Anucleus bordered by a membranous envelope is found in

genetic variation will increase because of a new habitat and food source.

explanation:

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this