The ozone layer helps prevent harmful UV rays from entering the atmosphere.
The process which planetesimals combine with other planetesimals is called Accretion.
There are other names which refer to as accretion. For example, Accretion geology is termed as the increase in the size of a tectonic plate by addition of materials which convergent boundary.
Accretion atmosphere is termed as the process by which water vapor which is in clouds forms water droplets around nucleation sites.
Accretion astrophysics is termed as the formation of planets and other bodies through a collection of material through gravity.
Insects, and some other invertebrates, exchange oxygen and carbon dioxide between their tissues and the air by a system of air-filled tubes called tracheae. Tracheae open to the outside through small holes called spiracles.
