Introduction Metamorphosis is the complete change of structures in larvae or egg form of organisms into an adult form regulated by many factors such as hormones. •In most animal species, however, embryonic development includes a larval stage with characteristics very different from those of the adult organism, which emerges only after a period of metamorphosis; […]
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Introduction to polyspermy The entrance of multiple sperm polyspermy leads to disastrous consequences in most organisms. In the sea urchin, fertilization by two sperm results in a triploid nucleus, in which each chromosome is represented three times rather than twice. Normally each sperm’s centriole divides to form the two poles of a mitotic apparatus, the
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Introduction of spermatogenesis Spermatogenesis is the process in which an animal produces spermatozoa from spermatogonial stem cells by way of mitosis and meiosis. Spermatozoa are the mature male gametes in many sexually reproducing organisms. Stages of Spermatogenesis The entire process of spermatogenesis can be broken up into several distinct stages, each corresponding to a particular type of cell in humans. In the following table, ploidy,
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Introduction All the material necessary for the beginning of growth and development must be stored in the egg, or ovum. Whereas the sperm eliminates most of its cytoplasm as it matures, the developing egg (called the oocyte before it reaches the stage of meiosis at which it is fertilized”) not only conserves the material it
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Sperms are male reproductive cells. Each sperm cell consists of a haploid nucleus, a propulsion system to move the nucleus, and a sac of enzymes that enable the nucleus to enter the egg. In most species, almost all of the cell’s cytoplasm is eliminated during sperm maturation, leaving only certain organelles that are modified for
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Acrosome reaction assists in fusion of plasma membrane of egg/ovum and sperm. Interaction between sperm and egg jelly results in the acrosome reaction. In most marine invertebrates, the acrosome reaction has two components. 1- The fusion of the acrosomal vesicles with the sperm cell membrane. 2- The extension of the acrosomal process. Acrosome Reaction in
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Fertilization is the process whereby the sperm and the egg—collectively called the gametes—fuse together to begin the creation of a new individual whose genome is derived from both parents. Fertilization accomplishes two separate ends: sex (the combining of genes derived from two parents) and reproduction (the generation of a new organism). Thus, the first function
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Developmental Biology studies the initiation and construction of organisms rather than their maintenance.It is a science of becoming, a science of process. Formation of orderly body from a single cell by passing through various stages is called Development. That formation takes place according to the instructions which are encoded in genes and transmitted from parents.
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