The fossil record

Question 1

how old is earth

Answer 1

4.5 billion years old

Question 2

what gives evidence of how old life is on earth

Answer 2

stromalities which are the first piece of evidence that life dates back to around 3.5 billion years ago

Question 3

stromatolities

Answer 3

rock that is made by photosynthesising bacteria

Question 4

what are the 8 steps of the geological timeline

Answer 4

1. prokaryotes 2. photosynthesis 3. eukaryotes 4. multicellular organisms 5. cambrian explosion 6. land animals 7. mammals 8. flowering plants

Question 5

extinction

Answer 5

the dying out of a species on a global or regional level

Question 6

benefits of eextinctions

Answer 6

they opened up new niches that allowed for the rapid evolution of organisms to fill these niiches

Question 7

benefits of ice ages

Answer 7

provide land bridges for travel (gene flow, migration, etc)

Question 8

negatives of ice ages

Answer 8

conditions of rapid burial for fossilisation are less likely, cold and less food for organisms to survive

Question 9

what causes extinction

Answer 9

human factors or natural catastrophies

Question 10

two mass extinction periods

Answer 10

wiping out of dinosaurs in the cretaceous period (65myo) and extinction of giant mammals (10,000 years ago)

Question 11

the fossil record

Answer 11

the information derived frommm fossils, is arranged in chronological order and helps us map the history of life on earth, placing species in appropriate geological tme franes

Question 12

fossils

Answer 12

the preserved body, impressions or traces of a dead organism that provides evidence of life from the past

Question 13

conditions of fossilisation

Answer 13

physical protection from scaverngers and decomposers, areas of rapid sediement accumulation, constant cool temps, low oxygen avliability and low light exposure

Question 14

what is the first step of fossilisation

Answer 14

the remanants of an organism are rapidly covered by sediemnt (with little exposure to factors thst may increase the rate of decomposition)

Question 15

second step of fossilisation

Answer 15

over time sediment layers build upon each other and compact until pressure cements them together to form sedimentary rock

Question 16

third step of fossilisation

Answer 16

within this rock, the fossilised remains can takke many forms

Question 17

5 steps in fossilisation of an animal

Answer 17

1. animal dies 2. the body is covered by sediment, the soft tissues decompose and hard body structures becoome fossilised 3. sediment layers accumulate and the resultant pressure forms sedimentary rock 4. earths movement raises layers of the rocks to the surface 5. the rock erodes exposing the fossilised body structures

Question 18

types of fossils

Answer 18

mineralised, mould, trace, index, transitional, cast

Question 19

perminerlised fossils

Answer 19

fossil formed when mineral rich groundwater deposits minerals into organic material

Question 20

how are mineralised fossils formed

Answer 20

part of the organism falls into the water, is rapidly covered by sediemnt, minerlas from surrounding rock.sediment leech into organism, organism breaks down and minerals replace it

Question 21

mould fossils

Answer 21

when a living thing decomposes undersneath sediement, creating a cacity in the shape of the dead organism

Question 22

cast fossils

Answer 22

a mould fossil is filled with sediment, the sedimentary rock with the mould erodes leaving a cast of the mould

Question 23

what does the fossil record show (5)

Answer 23

life in the past was simple, many species that used to exist are eextinct, many extant species didn’t exist in the past, where species lived and when. transitional species between ancestral and modern species

Question 24

index fossils

Answer 24

short-lived species whose fossils appear for a limited time in the fossil record, used to work out the relative ages of other fossils

Question 25

requirements of index fossils

Answer 25

distinctive, abundant, distributed worldwide, easily recognisable and existed for a short perriod of time

Question 26

transitional fossil

Answer 26

shows traits that are common to both its ancestral group and descendent group

Question 27

primitive traits

Answer 27

a feature of a species that was possessed by an eariler ancestral species

Question 28

derived traits

Answer 28

a feature unique to the descendent species and not found in the earlier ancestral species

Question 29

why are transitional fossils rare

Answer 29

because evolution doesn't occur at a steady pace (very fast then stops for a period or time - punctured equilibrium)

Question 30

trace fossils

Answer 30

fossil or structure indicating the presence of an organism rather than organisms themselves (e.g footprints, burrws, dung)

Question 31

what are the two ways fossils are dated

Answer 31

relative dating and absolute dating

Question 32

relative dating

Answer 32

determins the relative age of a fossil by comparing its position to other fossils or rock in surrounding rock strata, based on the law of fossil succession

Question 33

why can sedimentary rock be dated absolutely

Answer 33

as its made of sediments that have eroded from older sites

Question 34

law of fossil succession

Answer 34

the principle that fossils of the same age will be in the same layer of sedimentary rock and fossils found in higher/lower sedimentary layers will be younger/older

Question 35

what is the priunciple or correlation

Answer 35

uses index fossils to determine the relative age of rock strata

Question 36

absolute dating

Answer 36

used to detrmine the absolute age of a fossil by measuring the realtive amounts of radioisotopes with known half lifes to their products

Question 37

half-life

Answer 37

the time taken for the radioactivity of material taken in by a living organism to be reduced by half its initial value by a combination of biological elimination processes and radioactive decay

Question 38

3 principles of absolute dating

Answer 38

1. radioisotopes are unstable elements that will break down overtime into a more stable product 2. brekadown is mostly constant and can be modelled by calculatimg half-life 3. half-life describes the time taken for half the mass of a radioisotope to break down into its products

Question 39

carbon dating

Answer 39

determining the ratio of carbon-14 to carbon 12 to determine the age of a fossil

Question 40

how does carbon dating work

Answer 40

living organisms contain C14 naturally, afetr they die, the C14 within the organism is unstable and steadily breaks down into nitrogen 14, which is absorbed by the atomsphere

Question 41

carbon 14 half-life

Answer 41

5730 years

Question 42

for what fossils can caron dating be used

Answer 42

those that are younger than 50,000 years old

Question 43

Potassium 40 - Argon 40 dating

Answer 43

measuring the ratio of Potassium 40 - Argon 40 in lava deposits can give the exact age of the lava and therefore the appox age of the sedimentary rock above and below the lava can be estimated

Question 44

what are the negatives of Potassium 40 - Argon 40 dating

Answer 44

living things do not have potassium in them so Potassium 40 - Argon 40 dating can only be used to determine the realtive ages of fossils

Question 45

benfits of Potassium 40 - Argon 40 dating

Answer 45

can be used to date fossils older than 50,000 years old becauyse of the long half-life

Question 46

half life of potassium

Answer 46

1.3 billion years

Question 47

dating period

Answer 47

the range of time since fossilisation in which a particular radioisotope series can be used, beyond this there is not enough raqdioisotope present to determine age