Developmental Biology! The Cycle of Life.

The generalized life cycle in animal is one of the major triumphant  descriptive of embryology and each  animal, whether frog, human being or others has a similar stages of development. The stages of development between fertilization and delivery or hatching are uniformly called 'EMBRYOGENESIS.'





Embryonic has a six fundamental processes and we will mention as follow below:

1. Fertilization: this involves the fusion of the matured male and female sex cells and they are collectively called gametes. once the fertilization occurred, it stimulate the development of the egg into initial new specie and continue to the next stage called cleavage.

2. Cleavage is a continuous rapid mitotic divisions that immediately follow after fertilization and during this cleavage, mass number of zygote cytoplasm is divided into smaller cells called Blastomeres. At the end of cleavage formed the a sphere called blastula.

3. Gastrulation: After the fast rate of mitotic cell division slow down, the blastomeres undergoes a rearrangement of position relatives to one another. And the series of cell rearrangement is called gastrulation and at this stage, the embryo is called gastrula stage which this stage of gastrulation result to three germ layers that interact with each other to form organs of the body.

4. Organogenesis: Once the three germ layers is finally established, the cells interact with one another and rearranged themselves, then they produce tissues and organs; and the process is called organogenesis.

5. In some species, the organism that hatches from the egg is not sexually mature, but rather, the organism need to undergoes metamorphosis to become a sexually mature adult. According to wikipedia, 'Metamorphosis is a biological process by which an animal physically develop after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation."

6. in many species, the group of cells are put aside to formed the next generation. These mentioned cells are the precursors of the gametes. The germ cells are the collectively of the gametes and their precursor and they are set aside for productive physiology and others cells of the body are somatic cells. The separation of the somatic cells give rise to the individual body and the germ cells contributes to new generation.

References:

www.wikipedia.com
Developmental Biology ninth edition, by Scott F. Gilbert.