Each relationship categorized as mutualism or parasitism
Sea-lamprey eggs hatching on fish and feeding on the fish - Parasitism
Bees pollinating the flowers of plants - Mutualism
Mosquitoes sucking blood from the bodies of organisms - Parasitism
Lactobacilli digesting certain foods in the human body - Mutualism
Parasitism is a relationship between two organisms (plants or animals) in which one organism (the parasite) benefits at the expense of the other (the host) which is usually harmed. An example is; Mosquitoes sucking blood from the bodies of organisms (from the question). Mosquito is the parasite that benefits from the relationship, while the organisms from which it sucks blood are the hosts that are harmed.
Mutualism is a type of symbiotic relationship that occurs between two organisms of different species in which both organisms benefit from each other. An example is; Lactobacilli digesting certain foods in the human body (from the question). Both the bacteria (Lactobacilli) and humans benefit from the relationship. Lactobacilli help humans to digest certain foods, while the human body serves as shelter for Lactobacilli.
