Biology Test 283

Late wood, formed in the latter part of the growing season, indeed has fewer xylary elements with narrower vessels. This is because the cambium, the layer of cells in plants that gives rise to secondary xylem (wood), is less active in colder temperatures, which are typically associated with the later parts of the growing season, such as autumn and winter.

So, both Assertion A and Reason R are true. Moreover, Reason R correctly explains why Assertion A is the case: the decreased activity of the cambium in colder temperatures results in the formation of late wood with fewer, narrower vessels.

Therefore, the correct answer is :

Option D : Both A and R are true and R is the correct explanation of A.

Statement I : Endarch and exarch are the terms often used for describing the position of secondary xylem in the plant body.

This statement is incorrect. Endarch and exarch are used to describe the developmental sequence of primary xylem, not secondary xylem. In endarch condition, the first formed xylem is towards the centre (protoxylem) and the last formed xylem is towards the periphery (metaxylem), which is typical of stems. In the exarch condition, the first formed xylem is towards the periphery and the last formed xylem is towards the centre, which is typical of roots.

Statement II : Exarch condition is the most common feature of the root system.

This statement is true. The exarch condition, where the first-formed xylem is towards the periphery and the last-formed xylem is towards the centre, is indeed the most common feature of the root system.

So, the correct answer is :

Option C : Statement I is incorrect but Statement II is true.

Flowers, fruits, and leaves develop from apical meristem (primary tissue) that is responsible for primary growth. They lack lateral meristem which causes secondary growth. So, from the above discussion, it is clear that the flowers, fruits, and leaves of the woody dicotyledonous tree mainly consist of primary tissue.

Pericycle cells are thick-walled parenchymatous cells that lie next to the endodermis. Initiation of lateral roots and vascular cambium take place from these cells.

The vascular bundles are collateral and closed type in the monocot leaves and each one is surrounded by a bundle sheath which is a layer of thin-walled parenchymatous cells. So, the correct answer is ‘Mesophyll is not differentiated into palisade and spongy parenchyma.

The lungs are covered in a membrane called pleural membrane. The outer covering is called parietal pleura and the inner covering is called visceral pleura.

The correct answer is Option B : B and C only.

Statement A is incorrect. Basophils are actually the least abundant cells of the total white blood cells (WBCs), not the most abundant.

Statement B is correct. Basophils do secrete histamine, serotonin, and heparin. Histamine and serotonin are involved in inflammatory response, while heparin is an anticoagulant.

Statement C is also correct. Basophils are involved in the inflammatory response. They release chemicals such as histamine and serotonin that dilate blood vessels and attract other white blood cells to the site of inflammation.

Statement D is incorrect. Basophils do not have a kidney-shaped nucleus. That description is more appropriate for monocytes, another type of white blood cell.

Statement E is incorrect. Basophils are not agranulocytes. They are granulocytes, a category of white blood cells characterized by the presence of granules in their cytoplasm. Agranulocytes, which lack visible cytoplasmic granules, include lymphocytes and monocytes.

An ECG (Electrocardiogram) is a test that measures the electrical activities of the heart. Each wave in an ECG represents a certain part of the heart's electrical activity:

P wave : This wave occurs prior to the contraction of the atria (atrial contraction). It represents the depolarization of the atria.

QRS complex : This is a series of three graph deflections seen on a typical electrocardiogram. It corresponds to the depolarization of the ventricles, which initiates the ventricular contraction.

T wave : The T wave represents the repolarization (or recovery) of the ventricles.
By matching these descriptions with the options provided :

(A) P-wave - Depolarisation of atria (III)

(B) QRS complex - Depolarisation of ventricles (I)

(C) T wave - Repolarisation of ventricles (IV)

(D) End of T wave - End of systole (II)

So, the correct answer seems to be Option D : A-(III), B-(I), C-(IV), D-(II)

- P-wave: Depolarisation of atria

- Q-wave: Beginning of systole

- QRS complex: Depolarisation of ventricles

- T-wave: Repolarisation of ventricles

In the given figure depicting the respiratory passage in man, the unidentified parts are as follows: (A) Alveolar sac, (B) Secondary bronchus, (C) Alveoli, (D) Bronchioles, and (E) Trachea.