Agricultural Science 2015 Jamb Examination

Adequate sunshine before harvest is important for cotton because it keeps the cotton bolls dry and prevents fungal attacks. When there is too much humidity and insufficient sunshine, the bolls are likely to get mouldy, which reduces both quality and market value. Sunshine helps in drying the lint and ensuring clean, white, and healthy cotton.

This is a monohybrid cross involving a homozygous tall plant (TT) and a homozygous dwarf plant (tt). The gametes from the tall plant are all \( T \), while those from the dwarf plant are all \( t \). Crossing them gives:
\[ TT \times tt \Rightarrow Tt, Tt, Tt, Tt \]
All offspring are heterozygous tall (Tt). Hence, the result is 100% tall.

When two heterozygous tall plants (Tt) from the first filial generation are crossed, the genotypes of the offspring can be determined using a Punnett square.
\[ Tt \times Tt \]
Gametes: T and t from each parent.

Crossing gives:
TT, Tt, Tt, tt.

Therefore, the genotypic ratio is:\[ 1TT : 2Tt : 1tt = 1:2:1 \]
Phenotypically, this gives 3 tall : 1 dwarf, but the question is on genotypic ratio, which is 1:2:1.

Feed utilization in animals follows a natural physiological sequence:

1. Ingestion – the act of taking in food.
2. Digestion – mechanical and chemical breakdown of food into simpler soluble forms.
3. Absorption – soluble nutrients pass into the bloodstream or lymph.
4. Assimilation – absorbed nutrients are used by cells for growth, energy, and repair.

Therefore, the correct sequence is ingestion → digestion → absorption → assimilation.

Taungya farming is a system in which food crops are planted alongside forest trees during the early years of tree establishment. Farmers benefit from cultivating crops, while forest authorities benefit from tree planting and care. Selective exploitation refers to careful harvesting of mature trees, regeneration is the renewal of forest cover, and afforestation is planting trees in areas previously without forests.

Pineapple does not produce viable seeds for commercial purposes. Instead, it is vegetatively propagated. The most common planting material used by farmers is suckers, though crowns and slips can also be used. Suckers grow faster and ensure uniformity and earlier fruiting, which makes them the preferred method.

Plants with fibrous root systems typically belong to the monocot group. Sugarcane is a monocot and has numerous thin roots forming a fibrous system. Cotton, coffee, and cowpea are dicots and have tap root systems. Therefore, sugarcane is the correct example of a fibrous root system.

Grafting is a vegetative propagation method where a part of one plant (scion) is joined to another plant (rootstock) so that they grow as one. It does not involve gametes, nor is it just rooting from stems or transfer of a bud (which is budding). Instead, it is the physical joining of two related plants for desired traits such as disease resistance or improved yield.

Many crop pests are specific to certain host plants. If the same crop is grown continuously, the pest population builds up. By rotating crops, especially with unrelated species, the life cycle of the pest is disrupted because the host plant is unavailable. This reduces their population naturally. Crop rotation also helps soil fertility but its direct role in pest control is breaking pest life cycles.

Ginger is an underground stem crop. It propagates vegetatively using rhizomes, which are horizontal underground stems containing buds that sprout into new plants. Bulbs (like onion), corms (like cocoyam), and seeds are not used in ginger propagation.