Symbiosis describes a relationship in which both parties benefit. It has been theorized that eukaryotic cells evolved from a symbiotic relationship in which one prokaryote engulfed another. The engulfed cell gained protection from the environment, while the engulfing cell gained an energy source from the engulfed cell.

Commensalism describes a relationship in which one party benefits and the other is neither helped, nor harmed. Parasitism describes a relationship in which one party benefits, while the other is harmed. Amensalism describes a relationship in which one party is unaffected, while the other party is obliterated. Synnecrosis is a relationship that is deadly to both parties involved.

Mutualistic relationships exist when both organisms benefit from a shared relationship. In the correct answer choice, plants provide energy to the fungi through carbohydrates and the fungi provides nitrogenous compounds to the plant.

Human blood vessel and S. mansoni is a parasitic relationship, as the worm is actually damaging to the host. Cat and mouse is a predatory relationship. The barnacle and mollusk shell is commensalism, with the barnacle benefitting and no effect occurring on the mollusk shell.

Symbiosis is when two organisms live in close proximity and usually benefit each other, such as in mutualism. However, this is not always the case. Commensalism is a type of symbiosis and only benefits one of the organisms or has neutral effects. Parasitism is another form of symbiosis, where one organism benefits at the expense of its host. 

The biosphere consists of all parts of Earth that supports life. An ecosystem consists of communities of organisms interacting with their environment. A community consists of populations of various species living in close proximity and interacting. A population consists of organisms of the same species living in close proximity and interacting. An organism is a living being that can reproduce, react to stimuli, grow, and maintain homeostasis. An organ system consists of a group of organs working together to achieve a specific function. An organ is a group of tissues that performs a specific function. A tissue is a group of cells with similar structure working together to perform a specific function. A cell is the fundamental unit of life, and composes all living things.

An ecosystem consists of communities of organisms interacting with their environment. A community consists of populations of various species living in close proximity and interacting. A population consists of organisms of the same species living in close proximity and interacting.

Commensalism is a relationship in which one organism benefits and the other organism is neither benefited nor harmed. Mutualism is a relationship in which both organisms benefit. Parasitism is a relationship in which one organism benefits and the other organism is harmed. Predation is a relationship in which one organism hunts the other organism for food.

 An ecosystem consists of communities of organisms interacting with their environment. Abiotic components are nonliving aspects of the environment (sun, wind, soil, water, etc), and biotic components are living aspects of the environment.

The zebra benefits because the oxpecker rids the zebra of harmful parasites and the zebra receives a warning from the oxpeckers when predators approach; the oxpecker benefits because the parasites serve as a food source. In this scenario, both organisms benefit from the relationship. Commensalism is a relationship in which one organism benefits and the other organism is neither benefited nor harmed. Mutualism is a relationship in which both organisms benefit. Competition is a relationship where both organisms are harmed, as they seek the same limited resource. Predation is a relationship in which one organism hunts the other organism for food.

 A tick benefits as they use the blood as a food source, and the dog is harmed as it can receive diseases from the tick, and if the tick consumes enough of their blood, the dog can become anemic. Commensalism is a relationship in which one organism benefits and the other organism is neither benefited nor harmed. Mutualism is a relationship in which both organisms benefit. Parasitism is a relationship in which one organism benefits and the other organism is harmed. Predation is a relationship in which one organism hunts the other organism for food.