Question

Contrast monotremes, marsupials, and eutheriansin terms of how they bear young.

Short answer

Differences can be observed between monotremes, marsupials, and eutherians in how they deliver their young ones. Monotremes are organisms that lay eggs that hatch to give rise to young ones. Marsupials give birth to young ones who are very tiny and complete their development in the pouch of the mother.

Eutherians are organisms that give rise to fully developed miniature young ones.

Step-by-step solution

Different mechanisms of birth

Based on how an organism gives birth to young ones, they are classified as oviparous, viviparous, and ovoviviparous. The nature of the process by which organisms give birth to young ones depends on external and internal factors.

Monotremes

Monotremes are oviparous, meaning egg-laying mammals. These organisms lay thick calcareous eggs to protect the developing embryo. The eggs have an abundance of yolk to enable the growth and development of the fetus until the egg hatches.

Marsupials

Marsupials are organisms that possess pouch in the abdominal region. These organisms are viviparous, meaning; they give birth to young ones. However, the young ones that are produced are often very young, and hence they attach to the nipples of the female present inside the pouch until they fully develop.

Step 4:Eutherians

Eutherians are viviparous organisms that give rise to fully developed young ones that resemble adults. However, the young ones are smaller than the adults. These organisms possess a placenta during pregnancy that attaches to the developing fetus to facilitate nourishment.