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.
A meteor shower is a spike in the number of meteors or shooting stars that streak through the night sky. Most meteor showers are spawned by comets. As a comet orbits the Sun it sheds an icy, dusty debris stream along its orbit. If Earth travels through this stream, we will see a meteor shower.