Alternative pregnancy tests have been developed .
Biologists continue to use Xenopus as a model organism in developmental biology because their embryos are large and easy to manipulate , they are readily obtainable , and can easily be kept in the laboratory .
Although alternative pregnancy tests have been developed , biologists continue to use Xenopus as a model organism in developmental biology because their embryos are large and easy to manipulate , they are readily obtainable , and can easily be kept in the laboratory .