Question

which of the following characteristic was important for success of animals in terrestrial environments?
notochord
amniotic eggs
cranium
mammary glands

Explanation:

• Notochord: It is a flexible rod - like structure present in chordate embryos. It is mainly related to providing support during embryonic development and is not directly crucial for terrestrial success.
• Amniotic eggs: These eggs have a series of membranes (amnion, chorion, allantois, and yolk sac). The amnion encloses the embryo in a fluid - filled cavity, protecting it from desiccation (drying out). This adaptation allowed animals to reproduce on land without the need for an aquatic environment for their eggs.
• Cranium: A cranium is a part of the skull that encloses the brain. While a well - developed nervous system (housed in the cranium) is important for many animal functions, it is not as specifically tied to the transition to terrestrial life as amniotic eggs.
• Mammary glands: These are specific to mammals and are related to nourishing young with milk. They are not the key adaptation for the initial success of animals in terrestrial environments (many non - mammalian terrestrial animals exist).

Answer:

Amniotic eggs.