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Evolution - Differentiate acquired and inherited traits and explain speciation

Grade 10CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Acquired Traits: These are traits that an organism develops during its lifetime due to environmental factors, use or disuse of organs, or experiences. These changes occur in somatic cells (non-reproductive cells) and do not affect the DNA of the germ cells. Therefore, they are not passed on to the next generation.

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Inherited Traits: These are characteristics controlled by specific segments of DNA called genes, located in the germ cells (gametes). These traits are passed from parents to offspring across generations. Variation in these traits is the basis for evolution.

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Speciation: The process by which new and distinct species are formed from existing populations. This happens when a population becomes split into two or more sub-populations that can no longer interbreed.

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Geographical Isolation: Physical barriers like mountains or rivers that separate a population, preventing gene flow between the sub-populations.

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Genetic Drift: A random change in the frequency of alleles (gene variants) in a small population over time, which can lead to significant changes in the population's characteristics regardless of whether the trait is beneficial.

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Natural Selection: The process where organisms with favorable variations for their environment survive and reproduce more successfully, passing those traits to the next generation. The fitness of an individual is often denoted as ww.

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Reproductive Isolation: The final stage of speciation where two populations are so genetically different that they can no longer interbreed to produce fertile offspring, even if they come back into contact.

📐Formulae

p+q=1p + q = 1 (Where pp and qq represent the frequency of two alleles in a population)

p2+2pq+q2=1p^2 + 2pq + q^2 = 1 (The distribution of genotypes in a population)

Variation=Genetic Factors+Environmental Factors\text{Variation} = \text{Genetic Factors} + \text{Environmental Factors}

💡Examples

Problem 1:

In a laboratory experiment, the tails of mice are surgically removed for 21 successive generations. Will the mice in the 22nd22^{nd} generation be born without tails? Explain.

Solution:

No, the mice in the 22nd22^{nd} generation will still be born with tails.

Explanation:

The removal of a tail is an acquired trait. It involves a change in the somatic tissues (body cells) and does not alter the genetic makeup or DNA of the germ cells (sperm or eggs). Since evolution and inheritance depend on changes in the germ DNA, this physical change cannot be inherited by the offspring.

Problem 2:

Calculate the final population of a beetle colony if an initial population of 500500 undergoes a 10%10\% reduction due to a drought, but 2525 new beetles with a green color variation are born.

Solution:

500−50450+25475\begin{array}{r} 500 \\ - 50 \\ \hline 450 \\ + 25 \\ \hline 475 \end{array}

Explanation:

The initial population is 500500. A 10%10\% reduction is 500×0.10=50500 \times 0.10 = 50. Subtracting the deaths gives 450450. Adding the 2525 new variants results in a total population of 475475 beetles. The 2525 new variants represent the start of potential genetic drift or natural selection if the green color provides a survival advantage.

Problem 3:

What are the two most important factors that lead to the rise of a new species (Speciation)?

Solution:

  1. Geographical Isolation and 2. Genetic Drift (combined with Natural Selection).

Explanation:

Geographical isolation prevents gene flowgene\ flow between two populations. Over time, Genetic Drift and Natural Selection cause different changes to accumulate in each group until they become reproductively isolated, meaning they can no longer interbreed.