How Do Organisms Reproduce? – Reproduction in Unicellular and Multi-cellular Organisms
* Organisms like Hydra reproduce by building. 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, stem, 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 hypae 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.
Changes during Puberty
* Adolescence starts early in girls between 8 and 13 years as compared to 10 and 14 years in boys.
* Adolescence leads to reproductive maturity in both males and females.
* Body changes during puberty include increase in height, change in body shapes, voice change in boys, and development of sex organs.
* An increased action of sweat and sebaceous glands occurs during puberty.
* Puberty also results in mental, intellectual and emotional maturity.
* Secondary sexual characters are used to differentiate between males and females.
Gametogenesis
* In males, sperm is produced by a process called spermatogenesis.
* In females, ovum is produced by a process called oogenesis.
During spermatogenesis:
* The spermatogenesis divides mitotically to produce a primary spermatocyte
* The primary spermatocyte divides mitotically to form two secondary spermatocyte
* The secondary spermatocyte divides mitotically to form four equal, haploid, round spermatids.
* Round spermatids get differentiated into an elongated and tadpole – like spermatozoa or sperm.
During oogenesis:
* The germinal epithelium cells divide mitoyically to form gamete mother cells called oogonia.
* The oogonium divides again to form two primary oocytes.
The primary oocyte undergoes meiotic division to form a secondary oocyte and a polar body.
* The secondary oocyte matures into an ovum.