Biology Exam Notes: Units on Reproduction in Plants and Animals
Growth and Cell division
·Animals and plants are composed of units called cells
·Every cell in the human body is derived from just one original cell, called the zygote, which is formed from the fusion of and egg and a sperm.
·Cells have to be replaced when they wear out or are damaged.
·Just after cell division each daughter cell is about half the size of the parent cell. Before it divides again it gradually grows.
·The process by which one parent cell divides to produce two identical daughter cells
·Occurs in the human body during growth or replacement of dead cells
·Asexual reproduction often involves the simple process of mitoses.
·The DNA is copied (replication) chromosomes are duplicated
·A complete set of genetic instructions exist in each chromatid
·Chromosomes condense and become visible
·Spindle apparatus begins to form
·Nuclear membrane disappears
·the spindle fibres attach to the chromosomes
·the chromosomes line up at the spindle equator
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