ND2 Report Books 🔬

To show the organelle in which the chromosomes (and genes) reside.

• Medium size onion bulb, New razor blade, Water in small plastic water bottle
• 2 microscope slides with cover slips, Binocular microscope
• Stain/dye (iodine, Benedict solution or Fehling's solution)

The onion bulb was cut into two halves. One half was further cut into two quarters. A scaly leaf was removed from one quarter and bent backward until it broke. A small piece of epidermal layer was peeled and placed on a clean microscope slide with 1 to 2 drops of water. A cover slip was placed over it and viewed under X10 then X40 objective. The slide was removed, cover slip uncovered, 1 to 2 drops of stain added and cover slip replaced. Viewed again under X10 and X40 objectives.

Under low power (X10) onion epidermal cells appeared as elongated rectangular cells in regular pattern. Under high power (X40) cell wall, cytoplasm and nucleus were clearly visible. After staining the nucleus appeared more distinct and deeply stained.

The nucleus was successfully identified in onion epidermal cells after staining. The stain made the nucleus distinct under the microscope, confirming it is a definite organelle in plant cells where chromosomes and genes reside.

Functions of organelles:

• Cell wall: Provides structural support and shape to the plant cell
• Cell membrane: Controls movement of substances in and out of the cell
• Cytoplasm: Holds organelles and is site of many chemical reactions
• Nucleus: Controls all cell activities and contains genetic material (DNA)
• Vacuole: Stores water, salts and waste products, maintains cell turgidity
• Nuclear membrane: Encloses the nucleus and regulates movement of substances

Why is the nucleus the control centre? The nucleus contains DNA which carries all genetic information needed to direct all cell activities. It controls protein synthesis, cell growth, cell division and overall cell functioning. Without the nucleus the cell cannot carry out normal activities and will eventually die.

To show the behaviour of chromosomes in the stages of mitosis.

• Onion bulb seedlings in water culture, Binocular microscope
• 2 microscope slides with cover slips, Stains/dyes (iodine solution, Fehling's solution)
• Water in small water bottle, Razor blade or scalpel, Blotting/tissue paper

Two to three root tips of 1 to 2mm were cut onto a clean microscope slide and 1 to 2 drops of water added. Root tips were gently macerated into a thin squash using the tip of a pen. One to two drops of stain were added and spread thinly and evenly. The slide was viewed under X10 then X40 objective. Oil immersion was used and the slide was observed under X100 objective.

Under low power (X10) root tip cells appeared small and densely packed. Under high power (X40) and X100 chromosomes were visible in various stages of mitosis. Different stages were observed including interphase, prophase, metaphase, anaphase and telophase.

Mitotic cell division was successfully observed in onion root tip cells. The chromosomes were visible after staining and various stages of mitosis were identified. Mitosis produces two daughter cells genetically identical to the parent cell.

Types of chromosomes based on centromere position:

• Metacentric: Centromere at the centre, producing two equal arms
• Submetacentric: Centromere slightly off centre, one short arm and one long arm
• Acrocentric: Centromere near one end, one very short and one very long arm
• Telocentric: Centromere at the tip, producing only one visible arm

Stages of mitotic cell division: Interphase (DNA replication) → Prophase (chromosomes condense) → Prometaphase (nuclear membrane disappears) → Metaphase (chromosomes align at equator) → Anaphase (sister chromatids pulled to poles) → Telophase (two nuclei form) → Cytokinesis (two genetically identical daughter cells).

To show the behaviour of chromosomes during meiosis I and II.

• Prepared microscope slides of different stages of meiosis
• Binocular microscope, Prepared projector slides of meiosis stages
• Projector with screen, Power source

The microscope or projector was connected to the power source and operated. The prepared slides of different stages of meiosis were viewed studiously and short notes were made on each stage observed.

The various stages of meiosis I and meiosis II were observed on the prepared slides. In meiosis I, homologous chromosomes were seen pairing up and separating. In meiosis II, sister chromatids were observed separating. Four daughter cells were produced at the end of meiosis II each with half the chromosome number.

Meiotic cell division was successfully observed. The behaviour of chromosomes during meiosis I and II was distinct and identifiable at each stage. Meiosis produces four genetically different daughter cells each with half the chromosome number, important for sexual reproduction and genetic variation.

To identify the various degrees of dominance expression.

• Genetic corn, 4 beakers
• Access to experimental farm at Institute of Agricultural Research (IAR)

A field trip was made to an experimental farm grown with advance lines (pure breed) of maize or guinea corn or cassava. Uniformity and observable characteristics of the plants were noted. The genetic corn provided was shelled into a beaker. White grains were counted into one beaker and coloured grains into another. Counts were recorded accordingly.

The expression of dominant characters was observed in the field plants and genetic corn. Pure breed plants showed uniformity due to homozygosity. The ratio of coloured to white grains approximated 3:1, confirming Mendel's law of segregation and expression of dominance in heterozygous crosses.

Ratio and genetics: White = 232, Coloured = 768, Total = 1000. Ratio = 3:1. This confirms a monohybrid cross (Cc × Cc). Coloured (C) is dominant over white (c). Genotypic ratio 1CC:2Cc:1cc. Confirms Mendel's Law of Segregation.

To identify the various characteristics that qualify an organism for use in genetic experiments.

Rotten fruits were cut into halves and exposed by the laboratory windows. Daily observations were made for Drosophila colonization. Individual Drosophila were observed with a hand or table lens and characters recorded. Moist corn cob stalks were exposed by the laboratory corridors until fully infested with Neurospora. The Neurospora culture was observed with the hand lens for distinguishing characteristics.

Drosophila colonized the rotten fruits within a few days showing observable differences in body colour, eye colour and wing size. Neurospora grew on moist corn cob stalks showing orange coloured spores, thread-like mycelium and distinct growth patterns.

Both Drosophila and Neurospora were successfully cultured and observed. Their contrasting features and short generation times make them suitable for genetic experiments, allowing easy observation of inherited traits within a short period.

Drosophila: Short generation time (~2 weeks), large number of offspring, only 4 pairs of chromosomes, males and females easily distinguished, many contrasting traits observable with hand lens, cheap and easy to culture.

Neurospora: Short generation time, exists as haploid making gene expression directly observable, produces ordered tetrads useful for gene mapping, easy and cheap to culture, shows clear contrasting traits.

To identify genetic variations in a natural population of plants.

Seeds collected from wild herbaceous plants were raised in a nursery bed or planting pots with 2 to 3 seedlings per pot. As seedlings grew they were observed for phenotypic variation. All variable characters observed were listed and recorded.

Phenotypic variations were observed among individuals raised from the same wild seed collection. Differences were noticed in plant height, leaf shape, leaf colour, stem thickness and rate of growth.

Genetic variation was successfully observed among seedlings raised from wild seeds. Variations in measurable and non-measurable characters confirm that wild plant populations contain wide genetic diversity resulting from random genetic recombination during sexual reproduction.

To identify complete, partial and no dominance conditions in coat colour of mice.

• Black male mouse, White female mouse, Mouse cage, Mouse feed, Water, Mouse litter

A black male mouse and a white female mouse were kept together in a cage and fed daily. At maturity the mice mated and produced offspring. As the offspring grew their coat colours were noted and recorded.

The offspring showed variation in coat colour. Some had black coat resembling the male parent, some had white coat resembling the female parent, and some had grey coat showing a blend of both parents indicating partial dominance.

The coat colour distribution demonstrated the three conditions of dominance. Complete dominance was shown where offspring had purely black or white coat. Partial dominance was shown where offspring had grey coat. This confirms that inheritance does not always follow simple Mendelian patterns.

To compare the porosity and water retaining capacity of sandy, loamy and clay soils.

• Three measuring cylinders of 100cm³, Cotton wool, Three funnels, Water, Stop clock
• Dry sand, Dry clay, Dry loam

Loam and clay soils were ground into fine particles after drying in the sun. Equal masses of dry sand, clay and loam were placed separately into three funnels each blocked at the neck with cotton wool. The funnels were placed on top of three measuring cylinders. Equal amounts of water (60cm³) were poured into each funnel. The setup was allowed to remain for one hour and measurements were taken.

Sandy soil is most porous due to larger particles retaining the least water (16.7%). Clay soil is least porous retaining the most water (50%). Loamy soil is intermediate (33.3%). Loamy soil may retain more water than clay if it contains large quantities of organic matter.

To compare and determine the capillary action of different soil types.

• Three long glass tubes, Cotton wool, Trough, Stop clock, Water
• Dry sand, Dry clay, Dry loam

One end of each glass tube was closed with cotton wool. Each tube was filled separately with ground clay, sandy and loamy soils. The tubes were immersed at the cotton wool end into a trough containing water. The setup was allowed to remain for 3 to 6 hours and the rise of water in each tube was observed and recorded.

Clay and loamy soils have greater capillary action due to their tiny pore spaces which draw water higher through surface tension. Sandy soil has poor capillary action due to large pore spaces and large particle sizes.

To determine the population size of ants in a habitat.

The measuring tape was used to determine the area of the whole plot. The quadrat (1m × 1m) was placed at shoulder level and thrown randomly into the area of study. The number of ants inside the quadrat was counted and recorded. The throw was repeated 10 times. The average number of ants per m² was calculated and the area of the plot was used to determine the population size.

The quadrat method was successfully used to estimate the ant population at 3,500 ants. This method is useful for estimating populations of organisms that cannot be easily counted individually across a large area.

To determine the population size of earthworms using earthworm casts.

A measuring tape was used to determine the area of the whole plot. The quadrat (1m × 1m) was placed at shoulder level and thrown randomly. The number of earthworm casts inside the quadrat was counted and recorded. The throw was repeated 10 times.

The quadrat method was successfully used to estimate earthworm population at 3,000 earthworms. Earthworm casts are reliable indicators of earthworm presence and population density.

Why earthworm casts were used instead of earthworms directly: Earthworms live underground and are not visible on the surface. Digging to count them directly would destroy the habitat. Each cast on the surface reliably indicates an earthworm below. It is a faster, easier and non-destructive field method.

To determine Tridax population size.

A tape rule was used to determine the area under study. The rope was marked at convenient intervals. One end was tied to a peg at one end of the study area. The rope was stretched across and tied to a second peg. The number of Tridax plants touching the rope within intervals was counted and recorded. The process was repeated 5 times.

The line transect method was successfully used to estimate Tridax population and percentage cover. Repeating the transect 5 times gave a more accurate and reliable estimate of 6,500 plants.

To determine the population size of locust using the capture mark release recapture method (Lincoln Index).

• Sweep net, Marker or ink, Farmland, Tape rule

A tape rule was used to determine the farmland area. A sweep net was used to capture locusts. Captured locusts were marked with ink and released. After a period of time locusts were recaptured. The number of marked and unmarked locusts in the second capture was recorded and population size calculated using the Lincoln Index.

The capture mark release recapture method was successfully used to estimate locust population at 100 locusts. This method is reliable for estimating populations of mobile organisms.

To examine and describe the stratification in a forest.

Students took a field trip to Afaka aforestation reserve at kilometre 30, Buruku. The forest stratification was observed. Plants and animals on each stratum were observed and recorded. The forest floor was also observed and recorded.

Afaka aforestation reserve showed clear forest stratification with distinct layers from emergent to forest floor. Each layer supported different plants and animals adapted to its light, temperature and humidity conditions.

To isolate microbial populations from soil.

• Plate count agar (PCA), Sabouraud agar, Starch-casein agar
• Cyclohexamide stock solution, 80°C water bath, 50°C water bath
• 1ml pipettes, 9ml dilution blanks, Sterile saline (99ml), Soil sample

Total Bacteria: 1g of soil added to 99ml sterile saline (10⁻¹). Serial dilutions made. 1ml of 10⁻⁴ to 10⁻⁶ placed into duplicate plates. Melted PCA added, swirled, solidified. Incubated at 30°C for 48 hours.

Fungi: 1ml of 10⁻³ to 10⁻⁵ dilutions into duplicate plates. Sabouraud agar added. Incubated at 30°C for 5 to 7 days.

Actinomycetes: 2ml aliquots from 10⁻⁴ to 10⁻⁶ dilutions into starch-casein agar tubes. 1ml cyclohexamide added. Rolled, poured onto labeled plates. Incubated at 30°C for 5 to 7 days.

Endospores: Original 10⁻¹ suspension heated at 80°C for 15 minutes. Serial dilutions through 10⁻⁵. PCA added, incubated at 30°C for 48 hours.

Different microbial populations were successfully isolated using selective agar media and serial dilution. Heat treatment at 80°C selected for endospore forming bacteria, confirming the importance of selective media in microbial ecology.

To identify the tools and measuring instruments used in maintenance activities.

(i) To identify and connect a plug to a flexible wire. (ii) To change a bad plug and fix with a new one.

• Flexible wire, Cord, 5A, 13A and 15A plugs
• Screwdriver, Tester, Cutting plier, Multimeter

A wire was provided and the outer insulator cover was removed. The brown/red/white wire (Live) was cut at 1.5cm, blue/black/grey wire (Neutral) cut at 1.5cm, and green/yellow wire (Earth) left longer. The plug cover was removed with a screwdriver and the fuse taken out. Terminal fixing screw was loosened and cable secured. Green/yellow connected to centre terminal, neutral to left terminal. End of each terminal wire twisted and screws tightened. 13 amps fuse replaced and continuity checked with multimeter. Cover replaced, screw tightened and plug connected to test.

Three wires were successfully identified by colour codes. Live: brown/red/white. Neutral: blue/black/grey. Earth: green/yellow. After connection multimeter confirmed continuity and the testing lamp lit up confirming successful connection.

The 5A, 13A and 15A plugs were successfully connected to flexible wires following correct colour code wiring convention. Continuity testing confirmed all connections were correctly made.

• Always disconnect from power supply before working on any plug or wiring
• Ensure all terminal screws are firmly tightened before connecting to power supply

To identify the passive and active components.

Passive and active electronic components were successfully identified. Passive components such as resistors, capacitors and inductors do not require external power. Active components such as transistors, diodes and ICs require external power and can amplify or switch signals.

To use a multimeter to determine the resistance of a diode, transistor and capacitor.

Testing the Diode: Set multimeter to highest resistance range and zeroed. Positive side of diode connected to positive terminal, reading recorded. Connections reversed and reading recorded again.

Testing the Transistor: Red terminal to base and black to collector to check resistance. Connections varied between base, collector and emitter in different combinations and readings recorded.

Testing the Capacitor: Multimeter set to highest microfarad scale. Red probe at one terminal and black at the other. Readings observed and recorded.

The multimeter successfully tested the diode, transistor and capacitor. Diode showed low resistance in forward bias and high in reverse bias. Transistor showed expected resistance pattern. Capacitor showed initial deflection returning to high resistance confirming good condition.

To determine resistor values using colour code and multimeter.

Resistor values were successfully determined using colour code and multimeter. Minor differences between colour code value and multimeter reading were within the tolerance range confirming the resistors were in good working condition.

To use carbon resistor colour code to determine the resistance and tolerance of each resistor.

As many different carbon film resistors as possible were removed from the junk provided. The colour code of each resistor was used to determine the resistance and tolerance values for ten different types. The AVO meter set on OHM meter was then used to determine the resistance value of each resistor.

The colour code method was successfully used to determine resistance and tolerance values of ten different carbon film resistors. AVO meter readings confirmed colour code values with minor differences within tolerance range.

To determine the series and parallel combination of resistors and compare calculated values with multimeter readings.

• Assorted resistors, Voltmeter, Switch, Prototype board
• Connecting wires, Power supply unit (PSU), Multimeter

Series and parallel resistor combinations were successfully set up and measured. Calculated values agreed closely with multimeter readings. In series total resistance increased while in parallel total resistance was less than the smallest individual resistor. Voltage measurements confirmed that sum of individual voltages equals supply voltage.

To learn and perform the various methods used in cutting glass tubing and glass sheets in glass blowing operations.

• Glass tubing of various diameters, Glass sheets, Cutting knife and diamond knife
• Hot glass rod, Iron rod (1/8 inch, 12 inches long), Nichrome wire (9.5 inch, 28 gauge)
• 30 volts power source or step down transformer, Spring tong
• Cotton string and alcohol, Zinc white paste, Cold water in bucket
• Arc saw blade, Straight edge ruler and grease pencil, Bunsen burner

All seven glass cutting methods were successfully performed. Each method is suited to a specific glass type or diameter. Proper marking and correct application of heat or pressure are essential for achieving clean accurate cuts. Safety precautions must be observed at all times.

To learn and perform the various methods used in drilling and grinding glass in glass blowing operations.

• Steel wire, Drilling machine, Metallic mercury, Turpentine, Camphor, Water
• Moist foam ring, Molten lead, Graver, Cork pieces (convex and concave)
• Iron or steel laps, Fine sand, Emery, Pure lead or tin laps, Tin putty, Willow wood laps

The various glass drilling and grinding methods were successfully performed. Each method is suited to a specific type and thickness of glass. Proper lubrication with turpentine and water is essential during drilling. Grinding requires progressive use of abrasives from coarse to fine to achieve a smooth polished glass surface.