HSC Biology 2nd Paper Note 6th Chapter Human Physiology: Wastes and Excretion. Excretion is the process by which metabolic wastes and other non-useful materials, such as feces, are eliminated from an organism. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell. Excretion is an essential process in all forms of life. For example, in mammals urine is expelled through the urethra, which is part of the excretory system. In unicellular organisms, waste products are discharged directly through the surface of the cell.
HSC Biology 2nd Paper Note 6th Chapter Human Physiology: Wastes and Excretion
Green plants produce carbon dioxide and water as respiratory products. In green plants, the carbon dioxide released during respiration gets utilized during photosynthesis. Oxygen is a by-product generated during photosynthesis and exits through stomata, root cell walls, and other routes. Plants can get rid of excess water by transpiration and guttation. It has been shown that the leaf acts as an ‘excretophore’ and, in addition to being a primary organ of photosynthesis, is also used as a method of excreting toxic wastes via diffusion.
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