Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Darwinian Theory of Evolution is founded on two core concepts: Branching Descent (the pattern of evolution) and Natural Selection (the mechanism of evolution).
Natural Selection occurs because individuals with inherited traits that are better suited to the environment survive and reproduce at higher rates ().
Modern Synthetic Theory (Neo-Darwinism) explains evolution as a change in allele frequency within a population over time. It considers five factors: Gene Mutation, Genetic Recombination, Gene Flow, Genetic Drift, and Natural Selection.
Hugo de Vries proposed the Mutation Theory, stating that evolution is caused by sudden, large, and random mutations rather than the small, directional variations described by Darwin. He termed a single-step large mutation as 'Saltation'.
Adaptive Radiation: The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats), exemplified by Darwin's Finches and Australian Marsupials.
Hardy-Weinberg Principle: Allele frequencies in a population are stable and is constant from generation to generation (Genetic Equilibrium) if factors like mutation, gene flow, and natural selection are absent.
Genetic Drift: A change in allele frequencies due to chance events, particularly in small populations. Extreme cases include the Founder Effect and the Bottleneck Effect.
📐Formulae
💡Examples
Problem 1:
In a stable population of individuals, individuals show the recessive phenotype (genotype ). Calculate the frequency of the dominant allele and the frequency of the heterozygous genotype .
Solution:
- Frequency of homozygous recessive genotype .
- Frequency of recessive allele .
- Using , the frequency of dominant allele .
- Frequency of heterozygous genotype .
Explanation:
Applying the Hardy-Weinberg equilibrium equations where represents the frequency of the dominant allele and represents the frequency of the recessive allele.
Problem 2:
Contrast Darwinian variations and de Vriesian mutations.
Solution:
Darwinian variations are small, continuous, and directional (), leading to slow evolution. De Vriesian mutations are large, random, and directionless (), leading to sudden speciation.
Explanation:
This highlights the difference between the classical Darwinian view and the Modern Synthetic/Mutation theory regarding the speed and nature of evolutionary change.