Why is the oldest seafloor less than 180 million years when the oldest continental crust is about 4 billion years old?

Which animal group is the largest and contains more species from all the other living groups combined? is it mammals or

If jane has the blood type ab and marries john who has type o blood what are the possible phenotypes of their first kid?

Guinea pig coat color is determined by a single gene. the allele for black coat color is dominant to brown. in a cross between twoblack-haired guinea pigs, 20 offspring are born. if both parents were heterozygous, probability would predict that approximately howmany of the 20 offspring would have brown hair?