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1. Biology - Chapter 6 > The fossil record > Flashcards

The fossil record Flashcards

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1
Q

how old is earth

A

4.5 billion years old

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2
Q

what gives evidence of how old life is on earth

A

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

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3
Q

stromatolities

A

rock that is made by photosynthesising bacteria

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4
Q

what are the 8 steps of the geological timeline

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

extinction

A

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

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6
Q

benefits of eextinctions

A

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

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7
Q

benefits of ice ages

A

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

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8
Q

negatives of ice ages

A

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

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9
Q

what causes extinction

A

human factors or natural catastrophies

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10
Q

two mass extinction periods

A

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

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11
Q

the fossil record

A

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

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12
Q

fossils

A

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

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13
Q

conditions of fossilisation

A

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

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14
Q

what is the first step of fossilisation

A

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

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15
Q

second step of fossilisation

A

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

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16
Q

third step of fossilisation

A

within this rock, the fossilised remains can takke many forms

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17
Q

5 steps in fossilisation of an animal

A
  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
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18
Q

types of fossils

A

mineralised, mould, trace, index, transitional, cast

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19
Q

perminerlised fossils

A

fossil formed when mineral rich groundwater deposits minerals into organic material

20
Q

how are mineralised fossils formed

A

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

21
Q

mould fossils

A

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

22
Q

cast fossils

A

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

23
Q

what does the fossil record show (5)

A

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

24
Q

index fossils

A

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

25
Q

requirements of index fossils

A

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

26
Q

transitional fossil

A

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

27
Q

primitive traits

A

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

28
Q

derived traits

A

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

29
Q

why are transitional fossils rare

A

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

30
Q

trace fossils

A

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

31
Q

what are the two ways fossils are dated

A

relative dating and absolute dating

32
Q

relative dating

A

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

33
Q

why can sedimentary rock be dated absolutely

A

as its made of sediments that have eroded from older sites

34
Q

law of fossil succession

A

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

35
Q

what is the priunciple or correlation

A

uses index fossils to determine the relative age of rock strata

36
Q

absolute dating

A

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

37
Q

half-life

A

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

38
Q

3 principles of absolute dating

A
  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
39
Q

carbon dating

A

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

40
Q

how does carbon dating work

A

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

41
Q

carbon 14 half-life

A

5730 years

42
Q

for what fossils can caron dating be used

A

those that are younger than 50,000 years old

43
Q

Potassium 40 - Argon 40 dating

A

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

44
Q

what are the negatives of Potassium 40 - Argon 40 dating

A

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

45
Q

benfits of Potassium 40 - Argon 40 dating

A

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

46
Q

half life of potassium

A

1.3 billion years

47
Q

dating period

A

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

1. Biology - Chapter 6 (13 decks)

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