Textbook Question
True or false?
New major animal body plans have continued to evolve since the Cambrian about 550 million years ago.
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 6
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?
Verified step by step guidance1
Step 1: Identify the number of described species for each phylum mentioned in the problem. From Table 30.1, the number of described species is as follows: Arthropoda = 1,200,000, Mollusca = 85,000, Nematoda = 25,000, and Chordata = 65,000.
Step 2: Calculate the relative abundance of each phylum compared to Chordata. To do this, divide the number of described species for each phylum by the number of described species for Chordata. For example, for Arthropoda, the calculation would be: .
Step 3: Repeat the calculation for Mollusca and Nematoda using the same formula: for Mollusca and for Nematoda.
Step 4: Interpret the results. The relative abundance values will indicate how many species of arthropods, mollusks, and nematodes exist per species of chordate. Larger values suggest higher diversity in those phyla compared to Chordata.
Step 5: Consider whether these calculations are likely to be underestimates or overestimates. Discuss factors such as undiscovered species, biases in research focus, and the difficulty of cataloging smaller or less conspicuous organisms, which may lead to underestimates of species numbers in certain phyla.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Biodiversity and Species Richness
Biodiversity refers to the variety of life in a particular habitat or ecosystem, encompassing the number of different species, their relative abundance, and the genetic diversity within those species. Species richness is a key component of biodiversity, indicating the total number of different species present in a given area. Understanding biodiversity is crucial for assessing ecological health and the impact of environmental changes.
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Phyla of Animals
In biological classification, a phylum is a higher taxonomic rank that groups together organisms sharing a basic structural framework. Major animal phyla include Arthropoda, Mollusca, and Chordata, each characterized by distinct anatomical and physiological traits. For instance, arthropods have exoskeletons and jointed limbs, while chordates possess a notochord at some stage of development, highlighting the diversity of life forms.
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Estimating Species Abundance
Estimating species abundance involves calculating the number of individuals of each species within a community, often expressed relative to a reference group. In this context, the calculation of arthropods, mollusks, and nematodes per chordate species helps to understand their relative abundance. Such estimates can be influenced by factors like sampling methods and ecological interactions, leading to potential underestimates or overestimates of true biodiversity.
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Related Practice
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
Textbook Question
Why is it ecologically significant that animals are heterotrophic and multicellular?
Textbook Question
Evaluate this statement: Animals evolved from simple to complex.
Textbook Question
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.
Textbook Question
The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today.
Why are there so many species in some phyla, such as Cnidaria (see photo), but so few in others, such as Ctenophora?
Draw a horizontal axis to represent the number of species within phyla using a logarithmic scale (1, 10, 100, 1000 species, etc.). Then use Table 30.1 to map seven representative phyla from small to large at intervals of about an order of magnitude on this scale.