1.you cannot tell how the environment changed. with each generation, more guppies passed on the gene for small spots to their offspring.
Explanation:
the diagram doesn't show/say anything about the environment changing. it just shows that at time 1 there were an equal amount of guppies with small and large spots and then the second one had more guppies with small spots, meaning that they must've reproduced more and began to outweigh the guppies with large spots.
Usually a reputable resource will be found on an informational or scientific site (especially something that is .edu or .gov) and will have a date written and author credited.