THE BASES ON THE THEORIES OF EVOLUTION.pptx

presentation on evolution

1. BASES ON THE THEORIES OF EVOLUTION

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3. Structural Evidence for Evolution

4. Homologous structures: These are organs that have the same basic underlying structure but may have different functions in different species. Share a common origin in an evolutionary ancestor. Classic examples include the forelimbs of a human, bat, whale, and bird.

5. Analogous structures: These are organs that have a similar function but a different underlying structure. They arise due to convergent evolution, where unrelated organisms evolve similar adaptations to similar environmental pressures.

6. Vestigial structures: These are rudimentary organs or structures that have lost their original function in an organism but were important structures in an evolutionary ancestor. E.g., appendix in humans, the tailbone in humans and some apes, or the wisdom teeth in humans.

7. DNA Evidence for Evolution

8. Shared genetic code: All living organisms, from the simplest bacteria to the most complex animals, utilize the same basic genetic code. This universality points towards a common ancestor for all life on Earth.

9. Genetic similarity: The more closely related two species are, the more similar their DNA sequences will be. This similarity reflects their shared evolutionary history. By comparing the DNA of different organisms, scientists can construct phylogenetic trees that illustrate these relationships.

10. Mutations and Genetic Diversity: Mutations in DNA sequences occur over time. These mutations can be neutral, beneficial, or detrimental. Evolutionary processes like natural selection act upon these mutations, favoring beneficial traits and weeding out harmful ones.

11. Endogenous retroviruses: These are viruses that have inserted their genetic material into the host organism's genome and are passed down through generations. The presence of these viral sequences can be like a molecular fossil, recording past encounters with viruses and providing clues about the evolutionary history of the host organism.

12. Pseudogenes: These are DNA sequences that resemble functional genes but have accumulated mutations and are no longer functional. Their presence suggests that they were once functional genes in an ancestor but have become unnecessary over time and turned into pseudogenes.

13. Biogeographical Evidence for Evolution

14. Continental drift and distribution patterns: Closely related species are often found on continents that were once connected, suggesting they evolved from a common ancestor before the continents drifted apart. For example, the marsupials of South America and the Australian possums share a common ancestor that likely lived on the supercontinent Gondwana before its breakup.

15. Endemic species and island biogeography Species that land on islands and become isolated can evolve unique characteristics over time, adapting to the specific island environment. The Galapagos finches, famously studied by Charles Darwin, are a classic example. These finches, with their distinct beak shapes adapted to different food sources, all likely originated from a common ancestor that arrived on the Galapagos Islands

16. Vicariant events Vicariance refers to events that geographically isolate populations of a species. For example, a volcanic eruption splitting a habitat or a river changing course can create isolated pockets of the same species. Over time, these isolated populations may evolve independently into distinct species.

17. Multiple Choice Test: Evidence for Evolution