Why Are Australian Mammals All Marsupial While Mammals on Other

question 16

Multiple Choice

Why are Australian mammals all marsupial while mammals on other continents are mostly placental?

• A) The marsupial anatomy is better adapted to the environments of Australia than is the anatomy of placental mammals.
• B) The placental anatomy is better adapted to the environments of North and South America than is the anatomy of marsupial mammals.
• C) When the continents separated from one another, marsupials on Australia did not have the placental competitors that were present in the Americas.
• D) Marsupials out-competed the placental mammals in Australia.
• E) Australian mammals have a different common ancestor than mammals elsewhere in the world.

---

Definitions:

Arrector Pili

Small muscles attached to hair follicles that, when contracted, cause hair to stand on end - a phenomenon often associated with cold or fright, known as "goosebumps."

Dermal Root Sheath

The part of the hair follicle that provides a protective layer and is involved in hair growth, derived from the dermis.

Papillary Layer

The uppermost layer of the dermis, directly underneath the epidermis, rich in blood vessels and sensory neurons.

Melanosomes

Organelles within cells responsible for synthesis, storage, and transport of melanin, the pigment that gives color to skin, hair, and eyes.