Multicellular organisms

• Mitosis


  Cell division in which the nucleus divides into nuclei containing the same number of chromosomes
• Chromosome complement


  The characteristic number of chromosomes in a typical cell of an organism
• Importance of maintaining the chromosome complement in mitosis

  So that no genetic information is lost
• Importance of mitosis in multicellular organisms


  Growth and repair
• Importance of mitosis in unicellular organisms


  Reproduction
• Spindle fibres


  Protein threads produced during mitosis to pull chromatids apart
• Chromatids


  Two identical chromosomes that are separated during mitosis and contain the same genetic material
• Equator of the cell

  Middle of the cell, chromatids line up here to be pulled apart
• Chromsomes become visible during mitosis and duplicate to form chromatids

  
• Chromatids line up along the equator

  
• Spindle fibres pull chromosomes to opposite poles of the cell

  
• Cytoplasm divides, nuclear membrane reforms

  
• Stem cells


  Unspecialised cells in animals, can self-renew or specialise
• Stem cells are involved in...

  Growth and repair
• Specialisation of cells leads to the formation of...

  A variety of cells, tissues and organs
• Cell, tissue, _______, organ system, __________

  Organ, organism
• Central nervous system (CNS)


  Consists of the brain and spinal cord
• Nervous system


  Consists of the CNS and other nerves
• Cerebrum


  Area of the brain responsible for reasoning, memory, personality
• Cerebellum


  Area of the brain responsible for balance and coordination
• Medulla


  Area of the brain responsible for breathing and heart rate
• Sensory neurone


  Carries electrical impulses from the sense organ to the CNS (inter neurone)
• Inter neurone


  Carries electrical impulses from the sensory neurone to the motor neurone
• Motor neurone


  Carries electrical impulses from the CNS (inter neurone) to effectors
• Effector


  A muscle, organ of gland that acts in response to a stimulus
• Stimulus


  A signal to which an organism responds (touching a hot object, ball coming towards you)
• Importance of reflex actions


  Protect the body from harm/danger
• Hormones


  Chemical messengers that are carried in the bloodstream
• Endocrine glands


  Release hormones into the bloodstream
• Target tissue


  Has cells with complementary receptor proteins for specific hormones, so only that tissue will be affected by these hormones
• Haploid cell


  A cell containing only one set of chromosomes (sex cells)
• Diploid cell


  A cell containing two sets of chromosomes, one set inherited from each parent.
• Gamete


  Sex cell
• Fertilisation


  The fusion of the nuclei of the two haploid gametes to produce a diploid zygote
• Zygote


  A fertilised egg
• Discrete variation


  Single gene inheritance (e.g. blood type, tongue rolling)
• Continuous variation


  Controlled by more than one gene (polygenic inheritance), shows variation across a wide range of values, e.g. height and weight
• Gene


  Section of DNA that codes for a protein
• Allele


  Different forms of a gene
• Genotype


  Genes that an organism has, represented by letters e.g. Bb, BB or bb