Plankton is not the name of a plant or animal but more of a category for any drifting organism that inhabits the middle to upper levels of the ocean, namely the pelagic zone.
Most vets do spays, neuters, bone surgeries, spleen surgery, tumor removals, and intestinal surgeries. Heart surgery and more complicated surgeries are done by specialists that requires more schooling. If you want to be a vet, you have to have REALLY good grades and Vet school is MUCH harder to get into than human medical school.
Veterinarian Job Description: Veterinarians or doctors of veterinary medicine diagnose, and treat diseases and injuries of pets, such as dogs and cats, and farm animals, such as cattle or sheep: The veterinarian examines the animal to determine nature of disease or injury and treats the animal surgically or medically.