Observation

TThis was the most popular question answered by candidates. Candidates named the groups of microorganisms correctly although some of them failed the spelling of the groups. The examples of each group were poorly written too. The ways of controlling microorganisms were fairly answered. The candidates that could not list the abiotic factors that affect animals living at the bottom of the sea were giving answers for terrestrial habitat. Many candidates were able to answer (c)(i) and (ii) fairly well.

The expected answers are:

(a) (i) Groups of microorganisms

- Viruses;

- bacteria;

- protozoa;

- fungi;

- algae.

(ii) Examples

-Virus - Human Immunodeficiency Virus; Lassa fever virus; Polio virus; pox virus; rhinovirus; Human papillomavirus; bird flu virus; influenza virus; Ebola virus.

-Bacteria - Vibrio cholerae; Bacillus; Staphylococcus; Streptococcus, Clostridium; Gonococcus; Nitrobacter; Nitrosomonas/any correctly named

-Protozoa - Plasmodium sp.; trypanosome; Entamoeba; Onchocerca /any correctly named

-Fungi - Tinea sp, Candida sp; Histoplasma/any correctly named

-Algae - Euglena, Spirogyra, Chlamydia/any correctly named.

Note: Spellings must be correct to score; No abbreviations

(iii) Ways of controlling microorganisms

- High temperature/boiling/heating/oven drying/pasteurization/direct flaming;

- dehydration/sun drying;

- high salinity/salting;

- antibiotics;

- radiation/irradiation;

- antiseptic/disinfectant/germicide etc;

- immunization/vaccination/inoculation;

- freezing/low temperature/refrigeration

- sterilization/autoclaving/alcohol.

                              

(b)Abiotic factors that affect animals at the bottom of the sea

- Water pressure;

- light intensity;

- salinity;

- pH/hydrogen ion concentration;

- depth;

- temperature;

- oxygen concentration;

turbidity.

 

(c) (i) Human activities that may lead to extinction of species

- Destruction of habitats;

- Excessive logging/deforestation;

- Excessive farming/overgrazing;

- Oil spillage;

- Poaching/over hunting of particular species/over fishing;

- Release of chlorofluorocarbon into the atmosphere causing global warming;

- any correctly named example

- Use of pesticide/herbicides/toxic chemicals;

- Introduction of predator species like rats/cats;

- Building/construction/urbanization;

- Bush burning;

(i) Adverse effects of extinction of plant species on humans

- Man is deprived of beneficial substances that the species contained;

- Loss of medicinal plants;

- Scarcity of food/famine;

- Discontinuous generation;

- Loss of economic plants;

- Leads to Greenhouse effect/global warming;

- Imbalance in the ecosystem;

- Depletion of oxygen/accumulation of carbon dioxide;

- Human migration.