Tag: zoology

All vertebrates have a living endoskeleton. The characteristic of vertebrates without exception is the presence of a brain. The brain is set inside a bony box called as the cranium. Cranium is made up of eight bones. It protects the human brain from mechanical injury.
Therefore, the correct answer is option B.

• The heart of vertebrates is ventrally placed.
• The body of vertebrates consists of serially arranged vertebrae which comprises of a major part of their axial exoskeleton, the vertebral column or the backbone.
• The coelom of vertebrates is large and well developed and it is of enterocoelous type.

• The heart pumps only impure blood in sharks. Sharks have a two-chambered heart which is an S-shaped tube. It has an atrium and ventricle. The blood is pumped by the heart through the afferent branchial arteries to capillaries in the gills, where the blood is oxygenated). 
• The blood then flows through efferent branchial arteries, through the tissues of the body, and back to the heart in veins. Sharks have low blood pressures; the walls of the pericardium are rigid, creating suction within the pericardium to maintain the flow of blood. To circulate blood throughout their bodies, many sharks must swim continuously. 
• The blood flow is similar to humans because blood is pumped by the heart to the rest of the body by arteries and returned to the heart by veins. 
• A difference is that humans have 4-chambered hearts while sharks only have two chambers.

Viviparous sharks give birth to live young. The number of pups in a litter ranges from 2-20 or more. For example, the Bull sharks, Whitetip reef shark, Lemon shark, Blue shark, Mako, Porbeagle, Salmon shark, the Silvertip shark, and Hammerheads.

Herdmania is an ascidian urochordate.