Textbook Question
Which phylum is characterized by animals that have a segmented body?
a. Cnidaria
b. Platyhelminthes
c. Arthropoda
d. Mollusca
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Ch. 33 - An introduction to Invertebrates
Urry11th EditionCampbell BiologyISBN: 9789357423311
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Table of contents
- Ch. 1 - Evolution, the Themes of Biology, and Scientific Inquiry8
- Ch. 2 - The Chemical Context of Life8
- Ch. 3 - Water and Life6
- Ch. 4 - Carbon and the Molecular Diversity of Life9
- Ch. 5 - The Structure and Function of Large Biological Molecules9
- Ch. 6 - A Tour of the Cell6
- Ch. 7 - Membrane Structure and Function6
- Ch. 8 - An Introduction to Metabolism6
- Ch. 9 - Cellular Respiration and Fermentation10
- Ch. 10 - Photosynthesis7
- Ch. 11 - Cell Communication7
- Ch. 12 - The Cell Cycle10
- Ch. 13 - Meiosis and Sexual Life Cycles10
- Ch. 14 - Mendel and the Gene Idea14
- Ch, 15 - The Chromosomal Basis of Inheritance7
- Ch. 16 - The Molecular Basis of Inheritance9
- Ch. 17 - Gene Expression: From Gene to Protein9
- Ch. 18 - Regulation of Gene Expression10
- Ch. 19 - Viruses6
- Ch. 20 - DNA Tools and Biotechnology8
- Ch. 21 - Genomes and Their Evolution8
- Ch. 22 - Descent with Modification: A Darwininan View of Life6
- Ch. 23 - The Evolution of Populations5
- Ch. 24 - The Origin of Species6
- Ch. 25 - The History of Life on Earth6
- Ch. 26 - Phylogeny and the Tree of Life7
- Ch. 27 - Bacteria and Archaea8
- Ch. 28 - Protists7
- Ch. 29 - Plant Diversity I: How Plants Colonized Land7
- Ch. 30 - Plant Diversity II: The Evolution of Seed Plants7
- Ch. 31 - Fungi5
- Ch. 32 - An Overview of Animal Diversity4
- Ch. 33 - An introduction to Invertebrates6
- Ch. 34 - The Origin and Evolution of Vertebrates7
- Ch. 35 - Vascular Plant Structure, Growth, and Development8
- Ch. 36 - Resource Acquisition and Transport in Vascular Plants8
- Ch. 37 - Soil and Plant Nutrition10
- Ch. 38 - Angiosperm Reproduction and Biotechnology8
- Ch. 39 - Plant Responses to Internal and External Signals8
- Ch. 40 - Basic Principles of Animal Form and Function8
- Ch. 41 - Animal Nutrition7
- Ch. 42 - Circulation and Gas Exchange7
- Ch. 43 - The Immune System6
- Ch. 44 - Osmoregulation and Excretion6
- Ch. 45 - Hormones and the Endocrine System8
- Ch. 46 - Animal Reproduction8
- Ch. 47 - Animal Development8
- Ch. 48 - Neurons, Synapses, and Signaling6
- Ch. 49 - Nervous Systems8
- Ch. 50 - Sensory and Motor Mechanisms5
- Ch. 51 Animal Behavior6
- Ch. 52 - An Introduction to Ecology and the Biosphere7
- Ch. 53 - Population Ecology10
- Ch. 54 - Community Ecology9
- Ch. 55 - Ecosystems and Restoration Ecology8
- Ch. 56 - Conservation Biology and Global Change6
Chapter 33, Problem 5
In the following figure, which two main clades branch from the most recent common ancestor of the eumetazoans?
a. Porifera and Cnidaria
b. Lophotrochozoa and Ecdysozoa
c. Cnidaria and Bilateria
d. Deuterostomia and Bilateria
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Verified step by step guidance1
Identify the term 'eumetazoans' in the question. Eumetazoans are animals with true tissues, which excludes sponges (Porifera).
Understand the concept of clades. A clade is a group of organisms that includes a common ancestor and all its descendants.
Examine the evolutionary relationships among the groups mentioned in the options. Cnidaria (jellyfish, corals, etc.) and Bilateria (animals with bilateral symmetry) are two major clades within Eumetazoa.
Recall that Cnidaria represents a simpler body plan with radial symmetry, while Bilateria includes more complex animals with bilateral symmetry and three germ layers.
Conclude that the two main clades branching from the most recent common ancestor of eumetazoans are Cnidaria and Bilateria, as they represent the primary division within this group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Eumetazoans
Eumetazoans are a major clade within the animal kingdom, characterized by having true tissues. This group excludes sponges and includes all other animals, such as cnidarians and bilaterians. Understanding eumetazoans is crucial for identifying evolutionary relationships among animals, as they represent a significant divergence point in the animal phylogenetic tree.
Cnidaria
Cnidaria is a phylum within the eumetazoans that includes jellyfish, corals, and sea anemones. These organisms are primarily aquatic and are known for their radial symmetry and specialized cells called cnidocytes, which contain stinging structures. Cnidarians are one of the earliest diverging groups within eumetazoans, providing insight into early animal evolution.
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Porifera and Cnideria
Bilateria
Bilateria is a clade within the eumetazoans characterized by bilateral symmetry and three germ layers. This group includes most animal phyla, such as arthropods, mollusks, and vertebrates. Bilaterians are significant in evolutionary biology because their body plan allows for greater complexity and specialization, marking a major evolutionary advancement from simpler organisms like cnidarians.
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Related Practice
Textbook Question
The water vascular system of echinoderms
a. Functions as a circulatory system that distributes nutrients to body cells
b. Functions in locomotion and feeding
c. Is bilateral in organization, even though the adult animal is not bilaterally symmetrical
d. Moves water through the animal's body during filter feeding
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Textbook Question
Which of the following combinations of phylum and description is incorrect?
a. Echinodermata—bilateral symmetry as a larva, coelomate
b. Nematoda—roundworms, pseudocoelomate
c. Platyhelminthes—flatworms, gastrovascular cavity, acoelomate
d. Porifera—gastrovascular cavity, coelomate
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Textbook Question
In Figure 33.7, assume that the two medusae shown at step 4 were produced by one polyp colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to evaluate whether the following sentence is true or false; if false, select the answer that provides the correct reason. Although the two medusae are genetically identical, a sperm produced by one will differ genetically from an egg produced by the other.
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a. Both the medusae and the gametes are genetically identical.
b. Neither the medusae nor the gametes are genetically identical.
c. The medusae are not genetically identical, but the gametes are genetically identical.
d. The medusae are genetically identical, but the gametes differ genetically.
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