Biology 2024 Jamb Examination

Organic evolution refers to the gradual changes in living organisms over successive generations, leading to the development of new species and variations. It is driven by processes like natural selection, mutation, genetic drift, and adaptation. Human evolution is a subset of organic evolution, while physical and chemical evolution relate to non-living systems.

The cross is Rr × rr. Using a Punnett square: Rr produces gametes R and r, while rr produces gametes r and r. Possible offspring are Rr and rr, giving a 1:1 ratio.
Thus, the probability of an offspring being Rr is $\dfrac{1}{2}$. The other half will be rr.

Inbreeding is mating between closely related individuals, which increases the chances of harmful recessive genes pairing up. This can lead to an outbreak of hereditary diseases and genetic disorders. It does not directly cause dwarfism or competition but primarily raises genetic health risks.

Savannas are characterized by frequent wildfires. Thick, corky bark acts as a protective barrier against the intense heat of these fires, allowing the tree to survive. 

The zone labelled II in the diagram corresponds to the littoral zone, which is the shallow part of a body of water close to the shore. It receives sufficient sunlight to support aquatic plants and animals. The supra-tidal zone lies above the high tide line, the pelagic zone is the open water away from the shore, and the benthic zone refers to the bottom of a water body.

Insects exchange gases through a system of air tubes called tracheae. The tracheae open to the outside through small pores called spiracles, allowing oxygen to diffuse directly into body tissues and carbon dioxide to exit. The skin is used in some amphibians, Malpighian tubules are for excretion, and flame cells are excretory structures in flatworms.

During glycolysis, a net yield of 2 ATP molecules is produced per glucose molecule. Although 4 ATP are generated in total, 2 are consumed in the early steps, leaving 2 as the net gain. Therefore, the correct number is 2 molecules of ATP.

The diagram shows the kidneys, ureters, urinary bladder, and urethra, which together form the urinary system. This system is responsible for the removal of waste products from the blood and regulation of water and salt balance. The circulatory, reproductive, and nervous systems have entirely different structures.

Bile is produced in the liver but stored and concentrated in the gall bladder. It plays an important role in the emulsification of fats, aiding digestion. The stomach secretes gastric juice, the pancreas produces pancreatic enzymes, but only the gall bladder stores bile.

Loamy soil is a medium-textured soil that contains a balanced mixture of sand, silt, and clay, along with high organic matter. This makes it fertile, well-drained, and ideal for crop cultivation. Clay is heavy and waterlogged, sandy soil drains too quickly, while humus refers specifically to decayed organic matter rather than a soil type.