True or false: medical studies often use a relatively large sample (in this case, 3980) because disease occurrences can be rare and difficult to observe when only isolated populations are considered.

The answer in the statement above is true, it is because it is necessary to have large sample because diseases are unpredictable, which will be difficult especially on isolated populations are being considered. Having an isolated population could be hard to the researches because they only have a limited people to observe, that is why they needed a large sample in order to differentiate results and have enough sample to use.

an adaptation is a change or process by which an organism takes to be better suited for its environment. for example; migration is a behavioral adaptation, this is needed because birds are not built to last extremely cold climates. there are different adaptations because there are different species needing to adjust to different things, bears don't migrate; they hibernate.