3RD TERM

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Set up a small ecosystem making use of a large plain glass container/ empty aquarium. Observe your ecosystem for 2-3 months

MICRO – ORGANISMS AROUND US
Micro – organisms – Definition, classification of Micro – organisms (bacteria, fungi, protozoa, etc), concept of culturing.
PRACTICAL
-Experiment to demonstrate the presence of micro-organisms in the dirt under the finger nails
- Experiment to demonstrate the presence of micro-organisms in expired or exhaled air
- Experiment to demonstrate the presence of micro-organisms in food


SUGGESTED PRACTICALS

1. Experiment to Determine The Water Retaining Capacity of Soil Types
Title of experiment: To compare the porosity and water holding capacity of three soil types
Materials required: Three measuring cylinders of 100cm³, cotton wool, three funnels, water, dry sand, dry clay, dry loam, stop clock, balance.
Method: Stand the three funnels in the three measuring cylinders and block the funnels with cotton wool.
- Place an equal weight of dry sand, dry clay and dry loam in the three funnels respectively.
- Pour 50ml of water onto each sample at the same time and allow to drain.
- Allow the set up to stand for an hour or until the water has stopped dripping through each funnel.
- Read the level of water in the measuring cylinder.
Calculations:
(a) Rate of drainage / porosity is calculated from the amount of water collected in the measuring cylinder. The more the water, the more porous the soil sample. Usually porosity is highest in sandy soil because it has large pore spaces and large particle sizes, followed by loamy soil and then clay soil which has the least drainage because of its tiny pore spaces and fine particles .
(b) Water holding / retaining capacity is calculated as follows;
Volume of water added to soil = 50ml
Volume of water collected in cylinder = xml
Volume of water retained in the soil = (50-x) ml
The percentage of water retained in each of the soil samples will be
(50-x) x 100 = Y%
50
Observation: It is observed that water drained out from the sandy soil faster than the loamy soil and finally the clay soil. It was also observed that clayey soil retained more water than loamy soil and least retained by the sandy soil.
Conclusion: Sandy soil is more porous than loam which is more porous than clay. Clayey soil retained more water than the loamy soil and the sandy soil retained the least amount of water.

2. Experment To Compare The Capillary Action Of Soil Types
-Take three wide glass tubes and plug each at one end with cotton wool.
- Nearly fill the tubes with the three soil samples separately.
- Clamp the tubes upright in a trough of water,
- Allow the set-up to remain for 3-6 hours
- Observe every 30mins.
Observation: It will be observed that at the early stage of the rise of water in the three tubes, it was faster in sandy soil than the clay and loamy soil samples, however by the end of the experiment the water had risen to the highest levels in loam, followed by clay but remained at a low level in the sandy soil.
Conclusion: Loamy and clayey soils have greater capillary actions due to their tiny pore spaces. The presence of organic matter in loam also enhanced its capillary. The sandy soil had poor capillary action because of its large pore spaces and large particles.


SUGGESTED PRACTICALS:
1. Preparation of culture solution
2. Examine the presence of microbes in Air, water, saliva, under nail.
3. Classification of bacteria using different criteria