* NCERT 1. Reproduction in Organisms INTRODUCTION Biology in essence is the story of life on earth. While individual organisms die without fail‚ species continue to live through millions of years unless threatened by natural or anthropogenic extinction. Reproduction becomes a vital process without which species cannot survive for long. Each individual leaves its progeny by asexual or sexual means. Sexual mode of reproduction enables creation of new variants‚ so that survival advantage is enhanced
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The Sperm and Egg Testes are suspended outside the abdominal cavity by the scrotum‚ a pouch of skin that keeps the testes close or far from the body at an optimal temperature for sperm development. Somniferous tubules are inside each testis‚ and are where sperm are produced by meiosis. About 250 meters (850 feet) of tubules are packed into each testis. Spermatocytes inside the tubules divide by meiosis to produce spermatids that in turn develop into mature sperm. Sperm production
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surfaces; its anterior (A) and posterior (P); its left and right sides. * The haploid sperm and egg nuclei fuse to form the diploid zygote nucleus. Cleavage The zygote nucleus undergoes a series of mitoses‚ with the resulting daughter nuclei becoming partitioned off‚ by cytokinesis‚ in separate‚ and ever-smaller‚ cells. The first cleavage occurs shortly after the zygote nucleus forms. * A furrow appears that runs longitudinally through the poles of the egg‚ passing through the point at which the
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Mendel‚ Genes‚ and Inheritance Chapter 12 Why It Matters Red blood cells in sickle-cell disease One amino acid in the wrong position causes the disease 12.1 The Beginnings of Genetics: Mendel’s Garden Peas Mendel chose true-breeding garden peas for his experiments Mendel first worked with single-character crosses Mendel’s single-character crosses led him to propose the principle of segregation Mendel could predict both classes and proportions of offspring from his hypotheses
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Pregnancy Differentiation and Birth Fertilization (first week) - The process by which gametes from two parents combine to form one new cell (zygote). After Fertilization the zygotes continues down to the oviducts toward the uterus on its way approximately 24-36 hours after Fertilization the process of mitosis begins. Implantation – embryo attaches itself to the thickened lining of the uterus. Cleavage – When the cell divides rapidly after the egg is fertilized. Blastocyst – developing of the
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Reproduction Fact Sheet Male: Sperm Female: Ovum (egg) What happens to Gametes at Fertilisation? Fertilisation is the process where sperm (from the male) and the ovum (from the female) fuse together to form the zygote. Each gamete contains 23 chromosomes which combine together‚ in the zygote‚ to combine to a full set of 46 chromosomes – half from the father and half from the mother.. Summed up‚ it is where the male gamete and a female gamete join. The fusion of gametes enables the genetic information
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gender. However one’s emotional gender identity may be contrary to what society has deemed the individual. A single sperm cell which fertilizes an ovum‚ or egg‚ is called a zygote. A zygote contains all the information essential for the normal growth of a complete adult organism in its natural environment (Pinel‚ 2009). The zygote contains 23 pairs of chromosomes; half from the producer of the sperm and half
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survival of these developing zygotes. Internal Fertilisation * Animals that live or breed on land fertilise internally. * This keeps gametes inside the body so there is no chance of dehydration occurring * This occurs doing copulation or sexual intercourse. * The fertilised egg can be retained within the female and develop within or it may be enclosed in a shell such as the eggs of reptiles and birds. Methods of development * After fertilisation‚ a zygote can be expelled from the
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not a fetus‚ my mother‚ technically if ever placed in a situation for choosing between my mother and a fetus‚ deserves to live not the fetus. In addition‚ a “fetus” is the zygote formed upon conception. The zygote is not a person. Even though the zygote will become an adult‚ at this point the zygote has no rights since the zygote does not fulfill Warren’s requirements. Therefore‚ abortion i¬s justified since the fetus is not a “person.” Circular reasoning leads abortion to be morally justified. Circular
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Introduction to sexual reproduction in humans Reproduction is the process by which humans gives rise to new individuals. Sexual reproduction is the process that involves the fusion of two gametes‚ sperm (male gamete) and egg (female gamete). In human these gametes are produced in different sexes‚ the male and female. Reproduction in humans is performed by reproductive systems‚ the male and female reproductive systems. The main organs of male reproductive system are testis and gonads and of female
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