Why is mutation needed for evolution to occur even though it usually has little effect on allele frequencies

What is the chance of two parents with blood types ab and o producing an offspring with blood type o a.0% b.25% c.75% d.50%

When water freezes, it . contracts expands

'which of these statements about the scientific method is not true? all experiments must follow the same number of steps in the procedure. experiments may be repeated several times. some unexpected results can be beneficial. experimental results may or may not support the hypothesis.