<span>a. Fish have a single central heart; earthworms have several hearts.
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Multi cellular organisms are made up of billions of cells each specialized to a unique role and these cells are organized into structural and functional units such as tissues and organs.
For each cell and organ to function optimally, it requires oxygen and nutrients and needs carbon dioxide and metabolic waste taken away in a continuous, never ending process.
<span>A mechanism is needed to accomplish the important function of transporting the relevant materials to and from the cell. The circulatory system fits this bill splendidly. It is a specialized organ system which allows blood and lymph to flow through the entire body carrying nutrients such as glucose, amino acids and electrolytes as well as oxygen to each cell, at the same time carting away carbon dioxide and all sorts of metabolic waste over to excretory organs to be expelled from the body.
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I think it is the secondary ovarian follicle that contains the secondary oocyte.The stages of the ovarian cycle that the follicle will go through includes; a primary follicle contains an oocyte and begins producing estrogen. Then the secondary oocyte contains a secondary oocyte and produces estrogen and some progesterone, then the graafian follicle develops and the secondary oocyte is released a process we call ovulation. the corpus luteum produces progesterone and some estrogen and lastly the corpus luteum degenerates.
I know this answer but it is really commutated
Answer:
bad
Explanation:
since it can damage our organs
