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KEY CONCEPT Many organisms reproduce by cell division.

Explore the process of cell division and its significance in growth, repair, and reproduction. Learn about mitosis and meiosis, as well as different forms of asexual reproduction such as budding, binary fission, fragmentation, and vegetative reproduction.

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KEY CONCEPT Many organisms reproduce by cell division.

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  1. KEY CONCEPTMany organisms reproduce by cell division.

  2. Why do cells divide? • Growth (Mitosis) • Repair of damaged cells (Mitosis) • Replacement of old or worn out cells (Mitosis) • Reproduction • Sexual - Meiosis • Asexual – Binary Fission, Budding, Fragmentation, Vegetative reproduction 3D image of a mouse cell in the final stages of cell division (telophase). (Image by Lothar Schermelleh)

  3. DNA andhistones SupercoiledDNA DNA doublehelix Chromatin Chromosomes condense at the start of mitosis. • DNA wraps around proteins (histones) that condense it.

  4. chromatid telomere centromere telomere Condensed, duplicated chromosome • DNA plus proteins is called chromatin. • One half of a duplicated chromosome is a chromatid. • Sister chromatids are held together at the centromere. • Telomeres protect DNA and do not include genes.

  5. Parent cell centrioles spindle fibers centrosome nucleus with DNA Mitosis and cytokinesis produce two genetically identical daughter cells. • Interphase prepares the cell to divide. • During interphase, the DNA is duplicated.

  6. During prophase, chromosomes condense and spindle fibers form. • Mitosis divides the cell’s nucleus in four phases.

  7. During metaphase, chromosomes line up in the middle of the cell. • Mitosis divides the cell’s nucleus in four phases.

  8. During anaphase, sister chromatids separate to opposite sides of the cell. • Mitosis divides the cell’s nucleus in four phases.

  9. Mitosis divides the cell’s nucleus in four phases. • During telophase, the new nuclei form and chromosomes begin to uncoil. Cleavage furrow

  10. In animal cells, the membrane pinches (forms a cleavage furrow) closed. • In plant cells, a cell plate forms. • Cytokinesis differs in animal and plant cells. Cleavage furrow

  11. parent cell DNA duplicates cell begins to divide daughter cells Binary fission is similar in function to mitosis. • Asexual reproduction is the creation of offspring from a single parent. • Binary fission produces two daughter cells genetically identical to the parent cell. • Binary fission occurs inprokaryotes.

  12. Environment determines what form of reproduction is most advantageous. • Asexual reproduction is an advantage in consistently favorable conditions. • Sexual reproduction is an advantage in changing conditions.

  13. Hydra bud Yeast Some eukaryotes reproduce through mitosis. • Budding forms a new organism from a small projection growing on the surface of the parent.

  14. Fragmentation is the splitting of the parent into pieces that each grow into a new organism. • Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

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