Describe any three ways in which individuals with a particular trait may increase in population.
Describe any three ways in which individuals with a particular trait may increase in population.
An individual with a particular trait can increase in a population through the following three ways:
- Natural Selection (Survival Advantage): If a trait provides a survival advantage in a given environment, those individuals will survive better and reproduce more. For example, as mentioned in the text, bacteria that can withstand heat will survive better during a heat wave. Over generations, this advantageous trait is selected by environmental factors and increases in frequency.
- Genetic Drift (Accidental Survival): In small populations, an accidental event (like a natural calamity) can eliminate individuals of one trait, allowing individuals with another trait to survive and reproduce. This changes the gene frequency purely by chance, without providing any inherent survival advantage.
- Sexual Reproduction and Inheritance of Variations: Sexual reproduction maximizes the generation of successful variations. When these variations are inherited over succeeding generations, they accumulate. If the environment is favorable or neutral, these inherited variations can gradually spread and increase within the population.
Marking Scheme
- 11 Mark: Explaining Natural Selection with an example (e.g., heat-resistant bacteria).
- 21 Mark: Explaining Genetic Drift / accidental survival in small populations.
- 31 Mark: Explaining the role of sexual reproduction/inheritance of variations in accumulating and spreading traits.
Hint
Think about how natural selection (survival of the fittest), accidental events (genetic drift), and sexual reproduction help traits spread.
Quick Oral Answer
Traits can increase in a population through three main ways: Natural Selection (where a trait offers a survival advantage, like heat resistance in bacteria), Genetic Drift (where accidental events change trait frequencies in small populations), and through the accumulation of inherited variations via sexual reproduction.
Analysis & Explanation
This question explores how gene frequencies change in a population over time.
- Natural Selection is a directed process where the environment selects beneficial variants (e.g., heat-resistant bacteria surviving a heat wave).
- Genetic Drift is a random process that occurs primarily in small populations where chance events drastically alter allele frequencies.
- Sexual Reproduction acts as an engine for generating diverse combinations of traits, which can then be inherited and spread if they do not hinder survival.
Common Mistakes
- 1Confusing genetic drift with natural selection.
- 2Thinking that acquired traits (like muscle mass from exercise) can be inherited and increase in a population.
Interesting Facts
A single mutation in a bacterium can make it resistant to antibiotics. In the presence of antibiotics, natural selection ensures that only these resistant bacteria survive, rapidly increasing their population.
Spotted a mistake or something unclear?
Tell us — we fix reported answers fast.
Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2011?
This question carries 3 marks in the CBSE Class 10 Science 2011 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Heredity" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Accumulation of Variation during Reproduction" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2011 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2011 paper.