Structural Organisation in Animals Test - 55

In the given diagram, it represents the earthworm’s dorsal vessel. The earthworm has a closed vascular system with blood vessels. The dorsal vessel in the first thirteen segments acts as a distributing vessel and extends up to the cerebral ganglion. It gives off branches that supply blood to the anterior regions of the body.

So, the correct answer is ‘dorsal vessel’. The correct option is B.

[a] In rats, the right kidney is slightly higher than the left one due to the presence of liver on the right side and so, statement A is incorrect.

[b] Cockroaches possess ten pairs of spiracles, two thoracics, and eight abdominal. So, option b is correct.

[c] The alimentary canal of the earthworm is a straight tube throughout the length of the body consisting of (in the sequence), mouth and buccal chamber, pharynx, oesophagus, gizzard, stomach, intestine, and anus. So, option C is incorrect.

[d] The body of a frog is divisible into head and trunk and so, statement D is incorrect.

Therefore, the correct answer is option B.

The neurons in the earthworm are myelinated so they are covered with insulating fats. The neurons in earthworm are sensory in nature as well as motor and adjuster or associated neurons. Sensory carries the information from the brain while the motor carries the impulse back to the effector organs.

Order and path of blood flow from the ventral to dorsal blood vessels is

1.     Ventrointestinal blood vessel

2.     External intestinal plexus

3.     Internal intestinal plexus

4.    Dorsointestinal blood vessels

Thus correct order will be d, b, c, a. So, the correct option is D.

The abdomen in a male and female cockroach is made up of 10 segments. The 7th, 8th and 9th sterna form a genital pouch in females. In males, the genital pouch is present at the hind end of the abdomen. The male cockroach has thread-like anal styles, which are missing in the female cockroach. The 10th segment has a filamentous structure called the anal cerci, in both male and female cockroach. 

The open type of vascular system consisting of sinuses filled with blood is seen in the cockroach. The blood in a cockroach is colourless as it does not contain any respiratory pigment. This colourless blood is called haemolymph. The scientific name of cockroach is 'Periplaneta'. All the other options have a closed vascular system.

The dorsal chamber is also called salivary chamber which contains pharyngeal gland that is composed of many chromophil cells. Dorsally pharyngeal gland is lined by villi. The chromophil cells produce saliva containing proteolytic enzymes and mucin. Mucin makes the food soft and protease converts protein into an amino acid. The ventral chamber is a conducting chamber which conducts digested or undigested food material from the pharynx to the oesophagus.

The membrane between the 5th and 6th abdominal terga forms two deep pockets in the male, each pocket has two slit-like pouches which are probably glandular and produce a secretion which excites the female for copulation in the breeding season. These are called stink glands.

The tentorium is the internal skeleton which gives strength to the head capsule and provides a place for muscle attachment. It is formed by tube-shaped inward extensions of the exoskeleton. The mandibles, maxillary and the labia papillae are all visible. Hence tentorium plays an important role in the growth of the exoskeleton.