The Fossil Record

Question 1

Fossil

Answer 1

Preserved body, impressions or traces of a dead organism

Question 2

Fossil record

Answer 2

The information derived from fossils

Question 3

Conditions for fossil formation (7)

Answer 3

1. Rapid sediment accumulation
2. Constant cool temperatures
3. Low light availability
4. Protection from scavengers and decomposes
5. Hard body parts
6. Low winds
7. Constant humidity (moderate + stable)

Question 4

Steps in fossilisation

Answer 4

1. Organism is covered by sediment
2. Overtime, layers of sediment and pressure builds, forming sedimentary rock
3. Lack of oxygen, microorganisms and disturbances allow preservation to occur

Question 5

4 Types of fossils

Answer 5

Pre-mineralised fossils, trace fossils, mould fossils, cast fossils

Question 6

Pre mineralised fossil

Answer 6

Formed when minerals from groundwater replace most or part of the actual structure if the organism

Question 7

Trace fossils

Answer 7

A fossil indicating the existence of an organism rather than the organism itself (e.g nests, footprints, faeces)

Question 8

Mould fossils

Answer 8

Formed when an organism completely decays after being buried in sediment, leaving its impression only

Question 9

Cast fossils

Answer 9

Organism decomposes or leaves quickly, leaving a mold that gets filled with material and covered by sediment, creating a cast. This shows shape of organism without organic material

Question 10

Two main techniques for dating fossils

Answer 10

Relative and absolute dating

Question 11

Relative dating

Answer 11

Based on the law of fossil succession - fossils of the same age will be in the same layer of sedimentary rock, fossils found in lower sedimentary layer will be older. Also use index fossils to determine the age, and transitional fossils

Question 12

Index fossils

Answer 12

Used as a reference to easily determine the age of unknown fossils

Question 13

Index fossils must be…

Answer 13

-physically distinctive
-have had a large population
-have existed jn many geographical areas
-only lived within a short period of time

Question 14

Transitional fossils

Answer 14

A fossil that shows traits common to both its ancestral and descendant groups.

Question 15

What can a transitional fossil help with?

Answer 15

-help demonstrate evolutionary changes
-help the timeline

Question 16

Events of earth in order

Answer 16

Prokaryotes -> photosynthesis -> eukaryotes -> multicellular organism -> animals in land -> mammals -> flowering plants -> genus homo

Question 17

Absolute dating

Answer 17

Determines the absolute age of a fossil by measuring relative amounts of radioisotopes to their products

Question 18

Carbon dating

Answer 18

1. Carbon 14 breaks down into more stable product, nitrogen 14
2. After 5730 yrs of an organisms death, half of its carbon 14 atoms would have broken down into nitrogen 14

Question 19

Half lives

Answer 19

1 half life - 5730
2 half lives - 11 460
3 half lives - 17 190
4 half lives - 22 920

Question 20

Limitations of carbon dating

Answer 20

After 50 000 years, carbon dating will not work as most of the carbon 14 already would have broken down