پاسخ : English biology
well , as we know , some species of euglenids are mixotrophs , it means that in daylight with the presence of sun , they are autotrophic but when there's no sun , they can become heterotrophic which means they act as predators ! and feed on nutrients around them or other micro organisms
my guess is that they gain the second flagella in order to act better as a heterotroph by swimmin better , absorbing more beneficial things with purpose , and havin more power to catch other microorganisms and phagocyte them more easily . this way they would save more energy and power for themselves rather than chasing the pray with a lot of energy and gaining nothing to feed on
please let me know if it's right :106::63: