L2

Question 1

In order to become a useful fossil an organism must: (6 reasons)

Answer 1

1. Die and avoid destruction by biological (microbial decay, scavenging, trampling) or physical (weathering, erosion) processes
   2. To avoid this it must be transported into an environment where it Is deposited, buried and this incorporated into sediment (rock record)
      - Few areas of net accumulation, more areas of net erosion eg the sea
   3. The organism can then be fossilised by a variety of processes (taphonomy)
   4. That sediment must avoid diagenetic or metamorphic processes that alter the rock and destroy the fossil
   5. That sediment must avoid later destruction by erosion
   6. The fossil must become expose at the surface and discovered by someone who will study it

Question 2

Shells can have material altered by: (5 reasons)

Answer 2

Added, removed, recrystalised, preserved, unaltered

Question 3

Why is the fossil record incomplete? (4 reasons)

Answer 3

• Sediment only accumulates over a very small area of the Earth at any given time
• Only a tiny fraction of the organisms that ever live will be fossilised
• Most will subsequently be destroyed with the rock that contains them
• Only a small fraction of fossils ever formed will be collected and studied

Question 4

Bias of the fossil record (4 reasons)

Answer 4

• Certain organisms and parts of organisms are preferentially preserved (hard tissues eg teeth, shells)
  • Recalcitrant (hard) vs labile (soft)
  • Certain environments preferentially preserve sediment and hence fossils (marine environment results in greater preservation)
  • Older rocks are more likely to be destroyed (less of them), pull of the recent, more less old rocks in recent times
  • Collector bias (employment etc), decolonising helicopter science

Question 5

What organisms leave a fossil record? (5)

Answer 5

Bacteria
Protists
Plants
Fungi
Animals

Question 6

Bacteria

Answer 6

• Certain bacterial sheaths and structures built by bacteria (stromatolites)
  
  • Generally don’t preserve
  • Replace soft tissue in its place

Question 7

Protists

Answer 7

• Those that form exo or endoskeletons
  
  • (radiolaria/diatoms/forams/coccoliths etc) and resting cysts (dinos)
  • Reasonable potential however some groups are not represented

Question 8

Plants

Answer 8

• Woody tissues (lignin), cuticle (cutan), spores (sporopollenin)
  Good fossil record

Question 9

Fungi

Answer 9

• Chitinous spores and hyphae
  Tough to separate and identify

Question 10

Animals

Answer 10

• Those with recalcitrant exo and endoskeletons
  Very variable

Question 11

In what environments do sediments accumulate?

Answer 11

• Low sea level results in less shelf cover and vice versa
  • Edge of shelf is the edge of the continent
  • Sediment usually gets transported from mountains to plains, it is very rare for sediment to be fossilised in mountain plains
  • Fault lines sometimes cause floods bringing parts of sediment down into ground preserving
  • Majority of sediment is on the continental shelf, which is where most species richness is located (photic zone)
  • More shelf cover = more fossils
  • Sediment in deep ocean is often destroyed due to plate tectonics
  • Bias towards marine shelf living organisms
  • Tropical shelf zones result in high sediment
  • Red clay centre of ocean, not great preservation

Question 12

More shelf cover = …?

Answer 12

More fossils

Question 13

Where is it rare for sediment to become fossilised?

Answer 13

Mountains

Question 14

Where is the majority of sediment located?

Answer 14

On the continental shelf

Question 15

Environmental trends that may bias the fossil record over geological time: (3)

Answer 15

Sea level changes
Continental configuration (more/less shelf)
Atmospheric composition (oxygen levels)

Question 16

Sea Level changes (often related to long term climate trends and/or continental configuration)

Answer 16

• Current there is very shallow sea levels, most of Earth history is a greenhouse world with high sea levels

Question 17

2. Continental configuration (eg more/less shelf)

Answer 17

Effects area of shelf

Question 18

Atmospheric composition (effects weathering rates and hence sediment production, survival of fossils)

Answer 18

• Higher oxygen breaks down fossils quicker
  • Potential bias related to oxygen amount in the atmosphere

Question 19

Do fossil record patterns reflect biological signals or geological signals or both?

Answer 19

• Common cause hypothesis (both follow the same signal)
• Both reflect one another

Question 20

Steps to successfully interpreting the fossil record?

Answer 20

• Plot the spatial (palaeogeographical) and temporal distribution of fossils
• Date them from each fossil bed
• Map their locations from old continental areas
• Understand the nature of its incompleteness and its bias

Question 21

What are ghost ranges?

Answer 21

• Know they are present because of a sister group
• One didn’t give rise to the other

Question 22

Probabilities of range extensions

Answer 22

• Look at each bed and calculate fossil frequency and calculate fossil frequency and calculate which beds it is missing from
• If it is missing from most beds range extensions are likely
• If it is in every single bed and then dissapears, it is likely to be its true dissapearance

Question 23

analysis -Volume of rock deposited per time slice:

Answer 23

• More rock = more fossils
• More acute about biodiversity curves

Question 24

analysis-Exposed area of rock per time slice

Answer 24

• More exposed = more fossils

Question 25

Bog standard preservation versus exceptional preservation

Answer 25

• More common to be single component than whole body
  • Shell vs soft tissues etc
  • Can find out much more information from the fossil when it is whole preserved
  • Finding a single bone is not always great for looking at morphology, can lead to incorrect estimates

Question 26

What use is the fossil record? (4)

Answer 26

• If we didn’t have it there would be no knowledge of Evolution and extinction
• Can date fossil time periods
• Previous climates and atmospheric composition
• Provides a time frame for evolution

Question 27

Terrestrial deposits effectiveness:

Answer 27

Rare, often not good for preservation, often biased towards animals that live near water

Question 28

Dinosaur fossil record

Answer 28

• Good fossil record (bones and teeth)
  • But terrestrial (deposits rare, often not good for fossil preservation and biased towards animals that live near water)
  • Often found in land basins where sediments accumulate
  • First appeared in mid-late Triassic to late Cretaceous
  • Name find and put them into time frame and locations
  • Many new species are named when they may only be juveniles or females etc

Question 29

The classic dinosaur radiation is not the case of …?

Answer 29

Constant increase through time

Question 30

Dinosaur Radiation Unevenness

Answer 30

• Classic radiation is not the case of constant increase through time
  • Each time period varies in time length
  • As does each stage
  • Dinosaur richness is due to length of time period being uneven (longer)
  • Certain areas biased to study lead to uneven results
  • When bias is taken into account it becomes more even