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 7
Evaluate this statement: Animals evolved from simple to complex.
Verified step by step guidance1
Step 1: Understand the statement. The statement is saying that animals evolved from simple forms to more complex forms. This is a common understanding of evolution, but it's important to note that 'simple' and 'complex' are relative terms.
Step 2: Consider the evidence. The fossil record shows that the earliest life forms were much simpler than most organisms alive today. Over time, new traits and structures have evolved, leading to a greater diversity and complexity of life.
Step 3: Consider the process of evolution. Evolution is driven by natural selection, where traits that improve an organism's chances of survival and reproduction are more likely to be passed on to the next generation. Over time, this can lead to the development of new traits and greater complexity.
Step 4: Consider exceptions. While it's generally true that life has become more complex over time, this is not a hard and fast rule. Some organisms have actually become simpler over time, losing traits that they no longer need. This is known as 'regressive evolution'.
Step 5: Formulate a response. Based on the evidence and understanding of evolution, it can be said that the statement is generally true, but with some exceptions. Evolution often leads to greater complexity, but not always.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Evolution
Evolution is the process through which species change over time through mechanisms such as natural selection, genetic drift, and mutation. It explains how simple organisms can give rise to more complex forms through gradual adaptations to their environments. Understanding evolution is crucial for evaluating claims about the progression from simple to complex life forms.
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Introduction to Evolution of Populations
Phylogeny
Phylogeny refers to the evolutionary history and relationships among species. It is often represented in a phylogenetic tree, which illustrates how different species are related through common ancestors. This concept helps in understanding the complexity of animal evolution and the branching patterns that lead to diverse forms of life.
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Guided course
09:32Taxonomy and Phylogeny
Complexity in Biology
Complexity in biology often refers to the structural and functional intricacies of organisms. While some may interpret evolution as a linear progression from simple to complex, it is more accurate to view it as a branching process where complexity can arise in various forms, including multicellularity, specialization of cells, and behavioral adaptations. This understanding challenges the notion of a straightforward evolutionary ladder.
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06:15Origin of Complex Traits
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?
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.