The Fossil Record

Question 1

What is the fossil record and why is it useful?

Answer 1

The discovery and classification of living things based on anatomical and morphological features
-DNA sequencing is used nowadays but cannot be used on dead organisms

Question 2

What does the fossil record interpret and how are they different?

Answer 2

Endoskeletons = located inside the body- usually remain well preserved

Exoskeletons = located outside of body- most features lost as they are soft

Question 3

How is the relative age of sedimentary rocks determined?

Answer 3

By superposition- but can be some uplift so some older fossils can appear newer

Question 4

What is superposition?

Answer 4

layers of rocks laid on top of each other with the oldest being at the bottom

Question 5

Name and define 3 types of rock

Answer 5

Igneous = most abundant making up the mantle, oceanic crust and most of the continental crust

Metamorphic = already extisting rock (could be any type) that has been transformed via high heat, pressure or a combo of these factors into new rock e.g. marble transformed from limestone

Sedimentary = formed on/near earths surface via compression of ocean sediments or other processes like erosion, weathering

Question 6

what type of rocks are fossils found in?

Answer 6

sedimentary rock e.g. limestone

Question 7

What are indicator fossils?

Answer 7

Preserved remains of organisms that were very common, used to identify rocks of similar age elsewhere

Question 8

How can the age of the earth be determined? + what is a more accurate way to determine this?

Answer 8

depths of sedimentary rock + todays rates of deposition = age of earth

• measuring radioactive decay of igneous rocks provides a more precise method

Question 9

By measuring the radioactive decay of igneous rocks, how can this determine the age of the earth?

Answer 9

Igneous rocks are formed with ratio of isotopes- some can be unstable so their half life can be used to date old rocks

Question 10

What are igneous intrusions and how are they useful?

Answer 10

When molten magma has risen from the mantle through the sedimentary rock and cools below the earths surface
These can be used to date sedimentary rocks via the arranged rocks in layers from igneous intrusions

Question 11

Name the 4 key geological eras and how are they defined

Answer 11

1. Proterozoic
2. Paleozoic
3. Mesozoic
4. Cenozoic

• defined by the changes in fauna, with extinction playing a key role as it frees up niches within the environment that were previously occupied

Question 12

Define: Taphonomy

Answer 12

The study of conditions under which the remains of living things can be preserved or destroyed

Question 13

How is the fossil record biased?

Answer 13

Organisms living in river deltas/shallow seas where there are high rates of depositon have their remains preserved in sediments
Whereas organisms living on mountains have their remains eroded away
so organisms that lived in areas with high rates of deposition will be better represented in the fossil record

Question 14

What is a lagarstatten? + example

Answer 14

A sedimentary deposit that exhibits well preserved fossils- often used as a control when looking at poorly preserved fossils in order to determine what is missing

e.g. Burgess Shale- has 120 species that developed during Cambrian Period

Question 15

If an organism has a good fossil record, what can be measured?

Answer 15

The evolutionary rates

Question 16

What is an alternative theory of evolution and who suggested it?

Answer 16

Eldridge + Gould suggested punctuated equilibrium

Question 17

What is punctuated equilibrium and how is it different to Darwin’s theory?

Answer 17

Patterns of morphological constancy known as stasis followed by evolution that takes place in rapid bursts of time (500000 years in evolutionary time) where a big evolutionary change occurs, then a species re-enters a period of stasis with its new adaptation.

• Darwin suggested a more gradual process where small adaptations are happening all the time

Question 18

What does species diversity depend on?

Answer 18

rates of speciation + extinction

Question 19

What is the K-T event?

Answer 19

mass extinction event between the cretaceous and tertiary periods, where it was estimated that 70% of all species became extinct (including dinosaurs)

Question 20

What was the suggested cause of the K-T event and where does the evidence come from?

Answer 20

CAUSE = iridium layer found at K-T boundary which is usually extremely rare so suggests asteroid impact
EVIDENCE = a large crater in Mexico- but lots of evidence for lots of volcanic activity in the Deccan Traps in India

Question 21

What is the P-T event and what was the cause?

Answer 21

Mass extinction of the typical Palaeozoic ocean and almost all large land animals that occurred during the Permian and Triassic periods

CAUSE = unknown but volcanism is likely