Evidence for Evolution and Fossils Flashcards
Evidence for the theory of evolution:
has been show that characteristics are passed on to offspring in genes
fossil record - the remains of organisms from many years ago which are found in rocks
antibiotic resistance in bacteria - the selection pressure of antibiotics leads to advantageous mutations being selected for in bacteria populations so they are no longer killed when exposed to antibiotics
Fossils:
the ‘remains’ of organisms from millions of years ago, which are found in rocks
When are fossils formed?
from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
parts of organisms that have not decayed because oxygen or moisture were not present, meaning that the microbes that cause decay could not survive
when parts of the organism are replaced by minerals as they decay forming a rock structure of the original part e.g. teeth, shells, bones etc.
as preserved traces of organisms e.g. footprints, burrows and rootlet traces due to the ground hardening around them and forming a cast
How are fossils formed?
remains of dead organism covered in sediment
sediment builds up compressing dead organism
soft parts of organism decay or are eaten
bones / hard parts do not decay
so minerals enter bones and replace the bone turning it to stone
Why are there no/not many fossils of early forms of life?
many-early forms of life were soft-bodied and therefore decayed completely so there are few fossils of them
any traces left have been destroyed by geological activity
this is why scientists cannot be certain about how life began on Earth
What can we learn from fossils?
we can learn from fossils how much or how little different organisms have changed as life developed on Earth
used to show how the anatomy of organisms has changed over time
can be used to compare how closely related 2 organisms are through looking at the number of similarities they have
this information is used to create evolutionary trees
Why is the fossil record incomplete?
fossils formed under v. specific conditions
remains of the organism usually washed into water and buried by mud or silt
if there is any O2 at all the remains would decay and there would be nothing left
hard parts of organism e.g. shells, bones, teeth etc. replaced by minerals
if the organisms are completely soft-bodied like an earthworm - no hard parts so no fossils formed
very rare for all conditions to be met
even if fossils form they still need to be found
only weathering + erosion (beneath sea or river bed) can expose them (in rocks etc.) which takes a long time
Using fossils to estimate when species was alive:
compare to other fossils of known age (compare with fossil record)
age of rocks
depth underground where fossil was found
I- isotope dating
DNA analysis
Extinction:
occurs when there are no remaining individuals of a species still alive
Factors which may contribute to the extinction of a species:
Population growth
Habitat loss/destruction
Over consumption / over exploitation
Pollution
New predators may have evolved or migrated to the area
Have to compete with a species which has advantageous mutations for the same food source
Changes in environment which the species cannot adapt fast enough to
A new disease and there are no resistant alleles to it
Catastrophic event can wipe out a species e.g. meteroite
