Briefly describe the three phases included in most evolutionary models for the preservation of duplicate genes, and the evolutionary processes involved
What will be an ideal response?
First, the duplicated gene must rise to fixation (or high frequency) within a population due to drift, because most gene duplication events are initially selectively neutral. Second, one of the duplicate copies acquires a mutation that changes its function. Finally, the new, mutated allele rises to fixation (or high frequency) due to selection favoring the mutated allele with a new function.
[Graders: The final step does not require selection; in principle, the mutated allele could be selectively neutral and rise to fixation due to drift.]
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Which of the following situations would be MOST likely to produce a new species?
A. A group of polyploid individuals arises by an abnormal meioses. The polyploids can only produce viable offspring by mating with each other. B. Several individuals join an existing population and introduce several new, beneficial alleles. C. Several individuals colonize a new area and establish a population. Migration between the two populations is common. D. An existing species becomes subdivided by a glacier and the resulting groups remain physically isolated from each other for thousands of years. When the glacier melts, the two groups are able to interbreed. E. A volcano erupts and kills all of the frogs on an island, along with many other species. New frogs colonize the island and begin reproducing rapidly because there are no longer any frog predators.
Red blood cells in mammals ____
a. have a large nucleus when they enter circulation b. do not have a nucleus when they enter circulation c. are the only cells to lack hemoglobin d. develop in the yellow marrow e. function as part of the immune system
Which of the following statements concerning pore spaces is false?
a. Minerals are removed from soil via leaching. b. Water is held in the smaller pores, and air is found in the larger pores. c. They occupy approximately 50% of a soil's volume. d. They typically contain more carbon dioxide than found in the atmosphere. e. Immediately after a heavy rain, most pore spaces remain filled with air.
Any agent that can potentially cause cognitive, behavioral or physical harm to the developing embryo or fetus is a(n) ______.
a. psychoactive drug b. disease c. teratogen d. trophoblast