introduction to animals -...

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Chapter 25 • Workbook A • Copyright © by Pearson Education, Inc., or its affi liates. All Rights Reserved.

393

Introduction to Animals

Unity and Diversity of LifeQ: What characteristics and traits defi ne animals?

WHAT I LEARNED

25.1 What is an

animal?

25.2 How

have different

animal body plans

evolved?

WHAT I KNOW

SAMPLE ANSWER: Animals are different from other living things (bacteria, protists, fungi, and plants).

SAMPLE ANSWER: All animals are multicellular, eukarytotic, and heterotrophic. Their cells lack cell walls. Chordates exhibit four characteristics during some stage of their development: a dorsal, hollow nerve cord; a notochord; a tail that extends beyond the anus; and pharyngeal pouches.

SAMPLE ANSWER: Each animal group evolved a group of structures or “body plan” that is unique to that group.

SAMPLE ANSWER: The features of a body plan include levels of organization (cells, tissues, organs, organ systems); body symmetry; differentiation of germ layers; formation of a cavity between the digestive tract and the body wall; patterns of embryological development; segmentation; cephalization; and limb formation. The features of body plans provide evidence needed to build a cladogram, or phylogenetic tree, of animals.

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Lesson 25.1 • Workbook A • Copyright © by Pearson Education, Inc., or its affi liates. All Rights Reserved.

394

Name Class Date

25.1 What Is an Animal?

Lesson Objectives

List the characteristics that all animals share.

Differentiate between invertebrates and chordates.

List and discuss the essential functions that animals perform in order to survive.

Lesson Summary

Characteristics of Animals All animals are multicellular, heterotrophic, and eukaryotic. Their cells lack cell walls.

Types of Animals Animals are often classified into two broad categories: invertebrates and chordates.

Invertebrates ▶ do not have a backbone, or vertebral column.

• More than 95 percent of all animal species are invertebrates.

• Invertebrates are classified in at least 33 phyla, the largest taxonomic groups of animals. Examples of invertebrates are sea stars, jellyfishes, and insects.

Chordates ▶ exhibit four characteristics during some stage of development: a dorsal, hollow nerve cord; a notochord; a tail that extends beyond the anus; and pharyngeal pouches.

• A notochord is a supporting rod that runs through the body just below the nerve cord.

• Pharyngeal pouches are paired structures in the throat region.

• Most chordates develop a backbone, or vertebral column. They are vertebrates.

What Animals Do to Survive Animals must maintain homeostasis in order to survive. One important way to maintain homeostasis is feedback inhibition, also called negative feed-back, in which the product or result of a process limits the process itself. In order to maintain homeostasis, animals must

gather and respond to information; ▶obtain and distribute oxygen and nutrients; ▶collect and eliminate carbon dioxide and other wastes. ▶

They also reproduce.

Characteristics of Animals 1. Complete the graphic organizer to summarize the characteristics of animals.

Animals

have characteristics such as

Multicellular Heterotrophic Eukaryotic No cell walls

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Types of Animals 2. Are invertebrates rare? Explain your answer.

3. What is an invertebrate?

4. Why do invertebrates not form a clade?

5. What are some examples of invertebrates?

6. Look at the diagram of a chordate. Write the name of the labeled structure on the lines below.

7. Are all chordates vertebrates? Explain your answer.

8. What groups of animals are vertebrates?

9. Both snakes and earthworms have long, streamlined body shapes, but snakes are vertebrates and earthworms are not. Why are they classified differently despite their similarity in appearance?

Notochorda.

Pharyngeal pouchesd.

Tailc.

Hollow nerve cordb.

No, they are common. More than 95 percent of animal species are invertebrates.

An invertebrate is an animal that lacks a backbone, or vertebral column.

They are not a clade because they are defined by the absence of a characteristic.

No, some chordates never develop a backbone.

Vertebrates include fishes, amphibians, reptiles, birds, and mammals.

Animals are classified based on body plans, not similarity of appearance. Earthworms

do not have the characteristics of a chordate, so they are considered invertebrates.

Sea stars, worms, jellyfishes, and insects are invertebrates.

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11. The diagram on the left below shows the feedback inhibition that maintains temperature in a house. Complete the blank boxes in the diagram on the right below to show how body temperature is maintained in a human being.

12. Describe generally how an animal’s nervous and musculoskeletal systems work together to allow it to escape a predator.

13. In complex animals, what system collects metabolic wastes and delivers them to the respiratory and excretory systems?

14. In complex animals, which three body systems work together to obtain and distribute oxygen and nutrients?

What Animals Do to Survive 10. Complete the graphic organizer to define three ways that animals maintain homeostasis.

Animals Maintain Homeostasis

by

Thermostat turns furnace

off.

Sweating cools body.

House gets cold.

Thermostat turns furnace

on.

House gets hot.

Gathering and responding to information

Obtaining and distributing oxygen

and nutrients

Collecting and eliminating carbon

dioxide and other wastes

Body gets cold.

Body gets hot.

Shivering. Muscle activity generates heat.

The animal’s sensory receptors, which are part of the nervous system, sense a

predator. Its nervous system then sends signals to the musculoskeletal system to flee.

The animal’s muscles work with its skeleton to allow it to move away from the predator.

the circulatory system

the respiratory, digestive, and circulatory systems

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For Questions 15–24, write the letter of the correct answer on the line at the left.

15. What system gathers information through receptors for sound, light, chemicals, and other stimuli?

A. respiratory

B. circulatory

C. musculoskeletal

D. nervous

16. Most chordates have a large number of nerve cells concentrated into a

A. backbone.

B. notochord.

C. brain.

D. pharyngeal pouch.

17. How does muscle tissue generate force?

A. It stretches.

B. It shortens.

C. It inflates.

D. It dilates.

18. How do the skeletons of insects and vertebrates differ?

A. Insects have fluid skeletons. Vertebrates have external skeletons.

B. Insects have external skeletons. Vertebrates have internal skeletons.

C. Insects have internal skeletons. Vertebrates have external skeletons.

D. Insects have external skeletons. Vertebrates have fluid skeletons.

19. What process allows some aquatic animals to “breathe” through their skin?

A. diffusion

B. digestion

C. excretion

D. circulation

20. Which structure performs a function most similar to that of gills?

A. heart

B. intestine

C. blood vessel

D. lung

21. Which of these functions requires the coordinated actions of the digestive, circulatory, and excretory systems?

A. gathering O2 and distributing it to body systems

B. collecting and eliminating CO2 from tissues

C. acquiring nutrients and distributing them to body systems

D. collecting and eliminating metabolic wastes

D

D

A

B

B

C

D

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22. How do the respiratory system and excretory system differ in the wastes they eliminate?

A. The respiratory system eliminates carbon dioxide. The excretory system eliminates ammonia.

B. The respiratory system eliminates wastes that contain nitrogen. The excretory system eliminates carbon-based wastes.

C. The respiratory system eliminates oxygen and nitrogen. The excretory system eliminates ammonia.

D. The respiratory system eliminates ammonia. The excretory system eliminates carbon dioxide.

23. Which activity is required for survival of the species but not survival of the organism?

A. digestion

B. excretion

C. reproduction

D. circulation

24. What is an advantage of asexual reproduction?

A. It increases genetic diversity in a population.

B. It produces large numbers of offspring rapidly.

C. It increases a species’ ability to evolve.

D. It produces offspring that are genetically different from the parents.

25. In what ways do invertebrates differ from vertebrates? Identify at least three groups of invertebrates.

26. Suppose you were studying the cell walls of a multicellular organism under a microscope. Were you studying an animal? Explain your answer.

A

C

B

SAMPLE ANSWER: Invertebrates have no backbones. They don’t have a nerve cord, a

notochord, a tail, or pharyngeal pouches. Invertebrate groups include insects, worms,

sea stars, and jellyfishes.

No, it wasn’t an animal, because animal cells have no cell walls.

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introduction to animals -...

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