Heart-shaped ivies, sometimes called sweethearts, have a leathery look and are rarely lobed. Miniatures are slow growers and the smallest ivies. Their largest leaves are no bigger than 3/4 inches long and 1/2 inch wide; they make good terrarium subjects. An ivy plant can fall into more than one of these categories.
The second main cause of genetic variation is due to the high degree of neutrality of most mutations. Most mutations do not appear to have any selective effect one way or the other on the organism. The main cause is genetic drift, this is the effect of random changes in the gene pool. In humans, founder effect and past small population size (increasing the likelihood of genetic drift) may have had an important influence in neutral differences between populations.
Variation resulting from the appearance of mutations is called variation through mutation while that conditioned by subsequent recombination of genes as a result of interbreeding is called variation through recombination.roup variation includes the differences among aggregates of any rankâfrom differences among small groups of individuals within a population to differences among the kingdoms of living nature (animals and plants). In essence, the entire taxonomy of organisms is constructed on the comparative study of group variation.