1. a) The following table presents a sampled data set obtained from a medical examination conducted during the screening exercise of 103 admitted IJMB students. Use the data to answer the question that follows.
| S/No | Gender | Height (m) | Weight (Kg) | Blood Group | Genotype |
|---|---|---|---|---|---|
| 1 | M | 1.7 | 65 | A | AA |
| 2 | F | 1.45 | 68 | A | AS |
| 3 | M | 1.6 | 73 | O | AA |
| 4 | M | 1.8 | 64 | O | AA |
| 5 | F | 1.8 | 60 | O | AA |
| 6 | M | 1.65 | 65 | AB | AA |
| 7 | M | 1.67 | 65 | B | SS |
| 8 | F | 1.55 | 60 | O | AS |
| 9 | F | 1.6 | 45 | A | AA |
| 10 | F | 1.3 | 48 | O | SS |
i) What is the proportion of the sample to the number of the admitted IJMB students?
ii) If a ballot was cast to obtain the above data set, give the appropriate name for the sampling technique used.
iii) Represent the whole data of Blood group of the students on a pie chart.
iv) If the sample collected is a represented sample of the students admitted, what is the median weight of admitted students?
v) On the basis of gender, represent the data of the Genotype of the students on a bar chart.
vi) Write short notes on experimentation as a method of data collection.
b) Give the most appropriate word(s) or phrases which fill in the blank spaces in the questions below. Write down your answers in the booklet. Spellings of one-word answers must be correct to score.
i) A supportive cell with evenly thickened walls is a ______ cell.
ii) Growth movement in response to touch is called ______.
iii) Primary roots that grow vertically downwards and give off smaller lateral roots are called ______.
iv) An inflorescence in which the pedicels all arise from a common point at the apex of the peduncle is called ______.
v) A carotenoid pigment found in carrot is called ______.
vi) A simple, dry, and usually indehiscent fruit with seed attached to the fruit wall at only one point is called ______.
vii) A plastid that stores starch is called ______.
viii) Spores produced as a result of sexual reproduction in Mucor are called ______.
ix) Special roots found in parasitic vascular plants, which are used for attachment and absorption, are called ______.
x) The general name for vascular seed plants is ______.
2. Write short notes on ALL of the following:
a) Lichens
b) Air pollution
c) Heterospory
d) Asexual reproduction
3. Discuss the economic importance of Bacteria.
4. a) Citing relevant examples, describe three mechanisms of seed/fruit dispersal in angiosperms.
b) What is soil profile?
5. Write explanatory notes on the following:
a) Potato blight
b) Climate change
6. a) Describe the morphological range forms of algae giving NAMED examples.
b) Write short notes on the mitochondria.
BIOLOGY ANSWERS
Question 1
a) i) Proportion of the sample to the number of admitted IJMB students
Sample size = 103; number of admitted IJMB students = 103.
Proportion = 103/103 = 1 (i.e., the sample represents 100% of the admitted students).
ii) Sampling technique
Simple Random Sampling (Lottery/Ballot Method).
iii) Pie chart of Blood Group
Steps: Determine the frequency of each blood group (A, B, AB, O) in the full data set of 103 students. For each group, calculate:
Angle = (Frequency of group ÷ 103) × 360°
Draw a circle and use a protractor to mark out each sector according to its calculated angle, labeling each sector with its blood group and percentage.
iv) Median weight
Steps: Arrange all 103 weight values in ascending order. Since n = 103 (odd), the median is the value at position:
(n + 1)/2 = (103 + 1)/2 = 52nd value
The median weight is the weight value occupying the 52nd position in the ordered data set.
v) Bar chart of Genotype by Gender
Steps: Separate the data into Male and Female groups. Within each group, count the frequency of each genotype (AA, AS, SS). Plot a grouped (clustered) bar chart with Genotype on the x-axis, Frequency on the y-axis, and paired bars (Male/Female) for each genotype category, using a key/legend to distinguish gender.
vi) Experimentation as a method of data collection
Experimentation is a method of data collection in which one or more variables (independent variables) are deliberately manipulated under controlled conditions to observe their effect on another variable (dependent variable), while all other factors (controlled variables) are kept constant. It typically involves a control group for comparison and a treatment/experimental group. This method establishes cause-and-effect relationships, is repeatable and verifiable, and yields quantitative, objective data. It differs from observational methods, where data is collected without any deliberate manipulation of variables.
b) Fill in the blanks
i) Collenchyma
ii) Thigmotropism
iii) Tap root
iv) Umbel
v) Carotene
vi) Achene
vii) Amyloplast
viii) Zygospores
ix) Haustoria
x) Spermatophytes
Question 2
a) Lichens
Lichens are composite organisms resulting from a symbiotic (mutualistic) association between a fungus (mycobiont) and a photosynthetic partner, either a green alga or a cyanobacterium (photobiont). The fungal component forms the main body (thallus), absorbs water and minerals, and provides protection, while the photobiont manufactures food through photosynthesis and supplies it to the fungus. Lichens are classified by growth form into crustose (flat, crust-like), foliose (leaf-like), and fruticose (shrub-like) types. They colonize bare rock, tree bark, and soil, act as pioneer organisms in ecological succession, and serve as reliable bioindicators of air quality due to their high sensitivity to sulphur dioxide pollution.
b) Air pollution
Air pollution is the contamination of the atmosphere by harmful substances, including gases (carbon monoxide, sulphur dioxide, nitrogen oxides, ozone), particulate matter, and smoke, arising mainly from industrial processes, vehicle emissions, and the burning of fossil fuels. Its effects include respiratory and cardiovascular diseases in humans, damage to plant tissues (chlorosis, necrosis, reduced photosynthesis and yield), formation of acid rain, depletion of the stratospheric ozone layer, and contribution to global warming through the greenhouse effect. Control measures include use of catalytic converters, industrial emission filters, renewable energy adoption, and afforestation.
c) Heterospory
Heterospory is the production of two morphologically distinct types of spores by a single sporophyte plant: microspores, which are small and develop into male gametophytes, and megaspores, which are larger and develop into female gametophytes. It occurs in seed plants (gymnosperms and angiosperms) and in certain pteridophytes such as Selaginella and Marsilea. Heterospory represents an evolutionary advancement over homospory, as it allows for the differentiation of sexes at the gametophyte stage and is considered the evolutionary precursor to the seed habit.
d) Asexual reproduction
Asexual reproduction is a mode of reproduction that does not involve the fusion of gametes, resulting in offspring that are genetically identical to the parent organism (clones). Common methods include binary fission (bacteria, protozoa), budding (yeast, Hydra), spore formation (fungi, mosses, ferns), vegetative propagation (rhizomes, tubers, bulbs, runners), and fragmentation (algae, some invertebrates). It requires only a single parent, is generally rapid, and does not produce genetic variation, which can limit the population's ability to adapt to changing environmental conditions.
Question 3
Economic Importance of Bacteria
Beneficial roles:
- Agriculture: Nitrogen-fixing bacteria such as Rhizobium (in root nodules of leguminous plants) and free-living forms such as Azotobacter and Azospirillum convert atmospheric nitrogen into usable nitrogenous compounds, enriching soil fertility. Decomposer bacteria break down organic matter, recycling nutrients such as carbon, nitrogen, and sulphur back into the ecosystem.
- Food industry: Bacteria are used in fermentation processes, including production of yoghurt and cheese (Lactobacillus, Streptococcus), vinegar (Acetobacter), and pickled/fermented foods.
- Medicine: Certain bacteria (e.g., Streptomyces) are natural sources of antibiotics. Genetically engineered bacteria, particularly Escherichia coli, are used to mass-produce insulin, growth hormones, and vaccines. Probiotic bacteria support gut health.
- Industry: Bacteria are employed in biogas (methane) production, sewage and wastewater treatment, leather tanning, textile retting (e.g., flax processing), and bioremediation of oil spills and other pollutants.
- Biotechnology: Bacteria serve as host organisms and vectors in genetic engineering for the production of enzymes, hormones, and other recombinant proteins.
Harmful effects:
- Bacteria cause numerous diseases in humans, including tuberculosis, cholera, typhoid fever, tetanus, and pneumonia; in animals, such as anthrax and brucellosis; and in plants, such as bacterial wilt, crown gall, and fire blight.
- Certain bacteria cause food spoilage and food poisoning, e.g., Salmonella and Clostridium botulinum.
- Sulphur bacteria contribute to the corrosion of metal pipes and structures, and other bacterial species cause deterioration of stored food and industrial materials.
Question 4
a) Mechanisms of seed/fruit dispersal in angiosperms
-
Wind dispersal (Anemochory): Seeds or fruits possess adaptations such as wings, plumes, or a light weight that enable them to be carried by air currents over long distances. Examples: Tridax and dandelion (feathery pappus), sycamore and maple (winged samara), orchid seeds (extremely light, dust-like).
-
Animal dispersal (Zoochory):
- Epizoochory: Fruits bear hooks, spines, or sticky surfaces that attach to the fur, feathers, or skin of animals for transport, e.g., Xanthium (cocklebur), Desmodium, burdock.
- Endozoochory: Fleshy, brightly coloured, and edible fruits are consumed by animals, and the seeds—protected by a hard seed coat—pass through the digestive tract unharmed and are deposited elsewhere in the animal's droppings, e.g., mango, guava, tomato.
-
Mechanical/Explosive dispersal (Autochory): The fruit dries out and dehisces suddenly, generating tension that ejects the seeds forcefully away from the parent plant. Examples: pea and bean pods (Fabaceae), Impatiens (touch-me-not), Hura crepitans (sandbox tree).
b) Soil profile
A soil profile is a vertical cross-section of soil, from the ground surface down to the underlying parent rock, revealing a series of distinct horizontal layers called soil horizons. These are:
- O horizon: Uppermost layer composed of organic litter (leaves, decomposing plant and animal matter).
- A horizon (Topsoil): Rich in humus and organic matter, dark in colour, and supports the majority of plant root activity and microbial life.
- B horizon (Subsoil): Contains minerals, clay, and nutrients leached down from the A horizon; generally lighter in colour and lower in organic content.
- C horizon: Composed of partially weathered parent rock material, with little biological activity.
- R horizon (Bedrock): The solid, unweathered rock layer underlying the soil profile.
Question 5
a) Potato blight
Potato blight is a destructive plant disease caused by the oomycete (fungus-like organism) Phytophthora infestans. It primarily attacks the leaves, stems, and tubers of potato plants. Symptoms include dark brown to black water-soaked lesions on leaves and stems, a white fungal growth visible on the underside of leaves under humid conditions, and soft, brown rot of the tubers, which can extend into storage. The disease spreads rapidly in cool, moist weather via wind-borne spores and is historically significant as the cause of the Irish Potato Famine of the 1840s. Control measures include planting blight-resistant varieties, applying fungicides (e.g., copper-based sprays such as Bordeaux mixture), practicing crop rotation, ensuring good field drainage and air circulation, and removing and destroying infected plant debris.
b) Climate change
Climate change refers to significant, long-term alterations in global temperature patterns and weather systems. While climate has varied naturally over geological time, current climate change is largely attributed to human activities, particularly the burning of fossil fuels, deforestation, and industrial processes, which release greenhouse gases such as carbon dioxide, methane, and nitrous oxide into the atmosphere. These gases trap heat, intensifying the greenhouse effect and raising global temperatures. Consequences include melting of polar ice caps and glaciers, rising sea levels, increased frequency and severity of extreme weather events (droughts, floods, hurricanes), disruption of ecosystems and loss of biodiversity, and reduced agricultural productivity. Mitigation strategies include reducing fossil fuel consumption, promoting renewable energy sources, reforestation and afforestation programs, and international cooperation through agreements such as the Paris Agreement.
Question 6
a) Morphological range of forms of algae, with named examples
- Unicellular motile forms: Single-celled algae possessing flagella for movement. Example: Chlamydomonas, Euglena.
- Unicellular non-motile forms: Single-celled algae lacking flagella. Example: Chlorella.
- Colonial forms: Groups of individual cells living together in an organized colony, sometimes coordinated by cytoplasmic connections. Example: Volvox, Pandorina.
- Filamentous forms: Cells arranged end-to-end in chain-like filaments; may be unbranched or branched. Examples: Spirogyra and Ulothrix (unbranched); Cladophora (branched).
- Siphonaceous (coenocytic) forms: Multinucleate thallus lacking cross walls (septa) between nuclei. Examples: Vaucheria, Caulerpa.
- Parenchymatous/thalloid forms: Flattened, sheet-like, or complex multicellular thalli with tissue-like differentiation. Examples: Ulva (sea lettuce); large brown algae such as Laminaria (kelp) and Sargassum, which may possess holdfasts, stipes, and blades.
b) The mitochondria
The mitochondrion is a double-membrane-bound organelle located in the cytoplasm of eukaryotic cells, commonly referred to as the "powerhouse of the cell" due to its role in energy production. The outer membrane is smooth, while the inner membrane is folded into finger-like projections called cristae, which increase the surface area available for the enzymes involved in oxidative phosphorylation. The inner matrix contains enzymes of the Krebs (citric acid) cycle, mitochondrial DNA, and ribosomes, enabling the organelle to synthesize some of its own proteins. Mitochondria are the principal site of aerobic respiration, where organic molecules are oxidized to generate adenosine triphosphate (ATP), the primary energy currency of the cell. They are especially abundant in metabolically active cells, such as muscle and liver cells, and are believed, according to the endosymbiotic theory, to have originated from free-living aerobic bacteria that were engulfed by ancestral eukaryotic cells.