definition of heredity, principles of heredity, types of twins, Environment, internal, external environment and conclusion.

1. HEREDITY AND ENVIRONMENT
​ - By G.KALPANA M.SC,M.ED,M.PHIL.,
ASSISTANT PROFESSOR
● What is Heredity ? ……………………………. 2
● Principle of heredity transmission …………………………… 3
● Types of Twins …………………………… 6
● What is Environment? ………………………….. 12
● Educational Implications …………………………… 14
● Conclusion …………………………… 18

2. HEREDITY
​ ​ A Child resembles his sisters, brothers, parents, grandparents and
other members of the family more than the people unrelated to him at all.
What is it that causes such similarities and dissimilarities? The answer to
this is heredity which means that an offspring inherits most of the
personality traits of his parents and forefathers that make him resemble
them.
Douglas and Holland​ - One’s heredity consists of all the structure,
physical characteristics, functions or capacities derived from parents,
other ancestry or species​.​Try to answer this questions in how life begins,
● The male and female reproductive organs produce ​Germs cell.
● Males germ cell produce - ​Spermatozoa
● Females’ ovaries produce - ​ova
​Life is the result of union of these males and females cells. As a result
of coitus at the time of mating, numerous male germ cells try to come in
contact with the female germs cells. The males germs cells are deposited at
the mouth of the uterus. Try to make contact with single ovum. This

3. Fertilized ovum is the beginning of the life which starts the process of the
child’s development in the mother’s womb.
The Fertilized ovum consists of a semi-fluid mass called ​Cytoplasm.
The cytoplasm lies the nucleus which contains the ​Chromosomes.
The chromosomes exists in pairs. In the fertilized ovum ​zygote​.
Principles of Hereditary Transmission
● Development begins at conception, when a sperm cell from the father
penetrates an ovum from the mother, forming a zygote.
● A normal human zygote contains 46 chromosomes (23 from each
parent), each of which consists of several thou- sand strands of
deoxyribonucleic acid (or DNA) known as genes.
● Genes are the biological basis for the development of the zygote into a
person.
● Development of the zygote occurs through mitosis—new body cells
are created as the 23 paired chromosomes in each cell duplicate
themselves and separate into two identical new cells.
● Specialized germ cells divide by meiosis to produce gametes (sperm
or ova) that each contain 23 unpaired chromosomes. Crossing-over

4. and the independent assortment of chromosomes ensure that each
gamete receives a unique set of genes from each parent.
● Monozygotic (or identical) twins result when a single zygote divides to
create two cells that develop independently into two individuals.
● Dizygotic (or fraternal) twins result when two different ova are each
fertilized by a different sperm cell, then develop independently into
two individuals.
● Gametes contain 22 autosomes and 1 sex chromosome. Females’ sex
chromosomes are both X chromosomes; males’ sex chromosomes are
an X and a Y chromosome.
● Ova contains an X chromosome. Sperm contain either an X or a Y
chromosome. Therefore,fathers determine the sex of their children
(depending on whether the sperm that fertilizes the ova contains an X
or a Y chromosome).
● Genes produce enzymes and other proteins that are necessary for the
creation and functioning of new cells, and regulate the timing of
development. Internal and external environments influence how
genes function

5. ● There are many ways in which one’s genotype may affect
phenotype—the way one looks,feels, thinks, or behaves.
● Some characteristics are determined by a single pair of alleles, one of
which is inherited from each parent.
● There are four main patterns of genetic expression:
1. simple dominant-recessive inheritance,
2. Co-dominance inheritance,
3. sex-linked inheritance,
4. polygenic (or multiple-gene) inheritance.
​ ​Chromosomes​ (23 pairs )
↙ ↘
​ Father​- 23 chromosomes ​Mother​ - 23 chromosomes
Each chromosome consists of a number of minute particles called ​Genes.
The genes are the physical substances passed on from parents to offspring
and thus, are the real carries and determiners of the heredity traits.
​ Heredity refers to a biological mechanism as a result of which a child
gets something from his ancestral stock through his parents.

6. Types of twins
There are four types of twins:
● Diochorionic-diamniotic twins
This is either never divided (aka are fraternal twins) or
divided within the first four days and have two separate amniotic
sacs and placentas. This includes almost all fraternal twins.

7. ● Monochorionic-diamniotic twins
Share the same placenta, but have two amniotic sacs. This
occurs when the embryo splits in 4-8 days and includes 60-70% of
all identical twin pregnancies.
● Monochorionic-monoamniotic twins
Share the same amniotic sac and appear when the embryo
splits after 9 days.
● Conjoined twins
This occurs when division takes place later than 12 days
after fertilization.

8. Fraternal Twins Identical Twins
Fertilization
form
Two or more ova same time by
two different sperm cells
sometimes the
ovum splits into two
parts
Genetic To differ from siblings are
inherited from different sets of
chromosomes and gens
To differ siblings
are inherited,
different sets of
chromosomes and
gens
zygotic dizygotic monozygotic

9. Blood type May be different Always same
Gender Usually different Always same sex
Principles of Heredity:
The five important principles of heredity are:
1. Like begets like:
Each species breeds true to type. In other words, offsprings possess
characteristics and racial differe​nces, ​especially physical, similar to their
parents, e.g. tall parents generally have tall children.
2. Principle of variance:
Even if like tends to beget like, parents and offsprings are not exactly alike.
Resemblances of parents and their offsprings are never perfect. All tall
parents do not have tall children.

10. 3. Principle of convergence of two life streams:
Offsprings inherit physical and mental characteristics from parents and
their ancestors. A portion of inheritance comes from the maternal side and
remaining from paternal side that is the child’s maternal and paternal lines
contribute about 50% each of his inheritance. It is generally assumed that
½ comes from parents, 1/4 from his grandparents, 1/8 from his great
grandparents and so on from all the other more remote ancestors.
4. Principle of chance possibility:
As chance plays important role on inheritance, making absolute predication
is impossible because the pairing of the chromosomes is in the state of flux,
a cell to which the set of maternal or paternal chromosomes goes during the
reduction and division, the particular cell which unites with another in the
maternal and paternal lines, the pattern of genes in any chromosome; genes
carried in any particular chromosome; crossing over of genes from one
paired chromosome to another.
5. Principle of dominant and recessive:

11. One of the reasons for individual differences is some trials are dominant
while others are recessive causing apparent differences. The union of the
best traits of the father with the best traits of the mother produces talented
children. But such gifted may carry on the determines of genes, which are
average. There may be chances that when they produce a child, their
average traits combine and a child of average caliber may be born.
Principles of heredity observed help us to understand that:
(i)​ Many aspects of human behaviour and development ranging from
physical characteristics such as height, weight, eye colour, skin colour, etc.,
complex patterns of social and intellectual behaviour are influenced by a
person’s genetic endowment.
(ii) They also determine nature of physiological functioning cause physical
deformities.
(iii) The heredity mechanisms lead to resemblance between siblings as well
as the differences among the members of the family.

12. (iv) The heredity basis of individual differences lies in the unlimited variety
of possible gene combinations that can occur. These differences become
more pronounced with the age and maternity.
ENVIRONMENT
​ Environment is nothing but the sum total of the surroundings in
which an individual has to live. Psychologically an individual’s environment
is related to all those stimuli which he faces from the moment of
fertilization till death. Environment is generally divided into two
categories-natural and social. Natural environment refers to all those things
and forces on and around the earth that influence a person.
Social environment we mean the environment which the person sees
around himself on acquiring consciousness in the society, i.e., language,
religion, custom, tradition, means of communication, means of luxury,
family, school, social groups etc. ​By human society we mean those
institutions or organizations which human beings have established for their
own protection and security. Psychologists like Freud, Hurlock, Eills have

13. accepted the fact that the social environment is very much responsible for
changing human behaviour.
Environmental forces can be categorized into:
a. Internal environments.
b. External environments.
Internal Environment:
The environment received by the individual from his conception till his
birth in the womb of the mother, i.e. a period of about 9 months is called
internal environment. In this environment, the embryo receives the
nutrition through the bloodstream of his mother.
The physical and mental health of the mother including her habits,
attitudes and interests, etc. all constitutes the inner surrounding or internal
environment that affects the growth and development of the foetus along
with the emerging behaviour in future.

14. External Environment:
After the birth what the child gets in terms of environmental influences is
purely external in nature. These can be physical and social or cultural
influences. The physical environments like earth, river, mountains, weather
and climatic conditions, food, water, etc. constitute the external
environment.
The parents, family members, friends, classmates, teachers, members of
community and society, the means of mass communication and recreation,
religious places, etc. include social and cultural environments helping to
shape the personality and behaviour.
Educational Implications of Heredity and Environment
The knowledge of heredity and environment has a great influence on
human development. Human development is the product of both heredity
and environment. The development pattern of the children is determined
by both heredity and environment.

15. As per the developmental pattern of the children the educational pattern,
methods and learning environment should be made by the teacher in the
teaching-learning situation. So the knowledge of heredity and environment
helps the teacher in various ways which are discussed hereunder.
i. Knowledge of heredity and environment helps the teacher to know the
varying needs and abilities of the children.
ii. It helps to provide proper guidance to his children in the field of
educational, vocational and personal.
iii. It helps the teacher to classify the students as gifted, normal or slow
learner and arrange different types of education for them.
iv. It helps the teacher to provide better learning environment in the school.
v. It helps the teacher to know the principle of individual differences and
arrange the educational experience accordingly.
vi. It helps the teacher to study the behaviour of the children under
different situations.

16. vii. It helps the teacher to organize various curricular and co- curricular
programmes for the best benefit of the children.
So the knowledge of both heredity and environment is of utmost value to
the teachers, administrators and educational planners. If it is realized, the
system of education will be changed to a great extent.
Suppose we have got three children of three different grades of heredity
viz., superior, average and low (symbolically put as S, A and L). Suppose
there are three grades of the environment also (S, A and L). If the child with
superior heredity is put in superior environment, his personality will be
highly superior because S x S = S2. If he is put in average environment his
personality will be somewhat superior (S x A = SA).
The different combinations are as follows:
i. Superior heredity and superior environment, S x S = S2
ii. Superior heredity and average environment, S x A = SA
iii. Average heredity and superior environment, A x S = AS

17. iv. Average heredity and average environment, A x A = A2
v. Superior heredity and low environment, S x L = SL
vi. Low heredity and superior environment, L x S = LS
vii. Average heredity and low environment, A x L = AL
viii. Low heredity and average environment, L x A = LA
ix. Low heredity and low environment, L x L = L21
Conclusion​:
The Nature / Nurture Controversy:
The nature (heredity) – nurture (environment) debate really concerns the
relative importance of heredity and environment. Today no one believes
that nature alone completely determines the course of our development.
Psychologists agree that development is shaped by the interaction of
heredity and the environment.

18. Within this interaction our genetic endowment for many characteristics
provides us with a reaction range of possible levels that we may ultimately
reach depending on the availability of our experience in the environment.
In conclusion, both hereditary and environmental factors can influence a
person’s personality. Heredity sets the limitation which environmental
differences decide the concluding result. However, genetic factors have a
larger effect on personality traits. Through twins and adoption studies, and
the hereditary of schizophrenia, it can be seen that hereditary has a bigger
effect on personality as compared to family environment. Thus, studies of
heritability and limited parental influence all point to the notion that
personality traits are more of expressions of human biology rather than
products of life experiences.