Biology unit 2

• Mitosis


  1. Chromosomes replicate and become visible

  2. Nucleus breaks down

  3. Chromosomes line up along the equator

  4. Spindle fibres pull the chromatids apart

  5. Separated chromatids become chromosomes and nuclear membranes form

  6. Cytoplasm splits, two daughter cells are made

  
• Mitosis


  Process of cell division that provides new cells for growth and repair, and maintains the diploid chromosome complement
• In a human cell, there are 46 chromosomes. In the two cells made after mitosis (daughter cells), there will be 46 chromosomes in each cell.

  
• Stem cells


  Unspecialised cells which can divide to make more stem cells and have the potential to become different types of cell
• Specialisation


  When a stem cell becomes a specific type of cell, leading to the formation of a variety of cells, tissues and organs
• Levels of organisation


  • Cells
  • Tissues
  • Organs
  • Systems
• Nervous system


  • Made up of the brain, spinal cord and nerves
  • Central nervous system is made up of the brain and spinal cord

  
• Regions of the brain

  • Cerebrum
  • Cerebellum
  • Medulla
• Cerebrum


  Responsible for personality, logic, intelligence, memories
• Cerebellum


  Responsible for balance and coordination
• Medulla


  Responsible for breathing and heart rate
• Types of nerve cell


  • Sensory
  • Inter
  • Motor

  
• Reflex arc


  1. Receptors detect stimuli

  2. Sensory neurons pass information to inter neurons in the CNS

  3. CNS processes the information

  4. Inter neurons pass information to motor neurons

  5. Motor neurons enable a response at an effector

  
• Reflex


  Rapid, automatic responses that protect the body from harm
• Reflexes


  • Sneezing
  • Coughing
  • Blinking
• Hormones


  Chemical messengers released by endocrine glands into the bloodstream
• Target tissue


  Cells with complementary receptor proteins for specific hormones
• Blood glucose regulation


  1. Insulin is released when blood glucose rises, it instructs the liver to take up excess glucose and store it as glycogen

  2. Glucagon is released when blood glucose falls, it instructs the liver to break glycogen down into glucose and put it back into the blood

  
• Diabetes


  Condition caused when the body cannot regulate its blood glucose concentration

  
• Diploid


  Having 2 sets of chromosomes
• Haploid


  Having 1 set of chromosomes
• Gametes


  • Sperm
  • Egg
  • Pollen
  • Ovule
• Fertilisation


  Fusion of the nuclei of two haploid gametes to produce a diploid zygote, which divides to form an embryo
• Variation


  Differences that exist between the members of a species
• Types of variation


  • Discrete
  • Continuous
• Polygenic


  Characteristics controlled by more than one gene
• Genetic terms


  • Gene
  • Phenotype
  • Genotype
  • Allele
  • Dominant
  • Recessive
  • Homozygous
  • Heterozygous
  • P generation
  • F1 generation
  • F2 generation
• The predicted ratio of phenotypes is not always achieved because fertilisation is a random process and involves an element of chance.
• Water absorption and transport in plants


  1. Roots absorb water from soil by osmosis

  2. Water moves into xylem

  3. Xylem transports water up from roots
• Xylem


  • Dead tissue
  • Hollow tubes
  • Lignin present to withstand pressure changes
• Leaf structure


  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Vein
  • Lower epidermis
  • Guard cells
  • Stomata
• Transpiration


  Process of water moving through a plant and evaporating through the stomata
• Phloem


  • Living tissue
  • Companion cells
  • Sieve plates
• Blood


  Contains plasma, red blood cells and white blood cells, transports nutrients, oxygen and carbon dioxide
• Red blood cells


  • Biconcave shape, no nucleus, contain haemoglobin
• White blood cells


  • Phagocytes
  • Lymphocytes
• Phagocytes


  Carry out phagocytosis to destroy pathogens
• Lymphocytes


  Produce antibodies to destroy pathogens
• Blood vessels


  • Arteries
  • Veins
  • Capillaries
• Arteries


  • Have thick, muscular walls, narrow central channel, carry blood under high pressure away from the heart