2024 - JAMB Biology Past Questions and Answers - page 8

The correct answer is transpiration.* **Transpiration** is the process by which plants release water vapor into the atmosphere, primarily through tiny pores called stomata on their leaves.* **Guttation** is the process of water droplets being released from the edges of leaves, but it's not the primary way plants lose water to the atmosphere.* **Translocation** is the movement of substances (like sugars) within the plant.* **Evaporation** is the process by which water changes from liquid to vapor, but it's a general term and not specific to plants.

The webbed feet of frogs and toads are primarily adapted for swimming. The webbing between the toes increases the surface area of the feet, allowing the animal to propel itself through the water more effectively.

The common component of both blood and lymph is plasma. * **Plasma:** The fluid component of blood and lymph, responsible for transporting cells and other substances. * **Fats:** Are transported in the blood, but not a primary component. * **Red blood cells:** Primarily found in blood. * **White blood cells:** Primarily found in blood.

Countershading is a form of camouflage where an animal's coloration changes to create the appearance of a flat surface, helping it blend into its environment and remain unnoticed. This is an adaptive coloration strategy.

The formation of cilia and flagella in living cells is facilitated by centrioles. Centrioles are involved in cell division and the organization of the cytoskeleton, which includes the structures of cilia and flagella.

A dominant trait is always expressed, even if only one copy of the dominant allele is present.

The theory of natural selection, a core concept in evolutionary biology, is best explained by option C. Here's why:* **Natural selection** is the process where organisms with traits better suited to their environment tend to survive and reproduce more successfully.* **Option C, "The weaker offspring are eliminated,"** directly reflects this principle. Individuals with less advantageous traits are less likely to survive and pass on their genes, leading to a shift in the characteristics of a population over time.Let's look at why the other options are incorrect:* **A. There is no struggle for existence:** This is the opposite of what the theory suggests. Natural selection is driven by competition for resources, survival, and reproduction, creating a "struggle for existence."* **B. New species get better adaptation:** While adaptation is a result of natural selection, this statement does not fully explain the theory's core mechanism, which is the selective elimination of less fit individuals.* **D. Unused structures disappear later:** This describes the theory of "use and disuse," which is associated with Lamarckian evolution and not natural selection.

Cross-pollination involves the transfer of pollen from one plant to the stigma of a different plant. This process promotes genetic diversity, as the offspring inherit genes from two different parent plants. This genetic variation can lead to healthier offspring, viable seeds, and the potential for new varieties with improved traits. Self-pollination, wind pollination, and insect pollination don't necessarily lead to such significant genetic variations.

* **Haemoglobin** is the protein molecule in red blood cells (erythrocytes) that is responsible for carrying oxygen.* **Plasma** is the liquid portion of blood and does not directly carry oxygen.* **Oxyhaemoglobin** is the form of haemoglobin when it is bound to oxygen. Although it carries oxygen, haemoglobin itself is the pigment.* **Erythrocytes** are red blood cells, which contain haemoglobin, but they are not the pigment itself.

Rhizoids are root-like structures found in non-vascular plants like liverworts.* They function to anchor the plant to the substrate and absorb water and nutrients.* Liverworts have unicellular and unbranched rhizoids.