Biology: The Dynamic Science (MindTap Course List)
4th Edition
ISBN: 9781305389892
Author: Peter J. Russell, Paul E. Hertz, Beverly McMillan
Publisher: Cengage Learning
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Chapter 21, Problem 1ITD
Peter and Rosemary Grant of Princeton University have studied the ecology and evolution of finches on the Galápagos Islands since the early 1970s. They have shown that finches with large bills (as measured by bill depth; see Figure) can eat both small seeds and large seeds, but finches with small bills can only eat small seeds. In 1977, a severe drought on the island of Daphne Major reduced seed production by plants. After the birds consumed whatever small seeds they found, only large seeds were still available. The resulting food shortage killed a majority of the medium ground finches (Geospizafortis) on Daphne Major; their population plummeted from 751 in 1976 to just 90 in 1978. The Grants’ research also documented a change in the distributions of bill depths in the birds from 1976 to 1978, as illustrated in the graphs to the right. In light of what you now know about the relationship between bill size and food size for these birds, interpret the change illustrated in the graph. What type of natural selection does this example illustrate?
Source: P. R. Grant. 1986. Ecology and Evolution of Darwin’s Finches. Princeton University Press.
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Use the key info from the previous slide to make a prediction about the finches
In 1977, there was a severe drought on the island,
which caused many of the plants to die out. Because
the finches eat the seeds of many of these plants, the
population of birds had to compete for the seeds
that were available. Most seed-eating finches prefer to
eat the small, soft seeds (particularly during the
drought), leaving only the large, tough Tribulus
seeds for the finches not lucky enough to get to the
small seeds in time.
I predict that after the drought, .
Submit
Review the following figure, and then answer the two questions that follow.
a)Given that beak size in mature adults does not change, what factor is driving the change in average beak size in Galápagos finches over time?
Seed number
Seed size
Rainfall amounts
Both b. and c.
All of the above.
b)What would you predict about beak size if the Galápagos experiences a wet year?
More birds with small beaks will survive
More birds with large beaks will survive
Both a. and b.
All of the above
Clausen and colleagues proposed two hypotheses to explain this variation within a species: (1) There are genetic differences between populations of plants found at different elevations. (2) The species has developmental flexibility and can assume tall or short growth forms, depending on local abiotic factors. If you had seeds from yarrow plants found at low and high elevations, what experiments would you perform to test these hypotheses?
Select the three experiments.
Chapter 21 Solutions
Biology: The Dynamic Science (MindTap Course List)
Ch. 21.1 - If a population of skunks includes some...Ch. 21.1 - Prob. 2SBCh. 21.1 - What factors contribute to phenotypic variation in...Ch. 21.2 - Prob. 1SBCh. 21.2 - Why is the Hardy-Weinberg principle considered a...Ch. 21.2 - Prob. 3SBCh. 21.3 - Which agents of microevolution tend to increase...Ch. 21.3 - Which mode of natural selection increases the...Ch. 21.3 - In what way is sexual selection like directional...Ch. 21.4 - How does the diploid condition protect harmful...
Ch. 21.4 - Prob. 2SBCh. 21.4 - Prob. 3SBCh. 21.5 - How can a biologist test whether a trait is...Ch. 21.5 - Why are most organisms adapted to the environments...Ch. 21 - The reason spontaneous mutations do not have an...Ch. 21 - The phenomenon in which chance events cause...Ch. 21 - Prob. 3TYKCh. 21 - Prob. 4TYKCh. 21 - Prob. 5TYKCh. 21 - Which of the following represents an example of...Ch. 21 - A population of mice is at HardyWeinberg...Ch. 21 - If the genotype frequencies in a population are...Ch. 21 - An Eastern European immigrant carrying the allele...Ch. 21 - If a storm kills many small sparrows in a...Ch. 21 - Prob. 11TYKCh. 21 - Discuss Concepts Many human diseases are caused by...Ch. 21 - Prob. 13TYKCh. 21 - Apply Evolutionary Thinking Captive breeding...Ch. 21 - Prob. 15TYKCh. 21 - Design an experiment to test the hypothesis that...Ch. 21 - Peter and Rosemary Grant of Princeton University...
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