**1. a)** The following table presents data obtained from an experiment to determine the amount of biodiesel produced (ml/g of biomass) from the microalga *Scenedesmus* cultured under varying nitrogen concentration. Each treatment was replicated ten (10) times.
| Replication | 0 | 0.73 × 10⁻³ | 1.47 × 10⁻³ | 2.20 × 10⁻³ | 2.94 × 10⁻³ |
|---|---|---|---|---|---|
| 1 | 0.82 | 1.56 | 3.65 | 5.55 | 2.65 |
| 2 | 0.75 | 0.97 | 4.11 | 5.99 | 2.88 |
| 3 | 0.72 | 1.77 | 3.99 | 6.11 | 2.99 |
| 4 | 0.45 | 1.61 | 3.56 | 6.55 | 3.11 |
| 5 | 0.46 | 1.58 | 3.77 | 6.67 | 2.75 |
| 6 | 0.35 | 1.77 | 3.89 | 6.21 | 2.85 |
| 7 | 0.67 | 1.78 | 3.66 | 5.11 | 2.91 |
| 8 | 0.55 | 1.99 | 3.45 | 6.57 | 2.31 |
| 9 | 0.72 | 1.89 | 3.83 | 6.67 | 2.22 |
| 10 | 0.85 | 1.55 | 3.91 | 6.33 | 2.45 |
*Nitrogen Concentration in growth media (mg/L)*
Use the data in the table above to answer questions i to viii:
**i.** What is the range of the volume of biodiesel produced from each treatment (concentration of nitrogen)? — **6mks**
**ii.** What is the arithmetic mean volume of biodiesel produced from each treatment? — **6mks**
**iii.** Present the mean biodiesel produced from the treatments on a bar chart — **8mks**
**iv.** Define and calculate the median volume of biodiesel produced by each treatment? — **6mks**
**v.** Based on the outcome of this experiment, what nitrogen concentration will you recommend for the commercial culture of *Scenedesmus* for biodiesel production and why? — **2mks**
**vi.** Calculate the variance of the volume of biodiesel produced by the 2.94 × 10⁻³ treatment — **4mks**
**vii.** Calculate the standard deviation of the volume of biodiesel produced by the 2.94 × 10⁻³ treatment — **2mks**
**viii.** Calculate the standard error of the volume of biodiesel produced by the 2.94 × 10⁻³ treatment — **2mks**
---
## IMAGE 2
**2025 IJMBE BIOLOGY 1 contd.**
**b)** Write explanatory notes on the following statistical terms:
- i. Continuous variables — **1mk**
- ii. Methods of data collection — **2mks**
- iii. Pie Chart — **2mks** (approximated)
---
**2.** Answer the following questions by providing the most appropriate response in the blank spaces. Write down your answers in the answer booklet. Spelling of single word answers and scientific terms must be correct to score. **(20mks)**
- i. The seedless vascular plants are generally referred to as ___________
- ii. A plastid that stores starch is called ___________
- iii. The arrangement of the calyx and corolla in the floral bud is known as ___________
- iv. ___________ refers to the type of reproduction in algae in which the male and female gametes are morphologically identical
- v. The spores produced in ascomycotina are called ___________
- vi. Rod shaped bacteria are called ___________
- vii. The structure responsible for the absorption of water and nutrients in bryophytes is called ___________
- viii. The extinct class of the pteridophyta is called ___________
- ix. Organisms lacking membrane bound organelles in their cells are referred to as ___________
- x. The entire mass of hyphae in fungi is termed ___________
---
**3.** Give a brief explanation to the following terms:
- i. Synecology — **(5mks)**
- ii. Halophytes — **(5mks)**
- iii. Biological control — **(5mks)**
- iv. Pollution — **(5mks)**
---
**4.**
- a. In a **TABULAR FORM**, present the differences between the viruses and bacteria — **12mks**
- b. Write short notes on the types and range forms of lichens — **8mks**
---
**5.**
- a. What is photosynthesis? — **5mks**
- b. Write concise notes on vascular tissues — **15mks**
---
**6.** Write explanatory note on:
- a. Angiosperms — **10mks**
- b. Alternation of generation — **10mks**
---
Full Answers
# QUESTION 1 — Statistical Analysis of Biodiesel Data
## Data Table (Organized)
| Rep | 0 | 0.73×10⁻³ | 1.47×10⁻³ | 2.20×10⁻³ | 2.94×10⁻³ |
|---|---|---|---|---|---|
| 1 | 0.82 | 1.56 | 3.65 | 5.55 | 2.65 |
| 2 | 0.75 | 0.97 | 4.11 | 5.99 | 2.88 |
| 3 | 0.72 | 1.77 | 3.99 | 6.11 | 2.99 |
| 4 | 0.45 | 1.61 | 3.56 | 6.55 | 3.11 |
| 5 | 0.46 | 1.58 | 3.77 | 6.67 | 2.75 |
| 6 | 0.35 | 1.77 | 3.89 | 6.21 | 2.85 |
| 7 | 0.67 | 1.78 | 3.66 | 5.11 | 2.91 |
| 8 | 0.55 | 1.99 | 3.45 | 6.57 | 2.31 |
| 9 | 0.72 | 1.89 | 3.83 | 6.67 | 2.22 |
| 10 | 0.85 | 1.55 | 3.91 | 6.33 | 2.45 |
---
## (i) Range = Maximum − Minimum
**Formula: Range = Maximum value − Minimum value**
| Treatment | Max | Min | Range |
|---|---|---|---|
| 0 | 0.85 | 0.35 | **0.50** |
| 0.73×10⁻³ | 1.99 | 0.97 | **1.02** |
| 1.47×10⁻³ | 4.11 | 3.45 | **0.66** |
| 2.20×10⁻³ | 6.67 | 5.11 | **1.56** |
| 2.94×10⁻³ | 3.11 | 2.22 | **0.89** |
---
## (ii) Arithmetic Mean = Σx / n
**Formula: x̄ = Σx / n (where n = 10)**
**Treatment 0:**
Σx = 0.82+0.75+0.72+0.45+0.46+0.35+0.67+0.55+0.72+0.85 = **6.34**
x̄ = 6.34/10 = **0.634 ml/g**
**Treatment 0.73×10⁻³:**
Σx = 1.56+0.97+1.77+1.61+1.58+1.77+1.78+1.99+1.89+1.55 = **16.47**
x̄ = 16.47/10 = **1.647 ml/g**
**Treatment 1.47×10⁻³:**
Σx = 3.65+4.11+3.99+3.56+3.77+3.89+3.66+3.45+3.83+3.91 = **37.82**
x̄ = 37.82/10 = **3.782 ml/g**
**Treatment 2.20×10⁻³:**
Σx = 5.55+5.99+6.11+6.55+6.67+6.21+5.11+6.57+6.67+6.33 = **61.76**
x̄ = 61.76/10 = **6.176 ml/g**
**Treatment 2.94×10⁻³:**
Σx = 2.65+2.88+2.99+3.11+2.75+2.85+2.91+2.31+2.22+2.45 = **27.12**
x̄ = 27.12/10 = **2.712 ml/g**
---
## (iii) Bar Chart — Mean Biodiesel Production
```
Mean Biodiesel Production (ml/g) per Nitrogen Treatment
7.0 |
6.5 | ████
6.0 | ████
5.5 | ████
5.0 | ████
4.5 | ████
4.0 | ████ ████
3.5 | ████ ████ ████
3.0 | ████ ████ ████
2.5 | ████ ████ ████ ████
2.0 | ████ ████ ████ ████ ████
1.5 | ████ ████ ████ ████ ████
1.0 | ████ ████ ████ ████ ████
0.5 |████ ████ ████ ████ ████ ████
|__________________________________
0 0.73 1.47 2.20 2.94
Nitrogen Concentration (×10⁻³ mg/L)
Means: 0.634 | 1.647 | 3.782 | 6.176 | 2.712
```
> **Note:** Draw this as a proper bar chart in your answer booklet with clearly labeled axes, title, and uniform bars.
---
## (iv) Median
**Formula:** Arrange values in ascending order. For n=10 (even):
**Median = (5th value + 6th value) / 2**
**Treatment 0:**
Arranged: 0.35, 0.45, 0.46, 0.55, **0.67, 0.72**, 0.72, 0.75, 0.82, 0.85
Median = (0.67 + 0.72)/2 = **0.695 ml/g**
**Treatment 0.73×10⁻³:**
Arranged: 0.97, 1.55, 1.56, 1.58, **1.61, 1.77**, 1.77, 1.78, 1.89, 1.99
Median = (1.61 + 1.77)/2 = **1.690 ml/g**
**Treatment 1.47×10⁻³:**
Arranged: 3.45, 3.56, 3.65, 3.66, **3.77, 3.83**, 3.89, 3.91, 3.99, 4.11
Median = (3.77 + 3.83)/2 = **3.800 ml/g**
**Treatment 2.20×10⁻³:**
Arranged: 5.11, 5.55, 5.99, 6.11, **6.21, 6.33**, 6.55, 6.57, 6.67, 6.67
Median = (6.21 + 6.33)/2 = **6.270 ml/g**
**Treatment 2.94×10⁻³:**
Arranged: 2.22, 2.31, 2.45, 2.65, **2.75, 2.85**, 2.88, 2.91, 2.99, 3.11
Median = (2.75 + 2.85)/2 = **2.800 ml/g**
---
## (v) Recommended Nitrogen Concentration
**Recommended concentration: 2.20 × 10⁻³ mg/L**
**Reason:** This treatment produced the highest mean biodiesel yield of **6.176 ml/g of biomass**, which is significantly greater than all other concentrations. It also had the highest median (6.270). Therefore, for commercial culture of *Scenedesmus*, 2.20 × 10⁻³ mg/L nitrogen gives optimal biodiesel productivity.
---
## (vi) Variance of 2.94 × 10⁻³ Treatment
**Formula: s² = Σ(x − x̄)² / (n − 1)**
**Mean (x̄) = 2.712**
| x | x − x̄ | (x − x̄)² |
|---|---|---|
| 2.65 | −0.062 | 0.003844 |
| 2.88 | +0.168 | 0.028224 |
| 2.99 | +0.278 | 0.077284 |
| 3.11 | +0.398 | 0.158404 |
| 2.75 | +0.038 | 0.001444 |
| 2.85 | +0.138 | 0.019044 |
| 2.91 | +0.198 | 0.039204 |
| 2.31 | −0.402 | 0.161604 |
| 2.22 | −0.492 | 0.242064 |
| 2.45 | −0.262 | 0.068644 |
| **Total** | | **0.799760** |
**s² = 0.799760 / (10−1) = 0.799760 / 9 = 0.0889 ml²/g²**
---
## (vii) Standard Deviation of 2.94 × 10⁻³ Treatment
**Formula: s = √s²**
s = √0.0889 = **0.2981 ml/g ≈ 0.30 ml/g**
---
## (viii) Standard Error of 2.94 × 10⁻³ Treatment
**Formula: SE = s / √n**
SE = 0.2981 / √10 = 0.2981 / 3.1623 = **0.0943 ml/g ≈ 0.094 ml/g**
---
## (b) Statistical Terms
**i. Continuous Variables:**
These are quantitative variables that can take any numerical value within a given range, including decimals and fractions. They are measurable and not restricted to whole numbers. Examples include height, temperature, weight, and the biodiesel volumes in this experiment.
**ii. Methods of Data Collection:**
These are systematic approaches used to gather information for analysis. They include:
- **Observation** — directly watching and recording phenomena
- **Experimentation** — manipulating variables under controlled conditions
- **Interviews/Questionnaires** — gathering data from respondents
- **Secondary sources** — using existing records or literature
**iii. Pie Chart:**
A pie chart is a circular statistical diagram divided into sectors/slices, where each slice represents a category's proportion of the whole. The size of each slice is proportional to the percentage it represents. It is useful for showing relative frequencies or percentages of categorical data.
---
# QUESTION 2 — Fill in the Blanks
| No. | Answer |
|---|---|
| i. | Pteridophytes (Tracheophytes / Ferns) |
| ii. | Amyloplast |
| iii. | Aestivation (Estivation) |
| iv. | Isogamy |
| v. | Ascospores |
| vi. | Bacilli (Bacillus) |
| vii. | Rhizoids |
| viii. | Psilopsida |
| ix. | Prokaryotes |
| x. | Mycelium |
---
# QUESTION 3 — Brief Explanations
**i. Synecology:**
Synecology (also called community ecology) is the branch of ecology that studies the relationships between communities of organisms and their environment. It examines how different species interact with one another and with abiotic factors within an ecosystem, including competition, predation, and symbiosis. It contrasts with autecology, which studies individual species.
**ii. Halophytes:**
Halophytes are plants that are adapted to grow and survive in highly saline (salt-rich) environments such as salt marshes, mangrove swamps, and seashores. They have special physiological and morphological adaptations such as salt glands for excreting excess salt, succulent tissues for water storage, and modified osmotic pressure to absorb water in high-salt conditions. Examples include mangroves (*Rhizophora*) and *Salicornia*.
**iii. Biological Control:**
Biological control is a method of managing pests, weeds, or diseases by using living organisms (natural enemies) such as predators, parasites, or pathogens rather than chemicals. For example, introducing ladybirds to control aphids, or using *Bacillus thuringiensis* to control insect larvae. It is environmentally friendly and sustainable but requires careful management to avoid ecological imbalance.
**iv. Pollution:**
Pollution is the introduction of harmful substances or contaminants (pollutants) into the natural environment — air, water, or soil — causing adverse effects on living organisms and ecosystems. It can be physical (noise, heat), chemical (pesticides, heavy metals), or biological (sewage, pathogens). Sources include industrial activities, agriculture, transportation, and domestic waste. Pollution leads to health problems, biodiversity loss, and ecosystem degradation.
---
# QUESTION 4
## (a) Differences Between Viruses and Bacteria (Tabular Form)
| Feature | Viruses | Bacteria |
|---|---|---|
| **Cell structure** | Non-cellular (acellular) | Unicellular prokaryotes |
| **Size** | Smaller (20–300 nm) | Larger (1–10 µm) |
| **Genetic material** | DNA or RNA (not both) | Both DNA and RNA present |
| **Cell membrane** | Absent | Present |
| **Cell wall** | Absent (have protein coat/capsid) | Present (peptidoglycan) |
| **Reproduction** | Only inside a host cell (obligate intracellular) | Independent binary fission |
| **Metabolism** | No metabolic activity outside host | Have own metabolic machinery |
| **Ribosomes** | Absent | Present (70S type) |
| **Response to antibiotics** | Not affected by antibiotics | Most are sensitive to antibiotics |
| **Examples** | HIV, Influenza, Tobacco Mosaic Virus | *E. coli*, *Staphylococcus*, *Bacillus* |
## (b) Types and Range Forms of Lichens
Lichens are symbiotic organisms formed by a mutualistic association between a fungus (mycobiont) and a photosynthetic partner — either a green alga or cyanobacterium (photobiont). The fungus provides structure and water retention while the alga provides nutrients through photosynthesis.
**Types based on growth form:**
1. **Crustose Lichens** — These form a thin, crust-like layer tightly attached to their substrate (rocks, bark, soil). They cannot be removed without damaging the surface. They are the most common and widespread type. Example: *Lecanora*.
2. **Foliose Lichens** — These are leaf-like and lobed, loosely attached to the substrate and can be peeled off. They have a distinct upper and lower surface. Example: *Parmelia*.
3. **Fruticose Lichens** — These are shrub-like or hair-like, either erect or hanging, and are attached at only one point. They are the most complex structurally. Example: *Usnea* (old man's beard).
4. **Squamulose Lichens** — These form small, scale-like structures (squamules) partially attached to the substrate. They are intermediate between crustose and foliose.
**Ecological Range:** Lichens are pioneer organisms found in extreme environments — arctic tundra, deserts, bare rocks, tree bark, and mountains — making them indicators of air quality since they are highly sensitive to pollution.
---
# QUESTION 5
## (a) What is Photosynthesis?
Photosynthesis is the biological process by which green plants, algae, and some bacteria use light energy (from the sun), carbon dioxide (CO₂) from the atmosphere, and water (H₂O) from the soil to synthesize organic food (glucose) and release oxygen as a by-product.
**Overall equation:**
**6CO₂ + 6H₂O + Light energy → C₆H₁₂O₆ + 6O₂**
It occurs in two stages:
- **Light-dependent reactions** (in the thylakoid membranes) — water is split, ATP and NADPH are produced, oxygen is released
- **Light-independent reactions / Calvin Cycle** (in the stroma) — CO₂ is fixed into glucose using ATP and NADPH
## (b) Vascular Tissues
Vascular tissues are specialized conducting tissues in plants responsible for the transport of water, minerals, and organic nutrients throughout the plant body. They form the vascular system and are found in pteridophytes, gymnosperms, and angiosperms.
**Two main types:**
**1. Xylem:**
Xylem is responsible for the upward transport of water and dissolved mineral salts from the roots to the leaves (unidirectional). It also provides mechanical support.
- Components: Tracheids, vessel elements, xylem fibres, and xylem parenchyma
- Tracheids and vessels are dead at maturity with thick lignified walls
- Water moves by transpiration pull, root pressure, and capillarity
- Wood is largely composed of secondary xylem
**2. Phloem:**
Phloem transports organic food (sucrose and amino acids) produced during photosynthesis from leaves to other parts of the plant — both upward and downward (bidirectional). This process is called translocation.
- Components: Sieve tube elements, companion cells, phloem fibres, and phloem parenchyma
- Sieve tube elements are alive but lack nuclei; companion cells assist their function
- Movement occurs via pressure-flow (mass flow) mechanism
**Arrangement of Vascular Tissue:**
- In roots: xylem and phloem are arranged alternately in a radial pattern
- In stems: they form vascular bundles (collateral, bicollateral, or concentric)
- Together they form the **stele** (central vascular cylinder)
---
# QUESTION 6
## (a) Angiosperms
Angiosperms (Division Magnoliophyta/Angiospermae) are flowering plants in which the seeds are enclosed within a fruit (developed from the ovary wall). They are the most diverse and dominant group of plants on Earth, with over 250,000 species.
**Key Characteristics:**
- Produce flowers as reproductive structures
- Seeds are enclosed within fruits (hence the name — "angio" = enclosed, "sperm" = seed)
- Have double fertilization: one sperm fertilizes the egg (forming zygote), another fertilizes the polar nuclei (forming endosperm)
- Possess broad leaves with net-like (reticulate) or parallel venation
- Well-developed vascular system (xylem with true vessels)
- Can be herbaceous or woody, annual or perennial
**Two Main Classes:**
1. **Monocotyledons (Monocots)** — one seed leaf (cotyledon), parallel leaf venation, floral parts in multiples of 3. Examples: maize, rice, onion, grasses
2. **Dicotyledons (Dicots)** — two seed leaves, reticulate venation, floral parts in multiples of 4 or 5. Examples: mango, beans, hibiscus
**Importance:**
- Major source of food (cereals, fruits, vegetables)
- Provide timber, medicine, fibre, and ornamental value
- Critical to ecosystem function and pollinator support
---
## (b) Alternation of Generation
Alternation of generation (metagenesis) is the life cycle phenomenon in plants and some algae where two distinct multicellular phases alternate with each other — a **sexual (gametophyte)** phase and an **asexual (sporophyte)** phase.
**The Two Phases:**
**1. Gametophyte Generation (n — haploid):**
- Produces gametes (sex cells) by mitosis
- Is haploid (n chromosomes)
- Fertilization of male and female gametes produces a diploid zygote
- Dominant in bryophytes (mosses)
**2. Sporophyte Generation (2n — diploid):**
- Produces spores by meiosis (in sporangia)
- Is diploid (2n chromosomes)
- Spores germinate to form the gametophyte
- Dominant in pteridophytes, gymnosperms, and angiosperms
**Summary Cycle:**
Gametophyte (n) → gametes (n) → fertilization → Zygote (2n) → Sporophyte (2n) → meiosis → spores (n) → Gametophyte (n)
**Variation Across Plant Groups:**
- **Bryophytes:** Gametophyte dominant; sporophyte dependent on gametophyte
- **Pteridophytes:** Sporophyte dominant; gametophyte small and independent (prothallus)
- **Angiosperms/Gymnosperms:** Sporophyte completely dominant; gametophyte highly reduced and dependent
This alternation ensures genetic variation (through meiosis and fertilization) and is fundamental to plant evolution and reproduction.