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Natural Selection in Action

Natural Selection in Action. Section 6.3. Discussion. During the past several hundred years, a rapidly expanding human population has. media-2.web.britannica.com. caused some species to become extinct either from habitat destruction or overhunting.

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Natural Selection in Action

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  1. Natural Selection in Action Section 6.3

  2. Discussion • During the past several hundred years, a rapidly expanding human population has media-2.web.britannica.com • caused some species to become extinct either from habitat destruction or overhunting. • If people are as much a part of the environment as trees and birds are, are people’s actions just parts of natural processes?

  3. Changes in Population • Well adapted organisms are more likely to survive and reproduce. • Example: Before the Industrial Revolution, the peppered moth was mostly found in a light-grey form with little black speckled spots. These moths were able to blend in with the light-colored lichens and tree bark, and the less common black moth was more likely to be eaten by birds. en.wikipedia.org

  4. Changes in Population • Due to widespread pollution during the Industrial Revolution, many of the light-colored lichens died out, and the trees they rested on became blackened by soot, causing most of the light-colored moths to die off from predation. However, the dark-colored moths flourished because of their ability to hide on the darkened trees. en.wikipedia.org en.wikipedia.org

  5. Changes in Population • Since then, with improved environmental standards, light-colored peppered moths have again become common. • This evolved darkening of color due to industrialization is called melanism. en.wikipedia.org en.wikipedia.org • RealPlayer Videos\Evolution of the Peppered Moth - Bing Videos.flv

  6. Changes in Population • Something similar has occurred in the elephant population in Uganda, since most elephants in that region have tusks, which are very valuable. www.wildlife-pictures-online.com • In 1930, 99% of the male elephants had tusks (1% tuskless). Due to hunting, today around 15% of the male elephants are tuskless. Why? • Tuskless elephants are relatively safe and live to reproduce, unlike their brothers with tusks.

  7. Insecticides • When insecticides are used, most of the insects are killed. Those that survive are resistant to the chemical. They live to reproduce, and the insecticide doesn’t work as well on future generations – most offspring inherited the trait of being insecticide resistant. • Evolution takes time, but insects have a short generation time, so they can evolve more quickly than other species. www.drearth.com

  8. Insecticides

  9. Bacteria and Antibiotics • Something similar can occur when a bacterial infection is treated with antibiotics. • Some bacteria are less susceptible to the affects of the antibiotic. They may not be killed by it or may take longer periods of exposure for the antibiotic to work. www.faqs.org www.steadyhealth.com

  10. Bacteria and Antibiotics • This is why you should always take all of your prescription, even once you get to feeling better. Otherwise, the resistant bacteria will live and reproduce and you will get sick again. • Further treatment will be less effective, since more of the bacteria are resistant. www.aenvirocure.com

  11. Adaptive Coloration www.esr.org • Penguins, puffins, killer whales and blue sharks are just some of the ocean animals that have white bellies and black or dark blue dorsal surfaces. This type of coloration is called countershading. www.cs.usask.ca naturescrusaders.files.wordpress.com www.free-desktop-backgrounds.net

  12. Adaptive Coloration • When seen from below, the white underside helps the animal blend into the lighter sky above the water. • Viewed from above, the dark coloration makes the animals difficult to see against the ocean depths. www.doobybrain.com

  13. Sexual Selection • The selection of traits that is brought about by a specific pattern of mating. • In many organisms, members of one sex must compete with each other for access to mates. • The “choosiness” of one sex may drive the evolution of traits that confer no apparent advantage to the opposite sex. www.bio.davidson.edu img1.photographersdirect.com

  14. Sexual Selection • Females prefer to mate with colorful males, so colorful males have more offspring than noncolorful males. Colorful males are more likely to pass on their genes to the next generation, increasing the proportion of colorful males. • The long tails and colorful plumage of many male birds are considered examples of such “runaway sexual selection.” img.xcitefun.net • RealPlayer Videos\Sexual Selection and the Art of Courtship.flv s3.amazonaws.com

  15. Forming a New Species • New species can form if a group gets cut off from the rest of the population. • The new population adapts to its environment over generations, and eventually the new population is different enough from the old population that they can no longer interbreed, even if brought back together.

  16. Forming a New Species • Some species that have adapted to live in total darkness no longer even have eyes. Just as whales have evolved into legless forms, these species have completely adapted to life without light, and have evolved forms lacking eyes altogether. • Examples include blind cave fish, eels, salamanders, worms, shrimp, crayfish, spiders, beetles and crickets. webecoist.com forum.globaltimes.cn webecoist.com

  17. Forming a New Species www.torontozoo.com • The leopard frog and the pickerel frog are similar species and probably had the same ancestor species. • After separation, they began to mate at slightly different times of the year, so they can no longer interbreed.

  18. Forming a New Species • This process is called speciation and involves 3 basic steps. • Separation– part of a population becomes separated from the rest (possibly by new water or land formations) • Adaptation – natural selection will act on the separate populations in different ways, depending upon their environmental conditions. • Division – the two groups grow to be distinct from one another and can no longer interbreed – they have become different species. • RealPlayer Videos\Speciation.flv

  19. Speciation Example

  20. Speciation Example

  21. Speciation Example • RealPlayer Videos\A look at the finches of the Galapagos islands.flv • Watch the PBS video on Evolution: • http://video.pbs.org/video/1372073556/

  22. Nova Video: What Darwin Never KnewA video in 8 15-min parts • RealPlayer Videos\What Darwin Never Knew Part 1 8 NOVA HD.flv • RealPlayer Videos\What Darwin Never Knew Part 2 8 NOVA HD.flv • RealPlayer Videos\What Darwin Never Knew Part 3 8 NOVA HD.flv • RealPlayer Videos\What Darwin Never Knew Part 4 8 NOVA HD.flv

  23. Nova Video: What Darwin Never KnewA video in 8 15-min parts • RealPlayer Videos\What Darwin Never Knew Part 5 8 NOVA HD.flv • RealPlayer Videos\What Darwin Never Knew Part 6 8 NOVA HD.flv • RealPlayer Videos\What Darwin Never Knew Part 7 8 NOVA HD.flv • RealPlayer Videos\What Darwin Never Knew Part 8 8 NOVA HD.flv • Or watch the PBS video on Evolution (streamed video): • http://video.pbs.org/video/1372073556/

  24. References: • http://noahhunt.org/Peachick/peacocking.jpg • http://en.wikipedia.org/wiki/File:Biston.betularia.7200.jpg • http://en.wikipedia.org/wiki/File:Biston.betularia.f.carbonaria.7209.jpg • http://media-2.web.britannica.com/eb-media/76/100276-004-6C641F92.jpg • http://en.wikipedia.org/wiki/File:Lichte_en_zwarte_versie_berkenspanner.jpg • http://www.wildlife-pictures-online.com/image-files/elephant_tep-sc002m.jpg • http://www.drearth.com/advertising-resources/insecticides/homegarden-spray.jpg • http://www.faqs.org/photo-dict/photofiles/list/621/1026bacteria.jpg • http://www.steadyhealth.com/151174/Image/superbug_antibiotic.jpg • http://www.aenvirocure.com/DB_DATA/contams/organic/images/bacteria_ab.jpg • http://www.esr.org/ropex/ropex_penguins4sm.jpg • http://www.cs.usask.ca/faculty/bunt/travel/other.pix/Puffins.jpg • http://www.free-desktop-backgrounds.net/free-desktop-wallpapers-backgrounds/free-hd-desktop-wallpapers-backgrounds/66529365.jpg • http://naturescrusaders.files.wordpress.com/2009/06/great-white-shark-picture-01.jpg • http://www.doobybrain.com/wp-content/uploads/2009/03/pats0n-underwater-phtography.jpg • http://www.bio.davidson.edu/people/vecase/Behavior/Spring2009/Hartye/Media/Male_and_female_superb_fairy_wren.jpg • http://img.xcitefun.net/users/2009/08/107429,xcitefun-pet-birds-1.jpg • http://s3.amazonaws.com/readers/scienceray/2008/07/27/238861_10.jpg • http://www.torontozoo.com/adoptapond/guide_images/Leopard%20Frog.jpg • http://www.torontozoo.com/adoptapond/guide_images/Pickerel%20Frog.jpg • http://forum.globaltimes.cn/forum/attachment.php?attachmentid=37650&thumb=1&d=1283844936 • http://webecoist.com/wp-content/uploads/2010/08/Eyeless_2.jpg

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