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1. Mollusks
Arthropods
Insects
Insect Ecology
Echinoderms
Table of Contents
2. 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.
3. Snails and Slugs Gastropods use an organ called a radula, a flexible ribbon of tiny teeth, to obtain food.
4. Two-Shelled Mollusks A razor clam digs into the mud by changing the shape of its foot.
5. Comparing and Contrasting When you compare and contrast things, you explain how they are alike and different. As you read, compare and contrast three groups of mollusks by completing a table like the one below.
6. End of Section: Mollusks
7. Characteristics of Arthropods Members of the largest arthropod groups differ in several characteristics.
8. Crustaceans A crustacean is an arthropod that has two or three body sections, five or more pairs of legs, and two pairs of antennae.
9. Lyme Disease Cases The graph shows the number of cases of Lyme disease by age group reported by Connecticut during one year.
10. Lyme Disease Cases Cases per 100,000 people; the first bar indicates that for every 100,000 children under the age of 10, 200 had Lyme disease. Reading Graphs:
What variable is plotted on the y-axis? What does the first bar tell you?
11. Lyme Disease Cases 20–29 year-olds; just over 50 per 100,000 people were infected. Interpreting Data:
Which age group is least at risk for Lyme disease? Explain.
12. Lyme Disease Cases Children under 10 and people between the ages of 50 and 59 Interpreting Data:
Which two age groups are most at risk?
13. Lyme Disease Cases One or two students Calculating:
Suppose a particular school in Connecticut has 1,000 students aged 10–19. About how many of these students would you expect to get Lyme disease per year?
14. Asking Questions Before you read, preview the red headings. In a graphic organizer like the one below, ask a what or how question for each heading. As you read, write answers to your questions.
15. Links on Arthropods Click the SciLinks button for links on arthropods.
16. End of Section: Arthropods
17. Body Structure Insects are arthropods with three body sections, six legs, one pair of antennae, and usually one or two pairs of wings.
18. Life Cycle An insect with complete metamorphosis has four different stages: egg, larva, pupa, and adult.
19. 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.
20. Sequencing Sequence is the order in which a series of events occurs. As you read, make a cycle diagram that shows the steps in the complete metamorphosis of an insect. Write each step in a separate circle.
21. More on Insect Metamorphosis Click the PHSchool.com button for an activity about insect metamorphosis.
22. Insect Adaptations Click the Video button to watch a movie about insect adaptations.
23. End of Section: Insects
24. Percentages A percentage is a ratio that compares a number to 100. If 25 percent of 900,000 insect species eat other insects, how many insect-eating species are there? Set up a proportion and solve it.
Practice Problem
A swallow chick eats 200,000 insects. If 12 percent of the insects are beetles, how many beetles does it eat?
P = 24,000
25. Building Vocabulary Using a word in a sentence helps you think about how best to explain the word. After you read the section, reread the paragraphs that contain definitions of Key Terms. Use all the information you have learned to write a meaningful sentence for each Key Term.
26. Links on Insects Click the SciLinks button for links on insects.
27. End of Section: Insect Ecology
28. Characteristics of Echinoderms Echinoderms, such as this sea star, have a water vascular system that helps them move and catch food.
29. Water Vascular System Activity Click the Active Art button to open a browser window and access Active Art about the water vascular system.
30. Previewing Visuals When you preview, you look ahead at the material to be read. Preview Figure 24. Then write two questions you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
31. End of Section: Echinoderms
32. Graphic Organizer
33. End of Section: Graphic Organizer
