O positive is the most common blood type and most likely to be transfused.
O negative donors are the “Universal Donor.” People with O negative blood are universal red blood cell donors. This means that their red blood cells can be transfused to any blood type.
There's two effects that the islands have on the size of the animals, reducing of size, or increasing of size. The reducing of size is known as island dwarfism, while the increase in size is known island gigantism.
The effect of the island environment effects different types of animals in different manner, and it also has to be taken in account the size of the island. In general, the small animals tend to increase their size on the islands, while the large animals tend to decrease in size. The reason for this is that the smaller animals, because of the isolation, usually lack predators or they are very few, but also have sufficient amounts of food, thus they grow in size. The larger animals though, decrease their size because there isn't enough food on the islands to support them, thus with the decrease in size they consume less. Also, since they usually lack predators, they do not have to be large in order to defend themselves.
Distribution of phenotypes within a population may be impacted by different types of natural selection. These types of selection include;
Directional selection involves a change in the environment shifts of phenotypes observed. Example is the giraffe neck-length, where the length got longer and longer over time to reach the leaves at the top of trees.
Stabilizing selection , this is a selection where an average phenotype is favored. example is number of eggs laid by birds such that too many eggs will be a waste of energy because some chicks would starve.
Disruptive selection is a selection where individuals with an average value of a trait are affected most while those with values below average are affected least. Example small individuals are capable of hiding from predators while big individuals can not fit in the hiding place but instead will fight with predators.
