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MULTICELLULAR ORGANISMS (Transport system in plants (XYLEM (Is absorbed…
MULTICELLULAR ORGANISMS
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Reproduction
Every chromosome in one set has a matching partner in the other set that has the same length of DNA and the same genes. Cells that contain two sets of chromosomes are said to be diploid.
n sexual reproduction new organisms are produced from the fusing of the nucleus of a male sex cell with the nucleus of a female sex cell. This is called fertilisation. Sex cells are also known as gametes. Male gametes are made by male reproductive structures. Female gametes are made by female reproductive structures.
A gamete contains a single set of chromosomes in its nucleus and is said to be haploid. Compare the diagram of a haploid fruit fly gamete to the diagram of a diploid fruit fly body cell.
The male gamete is the sperm cell. Sperm are continuously produced in the testes of adult male mammals. During sexual intercourse sperm cells travel through the sperm duct, into the urethra and are released out of the end of the penis.
The female gamete is the egg cell. Egg cells are produced in the ovaries of the female mammal. Eggs are released from the ovaries into the oviducts.
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Absorption of materials
Oxygen and nutrients from food must be absorbed into the bloodstream to be delivered to cells for respiration.
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Humans require transport systems to supply their cells and remove waste products. Gas exchange occurs in the lungs and food molecules are absorbed by the digestive system.
The cells in the body need oxygen to release energy from food efficiently by carrying out aerobic respiration. A waste product of aerobic respiration is carbon dioxide.
Carbon dioxide must be removed from the body or it makes the blood dangerously acidic. Oxygen and carbon dioxide enter and leave the blood by diffusion through the lining of the lungs.
The lungs
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Air gets from the mouth and nose to the lungs through the windpipe (trachea). The trachea branches into two tubes called bronchi (one to each lung). The bronchi split into smaller and smaller tubes called bronchioles, which then end in microscopic alveoli (air sacs).
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