Book cover for Life: The Science of Biology

Life: The Science of Biology

David E. Sadava, David M. Hilliss, H. Craig Heller,May Berenbaum

ISBN #9781429219624

9th Edition

580 Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This section outlines the defining characteristics that separate animals from other life forms, such as multicellularity, heterotrophic metabolism, and specific developmental processes. It emphasizes the diversity of animal body plans and feeding strategies, showcasing how variations in symmetry, body cavity structure, segmentation, and appendages facilitate a wide range of ecological adaptations. The chapter further discusses the major animal clades—including protostomes, deuterostomes, sponges, placozoans, ctenophores, and cnidarians—highlighting both genetic and morphological evidence of their evolutionary relationships.

Learning Objectives

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Key Concepts

CONCEPT

DEFINITION

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Example Problems

Example 1

The body plan of an animal is $a,$ its general structure. $b$. the integrated functioning of its parts. $c .$ its general structure and the integrated functioning of its parts. $d$. its general structure and its evolutionary history. $e .$ the integrated functioning of its parts and its evolutionary history.

Example 2

A bilaterally symmetrical animal can be divided into mirror images by $a$ any plane through the midline of its body. $b$, any plane from its anterior to its posterior end. c. any plane from its dorsal to its ventral surface. $d$ any plane through the midline of its body from its anterior to its posterior end. $e .$ a single plane through the midline of its body from its dorsal to its ventral surface.

Example 3

Among protostomes, cleavage of the fertilized egg is a. delayed while the egg continues to mature. b. always radial. c. spiral, radial, or idiosyncratic. $d$. triploblastic. $e .$ diploblastic.

Example 4

Many parasites evolved complex life cycles because $a$. they are too simple to disperse readily. $b$. they are poor at recognizing new hosts. c. they were driven to it by host defenses. $d$. complex life cycles increase the probability of a parasite's transfer to a new host. $e .$ their ancestors had complex life cycles and they simply retained them.

Example 5

Bilateral symmetry $a$. is found only among bilaterians. b. is characteristic of all sponges. $c$. is characteristic of all ctenophores. $d$ is characteristic of all cnidarians. $e$ none of the above
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Step-by-Step Explanations

QUESTION

How do protostome and deuterostome developmental patterns differ in terms of gastrulation?\nStep-by-step Answer:\nStep 1: Begin with the fertilized egg undergoing cleavage; both groups start similarly.\nStep 2: Observe gastrulation where an indentation forms the blastopore.\nStep 3: In protostomes, the blastopore develops into the mouth and the anus forms later.\nStep 4: In deuterostomes, the blastopore becomes the anus first, and the mouth forms subsequently.\nFinal Answer: The key difference is that protostomes form the mouth from the blastopore, while deuterostomes form the anus from the blastopore.\n\n- Topic: Symmetry and Movement \nQuestion: How does bilateral symmetry support enhanced mobility compared to radial symmetry?\nStep-by-step Answer:\nStep 1: Define bilateral symmetry as the division of the body into mirror-image halves along a single plane.\nStep 2: Explain that bilateral symmetry typically leads to the development of a distinct head (cephalization) where sensory organs are concentrated.\nStep 3: Describe how a streamlined body with a clear anterior end aids in directional movement and complex behaviors.\nStep 4: Contrast with radial symmetry which, while useful for sessile or slow-moving organisms, does not support rapid directional movement.\nFinal Answer: Bilateral symmetry, with concentrated sensory and neural structures, enhances an animal\u2019s ability to move purposefully and interact dynamically with its environment.\n\n"

STEP-BY-STEP ANSWER:

Step 1: Begin with the fertilized egg undergoing cleavage; both groups start similarly.\nStep 2: Observe gastrulation where an indentation forms the blastopore.\nStep 3: In protostomes, the blastopore develops into the mouth and the anus forms later.\nStep 4: In deuterostomes, the blastopore becomes the anus first, and the mouth forms subsequently.\nFinal Answer: The key difference is that protostomes form the mouth from the blastopore, while deuterostomes form the anus from the blastopore.\n\n- Topic: Symmetry and Movement \nQuestion: How does bilateral symmetry support enhanced mobility compared to radial symmetry?\nStep-by-step Answer:\nStep 1: Define bilateral symmetry as the division of the body into mirror-image halves along a single plane.\nStep 2: Explain that bilateral symmetry typically leads to the development of a distinct head (cephalization) where sensory organs are concentrated.\nStep 3: Describe how a streamlined body with a clear anterior end aids in directional movement and complex behaviors.\nStep 4: Contrast with radial symmetry which, while useful for sessile or slow-moving organisms, does not support rapid directional movement.\nFinal Answer: Bilateral symmetry, with concentrated sensory and neural structures, enhances an animal\u2019s ability to move purposefully and interact dynamically with its environment.\n\n"
Final Answer: The key difference is that protostomes form the mouth from the blastopore, while deuterostomes form the anus from the blastopore.\n\n- Topic: Symmetry and Movement \nQuestion: How does bilateral symmetry support enhanced mobility compared to radial symmetry?\nStep-by-step Answer:\nStep 1: Define bilateral symmetry as the division of the body into mirror-image halves along a single plane.\nStep 2: Explain that bilateral symmetry typically leads to the development of a distinct head (cephalization) where sensory organs are concentrated.\nStep 3: Describe how a streamlined body with a clear anterior end aids in directional movement and complex behaviors.\nStep 4: Contrast with radial symmetry which, while useful for sessile or slow-moving organisms, does not support rapid directional movement.\nFinal Answer: Bilateral symmetry, with concentrated sensory and neural structures, enhances an animal\u2019s ability to move purposefully and interact dynamically with its environment.\n\n"

"- Topic: Protostomes vs. Deuterostomes \nQuestion: How do protostome and deuterostome developmental patterns differ in terms of gastrulation?\nStep-by-step Answer:\nStep 1: Begin with the fertilized egg undergoing cleavage; both groups start similarly.\nStep 2: Observe gastrulation where an indentation forms the blastopore.\nStep 3: In protostomes, the blastopore develops into the mouth and the anus forms later.\nStep 4: In deuterostomes, the blastopore becomes the anus first, and the mouth forms subsequently.\nFinal Answer: The key difference is that protostomes form the mouth from the blastopore, while deuterostomes form the anus from the blastopore.\n\n- Topic: Symmetry and Movement \nQuestion: How does bilateral symmetry support enhanced mobility compared to radial symmetry?\nStep-by-step Answer:\nStep 1: Define bilateral symmetry as the division of the body into mirror-image halves along a single plane.\nStep 2: Explain that bilateral symmetry typically leads to the development of a distinct head (cephalization) where sensory organs are concentrated.\nStep 3: Describe how a streamlined body with a clear anterior end aids in directional movement and complex behaviors.\nStep 4: Contrast with radial symmetry which, while useful for sessile or slow-moving organisms, does not support rapid directional movement.\nFinal Answer: Bilateral symmetry, with concentrated sensory and neural structures, enhances an animal\u2019s ability to move purposefully and interact dynamically with its environment.\n\n"

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Common Mistakes

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