# Neo-Darwinism and Evidences for Evolution Neo-Darwinism is the modern synthesis of evolutionary theory, which integrates Darwin's theory of natural selection with the principles of modern population genetics. It provides a clearer understanding of inheritance, variation, and the mechanisms of evolution. For related content on Darwin's original theory, see . ## Evidences in Favour of Evolution Theory The theory of evolution is supported by a wide range of evidence from various scientific disciplines. ### 1. Evidence from Biogeography Biogeography is the study of the geographical distribution of plants and animals on Earth. It provides insights into prehistoric climates, habitats, and how species have moved and evolved over time. **Core Principle:** Species originate in a specific area and then disperse outwards. Their current distribution is a result of their evolutionary history and the geological history of the Earth. **Specific Distribution Patterns:** The presence or absence of a species in a suitable environment can be explained by its origin and ability to reach that area. - Example: South America lacks native rabbits, despite having a suitable environment. This is because rabbits evolved elsewhere and had no natural way to cross the geographical barriers to reach South America. **Barriers to Distribution:** The dispersal of organisms is often restricted by various barriers: - Physical: Oceans, large deserts, mountain ranges. - Environmental: Unfavourable climate (temperature, rainfall). - Ecological: Presence of predators or superior competitors for resources. **Continental Drift:** The movement of tectonic plates over millions of years has separated and joined landmasses, significantly influencing the distribution of species. ### 2. Molecular Biology Evidence The similarity of molecules across a vast range of organisms points to a shared ancestry. This is often called biochemical homology. **Universal Genetic Material:** DNA is the hereditary material for all known living organisms, and it uses the same four nucleotides (A, T, C, G). The genetic code is nearly universal. **Universal Energy Currency:** ATP (Adenosine Triphosphate) is the primary energy currency molecule in all cells, from simple prokaryotes to complex animals. **Common Building Blocks:** All living things synthesize their proteins from the same set of 20 types of amino acids. **Shared Proteins:** Certain essential proteins are found across diverse species. - Example: Cytochrome c, a protein involved in the respiratory chain, is found in all aerobic organisms, with its amino acid sequence being more similar in closely related species. ### 3. Comparative Anatomy Evidence Comparative anatomy is the study of similarities and differences in the anatomical structures of different species. It reveals two key types of structures: homologous and analogous. | Feature | Homologous Structures | Analogous Structures | | :--- | :--- | :--- | | **Definition** | Structures with a common evolutionary origin but may have different functions. | Structures with different evolutionary origins but perform a similar function. | | **Internal Structure** | Internally similar (e.g., same bone pattern). | Internally different (e.g., bone vs. chitin). | | **Function** | Can be very different. | Usually very similar. | | **Evolutionary Pattern** | Divergent Evolution: A common ancestor radiates into different species adapted to different environments. | Convergent Evolution: Unrelated species independently evolve similar traits to adapt to similar environments or needs. | | **Example (Animals)** | The forelimbs of mammals (human arm, horse leg, whale flipper, bat wing). | Wings of a bird, a bat, and an insect. | | **Example (Plants)** | Sepals, petals, stamens, and carpels are all modified leaves. | Photosynthetic leaves of a tree vs. photosynthetic blades of algae. | **Homologous Structures and Divergent Evolution** These structures demonstrate how a basic plan inherited from a common ancestor has been modified to suit different ways of life. Vestigial Organs are a special type of homologous structure. They are reduced or non-functional remnants of organs that were functional in an ancestor. - Examples: The appendix and tail vertebrae (coccyx) in humans; remnants of leg bones in some snakes. **Analogous Structures and Convergent Evolution** These structures show how different lineages can adapt in similar ways when faced with similar environmental pressures.