Question 1 |
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Question 1
(ii) In a tabular form, state four differences between gaseous exchange
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ANSWER
1i
Question 2 |
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(i) four external factors;
(ii) State the importance of each of the products listed in 2(c) (i) above. [3 marks]
(ii) State why decomposers are important to flowering plants. [3 marks] |
ANSWER
NOT
ANSWER
Question 4 |
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(a) (i) What is conservation? [3 marks] |
ANSWER
4(a) (i) Conservation
Planned/wise/judicious use/management of the earth’s natural resources; in order to ensure sustenance/availability/continuity; and preservation of the quality of the natural/original nature of the environment.
(ii) Factors responsible for decline of abundance and variety of wildlife
- Commercial hunting which kills off animals indiscriminately;
- industrialization which involves clearing of forests;
- for various purposes/construction/farming/urbanization;
- destruction of habitats of wildlife by human activities;
- bush burning/noise pollution leads to wildlife migration;
- environmental pollution which releases dangerous materials that degrades environment making it unbearable for the wildlife;
- massive/excessive tree felling to make charcoal/domestic uses;
- lack of awareness/inadequate education of populace on the need for conservation;
- lack of adequate funding to enforce conservation policy.
(b) Ways by which the Government can improve the situation
- establishment of forestry departments;
- establishment of Environment Protection Agency to improve the situation;
- creation of Parks and Games Reserves/any correctly named example;
- to preserve/maintain plants and animals in their natural environment;
- conservation education carried out through tree planting/ campaigns against bush burning/ tree
felling /poaching;
- conservation laws to regulate tree felling; poaching/hunting of wild animals and bush burning;
- establishment of zoological gardens/ preserving endangered species.
(c) (i) Eutrophication
Excessive growth of plant life/algae/algal bloom; in water courses/bodies, caused by an increase in organic nutrients and minerals; leading to the death of aquatic organisms.
(ii) Causes of eutrophication
Overuse of fertilizers/plant nutrients which drain off into water bodies; sewage discharge; wastes from fish farming.
NOT
NOT
Question 7 |
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(a) Describe the carbon cycle. [10 marks] |
ANSWER
7(a) Description of the carbon cycle
Carbon occurs in the air/atmosphere/as carbon dioxide/dissolved in the oceans/seas/water bodies; and is circulated continuously; through the activity of microorganisms/decay bacteria/saprophytic organisms/fungi; which decompose the dead organisms; plants/animals release carbon dioxide and water; the carbon dioxide released increases the concentration of carbon in the atmosphere/ocean/sea/water bodies; this is further increased by respiration in plants and animals; combustion of wood/coal/peat/oil/fuel; some of the excess carbon dioxide is absorbed by the sea/water bodies and also used by plants in photosynthesis; organisms in seas/oceans/water bodies release carbon dioxide into the atmosphere/water.
(b) Functions of
(i) Nitrogen-Fixing Bacteria
Nitrogen fixing bacteria in the nodules of legumes; those living freely in soil; convert atmospheric nitrogen; into ammonia/ammonium compounds.
(ii) Nitrifying Bacteria
They live freely in the soil; oxidize/breakdown the ammonium compounds; to nitrites; which are then oxidized by others/Nitrobacter/named bacteria; to nitrates.
(iii) Denitrifying Bacteria
They live freely in the soil; these break down/oxidize ammonium compounds; into nitrogen; and oxygen; which is released into the atmosphere.
Question 8 |
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(a) (i) What is excretion? [2 marks] |
ANSWER
8 (b) Functioning of kidney as excretory organ
Blood from the renal artery enters the bowman’s capsule; through the afferent arteriole; ultra filtration occurs in the Bowman’s capsule; high pressure in the glomerulus causes the filtration of small molecules/amino acids/ glucose/ minerals salts/ water/ urea; out of the blood plasma into the cavity of the capsule; the filtrate/glomerular filtrate passes through the nephron; where selective reabsorption of useful metabolites/glucose/amino acids take place;
in the descending/first/proximal convoluted/coiled tubule; the reabsorption of salts and water is regulated in the loop of Henle; and the ascending/second/distal convoluted tubule/large waste molecules like creatine secreted at loop of Henle; depending on blood concentration; the filtrate continues into the main collecting duct/tube; where further reabsorption of water and salt takes place; the remaining fluid in the duct becomes urine.
(c) Excretory organs inss
(i) Insects – Malpighian tubules;
(ii) Earthworm – Nephridia/Nephridium
