Answer:
r- selection
Explanation:
Organisms respond to selection force by adjusting their reproduction rate, clutch size, and the age for reproduction. The species that acquire reproductive maturity earlier and reproduce at a faster rate are r-strategist and the selection force is r- selection. The members of these species are found in the habitat experiencing variations in climatic conditions, higher rates of negative ecological interactions such as predation.
These species produce a large number of offspring during one reproductive cycle and do not provide postnatal care to the young ones. According to the given information, the guppy population in the streams experience negative pressure of higher rates of predation. They adapt themselves to it by acquiring reproductive maturity at an earlier age and reproduce more frequently to ensure their survival.