It is a unicellular organism. Yeast are a polyphyletic group of species within the kingdom fungi. They are predominantly unicellular.
(a) Agree
It is probable that less sticklebacks will have pelvic spines in Bear Paw Lake, as it is a smaller region without as much competition. Predators may be much lower in such an environment, eliminating a need for such protection. In the ocean, however, there is much biodiversity and competition, so the fish need pelvic spines to protect themselves.
