biology

• Gas exchange in humans

  The process of exchanging gases (oxygen and carbon dioxide) between the lungs and the bloodstream
• Alveoli

  • Large surface area
  • Thin surface
  • Good blood supply
• Cartilage


  The tissue that forms C-shaped structures in the wall of the trachea
• Function of cartilage

  • Prevent collapse
  • Support
• Effects of diaphragm contraction on the thorax

  1. Increases in volume

  2. Decreases in pressure
• Sperm

  • Contains enzymes in acrosome
  • That breaks down jellycoat
  • Many mitochondria for respiration
  • Flagellum to swim
• Egg

  Energy store for development of embryo/ mitosis/ cell division
• Sperm and egg have haploid nuclei
• Gametes are haploid so zygote have 46 chromosomes
• Process of artificial insemination (AI)

  1. Sample of sperm collected

  2. Sperm washed

  3. Sperm inserted into vagina

  4. Sperm inserted at time of fertility
• Social implications of fertility treatments

  • Expensive
  • Risks of multiple births/ pregnancies
  • Poor success rates
  • Ethical issues with fertility treatment process
• Factors affecting loss of mass from the leaves of a plant

  • Temperature
  • Humidity
• How tissue of XYLEM is adapted for its function in the plants

  • Hollow, to reduce resistance
  • No end walls, to reduce resistance
  • Wide, to allow transport of large vol. Of water
  • Lignin to provide support
  • Waterproof to prevent water loss
• How mineral ions enter a plant


  1. Into root hair cell

  2. By active transport

  3. Against concentration gradient

  4. Using energy

  5. Using carrier proteins

  6. By diffusion
• How cholera bacterium causes diarrhoea

  • Bacteria releases a toxin
  • Causing chloride ion secretion into small intestine
  • Reducing water potential
  • Osmosis
  • Water moves into intestine
• How bacteria become resistant to antibiotics

  • Natural selection
  • Mutation
  • Bacteria without resistance die
  • Multiply
  • Pass on alleles to offsprings
• How to minimise effectiveness of antibiotics

  • Take antibiotic when needed
  • Complete course of treatment
• Conservation methods 

  • Protected areas
  • Education
  • Prevent hunting
  • Captive breeding programmes
• Risks in low population size

  • Inbreeding
  • Lack genetic diversity
  • Reduced to survive changes in environment
  • Increased risk of extinction
  • Small population
• Importance of shape for the function of an enzyme

  • Shape of active site is complementary to active site
  • To form more ESC
  • Specificity
• Features of the gas exchange surface that are visible

  • Thin 
  • Good blood supply
• Features of the gas exchange surface that are visible

  • Thin 
  • Good blood supply
  • Good ventilation with air
• Define TISSUE: a group of cells with similar structure (1) working together to perform a shared function (1)
• Function of cartilage in the gas exchange system

  • Keeps airways open 
  • Reduces resistance to movement of air
  • Protects airways
• Skin: group of tissues working together to perform specific functions
• Name of organ that coordinates the control of body temperature

  • Brain
• Describe how blood vessels are involved in maintaining a constant internal body temperature in cold environment

  • Vasoconstriction
  • Shunt vessels dilate/widen
  • Less blood flow to skin
  • Reduces heat loss from blood
• Uses of energy in HUMAN

  • Protein synthesis
  • Muscle contraction
  • Growth
  • Active transport
  • Cell division
• Name of ball of cells that implants into the uterus after fertilisation

  • Embryo
• Compare the development of a fetus in the early stages of pregnancy to its development in the late stages of pregnancy

  • Growth in all stages
  • Development during all stages
  • Increase in complexity in early stages
  • Increase in size in later stages
• Amniotic fluid: supports fetus as mechanical protection

                         Maintain constant temperature

                         Provide sterile environment

                         Allow movement of fetus

                         Allow development of bones and muscles
• Amniotic sac: enclose fetus

                        Secretes amniotic fluid

                        Prevents entry of bacteria from vagina
• Umbilical artery & pulmonary artery transport deoxygenated blood
• Name of the process that allows substances to move down a concentration gradient across the 

  • Diffusion
• Way HIV can be transmitted

  • (drug) injected into body
  • Blood transfusion
  • Exchange body fluids
  • Breast feeding
• inheritance : transmission of genetic information from generation to generation
• Describe how a breeder could determine the genotype of X

  • Perform a test cross
  • By breeding with (homozygous recessive)
  • DNA testing
• Evidence that can be used to determine how closely related organisms are

  • Pedigree diagrams
  • Compare DNA sequences
• Suggest why (animal X) is at risk of becoming endangered

  • Hunting/ poaching
  • Pollution
  • Disease
  • Lack of prey
  • Climate change
• Describe how species like (animal X) can be conserved

  • Legalisation against hunting
  • Captive breeding programmes