Natural selection where more individuals acquire a specific character value other than the mean character value, leads to:
- Stabilising change
- Directional change
- Disruptive Change
- Random Change
The Correct Option is B
Solution and Explanation
Natural selection is a process through which species adapt to their environment. It operates on the variation in traits among individuals in a population. When looking into how natural selection can change the distribution of a character value, it's crucial to understand what each type results in:
1. Stabilising Change: This occurs when natural selection favors the mean characteristic value, reducing variation and maintaining the status quo. Individuals with extreme values are eliminated.
2. Directional Change: This form of natural selection occurs when one extreme phenotype is favored over other phenotypes, leading the population mean to shift toward one of the extremes. More individuals in the population acquire a character value other than the current mean.
3. Disruptive Change: In this type of natural selection, extreme values for a trait are favored over intermediate values. This can result in a bimodal distribution of traits within the population.
4. Random Change: This is not a form of natural selection. It generally refers to changes in trait distribution due to random events, such as genetic drift.
Given the context that more individuals acquire a specific character value other than the mean, this suggests a shift towards one of the character extremes.
Therefore, the correct answer is: Directional Change
Top Questions on evolution
- (a) “The process of evolution of different species in a given geographical area starts from a point and literally radiates to other geographical areas.” Explain it with an example.
(b) Cite an example where more than one adaptive radiation has occurred in an isolated geographical area. Name the type of evolution your example depicts. - (a) "The process of evolution of different species in a given geographical area starts from a point and literally radiates to other geographical areas." Explain it with an example.
(b) Cite an example where more than one adaptive radiation has occurred in an isolated geographical area. Name the type of evolution your example depicts. - A few stages and their respective time period in the evolutionary history of human beings are mentioned in the flowchart given below:
- 15 mya — Primates walking like gorillas and chimpanzees existed.
- 3–4 mya — Man-like primates walked in Eastern Africa. Fossils of their bones were discovered.
- 2 mya — This ancestor lived in the East African grasslands and ate fruits.
- 1.5 mya — This hominid had a brain size of 900 cc and probably ate meat.
- [(a)] Name one primate about 15 mya.
- [(b)] Name one place where fossils of primates were discovered in Eastern Africa.
- [(c)] Name the ancestor that lived in the East African grasslands about 2 mya.
- [(d)] Name the hominid that was found around 1.5 mya.
The given graph shows the range of variation among population members, for a trait determined by multiple genes. If this population is subjected to disruptive selection for several generations, which of the following distributions is most likely to result?
Read the following passage and answer the questions that follow. According to evolutionary theory, every evolutionary change involves the substitution of a new gene for the old one and the new allele arises from the old one. Continuous accumulation of changes in the DNA coding for proteins leads to evolutionary differences. The chemical composition of DNA is basically the same in all living beings, except for differences in the sequence of nitrogenous bases. Given below are percentage relative similarities between human DNA and DNA of other vertebrates:
(a) What is the term used for the substitution of a new gene for the old one and the new allele arising from the old one during evolutionary process?
(b) Which one of the following holds true for the data provided in the above table?
- [(A)] Greater the evolutionary distance, greater are the differences in the nitrogenous bases.
- [(B)] Lesser the evolutionary distance, greater are the differences in the nitrogenous bases.
- [(C)] Greater the evolutionary distance, lesser are the differences in the nitrogenous bases.
- [(D)] Lesser the evolutionary distance, lesser are the differences in the nitrogenous bases.
(c) [(i)] To which category of evolution (divergent or convergent) does the following relationship belong? Justify your answer.
Human and Rhesus Monkey
OR[(ii)] Differentiate between Convergent and Divergent evolution.
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Concepts Used:
Evolution
Evolution is a process that occurs in changes in the genetic content of a population over time. Evolutionary change is generally classified into two: microevolution and macroevolution. The process of changes in allele frequencies in a population over time is a microevolutionary process. Three main mechanisms that cause allele frequency change are natural selection, genetic drift, and gene flow. On the other hand, macroevolution refers to change at or above the level of the species.