Snails...?

Question

compare the difference between 2 types of snails: one living on the rocks near the sea (in a wide dangerous place with waves and predators)and the other living in the narrow holes in rocks of the same place(a safe place but the problem is that its narrow).compare their life histories(size,maturity age,reproduction age,way of reproduction(r and k selection))assuming that all the conditions except the living place is the same.

Answer 1

r-selected species are those that live in unstable environments and therefore tend to have life histories that involve early age of reproduction.  Because r-selected species (like your snail that lives in the more dangerous habitat) start investing energy in reproduction early, they generally have smaller body sizes as well.  Additionally, they follow a reproductive strategy that involves producing lots and lots of offspring in hopes that a few manage to survive.

Alternatively, k-selected species aren't as subject to selective pressures and are therefore likely to live longer.  Because of this, they can delay reproduction until they are older (because they're likely to survive) and are therefore generally larger.  Also, because k-selected species have lower mortality rates, they do not have to produce as many offspring.