ORGANISMS REPRODUCE
The
production of new organisms from the existing organisms of the same species is
known as reproduction. Reproduction is important for survival of a species on
this earth. The growth of reproduction secure presenting of life on earth. Reproduction
through human beings secure that the human species will present to exist on
this earth for all the time to come. reproduction gives growth to more
organisms with the same basic feature as their parents. For example, human
beings ever produce human babies; cats ever produce kittens; dog ever produce
puppies and apple seeds ever produce apple plants.
METHODS OF REPRODUCTION
There are many various ways in which new
organisms are produce from their parents. Like Amoeba just split into two parts
to produce new Amoeba; hydra and yeast grow out of the parent’s body in the
form of a bud; and other organisms like birds ad snakes hatch out of the eggs
lay through their parents; whereas some organisms like human babies, cub,
kittens and puppies are born from their mother.
There
are two method of reproduction in living organisms:
1 Asexual reproduction, and
2 Sexual reproduction.
Reproduction cells (called sex cells, ‘gametes’ or ‘germ cells’)
1 Asexual Reproduction
The production of a new organisms
from a single parents absent the involvement of sex cells ( or gametes) is
called asexual reproduction.
Some of the example of asexual reproduction are : binary
fission in Amoeba; budding in Hydra; spore formation in Rhizopus fungus (or
bread mould0; regeneration in Planaria (flatworm) ; fragmentation in spirogyra
and vegetative propagation in flowering plants (like rose plants).
2 Sexual Reproduction
The production of a
new organisms through two parents by making use of their sex cells is called
sexual reproduction. In sexual
reproduction the sex cell of one parent fuses with the sex cell of the other
parent to from a new cell called ‘zygote’. This zygote then grows and develops
to form a new organisms. Thus, in sexual
reproduction, two parents are
essential to produce a new organisms. The two parents which are presentation in
sexual reproduction are called male and female. Our father is male and our
mother is female. The humans , fish, frog, hens, dogs, cats, horses, lions,
deer and elephants. Most of the flowering plants also reproduce through sexual reproduction.
SEXUAL REPRODUCTION IN ANIMALS
Male
and female
Our father and mother are male and female. Say
that our father has male sex and mother has female sex. This means that a man
is male and a woman is female.
An
animal having male sex cells called ‘sperms’ in its body is called male. An
animal having female sex cells called ‘ova’ ( or eggs) in its body is called
female.
The
cells present in sexual reproduction are called Gametes. The male gamete in animals is called ‘sperm’ and the
female gamete in animals is called ovum’ or ‘egg’ and ova are extremely small
cells which can be seen only the help of a high power microscope. Fusion of
gametes gives increase to a single cell called zygote. The cell which is formed
through the fusion of male gamete and a female gamete is called zygote. The
function of fusion of gamete is called fertilization.
Fertilization
The
fusion of man gamete with a woman gamete to form a zygote during the sexual
reproduction, is called fertilization. Also say that; The fusion of a sperm
with an ovum to from a zygote during sexual reproduction, is called
fertilization. The zygote grow and development to form of a new baby. The
unborn baby in the uterus in the first stages of development is called an
embryo.
In
human being The sperms made in the testes of man are introduced into the vagina
of the woman by penis during copulation (or mating). I this way, millions of
sperms are released into the vagina at one time. The sperms are highly active
and mobile. The sperms move up through cervix into the uterus. From uterus, the
sperms transfer into the oviducts. One of the oviducts exist an ovum or egg
cell released through the ovary during ovulation. Only one sperm fuses with the
ovum in the oviduct to form a zygote. This is called fertilization.
Quantity of
DNA Does Not Get Duplex During Sexual Reproduction
 |
| DNA |
The
gametes are particular style of cells called reproductive cells which present
only half the quantity of DNA (or half the number of chromosomes) as match to
the normal body calls of a organisms. for example man sperm has 23 chromosomes
and female egg has also 23 chromosomes. So, when a sperm and an egg fuse together during fertilization,
then the zygote formed will 23+23=46 chromosomes, which is the normal
chromosomes.
Puberty
The age at which
the sex hormones begin to be produced and the boy and girl become sexually
mature is called puberty. The testes produce the male sex hormone called
testosterone, and the ovaries produce two female sex hormones, oestrogen and
progesterone.
The many
changes which occur in boys at puberty are: Hair grow under armpits and in
pubic region between the thighs. Hair also grow on other parts of the body like
chest and face.
The many
changes which occur in girls at puberty are: Hair grow under armpits and in
pubic region. Mammary glands develop and enlarge. Extra fat is deposited in
different parts of the body like hip and thighs.
THE
MAN REPRODUCTIVE SYSTEM
The
human man reproductive system exist of the following organs ; Testes, Scrotum,
Epididymis, Vas deferens, Seminal vesicles, Prostrate gland and Penis. The
function of testes is to made the male sex cells called sperms and also to made
male sex hormone called testosterone. The testes of a man lie in small muscular
pouch called scrotum, outside the abdominal cavity. The scrotum temperature is
about 3◦C lower than the
temperature inside the body. The secretion of seminal vesicles and prostrate
gland provide nutrition to the sperms and also make their further transport
normal. the penis transfer the sperms from the male’s body into vagina in the
in the female’s body during mating for the purpose of reproduction.
FEMALE REPRODUCTIVE SYSTEM
The human female reproductive system exist of
the following organs : Ovaries, Oviducts (also called Fallopian tubes), Uterus,
and Vagina. Ovaries are the primary reproductive organs in a woman. The
function of ovaries is to make mature female sex cells called ova or eggs and
also to made the woman sex hormones. The oviducts are not directly connected to
ovaries but have funnel shaped opening which almost cover the ovaries. The two
oviducts connect to a bag like organ called uterus or )womb) at their other
ends. Vagina is also called ‘birth canal’ because it is by this transfer that
the baby is born after the completion of development inside the uterus of the
mother.
Menstruation : in normal healthy girl ovulation
takes place on the 14th day of the beginning of menstrual cycle of
28 days. In human female the ovaries start releasing ovum or egg once every 28
days from the age of puberty. The breakdown and removal of the inner, thick and
soft lining of the uterus along with its blood vessels in the form of vaginal
bleeding is called menstrual flow or menstruation.
Menarche and Menopause
The first occurrence of menstruation at puberty
is called menarche. The permanent stoppage of menstruation in a woman is called
menopause. At the age of about 45 to 50 years.
Development of Embryo
 |
| Embryo |
When the ovum is fertilized in the oviduct, then
a zygote is formed. The zygote divides rapidly by mitosis as it moves down
slowly in the oviduct and form a hollow ball of hundreds of cells. This hallow
ball of cells, now called an embryo, skins into the soft and thick lining of
the uterus and gets embedded in the it. The embedding of embryo in the thick
lining of the uterus is called implantation. After the implantation, a disc-like
special tissue develops between the uterus wall and the embryo (foetus), which
is called placenta the foetus is connected to placenta in mother’s body through
umbilical cord. It is by the placenta that all requirements of the developing
foetus like nutrition, respiration, and excretion etc. are met from mother
body. The time period from the fertilization up to the birth of the baby is
called gestation. the average gestation period in humans ( duration of human
pregnancy) is about 9 month or 38 week. Birth begins when the strong muscles in
the walls of the uterus start to contract rhythmically. The rhythmic
contraction of uterus muscles gradually pushes the baby out of the mother’s
body by vagina
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