Biology Test 351

In the given figure of TS of anther, the structure marked as A, B, C, D and E are respectively sporogenous tissue, tapetum, epidermis, middle layer and endothecium. Sporogenous tissue is a group of compactly arranged homogenous cells. It is irregular in shape with abundant food reserves. Tapetum is a layer of nutritive cells found within the sporangium, particularly within the anther, of flowering plants. It is important for the development of pollen grains. Epidermis is the common anther covering. Cells of middle layers degenerate to provide nourishment to the growing microspore mother cells. Endothecium is the inner lining of a mature anther of a flower.

Proton gradient is important because the breakdown of this gradient leads to the release of energy. This gradient which is created by the accumulation of H⁺ ion inside the luman. is broken down due to the movement of protons across the membrane to the stroma through ATP synthase.

Abscisic acid prepares plants to cope with stress conditions like drought etc. by inducing stomatal closure and other reactions. Hence it is named stress hormone.

Plants which are difficult to flower can be made to do so by spraying them with 2, 4, –D (2, 4 – dichlorophenoxy acetic acid) and NAA (napthalene acetic acid) which are synthetic auxins, e.g., litchi, pineapple.

Abscisic acid or ABA is an antagonist to gibberellins. This is discussed in the table given below

A frog (Rana tigrina) has lungs as its main respiratory organ, but during hibernation and aestivation and during its habitat in water, it respires through the skin.

Carbon monoxide combines more readily with haemoglobin than oxygen. It forms a stable compound, carboxyhaemoglobin, which reduces the amount of free haemoglobin available for carrying oxygen and starves the tissues of oxygen.

Sarcomere is part of myofibril between two successive Z-lines, which consists of two l-band halves, and an A-band between them.

Carbonic anhydrase is a zinc-containing enzyme present in RBCs. This enzyme, catalyzes the reversible reaction of carbon dioxide with water to form carbonic acid.

The air passes into the nasal chambers from the nostrils. A pair of external nostrils open above the upper lip. The nasal chambers open into the pharynx. The pharynx is the common passage for food and air.

The larynx is known as the sound-box in humans. The larynx has two pairs of vocal cords i.e. the upper or false vocal cords and the lower or true vocal cords. The vibration of the lower vocal cords during inspiration is responsible for the production of sound.

Lungs are a pair of respiratory organs situated on either side of the mediastinum. Each lung is further divided into lobes, which are separated from each other with the help of fissures. An oblique fissure is present in both the lungs which divides them into an upper and a lower lobe. However, the right lung has an additional horizontal fissure which divides it into upper, middle and lower lobe.