31. Invertebrates

The arthropods superficially resemble earthworms in that both groups __________, yet the two are distinctly different because arthropods, but not earthworms, __________.

A major characteristic of arthropods is __________.

In most insects, gas exchange is accomplished by __________.

In arthropods, molting is necessary because __________.

Sowbugs are really crustaceans, not insects. Therefore, a sowbug does not have __________.

The majority of animal species are __________.

An unidentified species of animal displays the following characteristics: bilateral symmetry, a complete digestive system, an open circulatory system, distinct body segmentation, and a series of molting stages during growth. To which of the following animal phyla does this species most likely belong?

Complete metamorphosis __________.

Which of the following animals is most closely related to spiders?

Which phylum is characterized by animals that have a segmented body? a. Cnidaria b. Platyhelminthes c. Arthropoda d. Mollusca

What is the function of the arthropod exoskeleton? a. The presence of an exoskeleton has given arthropods a good fossil record, because hard parts fossilize more readily than do soft tissues. b. It has no well-established function. (Trilobites had an exoskeleton, and they went extinct.) c. It provides protection and functions in locomotion. d. It makes growth by molting possible.

Why is the pea wrinkle-seed allele a recessive allele? a. It 'recedes' in the F2 generation when homozygous parents are crossed. b. The trait associated with the allele is not exhibited in heterozygotes. c. Individuals with the allele have lower fitness than that of individuals with the dominant allele. d. The allele is less common than the dominant allele. (The wrinkled allele is a rare mutant.)

The alleles found in haploid organisms cannot be dominant or recessive. Why? a. Dominance and recessiveness describe which of two possible phenotypes are exhibited when two different alleles occur in the same individual. b. Because only one allele is present, alleles in haploid organisms are always dominant. Ac. lleles in haploid individuals are transmitted like mitochondrial DNA or chloroplast DNA. d. Most haploid individuals are bacteria, and bacterial genetics is completely different from eukaryotic genetics.

One trait that is shared by the Lophotrochozoa and Ecdysozoa is                .

Which protostome phyla successfully made the transition from water to land? Select True or False for each phylum. T/F Mollusca T/F Arthropoda T/F Annelida T/F Nematoda

A plant with orange, spotted flowers was grown in the greenhouse from a seed collected in the wild. The plant was self-pollinated and gave rise to the following progeny: 88 orange with spots, 34 yellow with spots, 32 orange with no spots, and 8 yellow with no spots. What can you conclude about the dominance relationships of the alleles responsible for the spotted and unspotted phenotypes? What can you conclude about the genotype of the original plant that had orange, spotted flowers?

Which of the following groupings includes the largest number of species? (Explain your answer.) a. invertebrates b. arthropods c. insects d. vertebrates

Propose an explanation for why annelids and arthropods were thought to be closely related, before phylogenetic analyses in the late 1990s.

In peas, purple flowers are dominant to white. If a purple-flowered, heterozygous plant were crossed with a white-flowered plant, what is the expected ratio of genotypes and phenotypes among the F1 offspring? If two of the purple-flowered F1 offspring were randomly selected and crossed, what is the expected ratio of genotypes and phenotypes among the F2 offspring?

Use your understanding of insect evolution to predict two adaptations for terrestrial living that occurred in spiders.

Molecular comparisons place nematodes and arthropods in clade Ecdysozoa. What characteristic do they share that is the basis for the name Ecdysozoa? a. a complete digestive tract b. body segmentation c. molting of an exoskeleton d. bilateral symmetry

Pose a hypothesis to explain why the evolution of the wing was such an important event in the evolution of insects.

Suppose that a gene originally identified in nematodes (roundworms) is found to be homologous with a gene that can cause developmental abnormalities in humans. Would it be possible to use fruit flies as a model organism to study this gene? Explain.

Suppose that a gene originally identified in nematodes (roundworms) is found to be homologous with a gene that can cause developmental abnormalities in humans. Would it be possible to use fruit flies as a model organism to study this gene? Explain.

Imagine repeating the experiment on epigenetic inheritance that is shown in Figure 19.6. You measure the amount of radioactive uridine (U) incorporated into Hnf4a mRNA in counts per minute (cpm) to determine the level of Hnf4a gene transcription in rats born to mothers fed either a normal diet or a low-protein diet. The results are 11,478 cpm for the normal diet and 7368 cpm for the low-protein diet. For this problem, your task is to prepare a graph similar to the one at the bottom of Figure 19.6 that shows the normalized results for the low-protein diet relative to the normal diet. Normalizing values means that the value obtained from one condition is expressed as 1.0 (the norm; the normal diet in this case) and the values obtained from any other conditions (low-protein diet in this case) are expressed as decimal values relative to the norm.

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods. Which of the following nested groups best describes the taxonomic context for the San Lorenzo project? a. Animalia > Bilateria > Arthropoda > Ecdysozoa b. Protostomia > Lophotrochozoa > Ecdysozoa7 Arthropoda c. Arthropoda > Protostomia > Ecdysozoa > Bilateria d. Bilateria > Protostomia > Ecdysozoa > Arthropoda

You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows According to these data, is the curved-wing allele autosomal recessive, autosomal dominant, sex-linked recessive, or sex-linked dominant?

You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows Is the lozenge-eyed allele autosomal recessive, autosomal dominant, sex-linked recessive, or sex-linked dominant?

One of the key characteristics of arthropods is their jointed appendages. Describe four functions of these appendages in four different arthropods.

SCIENTIFIC THINKING In one of the experiments described in researchers tested the hypothesis that the highly successful arthropod body plan resulted from new genes that originated in the arthropod lineage. Draw a diagram showing the evolutionary relationship between arthropods and velvet worms and use it to explain why velvet worms were a good choice to test this hypothesis. What results would have supported the hypothesis?