6.3.5 fossils Flashcards
why is it that if one of the conditions to decay a fossil isn’t there it doesn’t decay
in tree resin it lacks oxygen and moisture means that decomposers cannot survive there to break down dead
organisms.
do things fossilise when replaced by minerals as they decay
Body parts such as teeth, shells and bones don’t decay easily and can last a long time after the
organism has died. * They are slowly replaced by minerals that form a rock-Like substance in the same shape as the
original body part. * They can often be seen distinctly within the
surrounding rock.
how are footprints fossilised
An impression leg. from footprints) can be left in
a soft material like clay. The impression becomes fixed as the clay
hardens. Sometimes an organism may be buried in clay but decays after the clay has hardened, leaving a
cast of the organism.
why are there very small traces of early organisms
they were soft bodied meaning they decay easily
why have traces of these fossils been destroyed
geological activity such as tectonic plates
what are evolutionary trees
diagrams that show the relationship between species over evolutionary time
speciation
when something evolves eg apes humans
