Activities

Activity 1: Miller’s Experiment Model

Aim: To understand the experimental setup used to simulate early earth conditions.

Procedure:

1. Study Figure 6.1 in the textbook.
2. Sketch the diagram of the apparatus and label the following parts:
   • Electrodes (for electric discharge/lightning).
   • Boiling water (for water vapour).
   • Condenser (to cool and collect liquid).
   • Flask containing CH4, NH3, H2, and H2O.
3. Discuss the significance of the 800°C temperature and the absence of oxygen.

Conclusion: The formation of amino acids from inorganic molecules provides strong experimental support for the Theory of Chemical Evolution.

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Activity 2: Classifying Homologous and Analogous Organs

Aim: To differentiate between divergent and convergent evolution using specific examples.

Procedure:

1. Examine the following pairs of organs:
   • (a) Forelimbs of Human and Cheetah.
   • (b) Wings of Butterfly and Bird.
   • (c) Tendrils of Cucurbita and Thorns of Bougainvillea.
   • (d) Flippers of Penguins and Dolphins.
2. Categorize them as 'Homologous' (similar anatomy) or 'Analogous' (similar function).

Results:

• (a) Homologous (Divergent Evolution)
• (b) Analogous (Convergent Evolution)
• (c) Homologous (Divergent Evolution)
• (d) Analogous (Convergent Evolution)

Conclusion: Homology indicates common ancestry, while analogy indicates adaptation to similar environments.

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Activity 3: Industrial Melanism Case Study

Aim: To analyze the effect of environmental changes on the survival of a population.

Procedure:

1. Read the description of the Peppered Moth (Biston betularia) in England.
2. Compare the survival rates of white-winged and dark-winged moths:
   • Pre-industrial period: Trees covered in white lichens.
   • Post-industrial period: Trees covered in dark soot.
3. Discuss why the count of melanic (dark) moths was low in rural areas even after industrialization.

Conclusion: This is a classic example of Natural Selection in response to anthropogenic (man-made) environmental changes.

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Activity 4: Hardy-Weinberg Equilibrium Exercise

Aim: To practice using the Hardy-Weinberg equation for population genetics.

Procedure:

1. Given: In a population, the frequency of a dominant allele 'A' is 0.7 (p = 0.7).
2. Calculate the frequency of the recessive allele 'a' (q).
   • p + q = 1 ⇒ q = 1 - 0.7 = 0.3.
3. Calculate the percentage of heterozygous individuals (Aa) in the population.
   • Frequency of Aa = 2pq
   • 2 × (0.7) × (0.3) = 0.42 or 42%.

Inquiry: If the actual frequency of heterozygotes in the next generation is 0.35, what does this indicate about the population? (Answer: Evolution is occurring; the population is not in equilibrium).