Biology 2009 Jamb Examination

The content of the part labelled III (the stomach) is acidic due to gastric juices, particularly hydrochloric acid. This acidity helps denature proteins and activates pepsinogen into pepsin for protein digestion.

It also provides defense against pathogens and ensures enzymes function properly, making the stomach an acidic environment essential for efficient digestion.

In a tolerance curve, the zones of physiological stress are areas close to the limits where organisms survive but poorly. These are usually at the edges of the curve (zones I and III).

The optimum zone is at the center (II), where organisms thrive best. Therefore, the stress zones are at the margins, represented by I and III.

Zone II is the area representing the growth zone. And it starts from 25^oC and attains maximum temperature at the peak which is 50^oC.

The structure labelled X (scolex of a tapeworm) is used for attachment to the host. It contains hooks or suckers that anchor the parasite to the intestinal wall.

This is essential for survival in the host because it prevents dislodgement and allows continuous access to nutrients.

The organism shown is a tapeworm, and its natural habitat is the small intestine of large vertebrates, where it attaches and absorbs pre-digested nutrients.

Other options such as streams, forests, or the stomach do not provide the correct specialized environment that matches its adaptation.

The stamen serves as the male reproductive structure in flowering plants.

It is made up of an anther, where pollen is produced, and usually a slender filament that supplies water and nutrients to the anther while also holding it in a position that supports efficient pollen release.

The structure of the flower shown in the diagram suggests bright petals and well-developed reproductive organs, which are typical adaptations for insect pollination. Such flowers are often scented and attractive to pollinators.

Unlike wind-pollinated flowers, which are usually small and inconspicuous, insect-pollinated flowers invest in color and nectar to attract insects. Therefore, the likely pollinating agent is insects.

The diagram shows a condition where light rays are focused behind the retina, which indicates hypermetropia (long-sightedness). This defect makes it difficult to see nearby objects clearly, though distant objects may still be visible.\n\nHypermetropia results from either a short eyeball or insufficiently curved lens. It is corrected by using convex (converging) lenses to bring the image onto the retina.

For hypermetropia, a convex (converging) lens is used to bend light rays inwards before they enter the eye. This adjustment ensures that the rays meet correctly on the retina instead of behind it.\n\nBy converging incoming rays, the corrective lens compensates for the shortened eyeball or reduced lens curvature, thereby restoring clear near vision.

Chewing the cud is a characteristic feature of ruminants, such as cattle, goats, and sheep. These animals have a complex stomach with multiple chambers, allowing partial digestion of plant material before regurgitating and rechewing it.\n\nThis process increases surface area for microbial breakdown, enhancing nutrient absorption from fibrous plant matter. It is a special adaptation to efficiently digest cellulose-rich diets.