Book cover for Campbell Biology Concepts & Connections

Campbell Biology Concepts & Connections

Martha R. Taylor, Jean L. Dickey, Eric J. Simon, Kelly Hogan, Jane B. Reece

ISBN #9780134296012

9th Edition

631 Questions

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82,520 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This chapter delves into the evolutionary history and diverse characteristics of major invertebrate phyla, highlighting the role of cell structure, body plan features, embryonic development, and homeotic genes in driving diversity. It also underscores the ecological importance of invertebrates, from water filtration to pollination, and addresses the challenges facing their conservation. By integrating both morphological and molecular data, scientists are able to construct phylogenetic trees that illuminate the evolutionary relationships among these varied organisms.

Learning Objectives

1

Explain the evolutionary history and diversity of major invertebrate phyla.

2

Describe the key body plan features (e.g., symmetry, tissue layers, embryonic development) that differentiate animal groups.

3

Analyze the role of homeotic genes in shaping animal morphology and diversification.

4

Evaluate the ecological roles and conservation challenges associated with invertebrates.

5

Interpret how molecular and morphological data are used to construct phylogenetic trees.

Key Concepts

CONCEPT

DEFINITION

Invertebrates

Animals that lack a vertebral column, exhibiting a wide range of body plans and structural adaptations.

Body Plan

The overall structural organization of an organism, including symmetry, tissue layers, and the pattern of embryonic development.

Symmetry

The arrangement of body parts around a central axis; can be radial, bilateral, or asymmetrical.

Tissue Layers

Distinct layers of cells originating from embryonic development, such as the diploblastic (two layers) or triploblastic (three layers) organization.

Homeotic Genes

Genes that regulate the development and positioning of body structures, playing a crucial role in determining the body plan.

Phylogenetic Tree

A diagram that shows evolutionary relationships among various biological species based on similarities and differences in their physical or genetic characteristics.

Bioactive Compounds

Chemicals produced by organisms that have effects on living tissues, often used in defense mechanisms or communication.

Ecosystem Services

The benefits that living organisms provide to ecosystems and humans, such as water filtration, pollination, and nutrient cycling.

Example Problems

Example 1

The table below lists the common names of the nine animal phyla surveyed in this chapter. For each phylum, list the key characteristics and some representatives. $$\begin{array}{|l|l|l|}\hline \text { Phylum } & \text { Characteristics } & \text { Representatives } \\\hline \text { Sponges } & & \\\hline \text { Cnidarians } & & \\\hline \text { Flatworms } & & \\\hline \text { Nematodes } & & \\\hline \text { Molluscs } & & \\\hline \text { Annelids } & & \\\hline \text { Arthropods } & & \\\hline \text { Echinoderms } & & \\\hline \text { Chordates } & & \\\hline\end{array}$$

Example 2

Identify the pattern of embryonic development shown in each drawing below and name the phylum (or phyla) that exhibit this pattern.

Example 3

Bilateral symmetry in animals is best correlated with a. an ability to see equally in all directions. b. the presence of a skeleton. c. motility and active predation and escape. d. adaptation to terrestrial environments.

Example 4

Jon found an organism in a pond, and he thinks it's a freshwater sponge. His friend Liz thinks it looks more like an aquatic fungus. How can they decide whether it is an animal or a fungus? a. See if it can swim. b. Figure out whether it is autotrophic or heterotrophic. c. See if it is a eukaryote or a prokaryote. d. Look for cell walls under a microscope.

Example 5

Which of the following groupings includes the largest number of species? (Explain your answer.) a. invertebrates b. arthropods c. insects d. vertebrates
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Step-by-Step Explanations

QUESTION

How can differences in body plan features be used to construct a phylogenetic tree for invertebrates?

STEP-BY-STEP ANSWER:

Step 1: Identify key morphological characteristics (e.g., symmetry, tissue layers, presence of specialized structures) in various invertebrate groups.
Step 2: Collect molecular data, such as differences in homeotic genes and other genetic markers, to pair with morphological traits.
Step 3: Compare these characteristics across different phyla to determine similarities and differences.
Step 4: Use the derived similarities and differences to group organisms into clades that likely share a common ancestor.
Step 5: Draw the phylogenetic tree, placing groups with more similarities closer together on the tree.
Final Answer: Differences in body plan features, along with molecular data, allow for the grouping of invertebrates into clades and the construction of a phylogenetic tree that reflects their evolutionary relationships.

Constructing a Phylogenetic Tree

QUESTION

How do homeotic genes influence the diversification of invertebrate body plans?

STEP-BY-STEP ANSWER:

Step 1: Understand that homeotic genes control the developmental fate of cells in specific regions of the embryo.
Step 2: Recognize that variations or mutations in these genes can result in significant changes in body structure.
Step 3: Analyze how changes in gene regulation can lead to the development of new features or the loss of existing ones.
Step 4: Connect these changes to the diversity observed among invertebrate phyla.
Final Answer: Homeotic genes regulate the placement and formation of body structures, and variations in these genes contribute to the evolutionary diversification of invertebrate body plans.

Role of Homeotic Genes in Development

QUESTION

What are some key ecological roles played by invertebrates, and why are they important?

STEP-BY-STEP ANSWER:

Step 1: Identify roles such as water filtration (e.g., sponges), pollination (e.g., insects), and production of bioactive compounds (e.g., various marine invertebrates).
Step 2: Understand that these roles are crucial for maintaining ecosystem balance and promoting biodiversity.
Step 3: Discuss how the decline or loss of invertebrate populations can lead to significant ecological disruptions.
Final Answer: Invertebrates contribute essential services like water filtration, pollination, and chemical production, which are vital for ecosystem health and biodiversity.

Ecological Roles of Invertebrates

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Common Mistakes

  • Assuming that all invertebrates have simple or primitive body plans.
  • Confusing radial symmetry with bilateral symmetry and not recognizing their distinct ecological implications.
  • Overlooking the significance of homeotic genes in developmental processes by attributing body plan differences solely to environmental factors.
  • Generalizing conservation status, without recognizing that threat levels vary greatly among different invertebrate groups.