Invertebrates (and higher animals<>can be placed<>$$$two groups<>based<>on how they develop as embryos$$$they<>develop<>
Animals with one copy of the mutant gene are physiologically normal, but when two such animals are mated, some of the embryos-embryos with two copies of the mutant gene-die in the womb.
Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.
Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as what?