7. (a) Explain the following terms. (1) moulting (ii) metamorphosis (iii) instar b) Describo the role of Indole acotic acid,Globerellins and Cytokinins as plant growth homones in the growth and development of plant (17 marks) (3 marks)

(a) Explanation of terms:<br /><br />(1) Moulting: Moulting, also known as molting, is the process by which certain animals, such as insects, crustaceans, and some fish, shed their exoskeletons or outer skin. This process allows the animal to grow and develop by replacing the old, restrictive exoskeleton with a new one that provides more space and support for the growing body. Moulting is essential for the growth and survival of these animals.<br /><br />(ii) Metamorphosis: Metamorphosis is a biological process in which an organism undergoes a significant change in its physical structure and form during its development. This transformation typically involves a series of distinct stages, such as the egg, larva, pupa, and adult. Metamorphosis is commonly observed in insects, amphibians, where the organism undergoes a dramatic change in appearance and function.<br /><br />(iii) Instar: An instar is a developmental stage in the life cycle of certain animals, particularly insects and crustaceans. During each instar, the animal undergoes growth and molting before progressing to the next stage. The number of instars varies among different species and can range from a few to several stages. Each instar represents a specific phase of growth and development until the animal reaches its final adult form.<br /><br />(b) Role of Indole acetic acid, Gibberellins, and Cytokinins as plant growth hormones:<br /><br />Indole acetic acid (IAA) is a type of auxin, a class of plant hormones that play a crucial role in the growth and development of plants. Auxins regulate various physiological processes, such as cell elongation, root growth, and leaf orientation. I is involved in the coordination of plant growth and response to environmental stimuli.<br /><br />Gibberellins are another class of plant hormones that have a significant impact on plant growth and development. They stimulate stem elongation, seed germination, and flowering. Gibberellins also influence the synthesis of other hormones, such as auxins and cytokinins, and regulate various metabolic processes within the plant.<br /><br />Cytokinins are a type of plant hormone that promote cell division and growth in plants. They play a vital role in the regulation of shoot and root development, as well as the balance between vegetative and reproductive growth. Cytokinins also influence the senescence of leaves and the response of plants to stress conditions.<br /><br />In summary, Indole acetic acid, Gibberellins, and Cytokinins are essential plant growth hormones that regulate various physiological processes and contribute to the overall growth and development.