answer 19

Inland in flood plains, basins or on the continental shelf

Question 20

What is the continental shelf?

Answer 20

Area of shallow seabed around the continent, where most life in the sea lives

Question 21

What are turbidity currents?

Answer 21

a rapid, downhill flow of water caused by increased density due to high amounts of sediment

Question 22

What is uplift?

Answer 22

Vertical elevation of land mass, oceanic crust may be put on land

Question 23

What happens to the fossil record when the sea level rises?

Answer 23

More continental shelf, so is higher rate of preservation. This occurs in green house world when there aren no ice sheets.

Question 24

What occurred in Central America during the Permian?

Answer 24

Inland sea flooding, an epicentral sea, due to extremely high sea levels

Question 25

How does continental configuration affect fossilisation trends?

Answer 25

Configuration has an effect on the amount of continental shelf

Question 26

How do continents move?

Answer 26

Via the Wilson cycle

Question 27

What happens to biodiversity when the continents are separated?

Answer 27

Increases, because there are more varied environments

Question 28

How does the atmosphere affect sedimentation rats?

Answer 28

Affects the weathering of rocks and therefore sediment formation and deposition

Question 29

What happens to a dead organism in high levels of oxygen?

Answer 29

More likely to decay as bacteria can survive better

Question 30

What are fossil ghost ranges?

Answer 30

intervals of geological time where a fossil lineage should exist, but for which there is no direct evidence

Question 31

What factors need to be counted in when assessing the bias and incompleteness of a fossil record in a rock sequence?

Answer 31

Ghost ranges
Probability of range expansions
Volume of rock deposited per time slice
Exposed area of rock per time slice

Question 32

What may be the greatest bias in the fossil record?

Answer 32

The divide between the poor to non-existent fossil record for organisms lacking mineralised skeletons, compared to excellent records for organisms with hard parts

Question 33

What are the main parts of dinosaurs that are preserved?

Answer 33

Bones and teeth, a relatively good fossil record

Question 34

Why is there a bias against land dinosaurs?

Answer 34

Terrestrial deposits are rare, so is a bad environment for preservation

Question 35

What is the pattern we in the total number of dinosaurs through time?

Answer 35

When accounting for the unequal length of each time stage, we see a levelling curve of increasing numbers

Question 36

What time periods did the dinosaurs live in?

Answer 36

Triassic, Jurassic and Cretaceous

Question 37

What is biostratigraphy?

Answer 37

The study of the relationship in time among groups of organisms