Question 8.
(a)
• P is the skin act as the first line of defence which act as physical barrier.
• Kretanised layer prevent the entry of pathogen.
• Acidic sebum act as chemical barrier by forming a protective film over skin, prevent growth of microorganisms.
• Sweat secreted lysozymes which capable of destroying bacteria.
• Q is leucocytes/neutrophil act as the second line defence mechanism.
• Q/Neutrophil act as phagocytes that attracted by chemical produced at the site of infection.
• Neutrophil surrounds and binds itself to the pathogen.
• Neutrophil engulf the bacterium to form phagocytic vacuole
• Enzymes are release into the vacuole to break down the bacterium
(b)Transmission
• Can usually be contracted to unprotected sexual activity
• Newborn babies can be infected from their mothers
across placenta and breast feeding
• Contaminated needles used by drug addict or tattooing.
• Unscreened blood transfusion of contaminated blood to an individual.
Prevention AIDS
Educational programmes about the risk of unprotected sex and sharing needles
• Use condoms to reduce risk
• Stay away from sex with many partners.
• Blood screening before transfusion Screening
(c) Comparing immunity based on Graph:
• X-Immunity obtained through injection with a vaccine ; Y- Immunity obtained through injection with a serum (which contains a specific antibody)
• X-Does not result in an immediate immunity against the disease; Y- result in an immediate immunity against a disease.
• X-Lymphocytes in the body will be activated to produce antibody, Vaccination act as a preventive measure against certain diseases ; Y-the immunity obtained from the first injection is temporary and injected when a person is infected with the disease.
• X-Artificially acquired immunity usually last for a long time; Y-the immunity lasts only for a short term and offers temporary protection.
• X- second injection ( booster) is necessary to increase the antibody production to a level that protects the person against the disease. ; Y-second injection is given when the person still infected and his antibodies has dropped below immunity level, therefore he needs antiserum injection against the disease.
Question 9(a)
• During the day, light stimulates photosynthesis in the guard cells.
• Guard cells synthesize glucose
• And generate energy for active transport
• Guard cells accumulate potassium ions from adjacent cells (through active transport)
• Guard cells become hypertonic
• And water from adjacent cells enters the guard cells by osmosis
• As a result, guard cells swell up and become turgid
• Since the inner cell walls of the guard cells are thicker than the outer walls,
• The guard cells bent outward and the stoma opens
(i) 36-23= 13 μg per cm2
ii) 39-19=20 μg per cm2
iii)
• Dry condition/ desert-
E1- Has embedded / sunken stomata
E2- Reduced water loss through transpiration
E3- Reduced leaves to become thorn
E4-Reduced/ less/decreased/few number of stomata
Transpiration....
F1- Air movement/ Wind
E1-movement of air carries away water molecules that have diffused from the leaves.
E2-the faster the air movement / wind speed, the greater the rate of transpiration.
F2- Temperature
E3-rise in temperature increases the kinetic energy of water molecules
E4-increases the rate of evaporation (lowers the relative humidity of the air)
F3- Light intensity
E5-light intensity is increased, the rate of evaporation from a plant increases (not that light affects evaporation as such)
E6-but that it causes the stomata to open, E7-thereby increasing water loss from the plant
F4- Relative humidity/Humidity
E8- High humidity surrounding the leaves reduce the evaporation of water from the stomata
E9-this causes transpiration to slow down
F1,F2,F3 and F4 = 4marks + Any 6 Explanation(E) Total= 10 M
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