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Islands Introduction

Explore the unique biogeography and geological features of islands and how they drive evolutionary change. Discover the fascinating adaptations of organisms on isolated islands and the mechanisms that shape their evolution.

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Islands Introduction

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  1. Islands Introduction Islands are similar because they are unique

  2. Islands Unit Overview • The Story: • This unit is about both biological and geological evolution. • Islands provide interesting, unusual examples of evolutionary change on a scale that is small and easy to understand. • While the results of island evolution tend to be very different from evolution on a continental landmass, the mechanisms are the same. Islands simply become the context to learn evolutionary mechanisms.

  3. Student Outcomes: • Understand the process of biological evolution on isolated island systems. • Observe the results of biological evolution and describe the specific mechanisms that drive it. • Connect the unique biological evolution of organisms on an isolated island system to the island’s geology. • Gain an understanding of earth’s geological processes involved in island formation by observing evidence of plate tectonics, and rock samples.

  4. I. What is an Island? A. Definition: Islands are isolated environments with unique living organisms (biology) and unique physical characteristics (geology) II. Why Do We Study Islands? Islands are similar because they are unique Islands are dynamic and often experience change, both biologically and geologically, more rapidly than continental landmasses Islands are smaller than continents, therefore easier to study. Islands allow us to study two major themes in science: Evolution (Biological Science) and Plate Tectonics (Earth Science). III. What Happens to Organisms on Islands Over Time? Migrate, Survive, Reproduce, Adapt, Evolve or Go Extinct

  5. IV. Effects Are Unique on Islands Species on islands are unique. Identify unique adaptations found in the organisms below. Dodo Bird (extinct) - Mauritius Giant Galapagos Tortoise - Galapagos Elephant Bird (extinct) - Madagascar

  6. IV. Effects Are Unique on Islands (continued) Species on islands are unique. Identify unique adaptations found in the organisms below. Giant burrowing cockroach - Australia Kiwi Bird - New Zealand Moa (extinct)

  7. IV. Effects Are Unique on Islands (continued) Species on islands are unique. Identify unique adaptations found in the organisms below. Pygmy hippopotamus - Madagascar Rattleless rattlesnake - Santa Catalina Island Tree climbing kangaroo - New Guinea

  8. IV. Effects Are Unique on Islands (continued) Species on islands are unique. Identify unique adaptations found in the organisms below. Tasmanian devil - Tasmania Lesser bird of paradise - Indonesia Komodo dragon - Komodo Island

  9. V. Causes Are Similar on Islands • The mechanisms that cause islands to be unique are similar: • Dispersal Ability - pioneer species are good at migrating to new locations • Size Change - organisms are larger or smaller than normal • Loss of Dispersal Ability - species easily lose ability to emigrate • Endemism - species tend to evolve and remain native to that area only • Relictualism - populations are small and have a greater chance of extinction • Loss of Defensive Adaptations - defense capabilities are reduced in predator-free environments • Archipelago Speciation - many species may evolve from one in the same island group • Adaptive Radiation - many species may evolve from one in the same location because they use different parts of the habitat

  10. VI. Mechanisms For Evolution are Similar on Islands • Natural Selection - “Best Fit” Survive • Ex. Camouflage, size, speed, adaptations, sex appeal, strength, intelligence, predictable human impact etc. • Genetic Drift - “Lucky” Survive • Ex. Extreme weather, isolation, epidemic diseases, genetic mutations, unequal gender balance, geologic activity etc.

  11. Mechanisms of Island Evolution What Biological Processes Make the Organisms on Islands So Unique? Numbers on these slides correspond to your HW.Presentation available @ www.redwood.org/stewartHighlight information in blue.

  12. Dispersal • Define dispersal: • The process of scattering or spreading from a certain area. • Give examples of how plants disperse their seeds. • Birds chance • Wind chance • Float chance • Shoots out of fruit natural • Spring open and scatter natural • Analysis: How is dispersal important to evolution on islands? How life arrives.

  13. Evolution and Natural Selection Evolution - • The process of modern organisms descending from ancient organisms; change over time. 4. Variation • Variations will be selected for or against. Organisms with more adaptive variations are more likely to survive and pass on their inherited variations. Fitness - Organisms with more successful offspring have a higher fitness: the combination of physical traits and behaviors that help an organism survive and reproduce in its environment. Measured by the number of successful offspring. Charles Darwin

  14. Evolution and Natural Selection 5. Survival of the Fittest - • Individuals with characteristics best suited to their environment survive. 6. NaturalSelection - • The process in nature that results in the most fit (best adapted) organisms producing offspring. 3 steps: variation --> selection --> reproduction. • The mechanism that drives evolution. 7. Adaptation - • The process that enables organisms and species to become better suited to their environments.

  15. Evolution and Natural Selection Evolution does NOT occur in the following ways: • A Desire to Change • Use and Disuse • Passing on Acquired Traits WRONG!

  16. Evolutionary Theory Evolves: Genetic Drift 8. What is genetic drift? Give 2 examples. • Genetic change in a population, occurring in the absence of natural selection, due to random, chance events. • Separation of populations so that they do not interbreed to produce fertile offspring. • One of the most common ways in which new species form is when populations are separated. • Examples of events leading to genetic drift: • mutation • chance dispersal • extreme weather • Geographic barriers

  17. Evolution of new species: Speciation • Speciation - • The process of new species evolving from pre-existing ones. This may be due to natural selection, genetic drift, or both. • Niche - • The combination of an organism’s habitat and it’s role in that habitat. (address + profession) Why can no two species occupy the same niche? • Competition arises for food and space. The most efficient species will survive and reproduce. Darwin’s Finches

  18. Evolutionary Theory Evolves: Genetic Drift Punctuated Equilibrium - • Rapid periods of speciation (evolution) due to genetic drift and other random (stochastic) factors after long periods of gradualism (deterministic) • Rapid speciation may occur when a small population of a species becomes isolated from the main part of the population or due to other factors.

  19. Evolutionary Theory Evolves: Genetic Drift 9. How are genetic drift and natural selection different?Evolution by natural selectionoccurs predictably, slowly and gradually. Evolution due to genetic drift is unpredictable and to some degree random (stochastic) 10. How are genetic drift and natural selection similar? Both lead to change over time (evolution). 11. Analysis: What is unique to the evolutionary process on islands and why? Islands are ISOLATED (distant) and small so genetic drift is more likely. AND factors influencing natural selection may be different. END

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