facial and body hairs, deepening of voice, and increase in sexually oriented behaviour. Increased aggression and other behaviours are also linked with testosterone production. The normal functioning of all hormones is crucial to our behavioural well-being. Without a balanced secretion of hormones, the body would be unable to maintain the state of internal equilibrium.
Without the increased secretion of hormones during the times of stress, we would not be able to react effectively to potential dangers in our environment. Finally, without the secretion of hormones at specific times in our lives, we would not be able to grow, mature and reproduce. H EREDITY : G ENES AND B EHAVIOUR We inherit characteristics from our parents in the form of genes. A child at birth possesses a unique combination of genes received from both parents.
This inheritance provides a distinct biological blueprint and timetable for an individual’s development. The study of the inheritance of physical and psychological characteristics from ancestors is referred to as genetics . The child begins life as a single zygote cell (mother’s ovum fertilised by father’s sperm). Zygote is a tiny cell with a nucleus in its center containing chromosomes.
These chromosomes with all genes are inherited from each parent in equal numbers. Chromosomes Chromosomes are the hereditary elements of the body. They are threadlike-paired structures in the nucleus of each cell. The number of chromosomes per nucleus is distinctive, and is constant for each living organism.
The gametic cells (sperm and ovum) have chromosomes but not in pairs. A new generation results from the fusion of a sperm cell and an egg cell. At the time of conception, the organism inherits chromosomes from parents, from the mother and from the father. Each of these chromosomes contains thousands of genes.
However, the sperm cell (fathers’) differs from the egg cell (mother’s) in one important respect. The 23rd chromosome of the sperm cell can be either the capital X or Y type of the English alphabet. If the X type sperm fertilises the egg cell, the fertilised egg will have an XX 23rd