Genetics and Evolution for UPSC Prelims
This module covers the fundamental concepts of Genetics and Evolution, crucial for the Science & Technology section of the UPSC Prelims General Studies paper. Understanding these topics will help you analyze biological processes, understand biodiversity, and interpret scientific advancements.
Fundamentals of Genetics
Genetics is the study of heredity and the variation of inherited characteristics. It explores how traits are passed from parents to offspring through genes.
A gene is a segment of DNA that codes for a trait, while an allele is a specific variant of that gene.
Mendelian Genetics
Gregor Mendel's work laid the foundation for modern genetics. His experiments with pea plants revealed fundamental principles of inheritance.
| Concept | Description | Example |
|---|---|---|
| Dominant Allele | An allele whose trait always shows up in the organism when the allele is present. | In pea plants, the allele for tallness (T) is dominant over the allele for shortness (t). |
| Recessive Allele | An allele that is masked when a dominant allele is present. | The allele for shortness (t) is recessive. |
| Genotype | The genetic makeup of an organism (e.g., TT, Tt, tt). | A pea plant can have genotype TT (homozygous dominant), Tt (heterozygous), or tt (homozygous recessive). |
| Phenotype | The observable physical characteristics of an organism. | A pea plant with genotype TT or Tt will have the phenotype of being tall. |
Understanding dominant and recessive alleles is key to predicting inheritance patterns. A recessive trait only appears if an individual inherits two copies of the recessive allele.
Introduction to Evolution
Evolution is the process by which populations of organisms change over generations. It explains the diversity of life on Earth.
Organisms with traits that enhance survival and reproduction in their environment pass those traits on more successfully.
Evidence for Evolution
Several lines of evidence support the theory of evolution, including fossils, comparative anatomy, embryology, and molecular biology.
Fossil records provide a historical timeline of life on Earth, showing transitional forms between different groups of organisms. For example, the fossil of Archaeopteryx shows characteristics of both dinosaurs and birds, illustrating a transitional stage. Comparative anatomy examines homologous structures (similar structures in different species due to common ancestry, like the forelimbs of humans, bats, and whales) and analogous structures (structures with similar functions but different evolutionary origins, like the wings of birds and insects). Embryology studies the developmental stages of embryos, revealing similarities that suggest common ancestry. Molecular biology compares DNA and protein sequences, with more closely related species showing greater similarity.
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Speciation
Speciation is the evolutionary process by which new biological species arise. It often occurs when populations become reproductively isolated.
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Genetics and Evolution: The Link
Genetic variation is the raw material for evolution. Mutations introduce new alleles, and natural selection acts upon this variation to drive evolutionary change.
Without genetic variation, evolution by natural selection would not be possible. Mutations are the ultimate source of all new genetic variation.
Key Terms for UPSC Prelims
Familiarize yourself with these terms: DNA, Gene, Allele, Genotype, Phenotype, Mutation, Natural Selection, Adaptation, Speciation, Homologous Structures, Analogous Structures, Fossil Record, Common Ancestry.
Learning Resources
Comprehensive video lessons and articles covering Mendelian genetics, DNA, genes, and inheritance patterns.
Explains the core concepts of evolution, natural selection, evidence for evolution, and speciation with clear visuals.
An engaging and fast-paced video series that covers the history of evolutionary thought, mechanisms, and evidence.
Articles from leading scientists explaining key evolutionary concepts, including natural selection and genetic drift.
A broad overview of genetics, its history, subfields, and applications, providing a good foundational understanding.
A detailed exploration of evolutionary theory, its evidence, mechanisms, and historical development.
Accessible explanations of evolutionary processes and their impact on life on Earth, suitable for general understanding.
A seminal essay by a prominent evolutionary biologist, highlighting the unifying role of evolution in biological sciences.
The official NCERT textbook chapter provides a structured and syllabus-aligned overview of genetics for Indian students.
The official NCERT textbook chapter covers evolutionary concepts, evidence, and mechanisms relevant to the UPSC syllabus.