In mutualism, both organisms benefit. In commensalism, one benefits and the other is unaffected; in parasitism, one benefits and the other is harmed. Some of these relationships are so close that we speak of the composite of two species as one unit; for example, we speak of the composite of algae and fungi as lichens.n commensalism, one benefits and the other is unaffected; in parasitism, one benefits and the other is harmed. Some of these relationships are so close that we speak of the composite of two species as one unit; for example, we speak of the composite of algae and fungi as lichens.
A meteoroid is a solid body in interplanetary space before it reaches the Earth's atmosphere. A meteor denotes the fiery streak or shooting star which appears when a tiny meteoroid strikes the Earth's atmosphere and burns up. Most meteors result from meteoroids no more than a few centimeters in diameter.
Leonids from space. A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories.