Question
Variation in a species may lead to the development of a beneficial characteristic. What could cause this variation, and how might it affect the frequency of other alleles associated with this trait?
▶️Answer/Explanation
Answer: A
| Option | Is it a valid cause of genetic variation? | Does it correctly affect allele frequency? |
|---|---|---|
| A | Yes – different allele combos come from meiosis + fertilisation | Yes – beneficial combos = increased frequency |
| B | Yes – sexual reproduction causes variation | Yes – But it’s the process, not the actual cause |
| C | Nope – acquired traits (like gym muscles) aren’t inherited | False effect too |
| D | Mutations may cause variation, but don’t always decrease allele frequencies | Not reliable or true always |
Question
Modified hairs, known as quills, cover the bodies of hedgehogs (*Erinaceus europaeus*) and short-beaked echidnas (*Tachyglossus aculeatus*). However, these structures do not share the same evolutionary origin. What could explain the presence of quills in both species?
A. Both species diverged gradually, but quills were conserved for successful survival.
B. Quills developed in response to similar environmental pressures.
C. Quills are homologous structures that result from adaptation to a similar predator.
D. They developed by adaptive radiation to survive in slightly different habitats.
▶️Answer/Explanation
Answer: B
Explanation:
Quills in hedgehogs and echidnas are analogous structures that evolved independently due to similar selective pressures (e.g., defense against predators).
Question
The graph shows variations in beak size for the bird Geospiza fortis on an island in the Galápagos archipelago.
What evidence from the graph indicates that disruptive selection is occurring?
A. An intermediate beak size is less common.
B. Median beak size is the most common.
C. Smaller beaks are favoured.
D. Larger beaks are favoured.
▶️Answer/Explanation
Answer: A
Explanation:
Disruptive Selection occurs when extreme phenotypes (both small and large beaks, for example) are favored, and intermediate phenotype (medium-sized beaks) is less common or not favored.
From the graph, intermediate beak sizes (medium-sized beaks) are shown to be less common and the frequencies of both smaller and larger beaks are higher, this is evidence of disruptive selection.
Disruptive selection leads to two distinct groups (small and large beaks), with the middle-sized beaks being selected against.
Question
What can lead to reproductive isolation after just one generation?
A. Polyploidy
B. Increased mutation rate
C. Changed allele frequencies
D. Independent assortment of chromosomes
▶️Answer/Explanation
Answer: A
Explanation:
- Polyploidy is when an organism has extra sets of chromosomes (e.g., 3n, 4n instead of 2n).
- It can happen suddenly in one generation, especially in plants.
- Polyploid organisms cannot breed with the original population due to mismatched chromosome numbers.
- This causes instant reproductive isolation, leading to new species formation.
Question
The genetic determination of dogs’ coats can be quite complex, with many different genes acting at the same time.
• The dominant allele E gives brown tones. The recessive allele e results in red tones.
• The colour intensity is due to another gene. The dominant allele B gives a dark colour, whereas the recessive allele b results in a light colour.
What would be the genotype of a light brown dog produced from a cross between a dark brown dog and a light red dog?
A. EEbb
B. EeBb
C. eeBb
D. Eebb
▶️Answer/Explanation
Answer: D
Explanation:
Question
How do the concepts of gradualism and punctuated equilibrium differ?
A. The timing of evolution
B. The mechanism causing evolution
C. The sequence of evolutionary events
D. The reality of evolution
▶️Answer/Explanation
Answer: A.
Explanation:
Gradualism and punctuated equilibrium are two models that describe how evolution occurs over time, and they mainly differ in the rate and timing of evolutionary change.
Gradualism:
- Evolution happens slowly and steadily over long periods.
- Small changes accumulate gradually, leading to new species.
- Fossil records would show smooth transitions.
Punctuated Equilibrium:
- Evolution happens in short, rapid bursts, followed by long periods of stability (little or no change).
- New species appear suddenly in the fossil record.
- Supports the idea of quick change due to sudden environmental shifts or mutations.