Biology Test 284

Auxin is a plant hormone known for its role in promoting cell elongation, especially in the stem. It regulates various aspects of growth and development by facilitating the stretching of cell walls, allowing cells to expand.

Root hairs are slender projections originating from epidermal cells that function in nutrient and water uptake as well as in anchoring the root in the soil.

In wild-type Arabidopsis, root hairs are formed by epidermal cells termed trichoblasts which overlie the boundary between two cortical cells

Xerophytes are plants found in the desert area.

They require the least amount of water. In deserts there is a scarcity of water thus the plants have to take their water from the underground water level.

Their stomata are of sunken type (deep-seated) like cup – shape depression as it helps them to prevent the loss of water through transpiration.

The stomata are minute pores that occur in the epidermis of the plants.

Each stoma remains surrounded by two kidneys or bean-shaped epidermal cells the guard cells.

The stomata may occur on any part of a plant except the roots.

The epidermal cells bordering the guard cells are called accessory cells or subsidiary cells.

The number and types of stomata vary in different plant species based on their Habitat.

The girdling experiment shows that phloem is the tissue responsible for translocation of food; and that transport takes place in one direction i.e. towards the root.

Gram, Arhar, Sunhemp, moong, pea & Lupin

Systolic blood pressure is the blood pressure during ventricular contraction,diastolic is during ventricular relaxationwhile ventricular contraction,blood is forcefully pumped into the respective arteries,hence systolic blood pressure is more.

Sa node represents the pacemaker of our heart which is specialised in generating impluses and initiation of heart beat. it maintains the rhythmic contractile activity of heart. so it can only determine rate of heart beat and not contraction of heart muscles. contraction of heart muscles depends on how intense the impulse is which mainly decided by the conducting fibres.

Lungs purify the CO2 and convert it into O2 The blood coming to the lungs contain deoxygenated blood because it is collected from the body tissues and is rich in CO2. After leaving the lungs..the blood is oxygenated.

During ventricular systole, the contraction of ventricular muscles causes the closure of bicuspid and tricuspid valves (AV valves), producing a low pitched 'lubb' sound. At the end of ventricular systole, semilunar valves close, producing the second heart sound, the 'dup'. Pulsation of the radial artery is due to rhythmic contraction and relaxation in the aorta. Initiation of the heart beat occurs in the SA node.

Solution: The alveoli are the primary sites for the exchange of gases. They are tiny, balloon-like structures in the lungs where oxygen is absorbed into the blood and carbon dioxide is released from the blood. This process is facilitated by the large surface area and thin walls of the alveoli, making them perfectly suited for gas exchange.