How have conditions for life on earth changed over time?
a.
separation of continents
c.
both a and b
b.
ice age
d.
neither a nor b

Once an egg cell is fertilized by sperm, the cell then, as the embryo develops, it receives nourishment and eliminates wastes by transferring substances from its blood to its mother's blood. a. becomes a fetus immediately and exits the womb b. begins to divide and implants itself in the wall of the uterus c. remains in the uterus without dividing for several months d. travels back to the ovaries until the fetus is developed

Adistinctive characteristic of mammals that is not observed in other vertebrates is

In sheep, the allele for belly fur (a) is dominant to the allele for no belly fur (a). a mother with the genotype aa and a father with the genotype aa produce an offspring.