Reproduction is the inherent property of the living organisms to continue their race by producing offsprings.Reproduction is of following two types:

(1)           Asexual reproduction                                           (2)           Sexual reproduction

Asexual Reproduction

The development of new individuals without the fusion of the male and female gametes is known as asexual reproduction. The asexual reproduction usually includes mitotic division of the body (somatic) cells. Therefore it is also known as somatogenic reproduction. The asexual reproduction is common only in lower plants and animals and it is of following types:

(1)           Binary fission                                    (2)           Budding

(3)           Gemmule formation                          (4)           Spore formation                 

(5)           Vegetative reproduction                    (6)           Regeneration

(1)   Binary fission: In the binary fission, the body splits in such a way that two equal and indentical halves are produced. It is most common in protozoans, bacteria and some lower metazoans. First of all the nucleus divides by amitotic or mitotic division and the division of the nucleus is followed by the division of the cytoplasm. It is of following types-

(a)   Simple type of binary fission, eg. Amoeba.

(b)   Transverse binary fission e.g. Paramecium.

(c)   Strobilation, eg. Aurelia

(2)   Budding: In certain multicellular animals, eg. hydra and fungi and body gives out a small outgrowth known as the bud, the bud is supported by the parent body and it ultimately develops into a new individual.

(3)   Gemmule formation: In certain metazoan animals, eg. fresh water sponges and in some bryophytes such as Marchantia, the asexual reproduction is carried on by  certain peculiar asexual bodies known as gemmules, which is composed of a group of undifferentiated cells which contain stored food material.

(4)   Spore formation: In many unicellular plants, fungi etc. the asexual reproduction by spore formation is very common under unfavourable conditions. In this process the condensation of protoplasm due to reduction in the water content results. These spores under favourable conditions absorb water and germinate to form a new plant.

(5)   Vegetative reproduction: A fragment or part of the plant grows to produce new plants. Fragmentation is very common in algae and fungi. In higher plants the vegetative propagation takes place under the following ways:

Sucker stem as in mint banana, which run horizontally under ground, can be separated and grown individually and each is able to develop into separate plant. The vegetative multiplication in the certain storage fleshy leaf like Bryophyllum has also been found very useful. If Bryophyllum leaf is cut and put on the surface of soil numerous new plant come out within few weeks from different fragments of original leaf.

(6)   Regeneration: In the life of an organism the loss of many kinds of cells and other structure occurs. These lost parts have to be restored if the organism has to lead a normal life. There is an inherent capacity in all organisms, to replace damaged on lost parts of tissues. This inherent capacity of regaining the lost part is known as regeneration. It can be defined as replacement, repair or restoration of the lost or damaged structures or reconstitution of a whole body from the small fragment of it during the post embryonic life of an organism.

Sexual Reproduction

The development of new individuals with the fusion of the male and female gametes is known as sexual reproduction. The sexual reproduction usually includes meiotic division of the body cells. The sexual reproduction is common in higher plants ,animals and Humans

Sexual reproduction in Plant [1]

Sexual Reproduction in Human

The development of new individual takes place by the fusion of the sex cells or male and female gametes. Gametes grow and mature inside the testes and ovaries, which are specialized organs to produce sperms in the males and ova in the females. Sexes in human beings are separate, that is male organ, the testes are found in male individuals and female organ, and the ovaries are found in female body. Once the egg (ovum) is fertilized it moves to uterus and gets implanted. Fertilization is internal.

Anatomy

The male reproductive system contains two main divisions: the penis, and the testes, the latter of which is where sperm are produced. Having the testes outside the abdomen best facilitates temperature regulation of the sperm, which require specific temperatures to survive. The female reproductive system likewise contains two main divisions: the vagina and uterus, which act as the receptacle for the semen, and the ovaries, which produce the female's ova. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the Fallopian tubes. At certain intervals, the ovaries release an ovum, which passes through the fallopian tube into the uterus.

If, in this transit, it meets with Spermatozoan, the sperm penetrates and merges with the egg, fertilizing it. The fertilization usually occurs in the oviducts, but can happen in the uterus itself. The zygote then implants itself in the wall of the uterus, where it begins the processes of embryogenesis and morphogenesis. When developed enough to survive outside the womb, the cervix dilates and contractions of the uterus propel the foetus through the birth canal, which is the vagina.

The ova, which are the female sex cells, are much larger than the spermatozoan and are normally formed within the ovaries of the fetus before its birth. They are mostly fixed in location with in the ovary until their transit to the uterus, and contain nutrients for the later zygote and embryo. Over a regular interval, in response to hormonal signals, a process of oogenesis matures one ovum which is released and sent down the Fallopian tube. If not fertilized, this egg is flushed out of the system through menstruation.

Process

Human reproduction is a long process, starting with sexual intercourse, followed by nine months of pregnancy before childbirth. Human reproduction takes place as internal fertilization by sexual intercourse. The sperm then travels through the vagina and cervix into the uterus or fallopian tubes for fertilization of the ovum. Upon successful fertilization and implantation, gestation of the fetus then occurs within the female's uterus, called pregnancy.

Pregnancy is the period of time during which the fetus develops, dividing via mitosis inside the female. During this time, the fetus receives all of its nutrition and oxygenated blood from the female, filtered through the placenta, which is attached to the fetus' abdomen via an umbilical cord. This drain of nutrients can be quite taxing on the female, who is required to ingest slightly higher levels of calories. In addition, certain vitamins and other nutrients are required in greater quantities than normal, often creating abnormal eating habits. Gestation period is 40 weeks in humans.

Once the fetus is sufficiently developed, chemical signals start the process of birth, which begins with the fetus squeezing through the vagina, and eventually out of the female. The newborn, which is called an infant in humans, should typically begin respiration on its own shortly after birth. Not long after, the placenta is passed as well. The end of the umbilical cord attached to the child's abdomen eventually falls off on its own.The mid-wife or nurse assisting the birth will usually detach the mother from the baby using a clamp, then cutting it off.

Animal Breeding

Animal husbandry is the study of rearing, feeding, management, production and utilization of all the economically important animals. Breeding is to improve the inferior stock by meeting with outstanding and improved type of animal so that they can render better service to man.

Inbreeding: It involves the mating of related individuals for 4.5 generations.

Close breeding: The mating of (a) full sister to full brother Undesirable recessive genes may be discovered by this system but the progeny become more susceptible to diseases. Homogeneity increases in this system.

Line breeding: The mating of animals of wider degrees of relationship than those selected for close breeding. Uniformity increases but the real individual merit is ignored in this system.

Out breeding: Breeding of unrelated individuals.

Out crossing: Mating of unrelated (up to 4-6 generations) pure breed animals within the same breed. Additive effects are obtained in this system for milk production, growth rate etc.

Cross breeding: Mating of animals of different breeds.

(a)   Criss crossing: The two breeds are crossed alternatively to utilise heterosis in both dams and progeny.

(b)   Triple crossing: Three breeds are crossed rotationally.

(c)   Back crossing: Mating of crossbred animal with one of the pure parent races.

Artificial Insemination (AI)

Deposition of semen artificially (manually) in the genitalia of the female at proper time of the reproductive cycle is called as Artificial Insemination (A1). The technique is important in the prevention of sexually transmitted diseases (STD) the same quantity of semen can serve 50 to 100 more females, and the superior quality semen can be  imported from foreign countries for AI.