Biology 2006 Jamb Examination

B. Vitamin A

Night blindness is caused by a deficiency of vitamin A, which is needed to form visual pigments in the retina for dim-light vision.

C. Water

The kidney excretes water in urine, the skin excretes water as sweat, and the lungs excrete water vapour. Hence water is common to all three.

C. Relaxation of the diaphragm

When the diaphragm relaxes, the thoracic cavity volume decreases, lung volume reduces, and air pressure increases inside the lungs.

C. Involve the use of chemical substances

The nervous system uses neurotransmitters, while the endocrine system uses hormones. Both rely on chemical messengers.

A. Heart

The pericardial cavity encloses the heart, protecting it with pericardial fluid that reduces friction during contractions.

D. Vertebrarterial canal

Cervical vertebrae are unique because they have a vertebrarterial canal through which the vertebral artery passes.

B. Left auricle

The left auricle (left atrium) of the rabbit’s heart receives oxygenated blood directly from the lungs via the pulmonary veins.

B. Reduction of oxygen by hydrogen

During aerobic respiration, oxygen is reduced by hydrogen atoms from NADH and FADH₂ in the electron transport chain, forming water.

B. Activate the enzymes

Water activates hydrolytic enzymes in seeds, which break down stored food into soluble forms to nourish the embryo during germination.

The pancreas is a mixed gland, meaning it produces both hormones (like insulin and glucagon) and enzymes (like amylase, lipase, and trypsin). 

• Exocrine Function (Enzymes):

  The pancreas's exocrine tissue produces digestive enzymes that are released into the pancreatic duct, which then transports them to the small intestine to aid in digestion. These enzymes include: 
  • Amylase: Breaks down carbohydrates. 
  • Lipase: Breaks down fats. 
  • Protease (trypsin and chymotrypsin): Breaks down proteins. 

• Endocrine Function (Hormones):

  The pancreas's endocrine tissue, specifically the islets of Langerhans, produces hormones that are released directly into the bloodstream. The main hormones produced are: 
  • Insulin: Lowers blood sugar levels. 
  • Glucagon: Raises blood sugar levels.