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
Ans. D
These are changes to DNA that can enhance existing traits, create new genes, or code for different proteins. Mutations can be caused by replication errors or by environmental and spontaneous changes to DNA.
This is a normal process that occurs when genetic material is rearranged as a cell prepares to divide.
Mating patterns
When organisms choose to mate with others based on certain traits, it can lead to nonrandom mating and shape the genetic combinations of future generations.
Genetic drift
This is when there are random fluctuations in the number of alleles in a population.
genetic variation in a species can lead to the development of a beneficial characteristic and affect the frequency of other alleles:
Genetic variation can introduce new traits in an organism, and if a trait is advantageous, it’s more likely to be passed on to the next generation. This process is called natural selection.
How it works
Natural selection favors genotypes that are better able to survive and reproduce. This leads to an increase in the frequency of the beneficial allele over time.
Rate of increase
The rate at which a beneficial allele increases in frequency depends on whether it’s dominant or recessive. A new dominant allele will increase rapidly, while a new recessive allele will increase very slowly at first.
Example
The peppered moth in England is a classic example of natural selection. Before industrialization, the light-colored allele was most common, but pollution from new industries stained the trees dark. The dark-colored allele became more common because it allowed the moths to camouflage themselves.
Other factors that can change allele frequencies include genetic drift, mutation, genetic recombination, and gene flow.
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
Ans. B
Quills in hedgehogs and porcupines evolved in response to similar environmental pressures from predators. This is an example of convergent evolution, where unrelated groups of animals develop similar features to adapt to similar environments.
Here are some other details about the quills of hedgehogs and porcupines:
Hedgehog spines are short, stout, and slightly curved. They are designed to bend when loaded axially and absorb mechanical energy, such as when the hedgehog falls from a height.
Porcupine quills
Porcupine quills are long and brittle, and they break easily when bent. They are designed to keep enemies away. When a porcupine’s quills become embedded in a predator, they fall out easily or the porcupine shakes its body to remove them.
Evolution
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
Ans:A
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
Ans:A
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
Ans:D
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
Ans:A