Textbook Question
Which of these characteristics does not apply to cnidarians?
a. Are diploblastic
b. Possess a gastrovascular cavity with one opening
c. Undergo metamorphosis
d. Have a central nervous system
Ch. 30 - An Introduction to Animals
Freeman8th EditionBiological ScienceISBN: 9780138276263
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Table of contents
- Ch. 1 - Biology: The Study of Life13
- Ch. 2 - Water and Carbon: The Chemical Basis of Life14
- Ch.3 - Protein Structure and Function10
- Ch.4 - Nucleic Acids and the RNA World10
- Ch. 5 - An Introduction to Carbohydrates10
- Ch. 6 - Lipids, Membranes, and the First Cells11
- Ch. 7 - Inside the Cell10
- Ch. 8 - Energy and Enzymes: An Introduction to Metabolism10
- Ch. 9 - Cellular Respiration and Fermentation11
- Ch. 10 - Photosynthesis12
- Ch. 11 - Cell-Cell Interactions12
- Ch. 12 - The Cell Cycle8
- Ch. 13 - Meiosis12
- Ch. 14 - Mendel and the Gene23
- Ch. 15 - DNA and the Gene: Synthesis and Repair15
- Ch. 16 - How Genes Work16
- Ch. 17 - Transcription, RNA Processing, and Translation16
- Ch. 18 - Control of Gene Expression in Bacteria16
- Ch. 19 - Control of Gene Expression in Eukaryotes12
- Ch. 20 - The Molecular Revolution: Biotechnology, Genomics, and New Frontiers15
- Ch. 21 - Genes, Development, and Evolution12
- Ch. 22 - Evolution by Natural Selection16
- Ch. 23 - Evolutionary Processes13
- Ch. 24 - Speciation15
- Ch. 25 - Phylogenies and the History of Life13
- Ch. 26 - Bacteria and Archaea15
- Ch. 27 - Diversification of Eukaryotes16
- Ch. 28 - Green Algae and Land Plants16
- Ch. 29 - Fungi18
- Ch. 30 - An Introduction to Animals9
- Ch. 31 - Protostome Animals15
- Ch. 32 - Deuterostome Animals17
- Ch. 33 - Viruses16
- Ch. 34 - Plant Form and Function16
- Ch. 35 - Water and Sugar Transport in Plants16
- Ch. 36 - Plant Nutrition13
- Ch. 37 - Plant Sensory Systems, Signals, and Responses16
- Ch. 38 - Flowering Plant Reproduction and Development16
- Ch. 39 - Animal Form and Function17
- Ch. 40 - Water and Electrolyte Balance in Animals16
- Ch. 41 - Animal Nutrition16
- Ch. 42 - Gas Exchange and Circulation16
- Ch. 43 - Animal Nervous Systems16
- Ch. 44 - Animal Sensory Systems16
- Ch. 45 - Animal Movement11
- Ch. 46 - Chemical Signals in Animals16
- Ch. 47 - Animal Reproduction and Development16
- Ch. 48 - The Immune System in Animals16
- Ch. 49 - An Introduction to Ecology15
- Ch. 50 - Behavioral Ecology16
- Ch. 51 - Population Ecology16
- Ch. 52 - Community Ecology20
- Ch. 53 - Ecosystems and Global Ecology17
- Ch. 54 - Biodiversity and Conservation Ecology18
Chapter 30, Problem 3
True or false?
New major animal body plans have continued to evolve since the Cambrian about 550 million years ago.
Verified step by step guidance1
Understand the concept of 'animal body plans': Animal body plans refer to the basic structural and functional design of an organism, including its symmetry, segmentation, and limb arrangement.
Review the Cambrian Explosion: The Cambrian Explosion was a period approximately 541 million years ago when most major animal phyla appeared in the fossil record. It is known for the rapid diversification of life forms.
Consider the evolutionary process: Evolution is a continuous process, but the emergence of entirely new major body plans is rare. Most changes involve modifications of existing plans rather than the creation of new ones.
Examine the fossil record: The fossil record provides evidence of the diversity and changes in life forms over time. It can help determine if new major body plans have appeared since the Cambrian period.
Evaluate scientific consensus: Scientists generally agree that while evolution continues to modify existing body plans, the appearance of entirely new major body plans has not been observed since the Cambrian Explosion.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cambrian Explosion
The Cambrian Explosion refers to a period approximately 541 million years ago when most major animal phyla appeared in the fossil record. This event is characterized by a rapid diversification of life forms, leading to the establishment of complex body plans. Understanding this period is crucial for assessing the evolution of animal body plans.
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Cambrian Explosion
Animal Body Plans
Animal body plans are the structural and functional designs of organisms, including symmetry, segmentation, and limb arrangement. These plans are established during embryonic development and are crucial for understanding evolutionary biology, as they determine the basic layout of an organism's anatomy.
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03:45Body Axes
Evolutionary Stasis
Evolutionary stasis refers to periods in which little evolutionary change occurs in organisms' body plans. After the Cambrian Explosion, many animal body plans have remained relatively unchanged, suggesting a stasis in major evolutionary innovations. This concept helps explain why new major body plans have not emerged since the Cambrian period.
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02:45History of Evolutionary Theory Example 1
Related Practice
Textbook Question
Why is it ecologically significant that animals are heterotrophic and multicellular?
Textbook Question
To estimate the relative abundance of the major phyla, calculate how many named species of arthropods, mollusks, and nematode worms exist per named species of chordate (the phylum containing vertebrates, including humans; see Table 30.1).
Do you think these calculations are likely to be underestimates or overestimates? Why?