Growth, nutrients, respiration,
reproduction are essential for living organisms for their survival.
Formation of new organism of same species by earlier existing organism is called as reproduction.
OR
A life process in which a living organism produces another living organism like itself is called
as reproduction.
Importance of
reproduction
2) It helps to maintain the population of that particular species.
Types of reproduction
There are two methods of reproduction in living organisms as follows :
1)
Asexual reproduction
2)
sexual reproduction
1) Asexual reproduction
The process of formation of new organism by an organism of same species
without involvement of gametes is called as asexual reproduction.
OR
The reproduction which involves only one parent is called as a sexual
reproduction.This is a fast mode of reproduction. it does not involve two
parents or two different gametes. The new organism has exact genetic
similarity with the parent.
2) Sexual reproduction
Reproduction
with the help of male and female gametes is called sexual reproduction.
A) Asexual reproduction
in unicellular organisms :-
1) Binary fission:-
The process in which the parent cell divides to form two similar daughter cells is
called as binary fission.
1) Binary fission takes place by
mitosis or mitosis.
2) It takes place when there are favorable
conditions and abundant food supply.
3) Prokaryotes, protest, mitochondria
and chlorella perform binary fission.
Ex- amoeba, paramecium, euglena, chlorella
etc.
Based on Axis of fission there are three subtypes of binary fission
a) Simple binary fission :- The plane of division can be in any direction due to lack of specific
shape.
Example:- Amoeba
b) Transverse binary fission :- The plane of division is a transverse.
Example:- Paramecium
c) Longitudinal binary fission :- The plane of division is in length wise direction.
Example :- Euglena
2) Multiple fission
During unfavourable conditions amoeba undergoes multiple fission. Amoeba takes its shadow
body in and forms cyst around it. Cyst is a protective covering around plasma membrane.
Inside the cyst amoeba undergoes repeated nuclear divisions. It is followed by cytoplasmic
division and manyamoebulae are formed. When favourable conditions appears the cyst breaks
and many amoebulae are released.
3) Budding in yeast
1) Yeast is unicellular fungus that
performs budding.
2) The parent cell produces two
daughter nuclei by mitotic division.
3) This results in a small bulging
bud on the surface of parent cell.
4) The daughter nucleus enters the bud. Bud grows and upon becoming big it separates from the
parent cell to have independent life as a new Yeast cell.
B) Asexual reproduction in
multicellular organisms
1) Fragmentation
Fragmentation is one of the type of a sexual reproduction in multicellular organisms. In this
type, the body of parent organism breaks up into many fragments and each fragment starts to
live as an independent new organism. Spirogyra grow up very fast and break up into many
small fragments when there are favourable conditions. Each newly formed fragment live
independently as a new spirogyra.
Examples:- spirogyra and sycon.
2) Regeneration
Regeneration is the sexual reproduction in planaria in which the body is broken up into two
parts and resulting
each part regenerates remaining part of the body.
Example:-
Planaria.
1) In case of hydra, there is development of bud on the specific parts of its body.
2) The bud formation that takes place
only under favourable conditions.
3) The bird is formed due to repeated division of regenerative cells of body wall.
4) Bud grows up progressively and
finally forms a small hydra.
5) Nascent hydrogen gets all the
nutrition from parent hydra.
6) When the budding hydra grows sufficiently it separates from parent hydra and grows
independently.
4) Vegetative propagation
1)
Reproduction
in plants with the help of roots stem and leaves and bud is called as
vegetative
propagation.
2) This method of reproduction is
only found in plants.
3) Plants like bryophyllum reproduces
with the help of buds present on leaf margin.
4) Potato, elephant foot &
colocasia propagates with the help of eyes.
5) Carrot and radish perform
vegetative propagation with the help of roots.
6) Sugarcane grasses ginger and
turmeric vegetative propagation by the bud present on nodes.
5) Spore
formation
1) Mucor reproduces asexually by
spore formation.
2) It has a filamentous body having
sporangium.
3) The spores are formed in
sporangium.
4) When sporangium bursts the sports
are released in the air.
5) Spore germinates in moist and warm
place and new fungal colony is formed.
Example:- Mucor, Agaricus, Rhizopus etc.
Sexual reproduction
The reproduction which involves male gametes and female gametes is called as sexual
reproduction. OR
The reproduction which involves male and female parents is called as sexual
reproduction.
Sexual reproduction involves two main processes that
means gamete formation and fertilization.
1) Gametes formation:-
Gametes are formed by the process of meiosis. In meiosis, the chromosome
number is reduced to half and diploid (2n) germ
cells forms haploid gametes (n).
2) Fertilization:-
The union between male gamete and female gamete to form a diploid zygote is
called as fertilization. The zygote divides mitotically to form embryo. The embryo
develops to form new individual.
Significance of sexual reproduction
1) In sexual reproduction the
recombined DNA is formed.
2) The diversity in living organisms
occurs due to genetic variation.
3)
Genetic variation helps the organism to adjust with the surrounding
environment.
Sexual reproduction in plants
Structure of a flower
1) Flower is a unit of sexual reproduction in plants. It consists of four floral whorls as calyx,
Corolla, androecium and gynoecium.
2) The calyx and Corolla are
accessory whorls. They are protective in nature.
3) Each part of calyx is called as
Petal while each part of corolla is called as sepal.
4) Androecium and gynoecium are necessary whorls because they participate in sexual
reproduction.
5) Androecium is a male reproductive
part while gynoecium is a female reproductive part.
6) Androecium consists of stamen and filament. Pollen grains are produced due to meiosis in
anthers.
7) Gynoecium consists of stigma, style and ovary. There are one or more ovules inside the
ovary.
Some useful terms
1)
Bisexual flower:-
A flower in
which androecium and gynoecium are present is called as bisexual flower.
Examples:-
Rose, Hibiscus, Bottle brush plant etc.
2)
Unisexual flower:-
A flower in which either androecium or
gynoecium is present is called as unisexual flower.
Examples:- Bitter gourd, papaya etc.
The flower in
which only androecium is present is called as male flower.
The flower in which only gynoecium is present is
called as female flower.
Pollination:
The process of transfer of pollen grains from anther to stigma is
called as pollination.
The pollination is carried out with the help of wind,
water, butterfly, bees, animals etc.
Types of pollination
1)
self pollination :-
The transfer of pollen grains from the anther to the stigma within the same flower is
called as self pollination.
2)
Cross pollination :-
The transfer of pollen grains from the anther to the stigma of another
flower borne on two different plants of same species is called as cross
pollination.
1. The pollen grains from the anther are transferred to the stigma of flower by pollination.
2. The pollen grains germinates on
the stigma.
3. As a result of germination long pollen tube and two male gametes are formed.
4. The pollen tube travels through
the style to the ovary.
5. Upon reaching there, the tip of the pollen tube bursts & two male gametes are released in
embryo.
6. One male gamete fuses with the egg
cell to form zygote.
7. While other male gamete fuse with polar nuclei forming th endosperm.
8. As two nuclei participate in this process therefore it is called double fertilization.
Give reasons
1) Flower
is the structural unit of sexual reproduction in plants.
*
Flower produces male and female gametes in androecium and gynoecium
respectively.
* The
double fertilization also takes place in flower.
*
Therefore, flower is called the structural unit of sexual reproduction in
plants.
2) Fertilization in plants is
called double fertilization.
*
Pollen grain on germination produces two male gametes in pollen tube.
* one male gamete fuses with the egg cell to form zygote while the second male gamete
fuses with two polar nuclei forming endosperm.
* In
this way, two nuclei participate in fertilization process so it is called
double fertilization.
Seed germination :-
Seed
germination is the process in which the seed develops into a new plantlet.
In the plants after fertilization the ovary develops into seed and ovary turns into fruit. Seeds
fallen on the ground due to bursting of the fruits start germinating. Only under favourable
conditions in the soil, this germination takes place. The zygote present inside the seed uses
food stored in endosperm of seed and hence develops from further to produce a new plantlet.
Sexual
reproduction in human being
Men have XY sex-chromosomes and women have XX sex - chromosomes. Reproductive
system with specific organs develops in the body of men and women due to these sex
chromosomes X chromosomes is present in men and women whereas Y chromosome is present
in men only.
Figure: Human male & female
reproductive system
Human male
reproductive system
1) Male reproductive system of humans
consists of testes, various ducts and glands.
2) Testes are in pair. Each testis
lies in the scrotum which lies outside the abdominal cavity.
3) Testis consists of numerous seminiferous tubules. The germinal epithelium of seminiferous
tubules forms sperms by undergoing meiosis.
4) These immature sperms are sent
forward through various tubules.
5) This sequence is as follow Rete testis Vas efferentia. Epididymis Vasa deferentia ejaculatory
duct urethra
6) During travelling sperms becomes
mature. They are made capable to perform process of
fertilization.
7) Seminal vesicles, single prostate gland and a pair of Cowper's gland secrete their secretions.
The secretions and the sperms together form semen.
8) This semen is deposited in the
vagina with the help of penis.
Human female reproductive system
1)
All
the organs of female reproductive system are located in lower abdomen.
2)
It
includes a pair of ovaries, a pair of fallopian tubes, single uterus and
vagina.
3) The uterus open out by
vagina. In vaginal walls there are Bartholin's glands.
4) The free end of fallopian
duct is funny like having an opening in the centre.
5) The oocyte released from the
ovary due to ovulation is picked up by this funnel.
6) The other end of fallopian duct opens into
uterus. There are cilia on inner surface of oviduct.
7) These cilia pushes the oocyte
to the uterus through the fallopian duct.
8) The fertilization of oocyte
can take place only in the middle part of the fallopian duct.
9) The lower end of uterus opens
into vagina. The contractions of uterus help in the process of
parturition.
10) Vagina is the birth canal as well as copulatory passage. It is also a passage l for menstrual
flow.
Formation of gametes
1)
Sperms
and ovum are formed by meiosis
2)
Sperms
are produced in testis while ovum is produced in ovaries.
3)
Man
can produce sperms from puberty till death.
4) In case of female, at the time of birth there are 2 to 4 million oocytes in the ovary of
female foetus.
5) From puberty, one mature oocyte is released from ovary every month till the age of 45
to 50 years.
6) Menopause is the stop age of function of female
reproductive system.
7) At the age of about 45 to 50 years due to less secretion of female hormones the
reproductive system functions completely stops.
Fertilization in
human being
Union of sperm and
ovum to form zygote is called fertilization.
1) Fertilization in humans is
internal. The semen is ejaculated in vagina during copulation.
2) In the semen there are few
millions of sperms. They swim from vagina through uterus and reach
fallopian ducts.
3)
Only
one sperm is required for fertilizing a single ovum that female produces.
Development and birth
v The fertilization takes place in
fallopian duct.
v The zygote formed undergoes rapid and
repeated mitotic divisions to develop embryo.
v Embryo is pushed towards uterus. In
uterus, it gets implanted & grows
for next 40 weeks
v The nutrition during this period is
provided by placenta which is an organ developed in pregnant mother.
v After completion of embryonic
development, the pregnant mother gives birth to a baby.
Menstrual
cycle
Menstrual cycle is the events of cyclic changes that takes place with the interval of 28 to30
days in mature women.
v Menstrual cycle is a natural process
which is controlled by four hormones.
v These four hormones are follicle stimulating hormone (FSH), luteinizing hormone (LH),
estrogen and progesterone.
v Under the influence of FSH, one of the several follicles in the ovary starts to develop along with
the oocyte
present in it.
v This developing follicle secrets
estrogen.
v Under the influence of estrogen, endometrium (uterine inner layer) grows or regenerates. Mean
while developing
follicle completes its development.
v Under the influence of LH, ovarian follicle burst and releases the mature oocyte out of the
follicle. This process
is called ovulation.
v The empty ovarian follicle after the ovulation becomes Corpus luteum. Corpus luteum produces
hormone progesterone.
v Endometrial glands secrete their
secretion under the effect of progesterone.
v The oocyte if fertilized is implanted
over this endometrium.
v If it is not fertilized the Corpus luteum become degenerate body called Corpus albicans. The
Corpus albicans
cannot secret estrogen and progesterone.
v Due to lack of these hormones, the
endometrial layer of the uterus collapses.
v The tissue debris, along with unfertilized egg is given out through the vagina as menstrual flow.
This
results in bleeding for about five days.
* If women is not pregnant, then this
menstrual cycle keeps on repeating with regularity.
Reproduction and modern technology
Some couples cannot have children due to various reasons. In women if there are problems
like irregularity in menstrual cycle, difficulties in oocyte production or implantation in uterus,
obstacles in the oviduct, etc then she cannot have childrens. Absence of sperms in the semen, slow
movement of sperms, anomolies in the sperm are the reasons
in case of males.
Modern technology in reproduction
1) In vitro fertilization (IVF) :-
IVF technique is done when there are problems like less
sperm count, obstacles in oviduct. In IVF, fertilization is done in the test tube. The embryo formed
is implanted in uterus of women for further growth.
2) Surrogacy :-
In women if there is problem regarding the implantation of embryo in uterus,
then help of another woman is taken. This woman is called
surrogate mother.
Oocyte from real mother is taken out and fertilized with sperms
collected from her husband. These gametes are fertilized outside in a test tube and then the
fertilized zygote is implanted in the surrogate mother. This technique is called as Surrogacy.
3) Sperm bank or Semen Bank :-
If man has problems with the sperm production, then the sperms are collected from the sperm Bank.
Sperm bank is the place where the donors donate the sperms & such sperms are kept Store. The
donors Identity is kept secret & he should also be physically and medically fit person.
Concept of In Vitro Fertilization
(IVF)
v IVF means in vitro fertilization.
v By this technique, childless couples
can be blessed by their own child.
v This technique is used for those couples which have problems like less sperm count, obstacle
in oviduct, etc.
v In this technique, oocyte from the mother are artificially fertilized with the sperms collected
from her husband in a test tube. This fertilization is done in a test tube. So it is called as test
tube baby.
v The embryo formed is implanted in
uterus of real mother at appropriate time.
Twins:-
Two embryos develop simultaneously in the same uterus and thus two offsprings are
delivered simultaneously. Such offsprings are called as twins.
Types of twins
There are two main types
of twins named as monozygotic twins and dizygotic twins.
1. Monozygotic twins
:-
The twins developed
from a single embryo are called monozygotic twins. If within 8 days of zygote
formation, cells of that embryo divide into two groups. Each one develops as
two separate embryos forming two monozygotic twins. These twins are genetically
exactly similar to each other. The gender of the twins is also same.
The Siamese twins develop from monozygotic twins, if
the embryonic cells are divided into two groups 8 days after the zygote formation. These are
conjoined twins where some parts of body are joined to each other. Also some organs are common
in Siamese twins.
2. Dizygotic twins:-
When two oocyte are
released from the ovary of women and both are fertilized by two separate sperms
then there is formation of dizygotic twins.
These
twins are formed due to two embryos that are separately implanted in the
uterus. Such twins are genetically different and may be same or different by
gender.
Reproductive health
v In India, there is a lack of awareness about reproductive health. Social customs, traditions,
illiteracy, shyness etc. keep the society under pressure. There is always indifference towards the
reproductive health of women.
v Reproductive health can be achieved
by keeping genitals clean.
v The cleanliness and hygiene during menstruation, the cleanliness of genitals and other private
parts are the
aspect of personal hygiene.
v Therefore, about reproductive health
one should have scientific and authentic information.
v Syphilis and gonorrhea are sexually transmitted or bacterial venral diseases which affect people
on a large scale.
Symptoms
of syphilis :-
Occurrence of chancre (patches) on various parts of body including genitals,
rash, fever, inflammation of joints, alopecia , etc.
Symptoms of gonorrhea :-
v Painful and burning sensation during
urination.
v Oozing off through penis and vagina.
v Inflammation of urinary tract, anus,
throat, eyes, etc.
Population explosion
v
Excessive growth of population within short duration is
called as population explosion.
v The problems due to population
explosion are unemployment, decreasing per capita income and increasing loan,
stress on natural resources, etc.
v For population control, therefore in
India, family planning is a must.
Sex determination in human being
v In humans, each diploid cell has 22 pair of autosomes and one pair of sex chromosomes
i.e. (44 + XX or 44 + XY).
v The genetic makeup of human male is
44 + XY while genetic makeup of female
is 44 + XX.
v Germ cells undergoes meiosis to form haploid gametes having chromosomal combination of
22 + X or 22 + Y.
v Male produces two types of sperms, 22
+X and 22+ Y.
v Female produces only one type of oocyte
i.e. 22 + X.
v Type of sperm of father decides the
sex of the child.
v If X bearing sperm fertilizes the oocyte, the girl is born and if Y bearing sperm fertilizes
oocyte, it is a boy.
v Thus father is responsible for the
sex of child in human being.
Give
scientific reasons :-
1. By the age of 45 - 50 women gets
menopause.
By the age of 45 to 50, the secretion of hormones which control the functioning of the
reproductive system is reduced gradually and then it stops. This causes end of menstrual cycle.
This results into menopause.
2. Older mothers have greater chances
of conceiving abnormal children.
v In older women, the oocytes released
from ovary during this phase are not normal.
v Their cell division is abnormal and
thus oocyte becomes abnormal too.
v If such abnormal oocytes are fertilized, the baby is born with many genetic problems like
Down's syndrome or
Turner's syndrome.
3. Indians should follow family
planning for controlling the population.
There is a population explosion in India. This results in to unemployment, decreasing per capita
income and increasing loan, stress on natural resources, etc. Only by controlling population,
these problems can be solved. Therefore Indians should follow family planning for controlling
the population.
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