. What are the major groups of echinoderms? '

Transcription

1 Chapter 11 Structure and Function of Invertebrates Echinoderms Key Concepts. What are the main characteristics of echinoderms?. What are the major groups of echinoderms? ' Section 5 Summary Echinoderms are invertebrates with an internal skeleton and a system of fluid-filled tubes called a water vascular system. The skin of most echinoderms is stretched over an internal skeleton, called an endoskeleton. The water vascular system consists of fluid-filled tubes within the echinoderm's body. Portions of the tubes can squeeze together, forcing water into structures called tube feet. Most echinoderms use their tube feet to move and to capture food. Almost all echinoderms are either male or female. Eggs are usually fertilized in the water. The fertilized eggs develop into larvae. The larvae eventually undergo metamorphosis and become adults. There are four major groups of echinoderms: sea stars, brittle stars, sea urchins, and sea cucumbers. Sea stars are predators. A sea star uses its tube feet to move across the ocean bottom and capture prey. A sea star will grasp a clam with all five arms and pull the shells open. Then the sea star feeds on the clam's tissues. Brittle stars have long and slender arms. Brittle stars use their arms to slither along the ocean bottom. They use their tube feet to catch food. Unlike sea stars and brittle stars, sea urchins have no arms. Spines cover and protect their bodies. Sea urchins move mostly by using bands of tube feet tha t extend out between the spines. They scrape and cut food with five teethlike structures. Sea cucumbers move by using tube feet on their underside. Sea cucumbers feed using their PearsonEducation, Inc., publishing as PearsonPrentice Hall. All rights reselved. 216

2 Structure and Function of Invertebrates Reviewand Reinforce Echinoderms Understanding Main Ideas Write the letter of the correctanswer on the line at the left. 1. Which of the followingis not a characteristicof echinoderms? a. 5-part radial syrrunetry b. endoskeleton c. live in freshwater d. water vascular system 2. Which of the followingis not an echinoderm? a. fiddler crab b. brittle star c. sea urchin d. sea cucumber 3. Which of the following is not a function of tube feet? a. move along ocean floor b. catch food c. grip surfaces d. digest food 4. The life cycle of an echinoderm includes all of the following except a. eggs b. metamorphosis c. pollination d. fertilization Answer the following. 5. Describe how a sea star captures its food. Building Vocabulary Fill in the blank to complete each statement. 6. The consists of fluid-filled tubes within the echinoderm's body. 7. An echinoderm has a(n) that supports its body. 8. Animals in the phylum are radially symmetrical invertebrates that live on the ocean PearsonEducation, Inc., publishingos PearsonPrenticeHoIl. All r~hls resejved. 73

3 Structure and Function of Invertebrates Sea Lilies Enrich The four groups of echinoderms discussed in the text make up the vast majority of today's living echinoderms. There is another living group, however, the sea lilies, or crinoids(kry-noydz). Although these echinoderms are rare today, their long history and complex fossil record make them important to scientists who study fossils. Sea lilies are filter feeders whose bodies vaguely resemble flowers. Instead of petals, however, these echinoderms have long arms lined with rows of tube feet that sweep food particles out of the water and move the particles toward the centrally located mouth. In most, their bodies have long stems. Unlike most modern echinoderms, sea lilies fasten themselves to solid objects on the bottom using the base of their stems. The sea lilies sometimes detach and move around. Modern sea lilies live mostly in very deep water, though some live on coral reefs. During much of the last 530 million years, however, they were found in a greater variety of habitats, and they were much more abundant. In many places, the hard plates of the sea lilies' endoskeletons make up large portions of the rocks deposited in the seas in which they lived. SeaLily Sand Dollar (a close relative of sea urchins) Sea Star Answer the questions below on a separate sheet of paper. 1. Echinoderms have five-part radial symmetry, a water vascular system, and an internal skeleton. Which of these characteristics are visible in all three illustrations? 2. The endoskeletons of echinoderms are not visible in these illustrations. How do we know that ancient sea lilies had them? 3. What part of the water vascular system is visible in the illustration of the sea lily? How does the sea lily use this part in a way different than the other echinoderms pictured use it? 4. While both sea lilies and sea cucumbers are filter feeding echinoderms, only sea lilies remain fastened to the sea floor. How do you think this difference would affect the habitats in which the two animals PearsonEducation, Inc., publishingas PeersonPrenticeHoIl. All r~hls reserved. 74

4 Chapter 11 Structure and Function of Invertebrates Section 4 Summary Arthropods Key Concepts. What are the general characteristics of arthropods?. What are the distinguishing structures of crustaceans, arachnids, centipedes and millipedes, and insects? Arthropods are invertebrates that have an external skeleton, a segmented body, and jointed attachments called appendages. The major groups of arthropods include crustaceans, arachnids, centipedes and millipedes, and insects. Arthropods have bilateral symmetry, an open circulatory system, a digestive system with t\vo openings, and sexual reproduction. All arthropods have a waxy exoskeleton, or outer skeleton, that protects the animal and helps prevent evaporation of water. Arthropods shed their outgrown exoskeletons in a process called molting. Jointed appendages give arthropods flexibility and enable them to move. An antenna is an appendage attached to the head that contains sense organs. A crustacean is an arthropod that has two or three body sections, five or more pairs of legs, and two pairs of antennae. Crustaceans live in watery environments and most have gills. Most crustaceans begin their lives as microscopic, swimming larvae. Crustacean larvae develop into adults by metamorphosis, a process in,,\'hich an animal's body undergoes dramatic changes in form. Arachnids are arthropods with two body sections, four pairs of legs, and no antennae. The first body section is a combined head and midsection. The hind section, called the abdomen, contains the arachnid's reproductive organs and part of its digestive system. Spiders and ticks are arachnids. Centipedes and millipedes are arthropods with two body sections and pairs of legs. Centipedes have one pair of legs attached to each segment, and some centipedes have over 100 segments. Millipedes, which may have more than 80 segments, have two pairs of legs on each segment. Insects are arthropods with three body sections, six legs, one pair of antennae, and usually one or two pairs of wings. The three body sections are the head, thorax, and abdomen. An insect's thorax, or midsection, is the section to which wings and legs are attached. The abdomen contains many of the insect's intemal organs. Insects begin life as tiny, hard-shelled, fertilized eggs. After they hatch, insects begin a process of metamorphosis that eventually produces an adult insect. Each insect species undergoes either complete metamorphosis or gradual metamorphosis. Complete metamorphosis has four stages: egg, la.rva, pupa, and adult. After a period of eating and growing, the larva goes hlto the next stage and becomes a pupa (plural: pupae).as a pupa, the insect is enclosed in a protective coverhlg and gradually changes into an adult. In contrast, gradual metamorphosis has no distinct larval stage. An egg hatches into a nymph that often resembles the adult PearsonEducotion, Inc., publishing os PearsonPrentice Holi. All rights reserved. 209

5 Structure and Function of Invertebrates Reviewand Reinforce Arthropods Understanding Main Ideas Read each description. Decide which animal group best fits each question. Write your answers on a separate sheet of paper. 1. They are invertebrates with an exoskeleton, segmented body, and jointed appendages. They have an open circulatory system and reproduce sexually. Their name comes from the Greek for "joint-leg." What are they? 2. They have highly segmented bodies with one pair of legs attached to each segment. Some of them have more than 100 segments. What are they? 3. They all have two body sections and eight legs. They are predators with fangs. None of them have antennae. What are they? 4. They have three body sections, six legs, one pair of antennae, and usually one or two pairs of wings. What are they? Building Vocabulary From the list below, choose the term that best completes each sentence. Use each term onlyonce. abdomen antennae thorax pupa exoskeleton metamorphosis molting complete metamorphosis 5. An arthropod's protects it and keeps it from drying out. 6. The heads of some arthropods have, which contain sense organs. 7. Some animals go through a process called during their life cycle in which their bodies undergo dramatic changes in form as they develop. 8. The hind body section of an arachnid is called its 9. The process of shedding an outgrown exoskeleton is called 10. When an insect becomes a(n), major changes in structure take place. 11. has four stages: egg, larva, pupa, and adult. 12.An insect's midsection is called PearsonEducation, Inc., publishingas PeersonPrenticeHoIl. All r~hls reserved. 70

6 Structure and Function of Invertebrates Enrich The Arthropod Evolutionary Tree When scientists say that two kinds of organisms are related, they mean that those two kinds of organisms had a common ancestor. The more recently that common ancestor lived, the more closely relate~ the two kinds of organisms are. A cladogramis a diagram that shows how closely related to each other different kinds of organisms are. It's a tree-shaped diagram with leaves, forks, and branches. The cladogram shows part of the arthropod evolutionary tree. At the top are the leaves, which are recent arthropods, such as insects, millipedes, and centipedes. Each fork in the diagram represents the shared ancestor of all arthropods above it. For example, fork o is the shared ancestor of millipedes and centipedes, while fork C is the shared ancestor of all insects, millipedes, and centipedes. Branches connect the ancestors with each other and with recent organisms. To find the most recent ancestor of any hovoorganisms just follow the branches down until you reach the first fork that connects them. You can also follow up from a fork, to find more and more recent organisms. The two organisms that have the same most recent ancestor are each other's closest relative. D Shared Ancestors 'C Millipedes, Centipedes B Shared Ancestors of Insects, Millipedes, Centipedes Shared Ancestors of Crustaceans, Insects, Millipedes, Centipedes A Shared Ancestors of all Arthropods of Answer the questions below on a separate sheet of paper. 1. Which fork occurred earlier, B or D? How do you know? 2. What does fork B represent? 3. What does fork E represent? 4. Which group are mites and ticks most closely related to? How do you PearsonEduennan,Inc., publishingas PearsonPrennceHoIl. All r~hls reserved. 71

7 Chapter 10 Structure and Function of Plants Section 1 Summary The Plant Kingdom Key Concepts. What characteristics do all plants share?. What do plants need to live successfully on land?. How do nonvascular plants and vascular plants differ?. What are the different stages of a plant's life cycle? Nearly all plants are autotrophs, organisms that produce their own food. All plants are eukaryotes that contain many cells. In addition, all plant cells are surrounded by cell walls. Like many other multicellular organisms, plants have levels of organization for structure and function. Tissues work together to form organs--ieaves, stems, and roots. A plant has two organ systems. Above grotmd is the shoot system, which consists of stems, leaves, and buds. Below ground is the root system, which absorbs water and nutrients and anchors the plant in the soil. Most plants live on land. To survive on land, plants must have structures that allow them to obtain water and other nutrients from their surroundings, retain water, transport materials in their bodies, support their bodies, and reproduce. Most plants have a waxy, waterproof layer covering their leaves called a cuticle. The cuticle helps keep water inside a plant cell rather than let it evaporate into the air. Some plants have vascular tissue, a system of tubelike structmes inside the plant through which food, minerals, and water move. All plants undergo sexual reproduction that involves fertilization, the joining of a spelm cell with an egg cell. The fertilized egg is called a zygote. Many plants can also reproduce asexually. Reproduction in plants by asexual methods is called vegetative reproduction. For example, many plants can grow from a cutting. Scientists informally group plants into two major groupsnonvascular plants and vascular plants. Nonvascular plants do not have a well-developed system of tubes for transporting water and other materials. They grow low to the ground and obtain water directly from their sun'oundings. Vascular plants have well-developed vascular tissue to transport and move materials quickly and efficiently throughout the plant's body. Vascular tissue also provides strength, stability, and support to a plant. Thus, vascular plants are able to grow quite tall. Plants have complex life cycles that include two stages, the sporophyte stage and the gametophyte stage. In the sporophyte stage, the plant produces spores, tiny cells that can grow into new organisms. A spore develops into the plant's other stage, called the gametophylestage.jn the gametophyte stage, the plant produces two kinds of sex cells: sperm cells and egg,c~lls. A sperm cell and egg cell join to form a zygote, which then develops into a PearsonEducation, Inc., publishing as PearsonPrentice Hall. All rights reserved. 171

8 Structure and Function of Plants The Plant Kingdom Understanding Main Ideas Answer thefollowing questions. 1. What characteristics do all plants share? Reviewand Reinforce 2. What do plants need to live successfully on land? Building Vocabulary From the list below, choose the term that best completes each sentence and write it in the blank. vascular tissue zygote cuticle gametophyte vascular plant nonvascular plant sporophyte 3. The internal transporting system through which water, minerals, and food move inside the plant is called 4. In the stage, the plant produces two kinds of sex cells. 5. A plant that does not have a well-developed system of tubes for transporting water and other materials is called a(n) 6. A(n) is a waxy, waterproof layer that covers the leaves and stems of most plants. 7. In the stage, the plant produces spores. 8. A plant with true vascular tissue is called a(n) 9. A fertilized egg is called PearsonEducation, Inc., publishingos PeersonPrenticeHoIl. All r~hls reserved. 37

9 Structure and Function of Plants Desert Survival Enrich You learned that allplants must have adaptations for obtaining and retaining water. This is especially true of plants that live in the desert. To obtain water, some desert plants have very deep root systems that can absorb moisture far underground. Others have shallow, horizontal root systems that can quickly absorb a large amount of water when it rains. The aboveground surfaces of many desert plants are covered with spines. These spines help to shade the plant from the sun and keep it from getting too hot. They also help to reduce water loss from the plant by shielding it from dry winds. Some plants in the desert have thick, fleshy stems that can store water for long periods of time. Many plants, such as the one shown below, survive dry periods by becoming dormant or inactive. When a plant is dormant, it needs very little water. leavesand flowersbegin to falloff flowers Answer the following questions on a separate sheet of paper. 1. What do you think causes the plant in the figure above to come out of dormancy and become active? 2. Why do you think the plant loses its leaves and flowers when it becomes dormant? 3. Do you think the plant shown above is more likely to have deep roots or shallow horizontal roots? Explain. 4. A desert plant called the creosote bush has a double root system: It has both shallow horizontal roots and deep vertical roots. Why would this type of root system be an advantage to a desert plant? 5. Do you think a desert plant is more likely to have a thin cuticle or a thick cuticle? PearsonEducolion, Inc., publishingos PearsonPrenticeHolloAll r~hls reserved. 38

10

11 Name Date Class Structure and Function of Plants Review and Reinforce Plants Without Seeds Understanding Main Ideas Replace each number in the table with the correct word or phrase. Characteristic Mosses 1. Hornworts contain vascular tissue no 2. no height 3. low-growing low-growing size small small 4. moisture needs 5. places high in moisture places high in moisture where they grow tree trunks or wet rocks moist rocks or moist soil 6. Answer the following questions on the lines provided. 7. In addition to ferns, what two other groups of plants are also seedless vascular plants? 8. What are plants that have vascular tissue called? 9. How do seedless vascular plants reproduce? Building Vocabulary Write the letter of the correct answer on the line at the left. 10. The structures that anchor a moss and absorb water and nutrients from the soil are called a. stems. b. rhizoids. c. sporophytes. d. gametophytes. 11. A frond is a. the leaf of a fern. b. the leaf of a horsetail. c. a moss. d. the gametophyte of a liverwort. Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved. 40

12 Name Date Class Structure and Function of Plants Enrich Spore Toss The tiny spore cases that grow on the undersides of fern fronds are called sporangia (singular sporangium). Some kinds of ferns can actually throw their spores using their sporangia. The sporangia of these ferns consist of a single layer of thin-walled cells plus an annulus. An annulus (plural annuli) is a row of thickened cells that encircles the sporangium. In moist conditions, an annulus is curved. When a fern does not have enough water, however, the cells of the annulus begin to dry out. This causes the annulus to pull on the sporangium and the sporangium begins to tear. Once the sporangium is torn completely open, the annulus snaps back to its original curved shape and throws the spores into the air, much like a catapult. Some ferns can toss their spores up to several meters. annulus spore sporangia Answer the following questions on a separate sheet of paper. Structure and Function of Plants 1. Write a caption for each of the illustrations shown above, using what you have learned about how some ferns release their spores. 2. Why is it advantageous to ferns to have their spores carried long distances by wind or water? 3. Some ferns do not throw their spores. Instead, their spores are carried away from their sporangia by the wind. What is one advantage that spore-throwing ferns have over these ferns? 4. What type of weather precedes the release of spores? Explain. Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved. 41