Question
Scientists studying ground finches (Geospiza fortis) on the island of Daphne Major in Galapagos found great differences in the shapes of the beaks.
What is the explanation for this variation in beak shape between the birds?
A. Ground finches grow larger beaks if there is competition for food.
B. They belong to different species.
C. They are adapted for different diets.
D. The more a beak is used by a ground finch, the larger it becomes.
▶️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 from Darwin’s studies, illustrating adaptive radiation—where species evolve different traits to exploit different ecological niches.
Let’s examine the options:
A. Incorrect. Beak size is not determined by use or competition during an individual’s life—it’s inherited, not acquired.
B. Not necessarily. While different finch species exist, the question is about the variation in beak shape, which is due to adaptation, not strictly species differences.
C. Correct. The variation in beak shape is an adaptation to different food sources. For example:
- Thicker, stronger beaks are suited for cracking seeds.
- Longer, thinner beaks are better for picking insects.
D. Incorrect. This is a Lamarckian idea, which has been disproven. Traits develop over generations via natural selection, not by use.
Question
Balkan green lizards, Lacerta trilineata, living in mainland Greece eat mostly insects but also small amounts of plants. The same species living on Greek islands (where insects are scarce) show a greater percentage of those physical traits useful for eating plants than the mainland lizards.
What is the biological explanation for these observations?
A. Variation in each lizard population allowed adaptation to occur.
B. Lizards migrated to areas where they were better adapted.
C. Lizards on the islands diverged due to lack of interbreeding with the mainland population.
D. Homologous structures have prevented separate species from evolving.
▶️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 (like lizards on islands vs. those on the mainland), they stop interbreeding. Over time, due to different environmental pressures—such as food availability—natural selection favors traits that are beneficial in each location. On the islands, where insects are scarce, traits that help in eating plants become more common.
This process leads to divergence in physical traits between the populations. Even though they are still the same species, this lack of gene flow allows different traits to evolve in each group, which can eventually lead to speciation.
Option Evaluation:
A. Incorrect – While variation is necessary for natural selection, this option misses the key point: isolation and lack of interbreeding are the driving forces for divergence here.
B. Incorrect – This implies lizards migrated because they were better adapted, which is not how evolution works. Adaptation happens after isolation, not before.
C. Correct – The lack of interbreeding between island and mainland lizards allowed divergent evolution due to different selective pressures (like diet).
D. Incorrect – Homologous structures are similar structures due to shared ancestry, but they don’t prevent evolution or speciation. This choice is unrelated to the question.
Question
What is the reason for antibiotics not damaging human cells?
A. The dose is too small to be harmful.
B. The dose is taken for only a short time.
C. Antibiotics occur naturally in humans.
D. Human metabolism is different from bacterial metabolism.
▶️Answer/Explanation
Answer: D. Human metabolism is different from bacterial metabolism.
Explanation:
Antibiotics are designed to target features that are unique to bacteria, not found in human cells. This is why they can kill or stop the growth of bacteria without harming human cells.
For example, many antibiotics:
- Block cell wall formation — human cells don’t have cell walls, so this doesn’t affect us.
- Interfere with bacterial ribosomes — bacterial ribosomes are structurally different from human ribosomes.
- Target bacterial enzymes — these enzymes are involved in processes humans don’t use or have very different versions of.
Because of these metabolic and structural differences, antibiotics can be selectively toxic: harmful to bacteria, but safe for humans.
Option Evaluation:
A. Incorrect – It’s not about dosage. Even a small dose of a harmful drug would affect human cells if it weren’t selective.
B. Incorrect – Short-term use reduces side effects but does not explain why antibiotics don’t damage human cells.
C. Incorrect – Antibiotics are produced by fungi or bacteria in nature, not humans. They are not “natural” to our bodies.
D. Correct – The key reason is that bacterial metabolism and cell structures are different from human ones, allowing antibiotics to target bacteria without harming us.
Question
Which conditions of temperature and pH are most suitable for coral reef development?
▶️Answer/Explanation
Answer: D
Explanation:
Coral reef development is most successful under the following conditions:
- Warm water temperatures, typically around 23–29°C (so 25°C is ideal in the given options).
- Alkaline (basic) pH, typically around 8.0–8.3, so 7.8 is closer to optimal than 6.8 (which is too acidic and harmful to coral).
Let’s review the options:
| Option | Temperature (°C) | pH | Suitability |
|---|---|---|---|
| A | 18 | 7.8 | Too cold |
| B | 25 | 6.8 | pH too low |
| C | 18 | 6.8 | Both poor |
| D | 25 | 7.8 | Ideal (Correct) |
Question
Describe the distribution of C. montagui and S. balanoides barnacles in Butter Lump Bay.
▶️Answer/Explanation
a. both species present throughout the range
b. C. montagui has small number of individuals «throughout»
OR
C.montagui occupies «mostly» upper shore/intertidal zone
c. S. balanoides «mostly» occupies low tide area
OR
S.balanoides has large number of individuals «throughout»