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.
The visible path of a meteoroid that enters Earth's (or another body's) atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite. Many meteors appearing seconds or minutes apart are called a meteor shower.