Biology Q&A Form IV: The Effects of Growth

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BIOLOGY QUESTIONS AND ANSWERS FOR FORM FOUR

Question: (i)-What is growth?

(ii)- What are the differences between growth and development

(iii)- What are the internal and external factors affecting growth in humans?

Answers:

(i) Growth is irreversible increase in size. It is usually accompanied by cell division. Growth can be shown by increase in mass, length, surface area and numbers.

 

(ii) Difference between growth and development

-Growth refers to increase in size, height, weight etc while development refers to improvement in the functioning of the body process.

-Growth is easily measured and observed while development cannot be measured easily.

-Growth is limited and it starts with birth to reach the maximum at maturity while development is a continuous, unending process all through life.

– Growth is limited to specific areas while development is concerned with various aspects and parts of body and behaviour as a whole.

 

(iii) INTERNAL FACTORS AFFECTING GROWTH IN HUMANS

1. HEREDITY

A person’s physical development is strongly affected by their genes inherited from their parents. Parent’s genes predetermine the limits of an individual’s height and other characteristics including the variability in eye colour, hair colour, body composition, and skin tone.

With physical attributes such as height, parents’ genes dictate the range of height their offspring can obtain. The variability in height is a result of many external factors in the environment including nutrition and events during the child’s growth.

 

2. HORMONES

Human growth is affected by biochemical products such as hormones. Hormones are regarded as growth-promoting substances. Probably all the endocrine glands influence growth. Most of the hormones are secreted by the endocrine glands and play a significant role in regulating the pattern of growth and development as per instructions of the genes.

 

EXTERNAL FACTORS AFFECTING GROWTH IN HUMANS

Growth is also affected by external factors which include the following:

 

NUTRIENTS

Growth is closely related to nutrition. A sufficiency of food is essential for normal growth. An adequate supply of nutrients is naturally essential for the normal growth of humans and the need varies with the phase of development.

 

For example: Zinc plays a part in protein synthesis and is a constituent of certain enzymes. A deficiency of zinc causes stunting, interference with sexual development and falling out of hair.

-Iodine is needed for the manufacture of the thyroid hormones; Bone will not grow properly without an adequate supply of calcium, phosphorus and other inorganic constituents such as magnesium and manganese.

 

-Iron is required for the production of haemoglobin; Vitamins play an important part in growth. Vitamin A is thought to be control the activities of osteoblasts. In vitamin C deficiency the intercellular substance of bone is inadequately formed. Vitamin D deficiency is the cause of rickets.

 

Malnutrition during childhood delays growth, and malnutrition in the years proceeding adolescence delays the onset of the adolescence. Malnutrition may also result to diseases which decrease the appetite or interfere with digestion and assimilation. A majority of malnourished children fail to achieve their full genetic potential of body growth and are thus stunted or wasted or both.

 

DISEASES

Diseases are alteration of the normal body functions, disorders or morbid conditions of the mind. Diseases slow down growth in humans and other animals. A child that suffers from diseases very often is likely to have his growth stunted or retarded. Such a child may end up having a small body or deformed body parts.

 

CULTURAL FACTORS

The physical growth of human beings is definitely affected by cultural factors. Culture differs from ethnic group to ethnic group. The body growth differences correlate with varied cultural groups. The physical growth of the body follows some adaptations in different geographical areas of distribution of the groups.

 

SOCIOECONOMIC FACTORS

Socioeconomic influence on human growth is also a well known factor. Children from different socioeconomic levels differ in average body size at all ages. It is clear that growth of the children and adults in those families with good financial status is always good compared to the case in poor families.

However, growth differences are more closely related to the home conditions than to the strictly economic status of the families.

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