Bacteria are prokaryotic cells. By contrast, animal, plant, and fungal cells are eukaryotic What is the main difference between prokaryotes and eukaryotes?

I think the answer is that prokaryotes have a nucleus and eukaryotes do not.

Explanation:

It is the first thing I think of when I think of a difference between the two.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .

the correct answer is:

a population changes in response to a change in the environment.