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Inquiry Questions

FIGURE 25.15
A new hypothesis for land plant evolution. Kingdom Plantae has been reduced to a clade within the green algal branch Streptophyta, and a new kingdom, Viridplantae, which includes the green algal branches Chlorophyta and Streptophyta, has been proposed. Within the Streptophyta, the relatively complex Charales are believed to be the sister clade to the land plants.
Contrast this phylogeny with the one predicted by the six-kingdom system in figure 25.9.
Answer: In the six-kingdom system (figure 25.9), only the land plants would be predicted to be members of the kingdom Plantae. The green algae would be classified as protists, not as members of the Viridplantae (green plant kingdom). The red algae would not be considered to be members of the Viridplantae in either scheme. A fundamental problem with the six-kingdom system is that the protists are a catchall group and many protists have only the most distant phylogenetic relationships to each other.

Self Test

1). There are over 300 different species of fiddler crabs. In all of these species, the adult males possess an enlarged front claw. Based on this feature, biologists group these different species together in the same genus, Uca. Therefore, the large claw is
    a). an outgroup.
    b). an analogous trait.
    c). a homoplasy.
    d). a synapomorphy.
Answer: d

2). The domestic dog, Canis familiaris, is related to wild dog species such as the gray wolf, Canis lupus. To which most exclusive category do the wolf and dog both belong?
    a). order
    b). family
    c). genus
    d). species
Answer: c

3). The simplest animals, the sponges (Parazoa), lack true tissues. All other animals (Eumetazoa) have distinct tissues. The presence of true tissues is a
    a). useful character for distinguishing amongst the eumetazoans.
    b). shared ancestral state.
    c). shared derived state.
    d). plesiomorphy.
Answer: c

4). Originally, organisms were classified according to a two-domain system that consisted of the bacteria and the eukaryotes. Recently, a three-domain system of classification has been proposed in which domain Bacteria was divided into domain Archaea and domain Bacteria. This is because
    a). there are so many different species of prokaryotes.
    b). of the large genetic differences between the archaebacteria and the bacteria.
    c). the archaebacteria have a nucleus like that of eukaryotes.
    d). the archaebacteria live in inhospitable environments, so they should be put in a different domain.
Answer: b

5). Which of the following is the most abundant group of organisms on earth?
    a). archaebacteria
    b). bacteria
    c). protists
    d). fungi
Answer: b

6). Biologists do not consider viruses to be alive. This is because viruses
    a). are unable to reproduce on their own.
    b). do not contain genetic material.
    c). do not contain proteins.
    d). are smaller than living organisms.
Answer: a

7). As more is learned about the molecular and genetic aspects of organisms, taxonomic groupings are changing. Which group of eukaryotes is the focus of most controversy related to their taxonomic groupings?
    a). bacteria
    b). protists
    c). animals
    d). fungi
Answer: b

8). According to new molecular and biochemical information, should the plants still be recognized as a distinct kingdom?
    a). Yes, the green algae are now considered to be in the kingdom Plantae.
    b). Yes, the green algae and the plants are now recognized to be unrelated.
    c). No, the plants and the green algae are now classified together in the kingdom Virdiplantae.
    d). No, the plants are now classified together within the Chlorophyta.
Answer: c

9). The relationship between the annelids and the arthropods is now thought to be
    a). monophyletic.
    b). polyphyletic.
    c). paraphyletic.
    d). unrelated.
Answer: b

Test Your Visual Understanding

1). Using the image from figure 25.8, fill in the following table to indicate the presence or absence of the derived character.
Light bones Breastbone Downy feathers Feathers with vanes, shafts, and barbs Aerodynamic feathers Arms longer than legs Other Dinosaurs Coelophysis Tyrannosaurus Sinosauropteryx Velociraptor Caudipteryx Archaeopteryx Modern Birds
Answer:
Light bones Breastbone Downy feathers Feathers with vanes, shafts, and barbs Aerodynamic feathers Arms longer than legs Other Dinosaurs 0 0 0 0 0 0 Coelophysis 1 0 0 0 0 0 Tyrannosaurus 1 1 0 0 0 0 Sinosauropteryx 1 1 1 0 0 0 Velociraptor 1 1 1 1 0 0 Caudipteryx 1 1 1 1 1 0 Archaeopteryx 1 1 1 1 1 1 Modern Birds 1 1 1 1 1 1

Apply Your Knowledge

1). Most biologists consider viruses to be nonliving because they are unable to replicate outside of a host cell. How might you argue against this position? What characteristics do viruses have them make them lifelike?
Answer: Viruses contain genetic material and thus are subject to natural selection as are all living organisms.

2). Phylogenetic relationships are established based on assumptions about evolutionary relatedness. It is assumed that the more similar two organisms are, the more closely they are related. What problems does the process of convergent evolution cause for systematists?
Answer: Convergent evolution is a process by which two unrelated species evolve to become more similar. This is due to the species use of similar habitats, which results in selection for similar adaptations. As a result of convergent evolution, systematists may classify two species as being closely related when in fact they are not.

3). Ethnobotanical research involves the exploration of plants that may have uses, particularly medical, for humans. Of what value is knowledge of systematics to an ethnobotanist?
Answer: Related species share biochemical similarities. If a certain species of plant is found to contain medicinal compounds, it would be worthwhile to examine related species to determine if they have similar compounds.








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