(i) The plastid found in the cells of yellow coloured petals.   (ii) The scientific study of human population.   (iii) The hormone secreted by beta-cells of islets of Langerhans.   (iv) The energy currency of a cell.   (v) The part of the brain which is concerned with memory.   (vi) The process by which living organisms obtain energy for their life activities.   (vii) Chemical substances obtained from certain micro-organisms that destroy harmful microbes.   (viii) A cytoplasmic organelle found only in an animal cell.