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Chap 24

Chap 24. Origin of Species. Changes within a species. Branching evolution which results in more species and more diversity. Accumulation of changes leading to a new species.

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Chap 24

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  1. Chap 24 Origin of Species

  2. Changes within a species

  3. Branching evolution which results in more species and more diversity Accumulation of changes leading to a new species

  4. If closely related species become SYMPATRIC or if ALLOPATRIC species start to hybridize and exchange genes they will become ONE species again. If species are to remain as separate species, then they must develop INTRINSIC REPRODUCTIVE ISOLATING MECHANISMS to prevent gene flow and remain separate

  5. Ecological Species Definition: if there is no gene flow between two populations because they prefer different parts of the ecology or habitat, they are considered separate species.

  6. Temporal Isolation

  7. Sexual selection

  8. Artemesiae and nebrascensis are considered PARAPATRIC SUBSPECIES although they live in adjacent areas they don’t mate, however there is still gene flow between the subspecies through matings with borealis and sonoriensis

  9. Bonus: write a good pneumonic device to memorize this

  10. Speciation starts off with EXTRINSIC ISOLATING MECHANISMS the populations are ALLOPATRIC p469 four conditions which favor allopatric speciation

  11. Gene flow is stopped or limited

  12. 3 Things that will cause the populations to form subspecies: • Different selection pressure. • Different mutations. • Different starting gene frequencies (founder effect) • Small populations may be subject to genetic drift (random change in gene freq.) • If the area is relatively unexploited, adaptive radiation may occur.

  13. Some races may become so specialized that they no longer interbreed with races

  14. A ring species range is so large that it circles back on itself – some ranges may circle around the earth

  15. No interbreeding between the extremes of the cline

  16. Because of sexual selection B and C don’t mate Because of ecological competition B and C become more different from each other.

  17. This process can occur many times as long as the ecology can support the different types of birds this results in adaptive radiation.

  18. 1. How many different species descended from the species that colonized the first island? Identify them. three; B, C, and D

  19. 2. Why is species A no longer present on these islands? How is that change different from what happened to species B? Species A evolved into species B and no longer exists as a separate species. Species B is the common ancestor of species C and D, and it continues to coexist with the two newer species.

  20. P471 Adaptive Radiation-flurries of allopatric speciation p451 four conditions which favor allopatric speciation

  21. Adaptive Radiation • the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities N 1.3 million years Dubautia laxa MOLOKA'I KAUA'I MAUI 5.1 million years Argyroxiphium sandwicense O'AHU LANAI 3.7 million years HAWAI'I 0.4 million years Dubautia waialealae 21.5 Dubautia scabra Dubautia linearis

  22. The bright yellow and red-crowned Yariguies brush-finch was found in a remote Colombian cloud forest.

  23. P 473

  24. SYMPATRIC SPECIATION Autopolyploidy- same species forms new sp Oenothera lamarkia 2N=14 Oenothera gigas 4N=28

  25. Allopolyploidy- two different species mate to form polyploid hybrid S. martima 2N=60 S. alternaflora 2N=62 S. anglica 2N=122 There are different ways for allopolyploidy to occur Odd # of chromosomes P 474 Meiotic error

  26. 476 Darwin Eldridge and Gould

  27. Evolution of the Genes That Control Development • Genes that program development • Control the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult 21.8

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