Answer: D
Explanation: the continents wee once connected. It was known as Pangea
Answer is A. A population becomes separated by environmental factors into two groups that do not reproduce with one another.
When a population of a species become geographically separated then gene flow between them stops. Over a period of time, the population may become genetically different in response to the natural selection due to different environments. Selection and genetic drift will act differently on these two separated populations. This will results into two separate species. This type of speciation is called allopatric speciation.
A nucleus consists of a nuclear membrane that surrounds it, within the membrane there is a nucleolus which can be compared metaphorically to the yolk of an egg in appearance. The nucleolus is surrounded by nucleoplasm which is quite like the cytoplasm.
Http://www.phschool.com/science/biology_place/biocoach/bioprop/folding.html hope it helpps
