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Evolution via natural selection

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This piece explores the fundamental principles of evolution via natural selection, emphasizing the necessity of individual variation, heritable traits, and differential fitness within populations. It poses intriguing hypothetical scenarios that question how evolution would be affected if all organisms shared the same size or traits. Additionally, the document delves into the characteristics of key animal phyla, including Echinodermata and Chordata, outlining their unique features and significance in the tree of life.

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Evolution via natural selection

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  1. Evolution via natural selection

  2. What would happen if all of the trees and dinosaurs were the same size?

  3. Individual variation is necessary for natural selection to occur

  4. What would happen if all the dinosaurs produced just one offspring?

  5. Differential fitness is necessary for natural selection to occur

  6. What would happen if offspring never resembled their parents? Parents: ✖ Offspring:

  7. Traits must be heritable for natural selection to occur ✖ Parents: Offspring:

  8. Conditions required for natural selection to occur: Individual variation:members of a species differ in their characteristics Mode of inheritance:parents pass on some of their traits to their offspring Differential fitness: some individuals leave more offspring than others due to their special inherited traits

  9. Change in population occurs because of differences in reproductive success. Organisms do not evolve because they want or need to change.

  10. Animal Diversity 2 • Deuterostomes: Echinodermata and Chordata

  11. Echinodermata & Chordata

  12. Echinodermata “Spiny skin” • Endoskeleton of spiny plates • Marine animals (no freshwater or terrestrial species) • Adults = radial; larvae = bilateral • Water vascular system (used for feeding, gas exchange, and locomotion) • Canals end in “tube feet”; opening = madreporite

  13. Chordata • Pharyngeal slits/pouches • Dorsal nerve cord • Notochord • Post-anal tail

  14. Pharyngeal slits

  15. Dorsal (hollow) nerve cord Nerve cord Notochord

  16. (versus solid, ventral nerve cord)

  17. Nerve cord Notochord Notochord Flexible rod that supports the nerve cord (becomes intervertebral discs in between vertebrae in humans.)

  18. Post anal tail

  19. (body extends past the anus...)

  20. Chordata • Pharyngeal slits • Dorsal nerve cord • Notochord • Post-anal tail

  21. Subphyla Cephalochordata Urochordata (tunicates) Vertebrata

  22. Cephalochordata Example: lancelets

  23. Urochordata

  24. Vertebrata

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