Theories of Evolution | Jamb Biology

Basics of Evolution

1. Definition of Evolution: The process through which organisms change over generations due to genetic variations and environmental pressures.
2. Organic Evolution: Refers to the totality of all changes in living organisms over time, leading to the diversity of life forms.
3. Significance of Evolution: Explains the origin of species, adaptation, and survival in changing environments.
4. Adaptive Changes: Traits that improve survival and reproduction are passed on to future generations.
5. Diversity of Life: Evolution accounts for the wide variety of organisms with unique structures and functions.
6. Common Ancestry: All organisms share a common ancestor and have diverged over time.
7. Natural Selection: A key mechanism where traits beneficial for survival are more likely to be passed on.
8. Fossil Evidence: Fossils show gradual changes in organisms over millions of years.
9. Genetic Variation: Differences in DNA among individuals provide raw material for evolution.
10. Environmental Influence: Changes in the environment drive the evolution of new traits.
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11. Microevolution: Small-scale changes within a population over a short time.
12. Macroevolution: Large-scale evolutionary changes, such as the formation of new species.
13. Extinction: The end of a species occurs when it fails to adapt to environmental changes.
14. Speciation: The process by which new species arise from existing ones.
15. Mutation: A change in DNA that introduces new traits into a population.
16. Genetic Drift: Random changes in gene frequency in small populations.
17. Gene Flow: Exchange of genes between populations, increasing variation.
18. Survival of the Fittest: Organisms with favorable traits are more likely to survive and reproduce.
19. Selective Pressure: Environmental challenges that influence which traits are advantageous.
20. Evidence of Evolution: Fossils, comparative anatomy, embryology, and molecular biology.
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Lamarck’s Theory of Evolution

21. Jean-Baptiste Lamarck: Proposed one of the first theories of evolution in the early 19th century.
22. Use and Disuse: Lamarck suggested that organs develop through use and shrink through disuse.
23. Inheritance of Acquired Traits: Changes an organism acquires during its lifetime can be passed to offspring.
24. Example (Giraffe): Lamarck believed giraffes’ long necks evolved because ancestors stretched their necks to reach leaves.
25. Environmental Influence: Changes in the environment lead to changes in organisms.
26. Progressive Evolution: Lamarck viewed evolution as a gradual and continuous process toward perfection.
27. Criticism: Lack of evidence for the inheritance of acquired traits.
28. Strengths: Lamarck emphasized the role of the environment in shaping traits.
29. Legacy: Paved the way for later theories by introducing the idea of change over time.
30. Relevance Today: Some of his ideas align with epigenetics, where environmental factors can influence gene expression.
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Darwin’s Theory of Evolution

31. Charles Darwin: Proposed the theory of natural selection in his book On the Origin of Species (1859).
32. Natural Selection: Process where individuals with advantageous traits survive and reproduce more successfully.
33. Variation: Darwin emphasized that individuals in a population vary in traits.
34. Struggle for Existence: More offspring are produced than the environment can support, leading to competition.
35. Survival of the Fittest: Only organisms best adapted to their environment survive and reproduce.
36. Common Descent: All species share a common ancestor and diverge over time.
37. Example (Finches): Darwin observed variations in beak shapes among finches on the Galápagos Islands, linked to their diets.
38. Evidence from Fossils: Fossil records show gradual changes in species over time.
39. Criticism: Darwin could not explain the source of variation (later explained by genetics).
40. Legacy: Darwin’s theory forms the foundation of modern evolutionary biology.
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Organic Evolution*

41. Definition: The sum of all adaptive changes occurring over a long time, resulting in the diversity of organisms.
42. Continuity of Life: Life evolves continuously, with no fixed endpoint.
43. Structural Changes: Organisms develop new body parts or lose unnecessary ones over time.
44. Functional Changes: Adaptations improve an organism’s ability to survive in its environment.
45. Example of Structural Changes: Birds evolved wings for flight.
46. Example of Functional Changes: Polar bears developed thick fur for insulation.
47. Diversity of Life Forms: Organic evolution explains why organisms vary in form, size, and behavior.
48. Environmental Adaptation: Changes in habitat drive evolution.
49. Natural History: Fossils provide a timeline of evolutionary changes in organisms.
50. Adaptive Radiation: One species diversifies into many to exploit different ecological niches.
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Contributions of Lamarck and Darwin

51. Lamarck’s Contributions: Introduced the role of the environment and the concept of change over time.
52. Darwin’s Contributions: Provided a mechanism (natural selection) for how evolution occurs.
53. Similarities: Both believed in gradual change and adaptation to the environment.
54. Differences: Lamarck focused on acquired traits, while Darwin emphasized inherited variation.
55. Legacy: Both theories contributed to our understanding of evolution, despite their differences.
56. Evidence Supporting Darwin: Fossils, comparative anatomy, and embryology.
57. Limitations of Lamarck: Lack of evidence for the inheritance of acquired traits.
58. Influence on Modern Biology: Darwin’s ideas laid the groundwork for genetics and molecular biology.
59. Modern Synthesis: Combines Darwin’s theory of natural selection with Mendelian genetics.
60. Unified Understanding: Today’s evolutionary theory integrates contributions from both Lamarck and Darwin.
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Evidence Supporting Organic Evolution

61. Fossil Records: Show transitional forms and gradual changes over time.
62. Comparative Anatomy: Similar structures in different species suggest a common ancestor.
63. Homologous Structures: Body parts with the same basic structure but different functions (e.g., forelimbs of humans and bats).
64. Analogous Structures: Body parts with similar functions but different structures (e.g., wings of birds and insects).
65. Vestigial Organs: Structures with no apparent function (e.g., human appendix) indicate evolutionary remnants.
66. Embryology: Similar embryonic development across species suggests common ancestry.
67. Molecular Biology: DNA and protein similarities among organisms support shared ancestry.
68. Geographic Distribution: Unique species on islands provide evidence of evolution due to isolation.
69. Artificial Selection: Humans breeding plants and animals (e.g., dogs, crops) demonstrate selective pressures driving changes.
70. Adaptation Examples: Peppered moths during the Industrial Revolution showed changes in color due to environmental pollution.

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