Theory question 106
Photosynthesis and Plant Nutrition(a)(i) Explain briefly chemosynthesis as a mode of nutrition. (ii) Give two examples of organisms that carry out chemosynthesis. (b) List three gases in the atmosphere with their percentage composition.
Gases in the atmosphere | Percentage composition
(c)(i) State four characteristics of a salt marsh habitat. (ii) Explain briefly how plants are modified for anchorage in a salt marsh habitat. (d)(i) List four bacterial diseases associated with poor food hygiene. (ii) State three effects of poor food hygiene. (e) A person was involved in a car accident and became unconscious due to excessive blood loss. Explain briefly how the blood lost could be restored. (f) State three differences between tillage and bush burning as farming practices.
Tillage | Bush burning
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(a)(i) Chemosynthesis is a type of autotrophic nutrition in which some bacteria make their own food from simple inorganic substances using energy released by oxidising chemicals (e.g. ammonia, nitrites, iron or sulphur compounds) instead of light.
(ii) Any two: Nitrosomonas; Nitrobacter; iron bacteria; sulphur bacteria (e.g. Thiobacillus).
(b) Any three: nitrogen about 78%; oxygen about 21%; argon (noble gases) about 0.9%; carbon (IV) oxide about 0.03%; water vapour variable.
(c)(i) Any four: water is salty/brackish and its salt level changes; flooded at high tide and exposed at low tide; soft, muddy, waterlogged soil; mud poor in oxygen; strong sunlight and high evaporation; tidal currents.
(ii) Mangrove plants have stilt (prop) roots growing from the stem and spreading into the mud, which hold them firmly against tides; extensive branching roots; breathing roots (pneumatophores) also help.
(d)(i) Any four: cholera; typhoid fever; bacillary dysentery; food poisoning (Salmonella, Staphylococcus); botulism; tuberculosis (from milk); diarrhoea caused by E. coli.
(ii) Any three: spread of food-borne diseases; diarrhoea, vomiting and dehydration; death; food spoilage and waste; loss of working/school days and money.
(e) He should be given a blood transfusion of matched (compatible) blood after cross-matching; meanwhile intravenous fluids (saline/plasma) restore volume; later the body replaces lost blood: bone marrow makes new red cells, liver makes plasma proteins; a diet rich in iron, protein and vitamins helps.
(f) Any three: tillage loosens and turns the soil / bush burning clears vegetation by fire; tillage improves aeration and drainage / bush burning does not; tillage keeps organic matter, which can be turned in / burning destroys organic matter and soil organisms; tillage does not pollute the air / burning releases smoke and CO2; burning exposes soil to erosion / tillage (done properly) causes less erosion; burning quickly releases potash (ash) / tillage does not.
Section C (candidates in Nigeria only). Use the tables for (b) and (f).