Design and carry out anatomical and physiological investigations related to transportation in plants and animals, growth in plants and reproductive system

Steps in Scientific Investigation

Every well-designed biological investigation follows a structured approach:

1. Identify the problem — State what you want to investigate as a clear question
2. Formulate a hypothesis — Make a prediction that can be tested
3. Identify variables — Distinguish:
   • Independent variable: what you change
   • Dependent variable: what you measure
   • Controlled variables: what you keep constant
4. Design the method — Write clear, step-by-step procedures
5. Collect data — Record observations and measurements systematically
6. Analyze results — Present data in tables, graphs, and describe trends
7. Draw conclusions — State whether the hypothesis is supported
8. Evaluate — Identify limitations and suggest improvements

Safety in the Laboratory

Before any practical work:

• Wear protective equipment (goggles, lab coat, gloves where needed)
• Handle sharp objects (razor blades, needles) with extreme care
• Know the location of safety equipment (eye wash, fire extinguisher)
• Handle chemicals with care—some stains (like safranin) and reagents are hazardous
• Never eat or drink in the laboratory

Aim

To investigate the movement of water through xylem tissue.

Materials

• Young bean seedlings or leafy shoots
• Potassium permanganate (KMnO₄) solution or eosin dye
• Razor blade
• Light microscope
• Microscope slides and coverslips
• Safranin stain
• Watch glass, petri dish, white tile

Procedure

1. Cut a fresh shoot of a young bean plant underwater (to prevent air bubbles entering the xylem).
2. Immediately place the cut end in dilute KMnO₄ or eosin solution.
3. Wait 10–15 minutes. Observe the movement of the colored solution up the stem.
4. Using a razor blade, cut thin transverse sections (TS) from different heights: near the base, middle, and top.
5. Mount each section on a slide, stain with safranin, and cover with a coverslip.
6. Observe under low power first, then higher magnification.

Expected Observations

• The dye moves upward through the vascular bundles
• Only xylem vessels appear stained (red with safranin)
• The stain reaches higher in younger, thinner stems

Analysis

The xylem tissue transports water and minerals because:

• Vessel elements and tracheids are dead cells at maturity
• They have lignified walls that prevent collapse
• Capillary action and transpiration pull drive upward movement

Aim

To identify and compare xylem and phloem tissues in monocot and dicot stems.

Materials

• Young maize (monocot) and bean (dicot) plants
• Sharp razor blade
• Microscope, slides, coverslips
• Safranin stain
• White tile, dropper

Procedure

1. Collect whole young maize and bean plants with roots intact.
2. Cut thin transverse sections of:
   • Young stem of maize
   • Young stem of bean
   • Young root of maize
   • Young root of bean
3. Stain sections with safranin (this stains lignified xylem red).
4. Mount and observe under the microscope.
5. Draw labeled diagrams of each section.

Key Observations

Aim

To examine and identify the formed elements of blood.

Materials

• Mammalian blood sample (from a local butcher—obtain ethically)
• Microscope, slides, coverslips
• Leishman's stain or Wright's stain
• Distilled water
• Capillary tubes

Procedure

1. Place a small drop of blood on a clean slide.
2. Use another slide to make a thin smear—hold the second slide at 45° and draw it backward to spread the blood.
3. Allow the smear to air dry.
4. Cover the smear with Leishman's stain for 2 minutes.
5. Add equal volume of distilled water and wait 3–5 minutes.
6. Wash gently with water and dry.
7. Observe under oil immersion (100× objective).

Expected Observations

• Red blood cells (erythrocytes): Biconcave discs, pink/orange (no nucleus in mammals)
• White blood cells (leukocytes): Larger, stained purple/blue, nucleated
• Platelets (thrombocytes): Small purple fragments

Aim

To examine the structure of a mammalian heart and trace the path of blood.

Materials

• Sheep or goat heart (obtain from local slaughterhouse)
• Dissecting board, dissecting instruments
• Scissors, forceps
• Container with water

Procedure

1. Obtain a fresh heart and rinse thoroughly to remove blood clots.
2. Identify the external features: atria, ventricles, aorta, pulmonary artery, superior and inferior vena cava.
3. Locate the coronary arteries on the surface.
4. Carefully cut along the right side of the heart (from pulmonary artery to apex) to open the right atrium and ventricle.
5. Identify the tricuspid valve between atrium and ventricle.
6. Repeat on the left side to see the bicuspid (mitral) valve.
7. Trace the path of blood:
   • Vena cava → Right atrium → Tricuspid valve → Right ventricle → Pulmonary artery
   • Pulmonary veins → Left atrium → Bicuspid valve → Left ventricle → Aorta

Key Points to Record

• The left ventricle has thicker walls than the right ventricle (systemic circulation requires higher pressure)
• Valves prevent backflow of blood
• The heart is a double pump: right side pumps to lungs, left side pumps to body

Aim

To observe and identify the stages of mitosis in onion root tips.

Materials

• Onion bulbs
• Small jars, water
• Acetic alcohol fixative (glacial acetic acid : ethanol = 1:3)
• Hydrochloric acid (1M)
• Aceto-orcein stain (or Feulgen stain)
• Microscope, slides, coverslips
• Razor blade, forceps

Procedure

1. Germinate onion bulbs by placing them in water over a jar (roots grow in 3–5 days).
2. Cut root tips (about 1 cm) and place in fixative for 2–24 hours.
3. Transfer to 1M HCl and warm in a water bath (60°C) for 5 minutes—this softens the tissue.
4. Stain with aceto-orcein for 5–10 minutes.
5. Place a root tip on a slide, add a drop of stain, and cover with a coverslip.
6. Gently squash the root tip with your thumb (or tap with a pencil).
7. Observe under the microscope, first at low power, then higher magnification.

Identification of Stages

• Interphase: Chromatin network, nuclear membrane intact, nucleolus visible
• Prophase: Chromosomes condensing, becoming visible
• Metaphase: Chromosomes align at the equator (metaphase plate)
• Anaphase: Chromatids separate and move to opposite poles
• Telophase: Two sets of chromosomes reach poles, nuclear membrane reforms
• Cytokinesis: Cell plate forms in plant cells (cell wall develops)

Aim

To measure and graph growth in plants and identify growth patterns.

Materials

• Bean or maize seedlings
• Ruler (mm)
• Graph paper
• Labels, markers

Procedure

1. Plant seeds in pots or soil cups.
2. Measure stem height from soil level to the tip of the main shoot.
3. Record measurements daily for 2–3 weeks.
4. Plot a graph of height (mm) against time (days).
5. Identify the growth pattern from the shape of the curve.

Expected Results

The graph typically shows a sigmoid (S-shaped) curve:

• Lag phase: Initial slow growth as the seed germinates
• Log (exponential) phase: Rapid cell division and elongation
• Plateau phase: Growth slows as the plant matures

Aim

To examine pollen grain structure and germination.

Materials

• Fresh flowers (such as hibiscus or sunflower)
• Microscope, slides, coverslips
• Sucrose solution (10%)
• Boric acid (0.01%)
• Stains (cotton blue or aceto-orcein)

Procedure

1. Collect fresh anthers from a flower.
2. Gently crush an anther on a slide to release pollen grains.
3. Add a drop of sucrose solution (provides nutrients for germination).
4. Add a drop of stain and cover with a coverslip.
5. Observe under the microscope.
6. To observe germination, place a drop of pollen-rich solution on a slide with sucrose-boric acid medium, cover, and leave for 2–4 hours.
7. Observe again—look for pollen tube emergence.

Observations

• Pollen grains are spherical with sculptured outer wall (exine)
• The exine has apertures (pores or furrows) where the pollen tube emerges
• In germinated pollen, you should see the tube nucleus leading the pollen tube

Aim

To observe meiotic stages in plant reproductive tissue.

Materials

• Fresh flower buds (young anthers are best)
• Acetic alcohol fixative
• Acetoorcein stain
• Microscope, slides, coverslips
• Razor blade

Procedure

1. Collect flower buds of different sizes (different stages of meiosis).
2. Fix anthers in acetic alcohol for at least 2 hours.
3. Place an anther on a slide, add stain, and squash gently.
4. Observe under high power (40× or 100×).

Key Stages to Identify

• Prophase I: Homologous chromosomes pair, crossing over may be visible
• Metaphase I: Paired homologous chromosomes at the equator
• Anaphase I: Whole chromosomes (not chromatids) separate to poles
• Telophase I: Two cells form (but chromosomes still have two chromatids)
• Prophase II, Metaphase II, Anaphase II, Telophase II: Similar to mitosis, producing four haploid cells

A good laboratory report should include:

1. Title — Clear statement of the investigation
2. Objective/Aim — What you intended to find out
3. Hypothesis — Your prediction
4. Materials — List all equipment and reagents
5. Method/Procedure — Numbered steps in past tense
6. Results — Tables, graphs, labeled diagrams
7. Discussion — Explain what the results mean; relate to theory
8. Conclusion — State whether the hypothesis was supported
9. Evaluation — Limitations and improvements

In Tanzania's agricultural sector, understanding plant transportation systems helps farmers diagnose why crops are wilting or not growing well. For example, if a tomato plant is wilting despite adequate watering, a farmer can apply the investigation skills learned here to check whether the xylem vessels are blocked or damaged—perhaps by bacterial wilt disease common in Tanzanian tomato farms. Similarly, knowledge of animal circulation helps veterinarians diagnose heart and blood disorders in livestock, which is valuable for dairy and beef farmers in regions like Morogoro and Kilimanjaro who depend on healthy animals for their livelihoods.