Invertebrates (and higher animals<>can be placed<>$$$two groups<>based<>on how they develop as embryos$$$they<>develop<>
If one or two            base pairs are changed (mutated), the embryo will fail to develop properly.
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?