
Concept explainers
Test your Understanding
Know and Comprehend
A radially symmetrical animal such as Hydra is likely to have (a) a forebrain (b) a nerve net (c) cerebral ganglia (d) a ventral nerve cord (e) cerebral ganglia and a nerve net

Introduction: Hydra is a freshwater organism of the phylum Cnidaria. They have very high regenerative ability. They are radially symmetrical invertebrates and have tentacles to capture their food.
Answer to Problem 1TYU
Correct answer: Radially symmetrical organisms such as Hydra have simple nervous systems like the nerve net. Hence, the correct answer is option (b).
Explanation of Solution
Reason for the correct answer:
Radial symmetry is generally present in simpler organisms such as Hydra. Organisms belonging to simpler classes in the animal kingdom have less complexed nervous systems. They usually have interconnected networks of neurons, and no central control system is present in such simpler neural systems. Such connection of neurons forms the nerve net.
Option (b) is given as “a nerve net”.
Radially symmetrical organisms such as Hydra have simpler body organization and simpler nervous systems such as the nerve nets. Hence, the correct answer is option (b).
Reasons for incorrect answers:
Option (a) is given as “a forebrain”.
A forebrain is a part of a complex nervous system that is found in higher organisms with a complex body organization. The forebrain is not found in simpler organisms such as Hydra. Hence, option (a) is incorrect.
Option (c) is given as “cerebral ganglia”.
Radially symmetrical organisms have simple nervous systems that do not have any control center. Cerebral ganglia act as a control center in the nervous systems. Hence, option (c) is incorrect.
Option (d) is given as “a ventral nerve cord”.
Ventral and dorsal sides can be defined only in organisms with bilateral symmetry. In organisms with simple body organization, there is no nerve cord present. Thus, radially symmetrical organisms cannot have a ventral nerve cord. Hence, option (d) is incorrect.
Option (e) is given as “cerebral ganglia and a nerve net”.
Simpler organisms do not have cerebral ganglia in their nervous systems. Hence, option (e) is incorrect.
Hence, options (a), (c), (d), and (e) are incorrect.
Organisms with radial symmetry in their body organization, such as Hydra, have a nervous system consisting only of nerve nets.
Want to see more full solutions like this?
Chapter 42 Solutions
EBK BIOLOGY
- What is this?arrow_forwardMolecular Biology A-C components of the question are corresponding to attached image labeled 1. D component of the question is corresponding to attached image labeled 2. For a eukaryotic mRNA, the sequences is as follows where AUGrepresents the start codon, the yellow is the Kozak sequence and (XXX) just represents any codonfor an amino acid (no stop codons here). G-cap and polyA tail are not shown A. How long is the peptide produced?B. What is the function (a sentence) of the UAA highlighted in blue?C. If the sequence highlighted in blue were changed from UAA to UAG, how would that affecttranslation? D. (1) The sequence highlighted in yellow above is moved to a new position indicated below. Howwould that affect translation? (2) How long would be the protein produced from this new mRNA? Thank youarrow_forwardMolecular Biology Question Explain why the cell doesn’t need 61 tRNAs (one for each codon). Please help. Thank youarrow_forward
- Molecular Biology You discover a disease causing mutation (indicated by the arrow) that alters splicing of its mRNA. This mutation (a base substitution in the splicing sequence) eliminates a 3’ splice site resulting in the inclusion of the second intron (I2) in the final mRNA. We are going to pretend that this intron is short having only 15 nucleotides (most introns are much longer so this is just to make things simple) with the following sequence shown below in bold. The ( ) indicate the reading frames in the exons; the included intron 2 sequences are in bold. A. Would you expected this change to be harmful? ExplainB. If you were to do gene therapy to fix this problem, briefly explain what type of gene therapy youwould use to correct this. Please help. Thank youarrow_forwardMolecular Biology Question Please help. Thank you Explain what is meant by the term “defective virus.” Explain how a defective virus is able to replicate.arrow_forwardMolecular Biology Explain why changing the codon GGG to GGA should not be harmful. Please help . Thank youarrow_forward
- Stage Percent Time in Hours Interphase .60 14.4 Prophase .20 4.8 Metaphase .10 2.4 Anaphase .06 1.44 Telophase .03 .72 Cytukinesis .01 .24 Can you summarize the results in the chart and explain which phases are faster and why the slower ones are slow?arrow_forwardCan you circle a cell in the different stages of mitosis? 1.prophase 2.metaphase 3.anaphase 4.telophase 5.cytokinesisarrow_forwardWhich microbe does not live part of its lifecycle outside humans? A. Toxoplasma gondii B. Cytomegalovirus C. Francisella tularensis D. Plasmodium falciparum explain your answer thoroughly.arrow_forward
- Select all of the following that the ablation (knockout) or ectopoic expression (gain of function) of Hox can contribute to. Another set of wings in the fruit fly, duplication of fingernails, ectopic ears in mice, excess feathers in duck/quail chimeras, and homeosis of segment 2 to jaw in Hox2a mutantsarrow_forwardSelect all of the following that changes in the MC1R gene can lead to: Changes in spots/stripes in lizards, changes in coat coloration in mice, ectopic ear formation in Siberian hamsters, and red hair in humansarrow_forwardPleiotropic genes are genes that (blank) Cause a swapping of organs/structures, are the result of duplicated sets of chromosomes, never produce protein products, and have more than one purpose/functionarrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage LearningBiology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning
- Biology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStaxBiology: The Unity and Diversity of Life (MindTap...BiologyISBN:9781305073951Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa StarrPublisher:Cengage Learning




