Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: Theoretically, natural selection moulds and shapes populations through differential fertility and mortality. Reason R: Sickle cell provides a persuasive argument for differential mortality, affecting populations in malarial environment, but evidence for differential fertility is far from unequivocal. In the light of the above statements, choose the most appropriate answer from the options given below
Assertion A: Natural Selection Mechanism
Assertion A correctly states that natural selection drives population changes by influencing reproductive success and survival rates. Organisms with traits better suited to their environment tend to survive longer and produce more offspring, thus shaping the population's genetic makeup over generations.
Reason R: Sickle Cell Example Explained
Reason R accurately describes the significance of the sickle cell trait in relation to natural selection. In areas where malaria is prevalent, individuals with the sickle cell trait (heterozygotes) possess a survival advantage due to partial immunity to malaria. This leads to differential mortality, as they are more likely to survive than individuals with normal hemoglobin (homozygous) who are susceptible to severe malaria, or those with sickle cell disease (homozygous recessive) who face severe health issues. However, Reason R correctly points out that the evidence linking the sickle cell trait specifically to differential fertility is less conclusive compared to the evidence for differential survival (mortality).
Relationship: R Correctly Explains A
Reason R serves as a specific, well-established example that illustrates the general principle outlined in Assertion A. The strong evidence for differential mortality in the context of sickle cell anemia and malaria directly supports the claim that natural selection acts through variations in survival rates. This classic example effectively explains how environmental pressures (malaria) interact with genetic variations (sickle cell trait) to shape population dynamics, thus making Reason R a correct explanation for Assertion A.
Conclusion: Final Answer Choice
Based on the analysis:
- Assertion A is correct.
- Reason R is correct.
- Reason R provides a valid explanation for Assertion A by illustrating the concept of differential mortality through a key evolutionary example.
Therefore, the most appropriate answer is that both A and R are correct, and R is the correct explanation of A.
Important Questions from Evolutionary Mechanisms
Given below are proposed analogous structures among organisms.
A. wings of birds and bats
B. wings of bats and tetrapod digits
C. tendrils of Vitis and tendrils of pumpkin
D. tubers of potatoes and sweet potatoes
E. fins of fish and flippers of a whale
Which one of the following options correctly states the analogous structures?
Biased gene conversion (BGC) has been proposed to cause changes in allele frequencies in a population. Select the statement that is NOT correct about BGC.
- Long - term patterns of evolution are shaped by large scale process(s) such as :
(I) Speciation
(II) Mass extinction
(III) Adaptive radiation
Choose the correct answer: - Speciation means :
Match List I with List II
List I (Term) List II (Definition) A. Sympatric
speciationI. The process by which organisms adapt to changed environmental conditions to form new species in
a relatively short period.B. Parapatric
speciationII. The process of differentiation and acquiring reproductive isolation within the same geographical
area.C. Adaptive
radiationIII. Population evolving in different geographical regions due to isolation. D. Allopatric
speciationIV. The process of speciation which occurs between adjacent populations within a broadly continuous
habitat.
Choose the correct answer from the options given below:
