IB DP Biology- B4.1 Adaptation to environment - IB Style Questions For SL Paper 1A -FA 2025
▶️ Answer/Explanation
Factors affecting transpiration rate:
- I. Increased CO₂ concentration → Causes stomatal closure, decreasing transpiration
- II. Increased temperature → Increases water vapor pressure gradient, increasing transpiration
- III. Decreased humidity → Increases water vapor pressure gradient between leaf and air, increasing transpiration
Only II and III increase transpiration rate.
✅ Answer: (C)
▶️ Answer/Explanation
Answer: C. They are adapted for different diets.
Explanation:
The image shows two ground finches from the Galápagos Islands with distinctly different beak shapes. This is a classic example of adaptive radiation—a process where species evolve different characteristics to occupy different ecological niches.
Let’s examine the options:
A. Incorrect – Beak size and shape are not determined by use or competition during an individual bird’s lifetime. These traits are inherited and shaped by natural selection over generations.
B. Not necessarily – Although there are multiple finch species, the variation in beak shape here is due to adaptation to different food sources, not simply species distinction.
C. Correct – The differences in beak shape are adaptations for feeding on different types of food. For instance:
• Thicker, stronger beaks help crack hard seeds.
• Longer, thinner beaks are better for feeding on insects.
D. Incorrect – This represents a Lamarckian concept (that traits develop through use), which has been disproven. Evolutionary changes occur via natural selection, not by acquired traits during an organism’s life.
▶️ Answer/Explanation
Answer: C. Lizards on the islands diverged due to lack of interbreeding with the mainland population.
Explanation:
When populations of the same species become geographically isolated (for example, island vs. mainland lizards), they stop interbreeding. Over time, different environmental pressures such as food availability lead to natural selection favoring traits that are more beneficial in each environment.
On the islands, where insects are scarce, lizards with traits that aid in eating plants are more likely to survive and reproduce. This results in gradual divergence between the island and mainland populations.
Because gene flow (interbreeding) between populations is reduced or absent, distinct traits accumulate in each group. This process can eventually lead to speciation if isolation continues.
Option Evaluation:
A. Incorrect – Variation is necessary for adaptation, but this option omits the crucial factor: isolation and lack of interbreeding cause divergence.
B. Incorrect – Evolution does not occur because individuals migrate to areas where they fit better; rather, adaptation happens through natural selection after isolation.
C. Correct – Lack of interbreeding between island and mainland lizard populations allowed divergent evolution in response to different diets and environmental pressures.
D. Incorrect – Homologous structures indicate common ancestry but do not restrict evolution or prevent speciation.