32 biology
Which tissue type or organ is not correctly matched with its germ layer tissue? ANSWER: nervous: mesoderm stomach: endoderm muscular: mesoderm skin: ectoderm
a
At one time, sponges were lumped into one phylum. Then, they were separated into several different phyla. Now, they are considered one phylum again. These changes indicate which of the following? ANSWER: Every phylogeny should be considered a hypothesis that must be revised in the light of new data. We need more fossil evidence of sponges. Molecular and morphological data often conflict when we try to reconstruct evolutionary history. The goal of making all taxonomic groups monophyletic is unrealistic.
a
Evidence of which structure or characteristic would be most surprising to find among fossils of the Ediacaran fauna? ANSWER: hard parts embryos true tissues bilateral symmetry
a
Sponges and ctenophores have both been proposed as basal metazoans. Which of the following types of data support the idea that sponges are the basal group? ANSWER: fossil steroids, molecular clock, lack of tissues in sponges, and structure of collar cells sequences of cadherin genes, cleavage type, structure of collar cells, and bilateral symmetry of adults sequences of collagen genes, bilateral symmetry of adults, cleavage type, and fossil steroids structure of collar cells, bilateral symmetry of larvae, sequences of cadherin genes, and molecular clock
a
The evolution of animal species has been prolific (current estimates of species numbers reach into the tens of millions). Much of this diversity is a result of the evolution of novel ways to ________. ANSWER: sense, feed, and move form an embryo and establish a basic body plan reproduce arrange cells into tissues
a
The last common ancestor of all animals was probably a _____. ANSWER: flagellated protist unicellular chytrid multicellular algae multicellular fungus
a
The last common ancestor of all bilaterians is thought to have had four Hox genes. Most extant cnidarians have two Hox genes, though some have three Hox genes. On the basis of these observations, some have proposed that the ancestral cnidarian's were originally bilateral and, in stages, lost Hox genes from their genomes. If true, this would mean that ________. ANSWER: the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral trait all radially symmetric animals should be grouped together in one clade Hox genes play little actual role in coding for an animal's "body plan" cnidaria may someday replace porifera as the basal bilaterians
a
Use the figure to answer the question. A: Morphological phylogeny. A phylogenetic tree is shown, beginning with an ancestral colonial flagellate, the Metazoa. This divides into the Porifera and the Eumetazoa. Eumetazoa divide again, into Cnidaria and another branching point. This point divides into the Ctenophora and the Bilateria. Bilateria divides into the Deuterostomia and the Protostomia. Deuterostomia divide into Ectoprocta, Brachiopoda, and a final division into Echinodermata and Chordata. Protostomia. Divides into Platyhelminthes and further branches, into Rotifera, Mollusca, a division into Annelida and arthropoda , and Nematoda B: Molecular phylogeny. A phylogenetic tree is shown, beginning with an ancestral protist (the metazoan). This divides with one direction leading to porifera, and the other leading to the Eumetazoa. This eumetazoa branch divides ago into cenophora, and another branching point which divides into the Cnidaria, and the group Bilateria. The bilateria branch divides into the Acoela (flat worms) in one direction, and a branching point in the other. This divides into the group Deuterostomia in one direction, and another branching point in the other. Dueterostomia branch into a branching point for hemichordata (shown with a worm) and Echinodermata (shown as a star fish), and in the other direction leads to chordate, shown as a snake. The second branch from Bilateria leads to another branching point. This divides into Lophotrochoazoa, which are the Platyhelminthes, Rotifera, Ectoprocta, Brachiopoda, Mollusca and Annelida. The other branch leads to Ecdysozoa, the Nematoda and Arthropoda. In the traditional phylogeny (A), the phylum Platyhelminthes is depicted as a sister taxon to the rest of the protostome phyla and as having diverged earlier from the lineage that led to the rest of the protostomes. In the molecular phylogeny (B), Platyhelminthes is depicted as a Lophotrochozoan phylum. What probably led to this change? ANSWER: The removal of the acoel flatworms (Acoela) from the Platyhelminthes allowed the remaining flatworms to be a monophyletic clade clearly tied to the Lophotrochozoa. Platyhelminthes' close genetic ties to the arthropods became clear as their Hox gene sequences were studied. Platyhelminthes ceased to be recognized as true protostomes. All Platyhelminthes must have a well-developed lophophore as their feeding apparatus.
a
Use the figure to answer the question. A phylogenetic tree is depicted as a mainline with a number of branches from the line. Specific points in development are marked. The first branch leads to the Choanoflagellates. Between that and the next branch, multicellularity and epithelial tissue develop. That next branch is to the Porifera (sponges); all organisms through the rest of the diagram are part of Animalia. Between this branch and the next, organisms develop diploblasty (ectoderm and endoderm) and radial symmetry. The next branch divides into the Cnidaria (jellyfish, sea anemones) and the Ctenophora (comb jellies). The next landmarks on the main line are bilateral symmetry and cephalization, and triploblasty (origin of mesoderm). The next branch is to the Acoelomorphia (acoels), and starting with this branch organisms are part of Bilateria. The next milestone is the development of Coelem. The next branch divides several times. Between the main line of the branch and further divisions occurs protostome development. Farther out this main division is a split, along one branch of which occurs Pseudocoelom, leading to development of Rotifera (rotifers). The second branch divides further: Acoelem develops leading to Platyhelminthes (flatworms), and the final division has two branches. Segmentation occurs along the first branch, which leads to Annelida (segmented worms); the other branch ends at the Mollusca (snails, clams, squid). Rotifera, Platyhelminthes, Annelida, and Mollusca are all part of Lophotrochozoa. Between protostome development and the branch that leads to the mollusks is another division. Occurs growth by molting. The end of that line divides into Nematoda (roundworms) and arthropoda (insects, spiders, stressed crustaceans); Pseudocoelom occurs on the branch to the nematodes, and segmentation occurs on the branch to the arthropods. These two groups are part of Ecdysozoa. Lophotrochozoa and Ecdysozoa comprise Protostoma The final section of the mainline shows the development of Deuterostome before a final division. Radial symmetry (in adults) occurs on the branch to the Echinodermata, and segmentation occurs on the branch to Chordata (vertebrates, ascidians). These last two groups are part of Deuterostoma. Which of the following statements is supported by the phylogeny in the figure? ANSWER: Animals with extremely different adult forms can be relatively closely related. Deuterostoma are more evolutionarily advanced than Porifera. Traits, once they evolve, are retained in later-evolving taxonomic groups. Animals show no evidence of convergent evolution in their traits.
a
Use the information to answer the question. Nudibranchs, a type of predatory sea slug, can have various protuberances (that is, extensions) on their dorsal surfaces. Rhinophores are paired structures, located close to the head, which bear many chemoreceptors. Dorsal plumules, usually located posteriorly, perform respiratory gas exchange. Cerata usually cover much of the dorsal surface and contain nematocysts at their tips. If nudibranch rhinophores are located at the anterior ends of these sea slugs, then they contribute to the sea slugs' ________. ANSWER: development of a head identity as lophotrochozoans lack of torsion segmentation
a
Use the information to answer the question. One small animal phylum (Placozoa) contains only two species, Trichoplax adhaerens (T. adhaerens) and T. reptans. T. adhaerens is the only species seen in over a century. Individuals are about 1 mm wide and only 27 m high, are irregularly shaped, and consist of a total of about 2,000 cells, which are diploid (2n = 12). There are four types of cells, none of which are nerve or muscle cells, and none of which have cell walls. Individual animals move using cilia, and any "edge" can lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells have never been observed. Embryos up to, but not past, the 64-cell (blastula) stage have been observed. On the basis of information in the paragraph, which of these should be able to be observed in T. adhaerens? ANSWER: eggs a coelom a radially symmetric larval form the process of gastrulation
a
Use the information to answer the question. Trichoplax adhaerens is the only living species in the phylum Placozoa. Individuals are about 1 mm wide and only 27 µm high, are irregularly shaped, and consist of a total of about 2,000 cells, which are diploid (2n = 12). There are four types of cells, none of which are nerve or muscle cells, and none of which have cell walls. Individual animals move using cilia, and any "edge" can lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage. Which of the following T. adhaerens traits is different from all other known animals? ANSWER:
a
What do all deuterostomes have in common? ANSWER: The pore (blastopore) formed during gastrulation becomes the anus. Embryos have pharyngeal pouches that may or may not form gill slits. Adults are bilaterally symmetrical. All have a spinal column.
a
What do animals ranging from corals to monkeys have in common? ANSWER: presence of Hox genes a mouth and an anus some type of body symmetry number of embryonic tissue layers
a
What was an early selective advantage of a coelom in animals? A coelom _____. ANSWER: contributed to a hydrostatic skeleton, allowing greater range of motion allowed cephalization and the formation of a cerebral ganglion was a more efficient digestive system allowed asexual and sexual reproduction
a
Whatever its ultimate cause(s), the Cambrian explosion is a prime example of _____. ANSWER: adaptive radiation a large meteor impact mass extinction evolutionary stasis
a
Which of the following is (are) unique to animals? ANSWER: nervous system signal conduction and muscular movement the structural carbohydrate, chitin flagellated gametes heterotrophy
a
Which of the following is a feature of the "tube-within-a-tube" body plan in most animal phyla? ANSWER: The mouth and anus form the ends of the inner tube. The outer tube consists of digestive organs. The two "tubes" are separated by tissue that comes from embryonic endoderm. The outer tube consists of a hard exoskeleton.
a
Which of the following would you classify as something other than an animal? ANSWER: choanoflagellate coral sponge jellyfish
a
Among protostomes, which morphological trait has shown the most variation? ANSWER: type of symmetry (bilateral versus radial versus none) type of body cavity (coelom versus pseudocoelom versus no coelom) number of embryonic tissue types (diploblasty versus triploblasty) type of development (protostome versus deuterostome)
b
Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal heterotrophy is that most animals derive their nutrition by ________. ANSWER: consuming living, rather than dead, prey ingesting materials preying on animals using enzymes to digest their food
b
If in the future the current molecular evidence regarding animal origins is further substantiated, which of the following statements would be correct with reference to fossil evidence that contradicts molecular evidence? ANSWER: The fossil record will, henceforth, be ignored. The fossil evidence will be understood to have been interpreted incorrectly because it is incomplete. Phylogenies involving even the smallest bit of fossil evidence will need to be discarded. The contrary fossil evidence will be seen as a hoax.
b
If you think of the earthworm body plan as a drinking straw within a pipe, where would you expect to find most of the tissues that developed from endoderm? ANSWER: lining the space between the pipe and the straw lining the straw forming the outside of the pipe forming the outside of the straw
b
In the future, phylogenetic studies should be conducted to ________. ANSWER: discover the relationships between nematodes and platyhelminthes resolve the branching patterns (evolutionary history) of the Lophotrochozoa discover the larval stages of echinoderms discover the Hox genes in sponges
b
Nine-banded armadillos give birth to four offspring at a time. An amazing fact about these offspring is that they are genetically identical to each other. This fact suggests ________. ANSWER: the young undergo metamorphosis the first cell division of the fertilized egg is perpendicular to the vertical axis of the egg the embryo undergoes radial and indeterminate cleavage the species is pseudocoelomate
b
One hypothesis suggests that the Cambrian explosion was caused by the rise of predator-prey relationships. This hypothesis is best supported by an increased incidence of which of the following fossil traces? ANSWER: organic material hard parts worm burrows larger animals
b
Some researchers claim that sponge genomes have homeotic genes, but no Hox genes. If true, this finding would _____. ANSWER: mean that extinct sponges must have been the last common ancestor of animals and fungi confirm the identity of sponges as "basal animals" mean that sponges must no longer be classified as animals require sponges to be reclassified as choanoflagellates
b
The common ancestor of the protostomes had a coelom. What does this suggest? ANSWER: There are no acoelomates within the protostomes. The body cavity evolved before the lophophore. There are no pseudocoelomates within the protostomes. All lophotrochozoans have a coelom.
b
The primary difference between a coelom and a pseudocoelom is ________. ANSWER: a coelom occurs in triploblastic animals, and a pseudocoelom occurs in diploblastic animals their developmental origin a coelom arises in the ectoderm, and a pseudocoelom arises in the endoderm the manner in which they cushion the internal organs
b
Use the figure to answer the question. A phylogenetic tree is depicted as a mainline with a number of branches from the line. Specific points in development are marked. The first branch leads to the Choanoflagellates. Between that and the next branch, multicellularity and epithelial tissue develop. That next branch is to the Porifera (sponges); all organisms through the rest of the diagram are part of Animalia. Between this branch and the next, organisms develop diploblasty (ectoderm and endoderm) and radial symmetry. The next branch divides into the Cnidaria (jellyfish, sea anemones) and the Ctenophora (comb jellies). The next landmarks on the main line are bilateral symmetry and cephalization, and triploblasty (origin of mesoderm). The next branch is to the Acoelomorphia (acoels), and starting with this branch organisms are part of Bilateria. The next milestone is the development of Coelem. The next branch divides several times. Between the main line of the branch and further divisions occurs protostome development. Farther out this main division is a split, along one branch of which occurs Pseudocoelom, leading to development of Rotifera (rotifers). The second branch divides further: Acoelem develops leading to Platyhelminthes (flatworms), and the final division has two branches. Segmentation occurs along the first branch, which leads to Annelida (segmented worms); the other branch ends at the Mollusca (snails, clams, squid). Rotifera, Platyhelminthes, Annelida, and Mollusca are all part of Lophotrochozoa. Between protostome development and the branch that leads to the mollusks is another division. Occurs growth by molting. The end of that line divides into Nematoda (roundworms) and arthropoda (insects, spiders, stressed crustaceans); Pseudocoelom occurs on the branch to the nematodes, and segmentation occurs on the branch to the arthropods. These two groups are part of Ecdysozoa. Lophotrochozoa and Ecdysozoa comprise Protostoma The final section of the mainline shows the development of Deuterostome before a final division. Radial symmetry (in adults) occurs on the branch to the Echinodermata, and segmentation occurs on the branch to Chordata (vertebrates, ascidians). These last two groups are part of Deuterostoma. Which morphological trait evolved more than once in animals, according to the phylogeny based on DNA sequence data found in the figure? ANSWER: bilateral symmetry segmentation protostome development coelom
b
Use the information to answer the question. Trichoplax adhaerens is the only living species in the phylum Placozoa. Individuals are about 1 mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about 2,000 cells, which are diploid (2n = 12). There are four types of cells, none of which are nerve or muscle cells, and none of which have cell walls. Individual animals move using cilia, and any "edge" can lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage. T. adhaerens' body symmetry seems to be most like that of ________. ANSWER: cnidarians most sponges worms tetrapods
b
Use the table to answer the following question. Organism Appearance Habitat/Activity Nutrient Acquisition Reproduction A Microscopic, unicellular, with a flagellum Swims around in freshwater pools Envelops and consumes other microscopic organisms Mates with others; young bud off B Shaped like a basketball, covered with purple filaments, multicellular Rolls slowly across grassy fields Thrives with access to only freshwater and sunlight Mates with others; young emerge from hardened spherical structures C Hard and branched, multicellular, covered in a sticky coating Attached to rocky surfaces Traps insects in sticky coating and dissolves them No mating; releases winged young that fly off and affix to bare rocks D Multicellular with cell walls Flies across fields Constructs nets to trap flying organisms, and sucks out internal fluids Mates with others, and disperses young ballistically As you are on the way to Tahiti for a vacation, your plane crash lands on a previously undiscovered island. You soon find that the island is teeming with unfamiliar organisms, and you, as a student of biology, decide to survey them (with the aid of the Insta-Lab Portable Laboratory you brought along in your suitcase). You select four organisms and observe them in detail, making the notations found in the figure. In which of the organisms listed would you search for photosynthetic genes? ANSWER: organism A organism B organism C organism D
b
Use the table to answer the question. Proposed Number of Hox Genes in Various Extant and Extinct Animals Last Common Ancestor of Bilateria Last Common Ancestor of Insects and Vertebrates Ancestral Vertebrates Mammals 4 7 14 38-40 What conclusion can best be drawn from the data in the table? ANSWER: Extant insects all have seven Hox genes. The expansion in number of Hox genes throughout vertebrate evolution cannot be explained merely by three duplications of the ancestral vertebrate Hox cluster. All bilaterian phyla have had the same degree of expansion in their numbers of Hox genes. Land animals have more Hox genes than do those that live in water.
b
What is the probable sequence in which the following animal clades originated, from earliest to most recent? ANSWER: bilaterians, deuterostomes, amniotes, vertebrates, tetrapods deuterostomes, bilaterians, vertebrates, tetrapods, amniotes bilaterians, deuterostomes, vertebrates, tetrapods, amniotes deuterostomes, bilaterians, amniotes, vertebrates, tetrapods
b
Which of the following genetic processes may be most helpful in accounting for the Cambrian explosion? ANSWER: binary fission gene duplication random segregation chromosomal condensation
b
You find a new species of worm and want to classify it. Which of the following lines of evidence would allow you to classify the worm as a nematode and not an annelid? ANSWER: It is segmented. It sheds its external skeleton to grow. It has a coelom. It is triploblastic.
b
You have before you a living organism, which you examine carefully. Which of the following should convince you that the organism is acoelomate? ANSWER: It possesses sensory structures at its anterior end. Muscular activity of its digestive system distorts the body wall. It has bilateral symmetry. It is triploblastic.
b
An organism that exhibits a head with sensory equipment and a brain probably also ________. ANSWER: is diploblastic is segmented is bilaterally symmetrical has a coelom
c
Cadherin proteins help animal cells stick (adhere) to each other. Choose which statement about cadherin in cancer cells that are metastasizing (spreading) throughout a patient's body is most likely correct. ANSWER: Cadherin proteins in metastasizing cancer cells are likely to have mutations that make them more "sticky." Mutations in cadherin proteins are unlikely to affect the metastasizing of cancer cells. Cadherin proteins in metastasizing cancer cells are likely to have mutations that make them less "sticky." Mutations in cadherin proteins accumulate at a constant rate that can be measured by a molecular clock.
c
Suppose a researcher for a pest-control company developed a chemical that inhibited the development of an embryonic mosquito's endodermal cells. Which of the following would be a likely mechanism by which this pesticide works? ANSWER: The mosquito would have trouble with respiration and circulation, due to impaired muscle function. The mosquito would develop a weakened exoskeleton that would make it vulnerable to trauma. The mosquito would have trouble digesting food, due to impaired gut function. The mosquito wouldn't be affected at all.
c
The protostome developmental sequence arose just once in evolutionary history, resulting in two main subgroups-Lophotrochozoa and Ecdysozoa. What does this finding suggest? ANSWER: The lophotrochozoans are monophyletic. The protostomes are a polyphyletic group. Division of these two groups occurred after the protostome developmental sequence appeared. These two subgroups have a common ancestor that was a deuterostome.
c
Use the table to answer the following question. Organism Appearance Habitat/Activity Nutrient Acquisition Reproduction A Microscopic, unicellular, with a flagellum Swims around in freshwater pools Envelops and consumes other microscopic organisms Mates with others; young bud off B Shaped like a basketball, covered with purple filaments, multicellular Rolls slowly across grassy fields Thrives with access to only freshwater and sunlight Mates with others; young emerge from hardened spherical structures C Hard and branched, multicellular, covered in a sticky coating Attached to rocky surfaces Traps insects in sticky coating and dissolves them No mating; releases winged young that fly off and affix to bare rocks D Multicellular with cell walls Flies across fields Constructs nets to trap flying organisms, and sucks out internal fluids Mates with others, and disperses young ballistically As you are on the way to Tahiti for a vacation, your plane crash lands on a previously undiscovered island. You soon find that the island is teeming with unfamiliar organisms, and you, as a student of biology, decide to survey them (with the aid of the Insta-Lab Portable Laboratory you brought along in your suitcase). You select four organisms and observe them in detail, making the notations found in the figure. In which of the organisms listed would you search for collagen?
c
Use the table to answer the following question. Organism Appearance Habitat/Activity Nutrient Acquisition Reproduction A Microscopic, unicellular, with a flagellum Swims around in freshwater pools Envelops and consumes other microscopic organisms Mates with others; young bud off B Shaped like a basketball, covered with purple filaments, multicellular Rolls slowly across grassy fields Thrives with access to only freshwater and sunlight Mates with others; young emerge from hardened spherical structures C Hard and branched, multicellular, covered in a sticky coating Attached to rocky surfaces Traps insects in sticky coating and dissolves them No mating; releases winged young that fly off and affix to bare rocks D Multicellular with cell walls Flies across fields Constructs nets to trap flying organisms, and sucks out internal fluids Mates with others, and disperses young ballistically As you are on the way to Tahiti for a vacation, your plane crash lands on a previously undiscovered island. You soon find that the island is teeming with unfamiliar organisms, and you, as a student of biology, decide to survey them (with the aid of the Insta-Lab Portable Laboratory you brought along in your suitcase). You select four organisms and observe them in detail, making the notations found in the figure. Which organism would you classify as an animal? ANSWER: organism A organism B organism C organism D
c
When a scientist describes the "body plan" of a phylum, he or she is implying that ________. ANSWER: mutations have arisen that allow only some shapes to be produced organisms direct their own evolution in order to maximize their success the body shapes we see now have been more successful than others in the past animals evolve according to a pre-ordained plan
c
Which of the following statements comparing symmetry in sessile and swimming animals is most probable? ANSWER: Radial symmetry occurs most frequently in animals that catch their prey by rapid swimming. Bilateral symmetry allowed animals to evolve nerves. Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot. Radial symmetry is more advantageous for active swimming than is bilateral symmetry.
c
Which of these statements, if accurate, would support the claim that the ancestral cnidarians had bilateral symmetry? ANSWER: All cnidarians are acoelomate. Cnidarians have fewer Hox genes than bilaterians. Cnidarian larvae possess anterior-posterior, left-right, and dorsal-ventral aspects. The presence of collar cells.
c
A researcher is trying to construct a molecular-based phylogeny of the entire animal kingdom. Assuming that none of the following genes are absolutely conserved, which of the following would be the best choice on which to base the phylogeny? ANSWER: genes involved in directing segmentation development genes involved in chitin synthesis genes involved in eye-lens synthesis collagen genes
d
A student encounters an animal embryo at the eight-cell stage. The four smaller cells that comprise 1 hemisphere of the embryo seem to be rotated 45° and to lie in the grooves between larger, underlying cells. If we were to separate these eight cells and attempt to culture them individually, then what is most likely to happen? ANSWER: Each cell may develop into a full-sized, normal embryo. Each cell may develop into a smaller-than-average, but otherwise normal, embryo. All eight cells will die immediately. Each cell may continue development, but only into a nonviable embryo that lacks many parts.
d
A student encounters an animal embryo at the eight-cell stage. The four smaller cells that comprise 1 hemisphere of the embryo seem to be rotated 45° and to lie in the grooves between larger, underlying cells. This embryo may potentially develop into a(n) ________. ANSWER: sea urchin turtle sea star earthworm
d
Arthropods invaded land about 100 million years before vertebrates. This fact most clearly implies that ________. ANSWER: arthropods evolved before vertebrates did extant terrestrial arthropods are better adapted to terrestrial life than are extant terrestrial vertebrates vertebrates evolved from arthropods arthropods have had more time to coevolve with land plants than have vertebrates
d
In examining an unknown animal species during its embryonic development, how can you be sure what you are looking at is a protostome and not a deuterostome? ANSWER: The animal is triploblastic. The animal is clearly bilaterally symmetrical. There is evidence of cephalization. You see a mouth, but not an anus.
d
In individual insects of some species, whole chromosomes that carry larval genes are eliminated from the genomes of somatic cells at the time of metamorphosis. A consequence of this occurrence is that ________. ANSWER: the descendants of these adults do not include a larval stage metamorphosis can no longer occur among the descendants of such adults such species must reproduce only asexually we could not clone a larva from the somatic cells of such an adult insect
d
Placing sponges as the basal metazoans on the basis of lack of tissues implies which of the following? ANSWER: Modern-day sponges have lost the ability to form tissues. Multicellular, modern-day choanoflagellates can form tissues. Sponges do not have nerve cells. Sponge ancestors never had tissues.
d
Soon after the coelom begins to form, a researcher injects a dye into the coelom of a deuterostome embryo. Initially, the dye should be able to flow directly into the _____. ANSWER: blastopore blastocoel pseudocoelom archenteron
d
Sponges and ctenophores have both been proposed as basal metazoans. Imagine that you wanted to provide additional evidence to help resolve this question. Which of the following projects would be the best next step? ANSWER: more extensive studies of DNA sequences in both groups more extensive study of DNA sequences in the bilateria measurements of molecular clocks from the Lophotrochozoa ultrastructural (that is, electron microscope) comparisons of choanoflagellates and sperm cells from arthropods
d
The fact that choanoflagellates and collar cells of sponges resemble each other supports the inference that ________. ANSWER: choanoflagellates and sponges are sister groups choanoflagellates and sponges evolved similar cell structures through convergent evolution choanoflagellates are more closely related to sponges than they are to protists choanoflagellates are animals
d
The larvae of some insects are merely small versions of the adult, whereas the larvae of other insects look completely different from adults, eat different foods, and may live in different habitats. Which of the following is most directly involved in the evolution of these variations in metamorphosis? ANSWER: the evolution of meiosis artificial selection of sexually immature forms of insects the origin of a brain changes in the homeobox genes controlling early development
d
The most ancient branch point in animal phylogeny is the characteristic of having _____. ANSWER: diploblastic or triploblastic embryos a body cavity or no body cavity radial or bilateral symmetry true tissues or no tissues
d
Use the figure to answer the question. A phylogenetic tree is depicted as a mainline with a number of branches from the line. Specific points in development are marked. The first branch leads to the Choanoflagellates. Between that and the next branch, multicellularity and epithelial tissue develop. That next branch is to the Porifera (sponges); all organisms through the rest of the diagram are part of Animalia. Between this branch and the next, organisms develop diploblasty (ectoderm and endoderm) and radial symmetry. The next branch divides into the Cnidaria (jellyfish, sea anemones) and the Ctenophora (comb jellies). The next landmarks on the main line are bilateral symmetry and cephalization, and triploblasty (origin of mesoderm). The next branch is to the Acoelomorphia (acoels), and starting with this branch organisms are part of Bilateria. The next milestone is the development of Coelem. The next branch divides several times. Between the main line of the branch and further divisions occurs protostome development. Farther out this main division is a split, along one branch of which occurs Pseudocoelom, leading to development of Rotifera (rotifers). The second branch divides further: Acoelem develops leading to Platyhelminthes (flatworms), and the final division has two branches. Segmentation occurs along the first branch, which leads to Annelida (segmented worms); the other branch ends at the Mollusca (snails, clams, squid). Rotifera, Platyhelminthes, Annelida, and Mollusca are all part of Lophotrochozoa. Between protostome development and the branch that leads to the mollusks is another division. Occurs growth by molting. The end of that line divides into Nematoda (roundworms) and arthropoda (insects, spiders, stressed crustaceans); Pseudocoelom occurs on the branch to the nematodes, and segmentation occurs on the branch to the arthropods. These two groups are part of Ecdysozoa. Lophotrochozoa and Ecdysozoa comprise Protostoma The final section of the mainline shows the development of Deuterostome before a final division. Radial symmetry (in adults) occurs on the branch to the Echinodermata, and segmentation occurs on the branch to Chordata (vertebrates, ascidians). These last two groups are part of Deuterostoma. Which of the following pairs of animals show that animals with widely different adult features can be each other's closest relatives? ANSWER: Cnidemia and Ctenophora Annelida and Rotifera Annelida and Nematoda Chordata and Echinodermata
d
Which of the following factors most likely contributed to the extinction of many Ediacaran life forms? ANSWER: loss of habitat due to increased temperatures, poisoning from high oxygen levels, and loss of developmental flexibility predation by new species, poisoning from high oxygen levels, and loss of habitat due to increased temperatures predation by new species, poisoning from high carbon dioxide levels, and loss of developmental flexibility predation by new species, faster movement by new species, and increased developmental flexibility by new species
d
Which of the following statements concerning animal taxonomy is accurate? ANSWER: In the kingdom Animalia, most clades based on body plan or fossils have been found to be incorrect. Animals are more closely related to plants than to fungi. Kingdom Animalia is polyphyletic. Animals are thought to have evolved from flagellated protists similar to modern choanoflagellates.
d
While looking at some seawater through your microscope, you spot the egg of an unknown animal. Which of the following tests could you use to determine whether the developing organism is a protostome or a deuterostome? See whether the embryo _____. ANSWER: develops a blastopore develops germ layers develops an archenteron exhibits spiral cleavage or radial cleavage
d
Why might researchers choose to use molecular data (such as ribosomal RNA sequences) rather than morphological data to study the evolutionary history of animals? ANSWER: Some phyla vary too widely in morphological characteristics to be classified accurately. Molecular data can be gathered in the lab, while morphological data must be gathered in the field. Morphological changes usually do not result from molecular changes. Molecular data can be used to give an estimate of the time since two groups split.
d
