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Reviewer: Evidences for Biological Evolution

1. Comparative Anatomy and Morphology (Tectology)

  • Homologous Structures: Similar structures with different functions, indicating common ancestry (e.g., human arm, bat wing, and whale flipper).

  • Analogous Structures: Different structures with similar functions, showing convergent evolution (e.g., wings of birds and insects).

  • Vestigial Structures: Reduced or non-functional organs that were useful in ancestors (e.g., human appendix, wisdom teeth).

2. Vestigial Organs

  • Body parts that have lost their original function due to evolution.

  • Examples: Human tailbone (coccyx), snake pelvic bones, flightless bird wings (e.g., ostrich).

3. Atavism and Reversion

  • Atavism: The reappearance of ancestral traits that were lost in evolution (e.g., humans born with a tail).

  • Reversion: Organisms showing primitive traits due to genetic mutations (e.g., extra toes in horses, reappearance of gill slits in humans).

4. Comparative Embryology

  • Embryos of different species show similar structures during early development, indicating common ancestry.

  • Example: All vertebrate embryos (fish, birds, mammals) have pharyngeal gill slits and tails at some stage.

5. Palaeontology (Study of Fossils)

  • Fossil records provide evidence of gradual changes in organisms over millions of years.

  • Transitional Fossils: Show intermediate traits between ancestral and modern species (e.g., Archaeopteryx – between reptiles and birds).

  • Types of Fossils:

    • Body Fossils: Preserved bones, shells, or entire organisms (e.g., dinosaur bones).

    • Trace Fossils: Footprints, burrows, or imprints showing activity of organisms.

6. Geographical Distribution

  • Organisms in different geographic regions show adaptations to their environments, proving natural selection.

  • Continental Drift & Evolution: Species in different continents show similarities due to common ancestry (e.g., marsupials in Australia vs. placental mammals elsewhere).

  • Endemic Species: Found only in specific regions due to isolation (e.g., Galápagos finches).

7. Connecting Links

  • Organisms that show characteristics of two different groups, proving evolutionary transitions.

  • Examples:

    • Archaeopteryx (between reptiles and birds).

    • Platypus (between reptiles and mammals).

    • Lungfish (between fish and amphibians).

8. Taxonomy

  • Classification of organisms based on evolutionary relationships.

  • Hierarchical System (Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species).

  • Phylogenetics: Study of evolutionary history using family trees.

9. Biochemistry and Physiology

  • Similar biochemical processes across species suggest common ancestry.

  • Examples:

    • All living organisms use DNA & RNA for genetic information.

    • Same basic metabolic pathways (e.g., glycolysis, cellular respiration).

    • Similar hormones (e.g., insulin in humans and pigs).

10. Molecular Records

  • DNA and protein similarities between species provide strong evidence for evolution.

  • Molecular Clock Hypothesis: Mutations accumulate at a steady rate, helping estimate evolutionary timelines.

  • Examples:

    • Humans share 98.7% DNA with chimpanzees.

    • Similar hemoglobin proteins in vertebrates.

11. Cytology (Cell Biology)

  • Cell Theory: All living organisms are made of cells, showing a common origin.

  • Similarities Across Species:

    • Prokaryotic vs. Eukaryotic cells.

    • Mitochondria and chloroplasts share DNA with bacteria (Endosymbiotic Theory).

12. Genetics

  • Mutation & Variation: Changes in DNA cause new traits, leading to evolution.

  • Natural Selection: Favorable traits become more common over generations.

  • Genetic Drift: Random changes in allele frequency in small populations.

  • Artificial Selection: Humans breeding organisms for specific traits (e.g., dog breeds, crop modification).

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