multicellular organisms - summary

• What is mitosis?

  Process of cell division
• Why is mitosis important?

  It provides new cells for growth and repair
• How many chromosomes are in a human cell?

  46 chromosomes
• How many chromosomes do daughter cells have after mitosis?

  46 chromosomes in each cell
• What are stem cells?

  Unspecialised cells that can divide
• What are the main stages of mitosis?

  1. Chromosomes replicate and become visible.
  2. Nucleus breaks down.
  3. Chromosomes line up along the equator.
  4. Spindle fibres pull chromatids apart.
  5. Chromatids become chromosomes with nuclear membranes.
  6. Cytoplasm splits to form two daughter cells.
• What is the role of stem cells?

  Involved in growth and repair
• Where can stem cells be obtained from?

  Embryo at a very early stage
• What is specialisation in stem cells?

  When a stem cell becomes a specific type of cell
• How do cells, tissues, organs, and systems relate?

  • Cells make up tissues.
  • Different tissues form organs.
  • Organs combine to create systems.
• What is the nervous system made up of?

  Brain, spinal cord, and nerves
• What does the central nervous system (CNS) consist of?

  Brain and spinal cord

  
• What are the three regions of the brain?

  Cerebellum, medulla, cerebrum
• What is the function of the cerebrum?

  Personality, logic, intelligence, memories
• What does the cerebellum control?

  Balance and coordination
• What is the role of the medulla?

  Controls breathing and heart rate
• What are the three types of nerve cells?

  Sensory, inter, and motor neurons

  
• What do receptors do?

  Detect stimuli
• How does information travel in the nervous system?

  As electrical impulses along neurons
• What are neurotransmitters?

  Chemicals that transfer messages between neurons
• What is a reflex arc?

  Arrangement of neurons for reflex actions
• What are reflexes?

  Rapid, automatic responses to stimuli
• What do endocrine glands release?

  Hormones into the bloodstream
• What are hormones?

  Chemical messengers in the body
• What is a target tissue?

  Tissue with receptors for specific hormones
• What regulates blood glucose concentration?

  Insulin and glucagon hormones

  
• What does insulin do?

  Instructs liver to store excess glucose

  
• What does glucagon do?

  Instructs liver to release glucose into blood

  
• What is diabetes?

  Condition where blood glucose is unregulated
• What type of cells are gametes?

  Haploid cells
• How many chromosomes do haploid cells have?

  23 chromosomes
• What is fertilisation?

  Fusion of nuclei of two haploid gametes
• What are the types of variation?

  • Discrete: distinct groups (e.g., blood group)
  • Continuous: range of values (e.g., height)
• What is polygenic inheritance?

  Characteristics controlled by more than one gene
• What are the key terms in genetics?

  • Gene: unit of chromosome
  • Phenotype: physical appearance
  • Genotype: set of genes present
  • Allele: forms of a gene
  • Dominant: shows in phenotype
  • Recessive: masked by dominant allele
  • Homozygous: same alleles
  • Heterozygous: different alleles
  • P: parent generation
  • F1: first generation
  • F2: second generation
• Why might the predicted ratio of phenotypes not be achieved?

  Fertilisation is a random process
• What do roots do in plants?

  Absorb water from the soil
• How does water move into root hairs?

  By osmosis from higher to lower concentration
• What does xylem transport?

  Water from roots to leaves
• What are the characteristics of xylem?

  • Dead tissue
  • Hollow tubes
  • Lignin present for pressure resistance