Parasites

Parasitic animals, such as tapeworms, can live inside of another organism with no harm. Organisms that live in guts has a specific surrounding that can pass through the acid of stomach with no harm. Organism, like the tapeworm, can regenerat, if the segment of the organism is ingested by another primary host, by attaching itself to the intestinal walls and resumes its growth by budding. When eggs are ingested, they hatch in the intestinal tract …

…or othre internal organs of their hosts. These worms have developed adaptations that enable them to avoid the host's immune response, such as during a developmental stage when they are protected by a cyst wall or an outer surface thta constantly changes, thereby making it difficult for the host immune system to target the parasite for attack. Many ectoparasites have developed structures, such as suckers, hooks, and teeth, which help penetrate the host's outer surface.