Read the passage and then answer the question.
Symbiotic relationships, which occur when one organism is dependent on another organism for survival, are typically categorized into three different types of relationships: parasitism, mutualism, and commensalism. In each of these relationships, the organisms involved are benefited or harmed in different ways.
Parasitic relationships are often the most familiar types of symbiotic relationships. A common example is a flea living on a dog. In cases like these, the parasite gains a viable habitat to support its life cycle, while the host is harmed.
In a mutualistic relationship, on the other hand, both organisms in the relationship are better off because of their arrangement; that is, they benefit mutually from their interactions. For example, lichen is composed of two organisms, an alga and a fungus. The fungus acts like a sponge, holding on to water that the alga needs. At the same time, the alga is constantly converting sunlight into energy, so the fungus, which cannot perform this function for itself, benefits from a reliable energy source. Lichen is, in turn, engaged in a commensalistic relationship with the tree that it grows on. In a commensalistic relationship, one organism benefits and the other organism neither benefits nor suffers. The tree provides lichen with a place to grow, but the tree is unaffected.
The passage defines three types of symbiotic relationships: parasitism, mutualism, and commensalism. It provides examples for each type of relationship.
In a parasitic relationship, one organism benefits while the other is harmed. An example given is a flea living on a dog, where the parasite gains a habitat while the host is harmed.
In a mutualistic relationship, both organisms benefit from their interactions. An example given is lichen, which consists of an alga and a fungus. The alga provides the fungus with energy from sunlight, while the fungus provides the alga with water.
In a commensalistic relationship, one organism benefits while the other is unaffected. An example given is lichen growing on a tree. The tree provides a place for the lichen to grow, but the tree is not affected by the presence of lichen.
The question is not given in the passage, so it cannot be answered.
What is the meaning of reliable as used in the passage?
In the passage, the word "reliable" is used to mean consistent and trustworthy. It refers to the fact that the alga in the mutualistic relationship with the fungus acts as a reliable source of energy, consistently converting sunlight into energy for the benefit of the fungus.
The passage talks about three types of symbiotic relationships: parasitism, mutualism, and commensalism. In parasitic relationships, one organism benefits while the other is harmed. An example given is a flea living on a dog, where the flea benefits by finding a habitat while the dog is harmed. In mutualistic relationships, both organisms benefit from their arrangement. The example of lichen is given, where an alga and a fungus work together. The alga provides energy from sunlight, which the fungus benefits from, and the fungus holds water, which the alga needs. In commensalistic relationships, one organism benefits while the other is neither harmed nor benefited. The example of lichen growing on a tree is given, where the tree provides a place for lichen to grow, but the tree is unaffected.
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