"Only variations that confer an advantage on an individual organism will survive in a population." Justify this statement.
"Only variations that confer an advantage on an individual organism will survive in a population." Justify this statement.
Official answer
The statement is justified because variations do not have equal chances of survival; their success depends on the environmental context. As per the text, 'different individuals would have different kinds of advantages' based on their variations. For example, in a population of bacteria, those that possess a variation to withstand heat will survive a heat wave, while others perish. This 'selection of variants by environmental factors' ensures that only those variations providing a survival advantage are passed on to the next generation. Over time, these advantageous variations accumulate, forming the basis for evolutionary processes, whereas disadvantageous or neutral variations may not persist if the environment becomes hostile to them.
Marking scheme
- 1.Statement that variations have unequal survival chances depending on the environment. (1 mark)
- 2.Example of heat-resistant bacteria surviving a heat wave. (1 mark)
- 3.Explanation of environmental selection as the basis for evolution. (1 mark)
Hint
Recall the example of bacteria in a heat wave mentioned in the text.
Quick oral answer
Variations provide different advantages. If the environment changes, only individuals with specific advantageous variations (like heat resistance) survive and reproduce, which is why only those variations persist in the population.
Common mistakes
- 1.Thinking that all variations lead to evolution immediately.
- 2.Ignoring the role of the environment in 'selecting' which traits are useful.
Analysis and explanation
The text explicitly states that variations are produced during reproduction (both asexual and sexual). However, it clarifies that not all variations are beneficial. The environment acts as a filter. If a variation helps an organism cope with environmental stress (like the heat-resistant bacteria example), that organism survives and reproduces. This process is known as natural selection. Variations that offer no advantage or are harmful reduce the organism's fitness, making it less likely to survive and pass those traits to the next generation.
Interesting facts
In asexual reproduction, variations are very minor and usually caused by small inaccuracies in DNA copying, yet even these can be life-saving in changing environments.
Question details
Q21 of 41 questions
- Board
- CBSE
- Class
- Class 10
- Subject
- Science
- Year
- 2011
- Section
- Section A
- Marks
- 3
- Type
- Short Answer
- Chapter
- Heredity
- Topic
- Accumulation of Variation
- Bloom's level
- Evaluate
- Syllabus topic
- Heredity; Accumulation of variation during reproduction
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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" 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.