bio sac 2 revision

• Asexual reproduction


  Reproduction of offspring from just one parent, genetically identical offspring
• Asexual reproduction


  1. Fission

  2. Budding

  3. Fragmentation

  4. Parthenogenesis

  5. Spore formation

  6. Vegetative reproduction
• Sexual reproduction


  Reproduction involving the union of male and female sex cells to form a unique individual
• Types of cells in multicellular organisms

  • Somatic cells
  • Germ cells
• Somatic cells


  All the cells in the body, except for sex cells (gametes)
• Germ cells


  The specialised sex cells that combine in reproduction (sperm, eggs)
• Formation of gametes


  Occurs by meiosis in specialised reproductive organs called gonads
• Haploid


  The number of chromosomes in gametes is halved
• Diploid


  The normal state of a eukaryotic organism, with one set of chromosomes from each parent
• Mitosis


  Asexual reproduction
• Meiosis


  Sexual reproduction
• Mitosis produces genetically identical daughter cells
• Meiosis produces genetically unique daughter cells
• Mitosis


  1. Interphase

  2. Prophase

  3. Metaphase

  4. Anaphase

  5. Telophase

  6. Cytokinesis
• Meiosis


  1. Interphase

  2. Prophase I

  3. Metaphase I

  4. Anaphase I

  5. Telophase I

  6. Prophase II

  7. Metaphase II

  8. Anaphase II

  9. Telophase II
• Apoptosis


  Programmed cell death, the removal of unwanted cells
• Pathways of apoptosis


  • Intrinsic (mitochondria) pathway
  • Extrinsic (death receptor) pathway
• Reasons for apoptosis


  • Ageing
  • Infection
  • Development
• Steps of apoptosis


  1. Separation from adjacent cells

  2. Collapse of cytoskeleton

  3. Cell shrinkage

  4. Breakdown of organelles and nucleus

  5. Blebbing of plasma membrane

  6. Budding of apoptotic bodies

  7. Phagocytosis of apoptotic bodies
• Excessive apoptosis can cause conditions like Alzheimer's
• Inhibited apoptosis can cause conditions like Syndactyly
• Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus.
• Meiosis is a type of cell division that produces gametes with half the normal chromosome number, essential for sexual reproduction.
• The stages of mitosis are prophase, metaphase, anaphase, telophase, and cytokinesis.
• Metaphase occurs when chromosomes line up along equatorial plane of cell.
• Prophase involves condensation of chromatin into visible chromosomes, nuclear envelope breaks down, centrioles move to opposite poles, spindle fibers form between them, and chromatids attach to spindle fibers.
• Metaphase occurs when chromosomes align along the equatorial plane of the cell.
• Prophase involves condensation of chromatin into visible chromosomes, formation of spindle fibers, and separation of centrioles to opposite poles.
• Anaphase begins when sister chromatids separate at centromere and move towards opposite ends of cell.
• Anaphase occurs when sister chromatids separate at centromere.
• Telophase occurs when nuclear envelope reforms around new sets of chromosomes.
• Anaphase begins with separation of sister chromatids at centromere, followed by movement of separated chromatids towards opposite ends of cell.
• Cytokinesis occurs when cytoplasm divides to form two identical daughter cells.
• Anaphase begins with contraction of microtubules, pulling sister chromatids apart towards opposite ends of the cell.
• Anaphase begins with separation of sister chromatids at centromere, followed by movement of separated chromatids towards opposite ends of the cell due to contraction of microtubules attached to kinetochores on chromosomes.
• Telophase includes formation of new nuclear envelopes around sets of chromosomes, decondensation of chromosomes back into chromatin, and completion of cytokinesis (division of cytoplasm).
• Cytokinesis is the final stage of mitotic cell division where the cytoplasm divides to produce two identical daughter cells.
• Telophase is characterized by decondensation of chromosomes, reformation of nucleus around chromosomes, and division of cytoplasm.
• Telophase includes decondensation of chromosomes, reformation of nucleus around chromosomes, and completion of cytokinesis by pinching off two daughter cells.
• Cytokinesis is the final stage of cell division where the cytoplasm divides to produce two new cells.