AQA GCSE Biology (8461), Higher tier · Inheritance, variation and evolution › Understanding of genetics and evolution
Practise Fossils. 11 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Some fossils are preserved traces of organisms rather than parts of the organisms themselves. Give one example of a preserved trace of an organism.
Footprints, burrows or rootlet traces
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Fossils are the 'remains' of organisms from millions of years ago, which are found in rocks.
(a) Which two of the following are ways in which fossils can form? Tick (✓) two boxes.[2]
An organism is completely broken down by decomposers
Parts of an organism are replaced by minerals as they decay
Parts of an organism do not decay because one or more of the conditions needed for decay are absent
The organism's DNA is copied into the rock
(b) Some fossils are preserved traces of organisms rather than parts of the organisms themselves. Give one example of a preserved trace of an organism.[1]
(c) Scientists cannot be certain about how life began on Earth. Give two reasons why.[2]
Show the answer and mark scheme
(a)Answer: Parts of an organism are replaced by minerals as they decay; Parts of an organism do not decay because one or more of the conditions needed for decay are absent
(b)Answer: Footprints, burrows or rootlet traces
footprints / burrows / rootlet traces
(c)
many early forms of life were soft-bodied, so they left few traces / fossils
(most of) the traces that did form have been destroyed by geological activity
Question 2Medium7 marks
Scientists found three fossils at different sites:
fossil A: an insect preserved in amber (hardened tree resin)
fossil B: the bones of a mammal that have turned to rock
fossil C: the footprints of a dinosaur in mudstone.
(a) The insect in fossil A did not decay. Explain why.[2]
(b) Describe how fossil B was formed.[2]
(c) Fossil C is a trace fossil. Suggest one thing scientists could find out about the dinosaur from its footprints.[1]
(d) Fossils can show how much or how little organisms have changed as life developed on Earth. Explain how.[2]
Show the answer and mark scheme
(a)
the amber prevented oxygen / air / water reaching the insect
(so) microorganisms / decomposers could not survive / decay the insect / the conditions needed for decay were absent
(b)
the bones were buried (in sediment) and slowly decayed
(and were) replaced by minerals (which formed rock)
(c)
its size / mass
whether it walked on two legs or four legs
how fast it moved (from the length of its stride)
whether it lived in groups (from several sets of tracks)
(d)
compare fossils from rocks of different ages
(with each other or with) living species, to see how similar / different their structures are
Question 3Hard8 marks
Most organisms that die decay completely. Occasionally, parts of organisms are preserved for thousands or millions of years.
Woolly mammoths that died more than 10 000 years ago have been found in frozen ground, with skin and muscle still present.
Human bodies about 2000 years old have been found in peat bogs. Peat bogs are waterlogged and acidic.
(a) Explain why the soft tissues of the mammoths did not decay.[2]
(b) Explain why the bodies in peat bogs decayed very slowly.[2]
(c) Most organisms that lived millions of years ago did not form fossils. Explain why.[2]
(d) A scientist said: 'The fossil record gives a biased picture of life in the past.' Suggest why.[2]
Show the answer and mark scheme
(a)
the temperature was too low / the ground was frozen
(so) microorganisms / decomposers could not grow / reproduce / their enzymes worked too slowly
(b)
waterlogged, so there is little / no oxygen
(so) aerobic decomposers cannot respire / survive
acidic conditions inhibit / kill microorganisms / denature the enzymes of decomposers
(c)
most organisms decayed completely because the conditions for decay were present
soft-bodied organisms / soft tissues decay quickly and leave no traces
the conditions needed for fossils to form (e.g. rapid burial, replacement by minerals) are rare
many fossils that formed have been destroyed by geological activity
(d)
organisms with hard parts, such as bones or shells, are much more likely to be fossilised
organisms living where sediment builds up (e.g. in water) are more likely to be fossilised
(so) soft-bodied organisms / organisms from some habitats are under-represented
(so) some groups appear rarer than they really were / are missing from the record