Reproduction and its Significance
* Reproduction is the process by which an organism gives birth to a new individual.
* DNA variation is useful for the survival of a species, during drastic changes in their environment.
* DNA variations are passed to the subsequent generations when they reproduce.
Reproduction in Unicellular and Multicellular Organisms
* Organisms like Hydra reproduce by budding. They use the regenerative cells for reproduction in the process of budding. A bud develops as an outgrowth due to repeated cell division at a specific site on the hydra. Each of these buds develops
into a new individual.
* Vegetative propagation is a process of reproduction by which new plant species develops through roots, stems and leaves of the parent plant.
* Spore formation can be observed in organisms like the rhizopus. Rhizopus is composed of thread-like structures called hyphae. The tiny blob-on-a-stick structure on each hyphae contains spores that are responsible for reproduction.
* Plant Tissue Culture is a method used to propagate plants under hygienic conditions. It is often used to produce clones of a plant.
* Asexual reproduction is quick and enables reproduction of plants that have lost the capacity to produce seeds.
Reproduction in Animals
* When the rate of growth of the body slows down, during the adolescent phase, the reproductive tissues begin to mature. This period is known as puberty.
* The male reproductive system consists of organs, which produce germ-cells and other organs that deliver the mature germ-cells to the site of fertilisation.
* The female germ-cells or eggs are made in the ovaries. These ovaries are responsible for the production of some hormones.
* The sperm enters through the vaginal passage during sexual intercourse. They travel upwards and reach the oviduct where they get to meet the egg. Then, fertilisation takes place.
* Sexually transmitted diseases include bacterial infections such as gonorrhoea and syphilis, and viral infections such as warts and HIV-AIDS.
Sexual Reproduction in Plants
* The two modes of reproduction are asexual and sexual.
* The reproductive parts of angiosperms are located in the flower.
* The flower may be unisexual when it contains either stamens or carpels or bisexual when it contains both stamens and carpels.
* Stamen is the male reproductive part and it is made up of three parts – filament, connective and anther. Anther produces pollen grains.
* Carpel is the female reproductive part and it is made of three parts – the ovary, the style and the stigma.
* The transfer of pollen from anther to stigma is known as pollination.
* Transfer of pollen grains in the same flower is known as self pollination while the transfer of pollen grains from one flower to another is known as cross pollination.
* Fertilisation is the fusion of the male germ cells with the female germ cells present in the ovule.
* Germination is the growth of an embryonic plant contained within a seed. It results in the formation of the seedling.