1.1 Changes in the environment of plants and animals
may cause them to die out. The fossil record
shows that new organisms arise, flourish, and after
a time become extinct. The record also shows
changes that lead to the formation of new species.
1.1.1 Scientists aren't certain about how life began due to lack of valid and reliable evidence.
There are gaps in the fossil record as some fossils haven't yet been found, the conditions for
fossilisation weren't present and early life forms were soft-bodied so they didn't form fossils.
126.96.36.199 Fossils are the 'remains' of organisms from many years ago, which are
found in rocks. Fossils may be formed in various ways: from the hard
parts of animals that do not decay easily; from parts of organisms that
have not decayed because one or more of the conditions needed for
decay are absent; when parts of the organism are replaced by other
materials as they decay and as preserved traces of organisms
(footprints, burrows and rootlet traces).
188.8.131.52.1 Many early forms of life were soft-bodied,
which means that they have left few traces
behind. What traces there were have been
mainly destroyed by geological activity.
184.108.40.206.1.1 We can learn from fossils how much or how
little different organisms have changed as life
developed on Earth.
220.127.116.11.1.1.1 Extinction may be caused by changes to the environment over geological time, new
predators, new diseases, competitors or a single catastrophic event.
18.104.22.168.22.214.171.124 New species arise as a result of isolation – two populations of a species become separated, for example
geographically. Due to genetic variation, each population has a wide range of alleles that control their
characteristics. Natural selection occurs in each population and the organisms with desired characteristics are
enabled to survive and continue to reproduce. Due to different situations, each population evolve differently
and eventually the two become so distinct, they can no longer breed successfully. This is called speciation.