3. Do all mammals have a
placenta?

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!
Mammals of the group
(platypus, echidnas) oviparous,
egglaying, and do not have placenta.
Mammals of marsupial group
(kangaroos, , opossums) do not
a placenta either; of this
group birth to embryonic
that then continue within
the mother’s . Placenta only forms
female placental mammals.