External and Internal fertilisation
Reproductive system of male and female frog
Viviparous and oviparous Animals
Dolly the clone
Sexual Reproduction: The reproduction in which
the both male reproductive organs and female
reproductive organs involved to give birth to new
individual is called sexual reproduction.
Like plants, the the reproductive parts in animals
also gametes that fuse to form a zygote. It is the
zygote which develops into a new individual.
MALE REPRODUCTIVE ORGANGS
The male reproductive organs include a pair
of testes, two sperms ducts and a penis. The
testes produce male gametes called sperms.
Millions of sperms are produced by the
FEMALE REPRODUCTIVE ORGANS IN
FEMALE REPRODUCTIVE ORGANS
The female reproductive organs are of ovaries,
oviducts[fallopian tubes] and the uterus. The
ovary produces female gametes called ova[eggs].
A single matured egg is released into oviduct by
on of the ovaries every month. Uterus is the
development of the baby takes place. Like the
sperm, an egg is also a single cell.
An ovum (plural ova, ovum meaning egg or egg cell) is
a haploid female reproductive cell or gamete. Both animals and
embryophytes have ova. The term ovule is used for the young
ovum of an animal, as well as the plant structure that carries the
female gametophyte and egg cell and develops into a seed
Sperm were first observed in 1677 by Antonie van
Leeuwenhoek using a microscope. The sperms
are produced by testes. Though sperms are very
small in size, each has head, a middle piece and a
tail. Each sperm is a single cell with all usual cell
The first step in process of reproduction is the fusion of a
sperm and an ovum. When sperms come in contact with an
egg, one of the sperms may fuse the egg. Such fusion of the
egg and the sperm is called Fertilisation
Fertilization involves the fusion of the male and the female gamete. The male and the
female gametes are released from the male and the female reproductive organs.
Sperms or male gametes are released from the male reproductive organ i.e., the penis.
These sperms then enter the female body through the vagina. Then, they travel
through the fallopian tubes where they meet the eggs. Hence, the process of
fertilization takes place in the fallopian tubes.
During fertilization, the haploid nucleus of the sperm and that of the ovum fuse with
each other to form the zygote. This zygote divides to form an embryo which in turn
develops into a foetus.
PROCESS OF FERTILISATION IN HUMAN BEINGS
INTERNAL FERTILISATION AND
The fertilisation which takes place inside
the female body is called Internal
Fertilisation in which the fusion of male
and female gamete takes outside the body is
called External fertilisation. Example: frog,
fish, starfish etc.
A zygote is always synthesized from the union of two gametes, and
constitutes the first stage in a unique organism's development. Zygotes are
usually produced by a fertilization event between two haploid cells—
an ovum (female gamete) and a sperm cell (male gamete)—which combine
to form the single diploid cell. Such zygotes contain DNA derived from both
the parents, and this provides all the genetic information necessary to form a
In some women oviducts are blocked. These women are unable
to bear babies because sperms cannot reach the egg for
fertilisation. In such cases, doctors collect freshly released egg
and sperms and keep them together for a few hours for IVF. In
case fertilisation occurs, the zygote is allowed to develop for
about a week and then it is placed in the mother’s uterus.
Complete development takes place in the uterus and the baby is
born like other babies. Babies born through this technique are
called test-tube baby
In vitro fertilization (IVF) is a process by which egg cells are
fertilized by sperm outside the womb, in vitro.
Fertilisation results in the formation of zygote which
begins to develop into embryo. The zygote divides
repeatedly to give rise to a balls of cells. The cells
then begin to form groups that develop into
different tissues and organs of body. This
developing structure is termed an embryo. The
embryo gets embedded in the walls of uterus for
The stage embryo in which all body parts
can been seen is called Foetus.
Foetus in the uterus
A female frog sitting on a mass of its
own spawn [eggs]
REPRODUCTION IN FROGS
During spring or rainy season, frogs and toads move to ponds and
slow flowing streams. When the male and female come together in
water, the female lays hundreds of eggs. A layer of jelly holds the
eggs together and provides protection to the eggs. As the eggs are
laid, the male deposits sperms over them. Each sperm swims
randomly in water with the help of its long tail. The sperms contact
with the eggs this results in fertilisation.
Though the animals lay hundreds of eggs and release millions of
sperms, all the eggs do not get fertilised ,this is because the eggs
get exposed in water movement, wind and rainfall. Also, there are
other animals in pond which may feed on eggs
Metamorphosis is a biological process of
transforming a larva into an adult. This involves
relatively sudden and abrupt changes in the
animal’s structure. Frogs and insects are
examples of organisms showing
Asexual reproduction is a mode of
reproduction that does not involve the
fusion of the male and the female
gamete. It requires only one parent, and
the offsprings produced are exact copies
of their parents.
It is a type of asexual reproduction in which a single cell divides
into two halves. Organisms that reproduce through binary fission
are bacteria and Amoeba. In Amoeba, the division of cells can take
place in any plane. It involves the division of its nucleus into two
nuclei, which is followed by the division of its body into two
halves. Each half of the body receives a nucleus.
BINARY FISSON IN AMOEBA
DIVIDING NULEUS DAUGHTER AMOEBAE
Budding involves the formation of a new individual from the bulges,
known as buds formed on the parent body. This method of
reproduction is common in Hydra. In Hydra, the cells divide rapidly at a
specific site and develop as an outgrowth, called the bud. These buds,
while being attached to the parent plant, develop into smaller
individuals. When these individuals become mature enough, they
detach from the parent’s body and become independent individuals.
Budding in Hydra
Animals which lay eggs outside their bodies are known
as oviparous animals. All birds, frogs, lizards,
crocodiles etc. belong to this group.
Animals which give birth to young ones are known
as viviparous animals. Animals like lions, tigers, dogs,
and humans belong to this group.
OVIPAROUS ANIMALS AND VIVIPAROUS ANIMALS
Dolly was the first cloned mammal, and is genetically identical to its
Cloning is creating an exact copy of a biological entity. A clone is created
by inserting the complete genetic material of a regular body cell from
a donor into a recipient. Sheep are viviparous animals, and
so propagate their offspring sexually. Sir Ian Wilmut from Roslin
Institute in Edinburgh, Scotland created Dolly.
DOLLY, THE CLONE
WORLD’S FIRST CLONED BUFFALO
WAS IN INDIA!
Scientists at India’s National Dairy Research
Institute, in the Indian state of Haryana, produced
the first cloned buffalo back in February 6 2008,
using DNA from the ear of an adult female—though
unfortunately, it died of pneumonia soon after its