**INSTRUCTION:** Answer questions ONE (1) and any THREE (3) other questions. Question ONE carries 40 marks. The others carry 20 marks each. Use clearly labeled diagrams to illustrate your answers wherever appropriate.
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**1.** The following data presents the yield (number of seeds produced per pod) in a newly released variety of cowpea from 10 (ten) samples in a trial experiment. The experiment was designed to investigate the effect of planting density on yield.
Use the information provided on the table to answer i to viii
| Sample No. | Planting Density (number of plants per stand) | | | | |
|---|---|---|---|---|---|
| | 1 | 2 | 3 | 4 | 5 |
| 1 | 07 | 08 | 10 | 07 | 04 |
| 2 | 08 | 08 | 08 | 06 | 03 |
| 3 | 06 | 09 | 11 | 05 | 05 |
| 4 | 07 | 07 | 07 | 06 | 03 |
| 5 | 06 | 07 | 09 | 05 | 05 |
| 6 | 08 | 09 | 09 | 06 | 02 |
| 7 | 07 | 07 | 10 | 07 | 03 |
| 8 | 06 | 08 | 08 | 06 | 04 |
| 9 | 07 | 09 | 07 | 05 | 05 |
| 10 | 08 | 08 | 11 | 05 | 04 |
i. Calculate the mean number of seeds produced from each treatment
ii. Present the means produced in (i) above in a bar chart
iii. Based on the means, what preliminary conclusions can you make on the outcome of the experiment
iv. Calculate the modal yield for each treatment
v. Calculate the median yield for each treatment
vi. Calculate the variance of the best treatment
vii. Calculate the standard deviation of the best treatment
viii. Calculate the standard error of the best treatment
ix. Calculate the range of the worst treatment
**2.** a) What are the similarities between algae and fungi?
b) Give the major diagnostic features of each class of the bryophyta
**3.** Briefly explain the following terms:
i. Heterospory
ii. Ecological succession
iii. Natural selection
iv. Alternation of generations
**4.** i. Enumerate the economic and ecological importance of algae
ii. What are the factors that contributed to the success of the pteridophytes as land plants
**5.** What are the structural advancements exhibited by the gymnosperms over the pteridophytes.
**6.** Citing relevant examples, give the different types of root modification in plants.
---
# COMPLETE SOLUTIONS
## QUESTION 1
### Data Table (for reference):
| Sample | T1 | T2 | T3 | T4 | T5 |
|--------|----|----|----|----|-----|
| 1 | 7 | 8 | 10 | 7 | 4 |
| 2 | 8 | 8 | 8 | 6 | 3 |
| 3 | 6 | 9 | 11 | 5 | 5 |
| 4 | 7 | 7 | 7 | 6 | 3 |
| 5 | 6 | 7 | 9 | 5 | 5 |
| 6 | 8 | 9 | 9 | 6 | 2 |
| 7 | 7 | 7 | 10 | 7 | 3 |
| 8 | 6 | 8 | 8 | 6 | 4 |
| 9 | 7 | 9 | 7 | 5 | 5 |
| 10 | 8 | 8 | 11 | 5 | 4 |
| **Sum** | **70** | **80** | **90** | **58** | **38** |
---
### (i) MEAN for each treatment
**Formula: Mean = Σx / n**
- **Treatment 1:** 70 ÷ 10 = **7.0**
- **Treatment 2:** 80 ÷ 10 = **8.0**
- **Treatment 3:** 90 ÷ 10 = **9.0**
- **Treatment 4:** 58 ÷ 10 = **5.8**
- **Treatment 5:** 38 ÷ 10 = **3.8**
---
### (ii) BAR CHART
```
10 | ████
9 | ████
8 | ████ ████
7 | ████ ████ ████
6 | ████ ████ ████
5 | ████ ████ ████ ████
4 | ████ ████ ████ ████
3 | ████ ████ ████ ████ ████
2 | ████ ████ ████ ████ ████
1 | ████ ████ ████ ████ ████
|----+----+----+----+----+
T1 T2 T3 T4 T5
Mean: 7.0 8.0 9.0 5.8 3.8
```
*(Y-axis = Mean number of seeds; X-axis = Treatment/Planting Density)*
---
### (iii) PRELIMINARY CONCLUSIONS
- Treatment 3 (3 plants per stand) produced the **highest mean yield** (9.0 seeds per pod).
- Yield **increases** from density 1 to density 3, then **decreases** beyond density 3.
- Treatment 5 (5 plants per stand) gave the **lowest mean yield** (3.8), indicating **overcrowding reduces yield**.
- **Conclusion:** There is an **optimal planting density of 3 plants per stand**. Beyond this, competition for nutrients, water, and light reduces yield — confirming that planting density significantly affects cowpea yield.
---
### (iv) MODE for each treatment
(Most frequently occurring value)
- **T1:** 7 appears 4 times → **Mode = 7**
- **T2:** 8 appears 4 times → **Mode = 8**
- **T3:** 9, 10, 11 appear; 9 appears 2×, 10 appears 2×, 11 appears 2× → **Mode = 9, 10, 11 (multimodal)** or no single mode
- **T4:** 5 appears 4 times → **Mode = 5**
- **T5:** 5 appears 3 times, 3 appears 3 times → **Mode = 3 and 5 (bimodal)**
---
### (v) MEDIAN for each treatment
(Arrange in ascending order, find middle value — for n=10, median = average of 5th and 6th values)
**T1 sorted:** 6, 6, 6, 7, **7, 7**, 7, 8, 8, 8
→ Median = (7+7)/2 = **7.0**
**T2 sorted:** 7, 7, 7, 8, **8, 8**, 8, 9, 9, 9
→ Median = (8+8)/2 = **8.0**
**T3 sorted:** 7, 7, 8, 9, **9, 10**, 10, 10, 11, 11
→ Median = (9+10)/2 = **9.5**
**T4 sorted:** 5, 5, 5, 5, **6, 6**, 6, 6, 7, 7
→ Median = (6+6)/2 = **6.0**
**T5 sorted:** 2, 3, 3, 3, **4, 4**, 4, 5, 5, 5
→ Median = (4+4)/2 = **4.0**
---
### (vi) VARIANCE of the Best Treatment (T3 — highest mean = 9.0)
**Formula: Variance (σ²) = Σ(x - x̄)² / n**
| x | x - x̄ | (x - x̄)² |
|---|--------|-----------|
| 10 | +1 | 1 |
| 8 | -1 | 1 |
| 11 | +2 | 4 |
| 7 | -2 | 4 |
| 9 | 0 | 0 |
| 9 | 0 | 0 |
| 10 | +1 | 1 |
| 8 | -1 | 1 |
| 7 | -2 | 4 |
| 11 | +2 | 4 |
| **Σ** | | **20** |
**Variance = 20 / 10 = 2.0**
---
### (vii) STANDARD DEVIATION of the Best Treatment (T3)
**Formula: SD = √Variance**
SD = √2.0 = **1.414**
---
### (viii) STANDARD ERROR of the Best Treatment (T3)
**Formula: SE = SD / √n**
SE = 1.414 / √10 = 1.414 / 3.162 = **0.447**
---
### (ix) RANGE of the Worst Treatment (T5 — lowest mean = 3.8)
**Formula: Range = Maximum − Minimum**
T5 values: 4, 3, 5, 3, 5, 2, 3, 4, 5, 4
- Maximum = 5
- Minimum = 2
**Range = 5 − 2 = 3**
## QUESTION 2
### a) Similarities between Algae and Fungi
1. Both are **non-vascular** (lack xylem and phloem).
2. Both are **non-flowering** and reproduce by **spores**.
3. Both lack true **roots, stems, and leaves** (no true organs).
4. Both are classified under the **Thallophyta** in older classification systems.
5. Both can reproduce **sexually and asexually**.
6. Both are **eukaryotic** organisms.
7. Both can be **unicellular or multicellular**.
8. Both can be found in **moist/aquatic environments**.
---
### b) Major Diagnostic Features of Each Class of Bryophyta
Bryophyta is divided into three classes:
#### 1. Hepaticopsida (Liverworts) — e.g., *Marchantia*
- Body is a **flat, ribbon-like thallus** with dorsiventral symmetry.
- Thallus is **lobed** (liver-shaped).
- Rhizoids are **unicellular** and smooth or tuberculate.
- Sporophyte is **simple** with limited independence.
- No true leaves; some have **leaf-like lobes**.
#### 2. Anthocerotopsida (Hornworts) — e.g., *Anthoceros*
- Thallus is **flat and rosette-shaped**.
- Sporophyte is **horn-like** (elongated, cylindrical), grows continuously from a basal meristem.
- Each cell contains **one large chloroplast** with a pyrenoid.
- Stomata present on the **sporophyte**.
- Rhizoids are **unicellular**.
#### 3. Bryopsida (Mosses) — e.g., *Funaria, Mnium*
- Plant body is **leafy and erect**, with stem-like and leaf-like structures.
- Leaves are **spirally arranged** on the stem.
- Rhizoids are **multicellular** and branched.
- Sporophyte is **well-developed** with a capsule, seta, and foot.
- Protonema stage present in the **life cycle**.
- Distinct **operculum and peristome** in the capsule.
## QUESTION 3 — Brief Explanations
### i. Heterospory
This is the production of **two distinct types of spores** by a plant — **microspores** (small, male) and **megaspores** (large, female). Microspores germinate into male gametophytes and megaspores into female gametophytes. It is seen in pteridophytes like *Selaginella* and *Marsilea* and is considered a forerunner to seed habit.
### ii. Ecological Succession
This is the **gradual and sequential change** in the composition and structure of a plant community over time in a given area. It begins with **pioneer species** colonizing bare/disturbed habitats and ends with a stable **climax community**. It can be **primary** (on bare rock/new land) or **secondary** (on previously inhabited land).
### iii. Natural Selection
This is the process by which **organisms with favorable heritable traits** survive and reproduce more successfully than those without such traits in a given environment. Proposed by **Charles Darwin**, it leads to **adaptation** over generations. Organisms better suited to their environment pass on their genes, causing gradual **evolutionary change**.
### iv. Alternation of Generations
This is the **alternation between a haploid gametophyte generation** (producing gametes by mitosis) and a **diploid sporophyte generation** (producing spores by meiosis) in the life cycle of plants and some algae. The gametophyte is **dominant in bryophytes**, while the sporophyte is **dominant in vascular plants** (pteridophytes, gymnosperms, angiosperms).
## QUESTION 4
### i. Economic and Ecological Importance of Algae
#### Economic Importance:
1. **Food:** Algae like *Spirulina* and *Porphyra* (nori) are consumed directly by humans; *Chlorella* is a protein supplement.
2. **Agar production:** Red algae (*Gelidium*) provide agar used in microbiology culture media and food industry.
3. **Alginates and carrageenan:** Extracted from brown and red algae; used as emulsifiers, stabilizers in ice cream, cosmetics, and pharmaceuticals.
4. **Fertilizers:** Used as organic manure in agriculture, especially in coastal areas.
5. **Biofuel:** Microalgae are a source of **biodiesel** and other biofuels.
6. **Iodine and bromine:** Commercially extracted from marine algae.
7. **Diatomite/Diatomaceous earth:** Fossilized diatom shells used in filtration, insulation, and as abrasives.
#### Ecological Importance:
1. **Oxygen production:** Algae (especially phytoplankton) produce **over 50%** of the world's atmospheric oxygen through photosynthesis.
2. **Primary producers:** Form the **base of aquatic food chains**, supporting zooplankton, fish, and other organisms.
3. **Carbon fixation:** Absorb large amounts of **CO₂**, helping regulate climate.
4. **Nitrogen fixation:** Blue-green algae (*Cyanobacteria*) fix atmospheric nitrogen, enriching soil and water.
5. **Habitat:** Provide shelter and breeding grounds for aquatic organisms.
6. **Bioindicators:** Sensitive to pollution; used to monitor water quality.
---
### ii. Factors That Contributed to the Success of Pteridophytes as Land Plants
1. **Development of true vascular tissue (xylem & phloem):** Allowed efficient transport of water, minerals, and food over long distances.
2. **Well-developed roots:** Provided anchorage and efficient water/mineral absorption from soil.
3. **True stems and leaves (megaphylls):** Increased surface area for photosynthesis.
4. **Lignified cell walls:** Provided mechanical support, allowing upright growth on land.
5. **Development of sporangia on leaves (sporophylls):** Ensured efficient spore dispersal on land.
6. **Dominant sporophyte generation:** The independent, photosynthetic sporophyte was better adapted to terrestrial life.
7. **Heterospory in some members:** A step toward seed habit, improving reproductive success on land.
## QUESTION 5
### Structural Advancements of Gymnosperms Over Pteridophytes
1. **Seed production:** Gymnosperms produce **seeds** (naked, on scales), providing the embryo with food reserves and protection — pteridophytes only produce spores.
2. **Pollen grains:** Gymnosperms have **pollen grains** that are wind-carried to the ovule, eliminating dependence on water for fertilization — a major terrestrial adaptation.
3. **Ovules:** Presence of **naked ovules** on megasporophylls, which later develop into seeds.
4. **Well-developed wood (secondary xylem):** Gymnosperms have **true wood** with abundant tracheids, enabling growth into large trees — pteridophytes lack true secondary growth.
5. **Cones (strobili):** Reproductive structures are organized into **cones**, making reproduction more efficient.
6. **Highly reduced gametophyte:** The gametophyte is entirely **dependent on the sporophyte**, which is more advantageous on land.
7. **Deep root systems:** More extensive roots for anchorage and water uptake in dry conditions.
8. **Needle-like leaves with thick cuticle:** Reduce water loss — an adaptation to dry/cold climates absent in pteridophytes.
9. **Siphonogamy:** Pollen tube development allows sperm to reach the egg **without swimming**, unlike pteridophytes which require water.
## QUESTION 6
### Different Types of Root Modification in Plants
Root modifications are adaptations of roots to perform **functions other than absorption and anchorage**.
#### 1. Storage Roots
Roots modified to store food (starch, water):
- **Taproot modifications:** e.g., *Daucus carota* (carrot — conical), *Beta vulgaris* (beet — napiform), *Raphanus sativus* (radish — fusiform)
- **Tuberous roots:** e.g., *Ipomoea batatas* (sweet potato)
#### 2. Prop Roots (Pillar Roots)
Adventitious roots growing from branches down to the soil for support.
- Example: *Ficus benghalensis* (Banyan tree)
#### 3. Stilt Roots
Adventitious roots arising from the lower nodes of the stem, providing support.
- Example: *Zea mays* (maize), *Pandanus* (screw pine)
#### 4. Pneumatophores (Breathing Roots)
Negatively geotropic roots that grow upward out of waterlogged soil for gaseous exchange.
- Example: *Avicennia*, *Rhizophora* (mangrove plants)
#### 5. Climbing/Clinging Roots (Epiphytic Roots)
Short, adventitious roots that help plants cling to surfaces.
- Example: *Piper betle* (betel vine), *Monstera*
#### 6. Haustorial Roots (Sucking Roots)
Roots of parasitic plants that penetrate host tissues to absorb water and nutrients.
- Example: *Cuscuta* (dodder — total parasite), *Striga* (partial parasite)
#### 7. Nitrogen-Fixing Roots (Nodulated Roots)
Roots with symbiotic nodules containing *Rhizobium* bacteria that fix atmospheric nitrogen.
- Example: *Glycine max* (soybean), *Arachis hypogaea* (groundnut)
#### 8. Assimilatory (Photosynthetic) Roots
Green roots that perform photosynthesis.
- Example: *Tinospora*, some orchids (*Taeniophyllum*)
#### 9. Floating Roots
Spongy roots that help aquatic plants float.
- Example: *Jussiaea* (water primrose)