Which on the following describes a cyclical change in an ecosystem? a) a population of juniper trees is replaced by poplar trees b) coyotes migrate to an area where no coyotes lived before c) an area receives less rain each year for many years d) the water level in lake ontario peaks and dips every few years

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.