Table of Contents Chapter Preview 11.1 What is an Animal? 11.2 Sponges and Cnidarians 11.3 Worms and Mollusks 11.4 Arthropods 11.5 Echinoderms 11.1 What is an Animal? 11.2 Sponges and Cnidarians 11.3 Worms and Mollusks 11.4 Arthropods 11.5 Echinoderms

Chapter Preview Questions 1. Which of the following animals appeared first during Earth’s history? a. fishes b. mammals c. worms d. reptiles

Chapter Preview Questions 1. Which of the following animals appeared first during Earth’s history? a. fishes b. mammals c. worms d. reptiles

Chapter Preview Questions 2. Which of the following structures is NOT found in animal cells? a. cell wall b. cell membrane c. mitochondria d. nucleus

Chapter Preview Questions 2. Which of the following structures is NOT found in animal cells? a. cell wall b. cell membrane c. mitochondria d. nucleus

Chapter Preview Questions 3. If an animal reproduces asexually, it a. has two parent organisms. b. undergoes conjugation. c. is genetically identical to its offspring. d. inherits two different sets of alleles.

Chapter Preview Questions 3. If an animal reproduces asexually, it a. has two parent organisms. b. undergoes conjugation. c. is genetically identical to its offspring. d. inherits two different sets of alleles.

Chapter Preview Questions 4. If an animal has specialized tissues and organs, the animal’s cells have undergone a. photosynthesis. b. osmosis. c. selective breeding. d. differentiation.

Chapter Preview Questions 4. If an animal has specialized tissues and organs, the animal’s cells have undergone a. photosynthesis. b. osmosis. c. selective breeding. d. differentiation.

What major functions do animals’ bodies perform? On a walk through the park, you stop to look closely at the leaves of a plant. You see an insect laying eggs. The eggs are the result of sexual reproduction. The cells in each insect egg contain many genes. Where do these genes come from? Explain your answer.

Use Clues to Determine Meaning The animals called cnidarians have two different body plans. One form looks something like a vase. The vase-shaped body plan is called a polyp. A polypís mouth opens at the top and its tentacles spread out from around the mouth. What a polyp is Additional information about a polyp

Apply It! 1. In your own words, what is the meaning of polyp? Sample: A polyp is a vase-shaped cnidarian. 2. What sentence contains the definition of polyp? Sentence 3 3. What other clues help you understand the meaning of polyp? The last sentence tells me it has a mouth that opens at the top and is surrounded by spreading tentacles.

End of Chapter Preview

Section 1: What is an Animal? How are animal bodies typically organized? What are the four major functions of animals? What is symmetry? How are animals classified?

Structure of Animals The cells of most animals are organized into higher levels of structure, including tissues, organs, and systems.

Structure of Animals The cells of most animals are organized into higher levels of structure, including tissues, organs, and systems.

Classification of Animals This branching tree shows how the major animal groups are related.

Links on the Animal Kingdom Click the SciLinks button for links on the animal kingdom.

Click the Video button to watch a movie about the animal kingdom.

End of Section: What Is an Animal?

Section 2: Sponges and Cnidarians? What are the main characteristics of sponges? What are the main characteristics of cnidarians?

Sponges Structures surrounding the central cavity of a sponge are adapted for different functions.

Structure of a Sponge Activity Click the Active Art button to open a browser window and access Active Art about the structure of a sponge.

Cnidarians Cnidarians have two basic body plans, the vase-shaped polyp and the bowl-shaped medusa.

Cnidarians Cnidarians use stinging cells to capture food and defend themselves.

Cnidarians The life cycle of a moon jelly has both a polyp and a medusa stage, and both sexual and asexual reproduction.

Click the Video button to watch a movie about invertebrates.

End of Section: Sponges and Cnidarians

Section 3: Worms and Mollusks What are the main characteristics of worms? What are the main characteristics of each phylum of worms? What are the main characteristics of mollusks? What are eth main groups of mollusks?

Characteristics of Worms Biologists classify worms into three major phyla—flatworms, roundworms, and segmented worms.

Life Cycle of a Dog Tapeworm This tapeworm is a parasite that lives in more that one host during its life cycle.

Roundworm Numbers Biologists counted all the roundworms living in a plot of soil. Then they calculated the percentage that lives in different depths of soil.

Roundworm Numbers Reading Graphs: Where in the soil was the largest percentage of roundworms found? In the first centimeter

Roundworm Numbers Calculating: What is the total percentage of roundworms found in the first 3-cm depth of soil? About 87%

Roundworm Numbers Drawing Conclusions: What is the relationship between the depth of soil and the abundance of roundworms in the soil? The deeper the soil, the fewer the worms

Segmented Worms Earthworms and other segmented worms have bodies made up of many linked sections called segments.

Characteristics of Mollusks Although they don’t look much alike at first, a snail, a clam, and a squid have the same basic body structures.

Snails and Slugs Gastropods such as this land snail have an organ called a radula, which tears and scrapes up food.

Click the PHSchool.com button for an activity about worms. More on Worms Click the PHSchool.com button for an activity about worms.

End of Section: Worms and Mollusks

Section 4: Arthropods What are the general characteristics of arthropods? What are the distinguishing structures of crustaceans, arachnids, centipedes and millipedes, and insects?

Characteristics of Arthropods Members of the largest arthropod groups differ in several characteristics.

Crustaceans A crustacean is an arthropod that has two or three body sections, five or more pairs of legs, and two pairs of antennae.

Body Structure Insects are arthropods with three body sections, six legs, one pair of antennae, and usually one or two pairs of wings.

Life Cycle An insect with complete metamorphosis has four different stages: egg, larva, pupa, and adult.

Life Cycle An insect with gradual metamorphosis has no distinct larval stage. An egg hatches into a stage called a nymph, which usually looks like the adult insect without wings.

Click the SciLinks button for links on arthropods.

Click the Video button to watch a movie about insect adaptations.

End of Section: Arthropods

Section 5: Echinoderms What are the main characteristics of echinoderms? What are the major groups of echinoderms?

Characteristics of Echinoderms Echinoderms, such as this sea star, have a water vascular system that helps them move and catch food.

Water Vascular System Activity Click the Active Art button to open a browser window and access Active Art about the water vascular system.

Diversity of Echinoderms There are four major groups of echinoderms: sea stars, brittle stars, sea urchins, and sea cucumbers. All have radial symmetry and are found in the ocean.

End of Section: Echinoderms

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