Among the non-mammalian vertebrates, the cloaca is an anatomical structure that function as a shared pathway for the digestive, excretory, and reproductive systems. Cloaca in vertebrates, common chamber and outlet into which the intestinal, urinary, and genital tracts open. It is present in amphibians, reptiles, birds, elasmobranch fishes, and monotremes. Cloaca is not present in placental mammals or in most bony fish.
Once an egg is fertilized by a sperm, a zygote is formed. The zygote divides into multiple cells in a process known as cleavage, triggering the beginning of embryonic differentiation. ... Cells in these three layers will give rise to different parts of the organism. The endoderm eventually becomes the gut.Mar 3, 2011
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The statements of the old cell theory are:
1. All organisms are composed of cells
2. The cell is the basic unit of life
3. Cells are produced from existing cells
The modern cell theory's statements are:
1. The cell contains hereditary information which is passed to daughter cells
2. All cells are basically the same in composition and activity
3. All basic functions occur in cells
4. Cell activities depend on intracellular structures
As is visible from the statements, the old cell theory was not as detailed and lacked the understanding of the function, structure and behavior of cells that the current theory possesses. This difference has come about after years of research, through which scientists understood the functions of cells and elaborated on the theory's statements.
