Question

although mammals were present during the same period as the dinosaurs, the extinction of dinosaurs gave mammals an opportunity to diversify. examine the characteristics below and determine which are unique to mammals, and which are not unique to mammals.

Explanation:

• Not unique to mammals:
• Top predator in aquatic habitats: Sharks (fish, not mammals) can also be top predators in aquatic habitats.
• Hard bones: Many vertebrates (e.g., fish, reptiles, birds) have hard bones.
• Flight: Birds and some insects can fly.
• Top predator in terrestrial habitats: Reptiles (e.g., some large crocodilians in pre - dinosaur and non - mammal eras) and non - mammalian dinosaurs were top terrestrial predators.
• Egg laying: Reptiles, birds, and some fish lay eggs.
• Unique to mammals:
• Milk produced by mammary glands: This is a defining characteristic of mammals.
• Sweat glands: While some other animals may have glandular structures, true sweat glands (eccrine glands in many mammals for thermoregulation) are unique to mammals in the context of the given characteristics.
• Body hair: Hair (or fur) is a unique mammalian feature among the major vertebrate groups.

Answer:

• Not unique to mammals: top predator in aquatic habitats, hard bones, flight, top predator in terrestrial habitats, egg laying.
• Unique to mammals: milk produced by mammary glands, sweat glands, body hair.