Food webs are unable to cross from one environment into another (e. g., from land to water). TRUE
FALSE

false, for example, if a frog eats flies, and the flies are land animals,  if they go extinct the frogs could die off, meaning any fish or water dwellers that eat the frogs can starve and cause a large chain reaction.

Hope this helps ^^

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).