3. Are the extra embryonic
membranes the same in all
vertebrates?

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
The presence of each embryonic
membrane varies according the
vertebrate class.

In and amphibians only the
sac is present. In and birds
besides the sact here are also
amnion, the chorion and allantois.

In placental mammals besides all these
the is present too.