Plant species A has a diploid chromosome number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be a. 14. b. 16. c. 28. d. 56.

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Understand the concept of allopolyploidy: Allopolyploidy is a type of polyploidy where an organism contains sets of chromosomes from two or more different species. This usually occurs when two different species hybridize and then undergo chromosome doubling.

Identify the chromosome numbers of the parent species: Species A has a diploid chromosome number of 12, and species B has a diploid chromosome number of 16.

Determine the chromosome contribution from each parent to the hybrid: In the case of allopolyploidy, the hybrid species C would initially have the sum of the chromosome numbers from species A and B before chromosome doubling. This sum is 12 (from A) + 16 (from B) = 28.

Apply the concept of chromosome doubling: After the initial hybridization, the chromosome number typically doubles to stabilize the genome. Therefore, the new diploid number for species C would be 28 x 2 = 56.

Choose the correct answer based on the calculation: The diploid number for species C, which is an allopolyploid of species A and B, would be 56. Therefore, the correct answer is d. 56.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Diploid Chromosome Number

The diploid chromosome number refers to the total number of chromosomes in a cell, organized in pairs. In this context, plant species A has 12 chromosomes (6 pairs) and species B has 16 chromosomes (8 pairs). Understanding diploid numbers is crucial for determining the genetic makeup of offspring, especially in hybridization scenarios.

Allopolyploidy

Allopolyploidy is a form of polyploidy that occurs when two different species hybridize and the resulting offspring have multiple sets of chromosomes from both parent species. In this case, species C arises from the hybridization of species A and B, leading to a new diploid number that is the sum of the diploid numbers of the parent species.

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Polyploidy

Related Practice

According to the punctuated equilibria model, a. given enough time, most existing species will branch gradually into new species. b. most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species. c. most evolution occurs in sympatric populations. d. speciation is usually due to a single mutation.

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Textbook Question

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification? a. The two forms interbreed often in nature, and their offspring survive and reproduce well. b. The two forms live in similar habitats and have similar food requirements. c. The two forms have many genes in common. d. The two forms are very similar in appearance.

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Textbook Question

Which of the following factors would not contribute to allopatric speciation? a. The separated population is small, and genetic drift occurs. b. The isolated population is exposed to different selection pressures than the ancestral population. c. Different mutations begin to distinguish the gene pools of the separated populations. d. Gene flow between the two populations is extensive.

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