Most animals reproduce sexually. The reproduction relies on the formation and therefore the fusion of male and feminine gametes.


1. Formation of Gametes (Gametogenesis)

       The formation of gametes is termed gametogenesis. during this process, diploid (2N) gamete mother cells undergo meiosis and form haploid (1N) gametes. The male and feminine gametes (sperms and egg cells or ova) are produced in specialized organs called gonads. Male gonads are known as testes (Singular: testis) while female gonads are called ovaries. the assembly of sperms in testes is named spermatogenesis and also the production of egg cells in ovaries is named oogenesis.


Spermatogenesis:

       Some cells present within the walls of the seminiferous tubules of testes divide repeatedly by mitosis to create a sizable amount of diploid spermatogonia. Some spermatogonia produce primary spermatocytes. Every primary spermatocyte undergoes meiosis-I and produces 2 (two) daughter cells recognized as secondary spermatocytes. These cells undergo meiosis-II. during this way, four haploid spermatids are produced from each primary spermatocyte. The spermatids are nonmotile and plenty of changes occur in them to convert them into motile cells. Their nuclei shrink and a few structures are formed, e.g. a corner known as an acrosome, a tail, and a mitochondrial ring. After these changes, the spermatids are called sperms (semens).


Oogenesis:

Some cells of the ovary prepare structures called follicles, within which many diploid oogonial are present. Some oogonial produce diploid primary oocytes. One of the first oocytes completes meiosis-I and produces two haploid cells. The smaller cell is named the first cell and also the larger one is named the secondary oocyte. The secondary oocyte completes meiosis-II and makes two haploid cells, i.e. a 2nd (second) cell and a gamete.


2. Fertilization:

      After the formation of gametes, fertilization occurs. There are two mechanisms by which fertilization can occur, i.e. external fertilization and internal fertilization. In external fertilization, egg cells are fertilized outside of the womb. External fertilization occurs mostly in an aquatic environment. It requires both the male and therefore the female animals to release their gametes into their surroundings at almost the identical time. For external fertilization, the animals must release a great number of gametes. In external fertilization, there's a risk of loss of gametes because of environmental hazards like predators. External fertilization occurs in many invertebrates and also the first two groups of vertebrates, i.e. fishes and amphibians.


        In internal fertilization, egg cells are fertilized within the reproductive tract of females. It Occurs in reptiles, birds, and mammals. Such animals provide protection for the developing embryo. After fertilization, reptiles and birds produce protective shells around their egg cells and then lay them.

         The shell is immune to water loss and damage. In mammals (except for egg-laying mammals) the development of brute into a new baby takes place within the mother body. During this case, there's extra protection. to the embryo and the mother also provides everything that the embryo needs.


3. Reproduction in Rabbit:

      Rabbits are small mammals found in several parts of the planet. They are employed in research as experimental animals.


Male Reproductive system:

     The male system of rabbits consists of a pair of testes that develop sperms, the jointed ducts that transport sperm to outer genitalia, and glands that add secretions to sperms. Testes are located in an exceeding bag of skin called the scrotum that hangs. below the body. Each testis consists of a mass of twined tubes called. the seminiferous tubules. In these tubules, the sperms (semens) are formed.

      When sperms are mature, they accumulate within the collecting ducts of Tests so they pass to the epididymis. From epididymis, sperms move. To a sperm duct called a channel. Both sperm ducts join the urethra. just below the bladder. The urethra carries both sperm and urine.

     Semen is that the material containing sperms in a fluid. It comprises 10% (ten percent) sperms and 90% (ninety percent) fluid. Because the sperms pass down the ducts from the testes to the urethra, the associated glands add various secretions. Seminal vesicles produce secretions that serve as nutrients for semen. The prostate produces a secretion that neutralizes the acidity of the fluid. Cowper’s glands make secretions that lubricate the ducts.


Female Reproductive System:

     The feminine genital system of rabbits consists of ovaries and associated ducts. Ovaries are small oval organs situated in the cavity just ventral to kidneys. Like most animals, female rabbits have a pair of females' internal reproductive organs. The outer region of the ovary produces egg cells. A cluster of specialized cells called follicles surrounds and nourishes each gamete. From the female's internal reproductive organ, egg cells are released in fallopian tubes.

      The opening of the fallopian tube lies near the ovary. Fertilization occurs in fallopian tubes and also the creature (zygote) is carried to the uterus. The uterus of a rabbit is split into two separate parts or horns. The uterus horns join and open into the vagina or passage. Cervix is that the portion of the uterus, which separates it from the passageway, where sperms of males are deposited. 


Fertilization and Development in Rabbit:

     Rabbits can breed throughout the twelvemonth but male rabbits are commonly sterilized during the summer months. Male rabbit deposits its sperms within the vagina (birth canal) of female. Spermatozoon swims through the cervix and uterus to fallopian tubes where they fertilize the egg cells, released from the ovary. After fertilization, the zygote is carried to the uterus. By this point, the zygote has started dividing and is now called an embryo. The embryo is implanted in uterus walls. A connector, called the placenta, is established between the embryo and uterus wall. The embryo develops into new offspring (rabbit kit) in 30–32 days, after which it's born.


4. Growth in Human Population and its Consequences:

    Pakistan’s population within the year 2007-2008 was 163,775,000. By the top of this decade, our population is predicted to exceed 176 million. Pakistan’s population had a comparatively high rate of growth in the past. When increment exceeds the carrying capacity of a locality or environment, it ends up in overpopulation. Many problems are related to human overpopulation. The overpopulated areas face a severe shortage of H2O and natural resources. Overpopulation ends up in deforestation and loss of ecosystems. It ends up in more pollution and heating. There's a high infant and child fatality rate in overpopulated areas thanks to poverty. Overpopulation hikes demands for more housing units, more health facilities, more jobs, more educational institutions, increase in food crops, etc. we've to test overpopulation otherwise we are going to need to face huge problems thanks to our limited resources. People should be educated about the issues of overpopulation. Pakistan’s Ministry of Population Welfare has taken a variety of steps to create people alert to the hazards of overpopulation and to stabilize the population to match our resources.