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Diversity - A daptations as Outcomes of Structural Change

Grade 9CBSE

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

🔑Concepts

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Adaptation refers to the structural or functional changes in an organism's body design that improve its chances of survival and reproduction in a specific environment.

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Charles Darwin first described the idea of evolution in his book, 'The Origin of Species' in 18591859. He proposed that diversity is the result of 'descent with modification'.

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Structural changes are often the basis for biological classification. Organisms with similar body designs are grouped together, reflecting a common evolutionary ancestry.

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Evolutionary relationships indicate that 'primitive' or 'lower' organisms have relatively simple body designs, whereas 'advanced' or 'higher' organisms have acquired more complex structural designs over time.

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The hierarchy of classification, from Kingdom to Species, is determined by the accumulation of structural adaptations. The most fundamental features (like the presence of a nucleus) define broad groups, while specific structural adaptations define species.

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Natural Selection acts on structural variations. If a variation VV provides a survival advantage in environment EE, the frequency of that trait increases in subsequent generations.

📐Formulae

Relative Fitness (w)=Survival rate of a specific phenotypeSurvival rate of the most fit phenotype\text{Relative Fitness (w)} = \frac{\text{Survival rate of a specific phenotype}}{\text{Survival rate of the most fit phenotype}}

Complexity∝Evolutionary Time\text{Complexity} \propto \text{Evolutionary Time}

P(Survival)=n(Adapted individuals)n(Total population)P(\text{Survival}) = \frac{n(\text{Adapted individuals})}{n(\text{Total population})}

Diversity Index=1−(∑n(n−1)N(N−1))\text{Diversity Index} = 1 - \left( \frac{\sum n(n-1)}{N(N-1)} \right)

💡Examples

Problem 1:

Explain the structural adaptation in a Cactus (XerophyteXerophyte) that allows it to survive in arid conditions compared to a normal mesophyte.

Solution:

In a Cactus, leaves are reduced to spines to minimize transpiration (Area≈0Area \approx 0), and the stem becomes succulent and performs photosynthesis.

Explanation:

The structural change from broad leaves to spines reduces the surface area exposed to sunlight, preventing water loss. The stem undergoes a structural change to store water and contain chlorophyll, effectively taking over the role of the leaf.

Problem 2:

In a population of 10001000 insects, 200200 developed a structural mutation in their cuticle that makes them resistant to a specific pesticide. After one year of pesticide use, the population of non-resistant insects dropped by 90%90\%, while the resistant ones doubled. Calculate the new ratio.

Solution:

Initial Resistant=200Initial Non-Resistant=800New Resistant=200×2=400New Non-Resistant=800×0.10=80New Ratio=400:80=5:1\begin{array}{r} \text{Initial Resistant} = 200 \\ \text{Initial Non-Resistant} = 800 \\ \hline \text{New Resistant} = 200 \times 2 = 400 \\ \text{New Non-Resistant} = 800 \times 0.10 = 80 \\ \text{New Ratio} = 400 : 80 = 5 : 1 \end{array}

Explanation:

This demonstrates how a structural change (the mutation in the cuticle) leads to a survival advantage, altering the diversity of the population through natural selection.

Problem 3:

Compare the structural differences between Monocots and Dicots as an outcome of divergent adaptation.

Solution:

Monocots have seeds with one cotyledon and parallel venation in leaves, while Dicots have two cotyledons and reticulate venation.

Explanation:

These structural differences in the embryo and leaf vasculature are key adaptations used to classify flowering plants (Angiosperms) into two distinct groups based on their evolutionary paths.