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Why are protists considered paraphyletic?
a. They include many extinct forms, including lineages that no longer have any living representatives.
b. They include some but not all descendants of their most recent common ancestor.
c. They represent all of the descendants of a single common ancestor.
d. Not all protists have all of the synapomorphies that define the Eukarya, such as a nucleus.
Introduction:
A protist refers to any eukaryotic organism that has a cell with distinct nucleic acids and other membrane-covered structures. They do not form a clade or a natural group.
Answer to Problem 1TYK
Correct answer:
Therefore, protists are considered paraphyletic as this organism group includes only the most recent common ancestors as their descendants.
Explanation of Solution
Explanation/justification for the correct answer:
Option (b) is given as the protists include only some descendants of their recent common ancestors. The protists are the unicellular eukaryotes. This group of organisms is simple, but very diverse. These organisms do not have common ancestors. They possess different cellular structures, varying life cycles as well as different locomotion modes. They possess characteristics of plants or animals or both. Hence, Option (b) is correct.
Explanation for incorrect answer:
Option (a) is given as they involve extinct forms including the lineages that do not have any living representatives. After studying different protists at the molecular level, it has been found that they do not have common ancestors. The protists have characteristics of the descendants of some of their recent common ancestors. So, it is a wrong answer.
Option (c) is given as they show all the descendants of a single common ancestor. The taxa, which represents the protists does not include all descendants of all of their ancestors. This means that they are paraphyletic and not monophyletic. So, it is a wrong answer.
Option (d) is given as not all protists consist of synapomorphies, which describe the eukarya like the nucleus. Therefore, the protists are paraphyletic because they include only some descendants of a single common ancestor. They do not include lineages that no longer have any living representatives. The protists are those eukaryotes that are neither animals, plants, nor fungi, but they all possess a well-defined nucleus. So, it is a wrong answer.
Hence, options (a), (c), and (d) are incorrect.
Therefore, it can be concluded that the protists are known as paraphyletic because they involve some descendants of their recent common ancestor.
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Chapter 27 Solutions
Biological Science (7th Edition)
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Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning