9.1 All cells come from existing cells

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9.1 All cells come from existing cells
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• Objectives
• Describe how cell reproduction contributes to
  repair and to growth.
• Contrast the two main ways that organisms
  reproduce.
• Key Terms
• asexual reproduction
• sexual reproduction

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• The division of cells into more cells enables
  living things to repair damage, to grow, and to
  produce offspring.

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• All of the trillions of cells in your body result
  from cell reproduction, a series of cell
  divisions that began with a single fertilized egg
  cell.

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• ReproductionWhile the production of new cells
  can result in growth and repair within organisms,
  cell division also has an essential role in the
  reproduction of entire organisms. Some organisms
  reproduce by simple cell division, in which a
  single cell or group of cells each duplicates its
  genetic material and then splits into two new
  genetically identical cells. This process, which
  is known as asexual reproduction, produces
  offspring that inherit all their genetic material
  from just one parent.

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• As a result, the offspring are genetically
  identical to one another and to their parent.
  Single-celled organisms such as Paramecium
  usually reproduce this way. Many multicellular
  organisms can also reproduce asexually at certain
  times. For example, some sea stars, when divided
  into two pieces, can regrow into two whole new
  individuals through simple cell division. And if
  you've ever grown a geranium from a leaf cutting,
  you've taken advantage of the plant's ability to
  reproduce asexually.

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• In contrast, when two parents are involved in the
  production of offspring, the process is called
  sexual reproduction. In sexual reproduction
  genetic material from each of two parents
  combines, producing offspring that differ
  genetically from either parent. Sexual
  reproduction involves the union of sex cells,
  such as an egg and a sperm