Questions
1. a) The following table presents a sampled data set obtained from an agricultural survey conducted on 95 farms in a farm settlement. Use the data to answer the questions that follow.
| S/No | Farm Type | Farm Size (Ha) | Yield (Tonnes) | Soil Type | Crop Grown |
|---|---|---|---|---|---|
| 1 | Arable | 2.5 | 8.2 | Loamy | Maize |
| 2 | Mixed | 1.8 | 5.4 | Clay | Cassava |
| 3 | Arable | 3.2 | 9.6 | Loamy | Rice |
| 4 | Plantation | 4.0 | 12.1 | Sandy | Oil Palm |
| 5 | Mixed | 1.5 | 4.8 | Clay | Cassava |
| 6 | Arable | 2.0 | 6.5 | Loamy | Maize |
| 7 | Plantation | 3.8 | 11.0 | Sandy | Oil Palm |
| 8 | Mixed | 1.2 | 3.9 | Clay | Yam |
| 9 | Arable | 2.7 | 7.8 | Loamy | Rice |
| 10 | Mixed | 1.6 | 5.0 | Sandy | Yam |
i. What is the proportion of the sample to the total number of farms in the settlement?
ii. If the farms were selected by writing all farm numbers on paper, folding them, and picking randomly, give the appropriate name for the sampling technique used.
iii. Represent the whole data of Farm Type on a pie chart.
iv. If the sample collected is a representative sample of the farm settlement, what is the median yield of the farms?
v. On the basis of Soil Type, represent the data of Crop Grown on a bar chart.
vi. Write short notes on the survey method of data collection.
b) Give the most appropriate word(s) or phrases which fill in the blank spaces in the questions below. Spellings of one-word answers must be correct to score.
i. A supportive cell with unevenly thickened corners is a ______ cell.
ii. Growth movement in response to gravity is called ______.
iii. Roots that arise from parts of the plant other than the radicle, such as stems or leaves, are called ______.
iv. An inflorescence in which flowers are borne along an elongated, unbranched axis on short stalks is called ______.
v. A green pigment involved in photosynthesis, found in chloroplasts, is called ______.
vi. A dry, dehiscent fruit that splits along one suture to release its seeds is called a ______.
vii. A plastid that gives flowers and fruits their red, orange, or yellow colours is called ______.
viii. Spores produced asexually in sporangia of Mucor are called ______.
ix. Modified leaves found in insectivorous plants, used to trap and digest insects, are called ______.
x. The general name for flowering plants is ______.
2. Write short notes on ALL of the following:
a) Mycorrhiza
b) Water pollution
c) Apomixis
d) Vegetative propagation
3. Discuss the economic importance of Fungi.
4. a) Citing relevant examples, describe three mechanisms of pollination in angiosperms.
b) What is soil erosion?
5. Write explanatory notes on the following:
a) Cocoa black pod disease
b) Desertification
6. a) Describe the morphological range of forms of fungi, giving NAMED examples.
b) Write short notes on the chloroplast.
Answers
Question 1
a) i) Proportion of the sample to the total number of farms
Sample size = 95; total number of farms in the settlement = 95.
Proportion = 95/95 = 1 (i.e., the sample represents 100% of the farms).
ii) Sampling technique
Simple Random Sampling (Lottery/Ballot Method).
iii) Pie chart of Farm Type
Steps: Determine the frequency of each farm type (Arable, Mixed, Plantation) in the full data set of 95 farms. For each type, calculate:
Angle = (Frequency of type ÷ 95) × 360°
Draw a circle and use a protractor to mark out each sector according to its calculated angle, labeling each sector with its farm type and percentage.
iv) Median yield
Steps: Arrange all 95 yield values in ascending order. Since n = 95 (odd), the median is the value at position:
(n + 1)/2 = (95 + 1)/2 = 48th value
The median yield is the value occupying the 48th position in the ordered data set.
v) Bar chart of Crop Grown by Soil Type
Steps: Separate the data into Loamy, Clay, and Sandy soil groups. Within each group, count the frequency of each crop (Maize, Cassava, Rice, Oil Palm, Yam). Plot a grouped (clustered) bar chart with Crop on the x-axis, Frequency on the y-axis, and paired/grouped bars for each soil type category, using a key/legend to distinguish soil type.
vi) Survey method of data collection
The survey method is a technique of data collection that involves systematically gathering information from a defined sample of individuals or units within a population, typically through questionnaires, interviews, or direct observation, without manipulating any variables. It provides a broad overview of characteristics, opinions, or conditions within a population at a given point in time, is relatively cost-effective for covering large populations, and can be conducted once (cross-sectional) or repeated over time (longitudinal). Unlike experimentation, the survey method does not establish cause-and-effect relationships, since no variable is deliberately controlled or manipulated; it simply records existing conditions as they are found.
b) Fill in the blanks
i. Collenchyma
ii. Geotropism (gravitropism)
iii. Adventitious roots
iv. Raceme
v. Chlorophyll
vi. Follicle
vii. Chromoplast
viii. Sporangiospores
ix. Insectivorous (pitcher/trap) leaves
x. Angiosperms
Question 2
a) Mycorrhiza
Mycorrhiza is a symbiotic (mutualistic) association between the roots of a vascular plant and a fungus. The fungal hyphae extend the effective surface area of the root system, greatly enhancing the plant's uptake of water and mineral nutrients, particularly phosphorus, from the soil, while the plant supplies the fungus with carbohydrates produced through photosynthesis. Two main types exist: ectomycorrhizae, where fungal hyphae surround the root surface and penetrate between (but not into) cortical cells, common in forest trees; and endomycorrhizae (arbuscular mycorrhizae), where hyphae penetrate directly into root cortical cells, common in most crop plants. This association improves plant growth, drought resistance, and resistance to some soil pathogens.
b) Water pollution
Water pollution is the contamination of water bodies (rivers, lakes, groundwater, and oceans) by harmful substances, including industrial effluents, agricultural runoff (fertilizers and pesticides), sewage, oil spills, and plastic waste. Its effects include eutrophication (excessive nutrient enrichment causing algal blooms and oxygen depletion), death of aquatic organisms, contamination of drinking water supplies leading to waterborne diseases, and disruption of aquatic ecosystems. Control measures include treatment of industrial and domestic waste before discharge, regulation of agricultural chemical use, proper disposal of plastics, and enforcement of environmental protection laws.
c) Apomixis
Apomixis is a form of asexual reproduction in flowering plants in which seeds are produced without fertilization, so that the resulting offspring are genetically identical to the parent plant. It may occur through the development of an embryo directly from a diploid cell of the ovule (such as the nucellus or integument) without fusion of gametes, bypassing the normal processes of meiosis and fertilization. Apomixis is of agricultural importance because it allows desirable hybrid characteristics to be fixed and propagated through seed indefinitely, without the genetic segregation that would normally occur through sexual reproduction. Examples occur in citrus, mango, and some grasses such as Kentucky bluegrass.
d) Vegetative propagation
Vegetative propagation is a form of asexual reproduction in plants in which new individuals arise from vegetative (non-reproductive) parts of the parent plant, such as stems, roots, or leaves, without the involvement of seeds or spores. Natural methods include propagation by rhizomes (ginger), tubers (potato), bulbs (onion), corms (cocoyam), runners (strawberry), and suckers (banana). Artificial methods used by farmers and horticulturists include cutting, grafting, budding, and layering. This method produces offspring genetically identical to the parent (clones), allows rapid multiplication of desirable varieties, and is faster than propagation from seed, though it does not generate genetic variation.
Question 3
Economic Importance of Fungi
Beneficial roles:
- Food industry: Yeasts (Saccharomyces cerevisiae) are used in baking (leavening bread) and brewing (fermenting alcohol). Certain fungi, such as Penicillium species, are used to ripen and flavour cheeses (e.g., Roquefort, Camembert). Edible mushrooms (e.g., Agaricus) are cultivated and consumed as food, valued for their protein content.
- Medicine: Penicillium notatum is the natural source of the antibiotic penicillin. Other fungi produce important pharmaceutical compounds, including statins (cholesterol-lowering drugs) and immunosuppressants used in organ transplantation.
- Agriculture: Mycorrhizal fungi improve nutrient and water uptake in crop plants. Certain fungi are used as biological control agents against insect pests and plant pathogens.
- Industry: Fungi are used in the production of citric acid, enzymes (e.g., amylase, protease used in detergents and food processing), and in the fermentation industry generally.
- Decomposition: Saprophytic fungi break down dead organic matter, recycling nutrients such as carbon and nitrogen back into ecosystems, playing an essential role as decomposers.
Harmful effects:
- Fungi cause numerous plant diseases, including rusts, smuts, and blights, resulting in significant losses of crops such as wheat, maize, and cocoa.
- Certain fungi cause diseases in humans and animals, such as ringworm, athlete's foot, and candidiasis.
- Some fungi produce toxic substances (mycotoxins), such as aflatoxins produced by Aspergillus species on stored groundnuts and grains, which are harmful to humans and livestock if consumed.
- Fungi cause spoilage of stored food, timber, textiles, and other materials through decay.
Question 4
a) Mechanisms of pollination in angiosperms
Wind pollination (Anemophily): Flowers produce large quantities of small, light, smooth pollen grains that are carried by air currents from the anthers to the stigma. Such flowers are typically small, dull-coloured, scentless, and lack nectar, and often have feathery, exposed stigmas to trap airborne pollen. Examples: maize, grasses, and guinea corn.
Insect pollination (Entomophily): Flowers attract insects (bees, butterflies, moths) through bright colours, strong scent, and nectar production; pollen grains are typically larger, sticky, or spiny to adhere to the insect's body and are transferred as the insect moves between flowers. Examples: hibiscus, pumpkin, and citrus flowers.
Animal (bird/bat) pollination (Ornithophily/Chiropterophily): Flowers pollinated by birds (e.g., sunbirds) are typically brightly coloured (often red), odourless, and produce copious dilute nectar held in tubular structures suited to the bird's beak, while flowers pollinated by bats open at night, are pale-coloured, and emit a strong musky scent. Examples: banana flowers (bird-pollinated), baobab flowers (bat-pollinated).
b) Soil erosion
Soil erosion is the process by which the topsoil layer is worn away and removed by natural agents, principally water (through surface runoff) and wind, often accelerated by human activities such as deforestation, overgrazing, and poor farming practices that leave soil exposed and unprotected by vegetation. It results in loss of fertile topsoil and nutrients, reduced agricultural productivity, siltation of rivers and dams, and land degradation. Control measures include afforestation, contour ploughing, terracing on slopes, cover cropping, construction of windbreaks, and maintaining vegetative cover on exposed land.
Question 5
a) Cocoa black pod disease
Cocoa black pod disease is a destructive disease of cocoa caused by the fungus-like oomycete Phytophthora palmivora (and related species). It affects pods, leaves, and stems of the cocoa plant. Symptoms include dark brown to black water-soaked spots on the pods that rapidly enlarge and turn the entire pod black and hard, rendering the beans inside unusable, along with a white fungal growth sometimes visible on infected pod surfaces under humid conditions. The disease spreads rapidly during periods of high humidity and rainfall via wind-borne and rain-splashed spores, and is a major cause of yield loss in cocoa-producing regions. Control measures include regular removal and destruction of infected pods, applying copper-based fungicides, pruning to improve air circulation within the canopy, and planting disease-resistant cocoa varieties.
b) Desertification
Desertification refers to the process by which fertile land progressively becomes degraded and transformed into arid, desert-like conditions, typically occurring in semi-arid regions bordering existing deserts. It is caused mainly by a combination of natural climatic factors (prolonged drought, low and erratic rainfall) and human activities, including overgrazing, deforestation, poor irrigation practices, and unsustainable farming methods that strip the land of vegetation cover. Consequences include loss of arable land and reduced agricultural productivity, displacement of human populations, loss of biodiversity, and increased frequency of dust storms. Mitigation strategies include afforestation and reforestation programs (such as shelterbelt/"green wall" projects), sustainable land-use and grazing management, water conservation and efficient irrigation techniques, and international cooperation to combat land degradation.
Question 6
a) Morphological range of forms of fungi, with named examples
- Unicellular forms: Single-celled fungi that reproduce mainly by budding. Example: Saccharomyces (yeast).
- Filamentous (mycelial) forms: Body composed of thread-like hyphae forming a mycelium; hyphae may be non-septate (coenocytic) or septate. Examples: Rhizopus and Mucor (non-septate, bread moulds); Penicillium and Aspergillus (septate moulds).
- Dimorphic forms: Fungi capable of existing in both a unicellular (yeast-like) form and a filamentous (mould-like) form, depending on environmental conditions. Example: Candida albicans.
- Fleshy/fruiting body forms: Large, complex, multicellular reproductive structures composed of tightly packed hyphae, forming the visible "mushroom" or toadstool. Examples: Agaricus (field mushroom), Ganoderma (bracket fungus).
- Lichenized forms: Fungi existing in a symbiotic association with algae or cyanobacteria, forming a composite thallus. Example: Usnea, Parmelia.
b) The chloroplast
The chloroplast is a double-membrane-bound organelle found in the cells of green plants and algae, serving as the principal site of photosynthesis. The outer membrane is smooth, while the inner membrane encloses a fluid matrix called the stroma, within which is embedded a system of flattened, membranous sacs called thylakoids, stacked into structures known as grana and interconnected by stroma lamellae. The thylakoid membranes contain the green pigment chlorophyll and other accessory pigments, which absorb light energy for the light-dependent reactions of photosynthesis, while the stroma contains the enzymes of the Calvin cycle (light-independent reactions), where carbon dioxide is fixed into glucose. Chloroplasts also contain their own DNA and ribosomes, enabling them to synthesize some of their own proteins, and are believed, according to the endosymbiotic theory, to have originated from free-living photosynthetic cyanobacteria engulfed by ancestral eukaryotic cells.