Structural Organisation in Animals Test - 28

Nissl bodies are large granular bodies, that stain with basic dyes, forming the reticular substance of the cytoplasm of neurons, composed of rough endoplasmic reticulum and free polyribosomes. It is the site of protein synthesis in neurons.

There is a single female genital pore present on the 14th segment in the body of an earthworm. As the 14th segment also has clitellum around it, thus the pore is present on the clitellum. So, the correct answer is option C.

Periplaneta americana (American cockroach) differs from Blata orientalis (Oriental cockroach) in having well-developed wings. The organism bears two pairs of wings. The forewings, known as tegmina arises from mesothorax and is dark and opaque. The hind wings arise from metathorax and are used in flight. Oriental cockroach appearing to be wingless at a casual glance but has two very short and vestigeal wings just below the head. 

• A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. 
• Ligaments join one bone to another bone.
• Cartilage is a flexible connective tissue in animals, including the joints between bones, the rib cage, the ear, the nose, the bronchial tubes and the intervertebral discs. 
• It is not as hard and rigid as bone, but it is stiffer and less flexible than muscle.

The cockroach has a dorsoventrally flat, compressed body which is covered by a hard, chitinous exoskeleton. It is in the form of separate plates. The dorsal plate is called tergum and the ventral plate is called sternum. Laterally, the plates are joined by pleura. So, outer border of tergum bends downwards in cockroach and attaches with pleura. So, the correct answer is option C.

Given cells are polygonal in shape, tightly packed and possess centrally located nucleus. 

1. Cheek cells are loosely packed and secrete mucus. Hence, option A is incorrect. 
2. Parenchyma cells are loosely packed cells with large intercellular spaces. Hence, option C is incorrect. 
3. Onion peel cells possess a cell wall, large vacuole, and nucleus located at the periphery. Hence, option D is incorrect. 
4. Squamous epithelium cells are tightly packed, flat, polygonal cells. Animal cells possess a centrally located nucleus. Therefore, option B is correct.  

Spindle-shaped cells are present in smooth muscles. 
Heart muscles or cardiac muscles contain intercalated discs.
Muscle cells are composed of muscle fibers or myocytes. These muscle fibers are in turn composed of many chains of myofibrils. Myofibril consists of long proteins like actin, myosin and titin and other accessory proteins. All these proteins are organized into thin and thick filaments, which repeat along the length of the myofibril. The sarcomere is contractile unit of striated muscle. It is present in between two Z lines. 

Cockroach belongs to Arthropoda which is covered by an exoskeleton. The body is divided into three regions head, thorax and abdomen. They have a true coelom and have open spaces known as sinus. The segmentation is internal as well as internal while in hydra, tapeworm and leech only external segments are present 

The structures, which are similar in their morphology, anatomy, genetics and embryology but dissimilar in their function are called as homologous organs. The thorn of bougainvillea and tendril in cucurbita are homologous organs. Both arise from an axillary bud. They perform different functions. Thorn provides protection and tendril provide support for climbing. They have anatomical similarity but they differ functionally hence they are called homologous organs. The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it, while maintaining visibility. Some reptiles, birds, and sharks have full nictitating membrane. Blind spot is a small portion of the visual field of each eye that corresponds to the position of the optic disk (also known as the optic nerve head) within the retina. They are not vestigial organs. Wings of bee and wings of crow are examples of analogous organs because of having a similar function. Nephridia coiled tubular duct-like organs, filter and remove waste from an earthworm's body. The excretory organ of cockroach is the malpighian tubules. It is found at the junction of the midgut and hind gut and are about 150 in number. 

The earthworm consists of a true coelom which is present between the body wall and alimentary canal. Coelomic fluid is present in the coelom that acts as  a hydraulic skeleton. It is helpful in contraction and relaxation of the muscles in the earthworm's body. Alimentary canal aids in digestion. Typhlosole is present in the digestive system of an earthworm and enhances the surface for digestion and absorption of food. So, the correct answer is option A.