Evolution in Hawaii A Supplement to 'Teaching About Evolution and the Nature of Science' (2004) / Chapter Skim
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Teaching Exercise: Tracing the Evolutionary Origins of Picture-Winged Drosophila Species
Teaching Exercise: Tracing the Evolutionary Origins of Picture-Winged Drosophila Species
Pages 29-47
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From page 29... ...
In the ~~t activity, students read a background document describing the drosophilid flies of Hawaii, their courtship rituals, their descent from a common ancestral species, and the speciation processes that led to their current diversity. The reading concludes with several review questions that can provide the basis for written responses or a classroom discussion.
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From page 30... ...
The great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms. Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms.
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From page 31... ...
Technology used to gather data enhances accuracy and allows scientists to analyze and quantify results of investigations. Scientific explanations emphasize evidence, have logically consistent arguments, and use scientific principles, models, and theories.
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From page 32... ...
Speciation also has often followed founder events, when a single fertilized fly or several flies either traveled or were transported from one island to another island or between habitable but geographically isolated portions of the same island. Successful colonization is more likely when founders from older islands in Hawaii move to younger islands, since younger islands generally contain fewer competing species of drosophilids.
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From page 33... ...
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From page 35... ...
-- -- -- -- -- -- -- -- -- -- ~ -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -:: :: :: ~~t~ ~~f ~~ p~ fth ~ ~ ~~ ~ ~ ~ h ~d .............................................................................................................................
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From page 41... ...
* The evolutionary relationships of these four species are explored in detail in the exploration phase of the exercise.
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From page 42... ...
Many drosophilid species have elaborate sex lives. First the males establish a mating territory called a lek.
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From page 43... ...
The polytene chromosomes of the Hawaiian drosophilids, along with other genetic data, point toward a common origin for these very different species of flies. Polytene chromosomes also can be used to trace the evolutionary history of individual drosophilid species.
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From page 44... ...
Because of their volcanic origins, the Hawaiian islands have different ages, with the younger islands to the southeast. As each new island rose from the waves, small populations of flies or single fertilized females made their way from older islands to newer ones, where their descendants could become increasingly distinct from the ancestral species.
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From page 45... ...
As shown in Figure 1, phylogenetic trees depict the evolution of two or more descendant species Tom a single ancestral species, with lines connecting the ancestral species to the descendant species. In the drosophilid flies of Hawaii, these descendant Ados ~°~"d~ ~ :~; ~~ ~ ~ An evolutionary tree of the living groups of mammals Demonstrates their relationships, though some of the Details of the tree remain controversial or ambiguous.
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From page 46... ...
The oldest islands are to the northwest and the youngest islands are to the southeast. If two species Descended from a common ancestral species Differ by the presence of a chromosomal inversion, when must the inversion have occurred?
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From page 47... ...
Elaboration In the elaboration phase of the investigation, additional data from Table 1 or the data from Table 2 can be analyzed. Using all the data in Table 1 permits the construction of a much larger phylogenetic tree showing the evolutionary relationships among the 13 species of flies described in the table.
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