sentence2_structure: Invertebrates (and higher animals<>can be placed<>$$$two groups<>based<>on how they develop as embryos$$$they<>develop<>
sentence1: Animals can be transferred from one place to another as embryos in test tubes, implanted into foster mothers and then, when they have grown, they can be used in breeding programs.
sentence2: Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.
question: Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as what?