cell division and diversity

• Mitosis and the cell cycle produce identical daughter cells for growth and asexual reproduction
• Cells produced by mitosis are genetically identical, leading to no genetic variation
• Cell cycle stages: formation, growth, division to form daughter cells, controlled by checkpoints
• Mitosis:

  • Produces identical cells
  • Four stages: prophase, metaphase, anaphase, telophase
• Cytokinesis:

  • Parent and replicated organelles move to opposite sides of the cell
  • Cytoplasm divides to produce two daughter cells
• Interphase:

  • Cell grows and prepares to divide
  • Chromosomes and some organelles are replicated
  • Chromosomes begin to condense
• Prophase:

  • Nuclear envelope breaks down and disappears
  • Chromosomes condense
  • Centrioles move to opposite poles for spindle formation
• Metaphase:

  • Chromosomes move to the equator and attach to spindle fibres via centromeres
• Anaphase:

  • Sister chromatids are separated
• Telophase:

  • Nuclear envelope reforms, creating two daughter cells
  • Spindle is broken down and disappears
  • Chromosomes uncoil
• Meiosis:

  • Gives rise to genetic variation
  • Produces haploid gametes with half the number of chromosomes
• Genetic variation achieved through:

  • Crossing over of chromatids
  • Independent assortment of chromosomes
• Meiosis I:

  • Homologous chromosomes separate
  • One chromosome of every pair per gamete
• Meiosis II:

  • Sister chromatids separate
  • Leads to formation of four haploid daughter cells
• Cellular organisation:

  • Cells form tissues to perform common functions
  • Organs are groups of tissues working together
  • Organ system composed of many organs working together
• Tissue types and functions:

  • Xylem: transport water and minerals, provide structural support
  • Phloem: involved in translocation of food substances
  • Epithelial: lining/covering surfaces
  • Connective: providing support
  • Muscle: specialised for movement
  • Nervous: specialised for impulse conduction
• Stem cells:

  • Undifferentiated cells with ability to develop into various kinds of cells
  • Uses in research, medicine for tissue repair, treating neurological disorders
• Differentiation: process of cell specialised for a particular function
• Specialised cells:

  • Sperm cells: male gametes
  • Palisade cells: basic plant cell type for photosynthesis
  • Root hair cells: increase surface area for water absorption
  • Guard cells: control opening and closing of stomata