GROWTH &

DEVELOPMENT:AN OVERVIEW

GrowthAn increase in the size of bodily parts or of the organism as a whole. It signifies quantitative changes.

DevelopmentThe orderly and sequential changes that occur with the passage of time as an organism moves from conception to death.

Also referred to as gradual growth which indicates changes in character.

MaturationProcess wherein

development in the individual is due to bodily changes determined by heredity.

Nature Vs.

Nurture

Nature

Refers to a person’s inherited characteristics, determined by genetics.

Nurture

Refers to a person’s experiences in the environment.

Heredity: The Genetic

Side

Refers to the sum total of characteristics biologically transmitted through parents to offspring and direct determining physical constitution and traits. It is nature’s way of passing on to children the actual and potential characteristics of parents.

Heredity

Two Types of Cells of Human Being•Body or Somatic Cells•Germ or Reproductive Cells

Heredity is concerned with germ cells.

Each of these cells has a nucleus which contains set of 46 chromosomes arranged in 23 pairs.

Chromosomes-Are the physical vehicles that contain the estimated quarter of a million genes that each human being possesses.

Genes- Are large molecules of deoxyribunucleic acid (DNA)- Are the actual hereditary units that combine and act to determine the individuals unique physical structure.

Human Inheritance

In the nucleus of the zygote , the hereditary materials of both the mother and father combined

Defective genes produce defective characteristics and normal genes, normal characteristics under the average normal environmental conditions.

General Rule:The normal gene is dominant and the defective gene, recessive.

The 46 chromosomes contain the individual’s genotype, the full set of genes inherited from both parents. How the individual actually looks and acts is his or her phenotype.

Chromosomal

Abnormalities

1. Down’s Syndrome

Most common chromosomal birth defect which is often referred to as mongolism.

Usually caused by the presence of an extra chromosome.

It is characterized by severe mental retardation, skeletal deformities and abnormally—wide set eyes.

2. Turner’s Syndrome or Sexual

InfantilismThis results in females having a single X chromosome, instead of the normal XX.

This disorder usually involves failure to develop sexual characteristics; the individual that has the female genetalia but lacks ovaries, hence, cannot become pregnant.

Although usually of normal intelligence, the individual shows specific cognitive defects which is called VISUAL AGNOSIA - inability to discriminate or recognize the form of objects.

also known as "Gonadal dysgenaesis"

3. Klinefelter’s Syndrome

This occurs in perhaps one in every 400 males. The male is characterized to have an extra X chromosome, hence a combination of XXY.The individual is physically a male, with penis and testicles, but marked feminine characteristics. He has feminized breast development, and small testes that do not produce sperm.

4. XYY Abnormality

This is another sex chromosome abnormality in males which results in abnormality large, aggressive males who may become aggressive criminals.

Principles of Growth

and Development

1. Growth and development is a continuous process, but it does not proceed at a uniform rate.

2. Growth and development may be accelerated or retarded.

3. The process of growth and development are influenced by heredity and environment.

4. Growth is unique. Some functions that result from growth are unique to the species like crawling, standing and walking. These are called phylogenetic functions. While functions that are unique to the individual are called ontogenetic functions, like for example, skating and bicycling which are acquired through practice and not because one is a member of the species.

6. Growth is sequential. Human beings tend to develop in an orderly and predictable sequence. The infant gradually becomes mobile by lifting first his head, then his chest, and then his abdomen. He sits, crawls, stands alone and then walks in that order. The sequence is orderly, but the timing may be varied.

7. Development is a product of maturation and learning.

8. The various aspects of development are integrated. For example, gains in one phase of growth depends on gains in other aspects, like emotional growth depending on social growth and cognitive development depending on physical growth.

Principles of Maturation

According to Bee (1975)

1.Principle of DirectionalityDevelopment governed by maturation has a clear directionality. In the case of fetal development, there are two directions. Development proceeds from the head downward (cephalocaudal) and from the trunk outward (proximodistal).

2.Principle of functional asymmetry This refers to the tendency of human to develop asymmetrically. Example: handedness.

3. Principle of self-regulating fluctuation Development does not proceed at the same even pace along all fronts simultaneously. For example: the child does not usually begin talking extensively until he has learned to walk.

General Principles of

Heredity

1. Heredity is determined at the moment of conception.

2. Variations occur for within the species there are differences. No two individuals are exactly alike.

3. Inheritance is not merely from the father and the mother, but also from the two lines of ancestry of both families.

5. All hereditary qualities are not apparent at birth.

6. Heredity involves a general capacity to do certain things rather than a specific ability, that is, what is inherited is the total of potentialities which can manifest themselves only in the course of development under suitable conditions.

7. Acquired characteristics are not inherited.