C) one that must be imported to the U.S.
They are formed with the flow of air or water.
The answer is Spiral. Spiral does not represent a type of nebula. There are only 3 types of nebula : Reflection, Emission & Dark. Reflection Nebulaedoes not emit its own light. Instead, it scatters the blue light from a nearby cool star. Emission Nebulae emits own light. Glow very brightly, and are frequently the birthplace of stars. Dark Nebulae also called "absorption nebulae", they block light from brighter objects behind them and can only be seen as an outline in front of a bright nebula or field of stars.
Explanation:
Genetic variation is increased by meiosis
Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote. Recombination or crossing over occurs during prophase I
Answer:
pioneer species
Explanation:
Primary succession begins in barren areas, such as on bare rock exposed by a retreating glacier. The first inhabitants are lichens or plants—those that can survive in such an environment. Over hundreds of years these “pioneer species” convert the rock into soil that can support plants.