Biology 2007 Jamb Examination

A. Vibrissae

Giant African rats rely heavily on tactile sense while navigating dark underground burrows. Vibrissae (whiskers) are sensitive hairs that detect vibrations and obstacles, guiding their movement where vision is limited.

C. clay → silt → sand → gravel

Particle size in soils ranges from smallest to largest: clay (fine), silt (medium), sand (coarse), and gravel (largest). This classification is based on soil texture and the ability to retain water.

B. Virus

Bird flu (avian influenza) is caused by influenza viruses, particularly type A. These viruses infect birds and can occasionally cross to humans, causing disease outbreaks.

C. Mistletoe on an orange tree

Mistletoe derives water and nutrients from its host tree while harming it. This is a classic parasitic relationship, unlike commensalism (B, D) or saprophytism (A).

B. Poor development of roots and xylem tissues

Hydrophytes live in water or very moist habitats. Reduced root systems and poorly developed xylem allow buoyancy and efficient water absorption directly from surroundings.

B. 60%

The calculation of water content uses the formula:

\[ \text{% of water} = \dfrac{\text{Wt. of water}}{\text{Wt. soil}} \times 100 \]

Here, weight(Wt) of wet soil = 10g - 5g = 5g (soil + water minus crucible),

weight(Wt) of dry soil = 8g - 5g = 3g,

weight(Wt) of water = 5g - 3g = 2g,

So, \[ \text{% of water} = \dfrac{2}{5} \times 100 = 40\% \]

Correct answer is 40% (option D).

C. Biosphere

The biosphere encompasses all ecosystems on Earth, including all living organisms and their interactions with the abiotic environment. It is the most inclusive ecological level.

D. Tropical rain forest

Nigeria's mangrove swamps are found along the coastal tropical rainforest belt, where tidal waters and high rainfall create suitable habitats.

B. Competition

Biotic factors are living influences in an environment. Competition among organisms for resources like food, space, or mates directly affects population distribution and abundance.

D. Plateau

Plateau State contains highlands and mountainous regions where distinct montane vegetation occurs, unlike the other listed states which are lowland or savanna areas.