Question

Which character is not the same in aves and mammals?
A. Single systemic arch
B. Metanephric kidney
C. Seven cervical vertebrae
D. Homoisotherms

Answer 1

Aves is a group of birds. Birds are characterised by the presence of feathers, toothless beaks, shells with hard shells, and a heart with four chambers. Birds have a hollow skeleton so that they are lightweight and can fly at ease.

Complete answer:
-Invertebrates, there are three excretory organs. Mesonephros is one of them. In aquatic vertebrates, it is the main excretory organ. In reptiles, birds and mammals it acts as a temporary kidney. It is a developmental stage of the kidneys in humans. Thus, metanephric kidneys are present in both mammals and birds.
-Arch four is the systemic arch. It forms the right subclavian artery. In amphibians and reptiles, two arches are retained. Birds and mammals lose one of the arches.
-The term homoisotherm refers to an organism that maintains its body temperature in compliance with the environmental temperature. They do this through their body metabolic activities. Most of the birds are homeothermic. They maintain a constant body temperature whatever be the environmental condition. Mammals also maintain a constant body temperature that is nearly ${98^ \circ }F$.
Mammals have seven cervical vertebrae. Birds have a more flexible neck. Their cervical region has more vertebrae than what is present in all the other animals. Birds have a cervical vertebra with $13 - 25$bones.

Hence, the correct answer is option (C).

Note: The body temperature of birds may vary within a range of up to ${1^ \circ }C$. Birds are warm-blooded just like mammals. The normal body temperature of birds is around ${106^ \circ }F$.