Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
Water doesn't absorb heat as quickly as sand
Red cells take up 40%-50% of the total blood volume
hypothesis can be reject or wrong because it's what somone thinks as a theory also it aslo cannot be proven correctly
and it aslo has to he tested many times
He observed 15 different finch species that originated as one ancestral bird. all differing in body shape, beak size, and mating habbits