Ch. 18 The Evolution of Invertebrate Diversity

Taylor - Campbell Biology: Concepts & Connections 10th Edition

Taylor, Simon, Dickey, Hogan10th EditionCampbell Biology: Concepts & ConnectionsISBN: 9780136538783Not the one you use?Change textbook

Taylor, Simon, Dickey, Hogan 10th Edition

Ch. 18 The Evolution of Invertebrate Diversity

Problem 20

Chapter 18, Problem 20

A marine biologist has dredged up an unknown animal from the seafloor. Describe some of the characteristics that could be used to determine the animal phylum to which the creature should be assigned.

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Examine the symmetry of the animal's body. Determine if it has radial symmetry (e.g., like jellyfish), bilateral symmetry (e.g., like fish), or no symmetry (e.g., like sponges). This can help narrow down the phylum.

Inspect the presence and type of body cavity (coelom). Determine if the animal is acoelomate (no body cavity), pseudocoelomate (a body cavity not fully lined with mesoderm), or coelomate (a fully lined body cavity).

Analyze the type of digestive system. Check if the animal has a complete digestive tract (with a separate mouth and anus) or an incomplete digestive system (a single opening for ingestion and excretion).

Observe the presence and structure of specialized tissues or organs. For example, look for features like a notochord (characteristic of chordates), segmentation (e.g., in annelids or arthropods), or stinging cells (cnidocytes, characteristic of cnidarians).

Examine the animal's external and internal structures under a microscope. Look for specific features such as exoskeletons, jointed appendages, or cilia, which can provide clues about its classification into a specific phylum.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Animal Phyla Classification

Animal phyla classification is a hierarchical system used to categorize animals based on shared characteristics and evolutionary relationships. Each phylum represents a major group of animals that share fundamental structural features, such as body symmetry, tissue organization, and developmental patterns. Understanding the classification system helps in identifying the unknown animal by comparing its traits to those of known phyla.

Morphological Characteristics

Morphological characteristics refer to the physical traits of an organism, including body shape, size, symmetry, and the presence of specialized structures. These traits are crucial for classification, as they can indicate evolutionary relationships and functional adaptations. For example, the presence of a backbone can help distinguish vertebrates from invertebrates, guiding the identification of the animal's phylum.

Genetic and Molecular Analysis

Genetic and molecular analysis involves examining the DNA and genetic material of an organism to determine its evolutionary relationships and classification. Techniques such as DNA sequencing can reveal similarities and differences at the molecular level, providing insights into the animal's lineage. This approach is increasingly important in modern taxonomy, as it can confirm or refine classifications based on morphological data alone.

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Related Practice

Textbook Question

Match each description on the left with the corresponding term on the right Closest relatives of chordates

a. annelids

b. nematodes

c. sponges

d. arthropods

e. flatworms

f. cnidarians

g. molluscs

h. echinoderms

i. chordates

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Textbook Question

Compare the structure of a planarian (a flatworm) and an earthworm with regard to the following: digestive tract, body cavity, and segmentation.

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Textbook Question

One of the key characteristics of arthropods is their jointed appendages. Describe four functions of these appendages in four different arthropods.

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Textbook Question

In one of the experiments described in Module 18.13, researchers tested the hypothesis that the highly successful arthropod body plan resulted from new genes that originated in the arthropod lineage. Draw a diagram showing the evolutionary relationship between arthropods and velvet worms and use it to explain why velvet worms were a good choice to test this hypothesis. What results would have supported the hypothesis?

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