Question

Which of the following is associated with founder and bottleneck effect?
A. Stabilizing selection
B. Directional selection
C. Disruptive selection
D. Genetic drift
E. Convergent evolution

Answer 1

The population bottleneck effect, which happens when there is a disaster, is one of the ecological phenomena, reducing a population to a small handful and leaving smaller variations among the surviving individuals. Similarly, the founder effect emerges whenever a new colony of small size and diminished genetic diversity begins with few members of the original population.

Complete answer: Two cases of genetic drift exist:
i. Founder effect- Occasionally one or a few people separate and become, at some distance from their place of origin, the founder of a new, isolated population. All of the alleles existing in the source population are not likely to be present in these pioneers. Thus, some alleles from the new population may be lost and others may change in frequency drastically. The founder effect is called this.
ii. Bottleneck effect- Although organisms do not move from place to place, the size of their populations may sometimes be drastically reduced. This can occur as a result of flooding, drought, or any other environmental change. A discrete genetic sample of the original population may constitute the few surviving individuals. The resulting modifications and loss of genetic diversity are known as the bottleneck effect.
Let us look at all the options to get the right answer.
-When the world does not alter, stabilizing selection occurs. Natural selection needs to create change and there is no pressure for well-adapted species to change if an ecosystem does not change. Fossil evidence suggests that many organisms remain unchanged over long geological periods.
-Directional selection happens if the climate changes in a specific way and, thus, organisms are selectively forced to adapt in response to changes in the environment. Industrial Melanism, for instance. The light peppered moth and the dark moth show a phenomenon of industrial melanism. It is an evolutionary mechanism in which darker people triumph over lighter people because natural selection is the product of the industrial revolution. Darkened variants of around 80 species of moths have evolved throughout the United Kingdom at different frequencies over the last 100 years.
-Disruptive selection arises when selection pressure that prefers two opposite characteristics can be created by an environmental change. Grass plants at Welsh copper mines, for instance, Copper-containing contaminated soil is lethal to normal grass plants, but a chance mutation enabled one plant to grow. This plant, but only on the polluted soil, prospered and reproduced. It grew more slowly than usual plants on normal soil and was easily out-competed.
-Genetic drift is a generation-long, spontaneous shift in allele frequencies. Frequencies of unique alleles can change dramatically in small populations by chance alone. Such shifts happen at random, as if frequencies were floating, and are often referred to as genetic drift.
-Convergent evolution is the phenomenon during which, in response to common environmental conditions, species with distinct evolutionary histories acquire similar phenotypic adaptations.
Hence option D, i.e., Genetic drift, then, is the right answer.

Note: Genetic drift, apart from natural selection, does not depend on the beneficial or harmful effects of an allele. Conversely, drift changes allele frequencies purely by chance, as random subsets of individuals (gametes of those individuals) have been collected to develop the next generation. Cases in which a small population is formed from a larger population are the founder effect and the bottleneck effect.