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Using your vocabulary words, make notecards/flashcards that you can use outside of class to study.
Work on your Directed Reading in class every chance you get. Remember that I will assist you on the harder questions. This assignment is due the day we take the test on this chapter. Use the information in this assignment as a study guide for your test.
This study guide is to help you study for your test. It should not be the only item you use to study w hen preparing for the test. Remember to complete your Directed Reading for every chapter along with writing your vocabulary words on notecards to help you remember them. And always remember to listen carefully in lecture because all of the information in this study guide will be covered.
Vertebrates and Invertebrates
Scientists make a major distinction between vertebrates, animals with a backbone or a spine, and invertebrates, animals without a backbone. Humans and other mammals are vertebrates, as are fish, amphibians, reptiles, and birds. Vertebratesare included in the phylum Chordata. Although they are themost widely recognized and familiar of all animals, vertebratesmake up only about 3 percent of the more than 1 million speciesof animals. Vertebrates are categorized by bilateral symmetryand cephalization.
About 97 percent of the animal kingdom are invertebrates.Invertebrates include sponges, jellyfish, starfish, worms, mollusks, insects, and crabs. Some species of invertebrates haveradial symmetry, and some bilateral. Some, but not all, speciesare characterized by cephalization.
Sponges
Sponges are so unlike other animals that they are sometimes putin their own subkingdom. Sponges have the simplest body organization of any animal.They have no head, no mouth, and no digestive, circulatory, or nervous system. Early naturalists classified sponges as plants, or as plant-animals, mainly because of their branchlike forms and their inability to move around. Sponges were not classified as animals until the mid-1800s, when scientists first began to closely study sponges and their method of feeding.
Most sponges live in shallow seas, though some have beenfound at depths of 8,500 m (27,800ft.).A few species live infresh water. In size, sponges range from less than 1 cm (0.4 in.)to more than 2 m (6.6ft.).In color, they range from white andgray to brilliant shades of red, yellow, green, purple, and black. Sponges have many shapes—they may look like balls, discs, vases, goblets, branching shrubs, or small trees. The approximately 5,000 species of sponges make up the phylum Porifera (puh RIHF uhr uh). Porifera means "pore bearing." Sponges have been described as looking like sacks full of holes.
Characteristics of Sponges
Once a sponge attaches itself to a rock, shell, or other submerged object, it does not move. Sponges feed by filtering food and nutrients out of the water. The body wall of a sponge consists of two layers of cells, with a jellylike layer between them.The outer layer is called the ectoderm, and the inner layer theendoderm. The body wall surrounds a cavity through which water flows. Water is drawn in through the incurrent pores in the ectoderm and leaves through a larger opening called the osculum(AHS kyuh luhm). The water carries food and dissolved oxygen. Cells that digest the food, called collar cells or choanocytes (koh AN uh syts), are located in the endoderm. Each collar cell has a flagellum.
The movement of the flagella sets up a current of water through filaments that make up the collar of the cells. The filaments catch and remove bacteria, unicellular algae, and other microorganisms from the water. This food is drawn into the collar cells and digested. Amoeba-like cells called amoebocytes (uh MEE buh syts) in the jellylikelayer carry the nutrients to the other body cells and take awaywaste matter.
Without some kind of skeletal structure, sponges would collapse under their own weight. The composition of their skeletalstructure is the basis of classification of sponges. Some spongeshave skeletons made of spicules (SPIHK yoolz), tough interlocking spikes of either calcium or silicon. Other sponges haveskeletons made of a flexible protein called spongin. Bath sponges, for example, have skeletons composed of spongin,which makes them firm but soft. Some sponge skeletons are amixture of both spicules and spongin.
Sponges may grow individually or in colonies. Somecolonies are so dense that it is difficult to distinguish one sponge from its neighbor.
Sponges have a remarkable ability to regenerate—that is,to grow new parts to replace those that are lost. A sponge notonly can regenerate parts of its body, but can also regenerate the entire body from fragments.A sponge can also reform if ithas been separated into single cells by being pushed through afine silk cloth. The cells will move around, form clumps, andthen larger groups. Within a few days the group of cells willreform into several new sponges. If sponges of two differentspecies are pushed through a screen and mixed together, thefragments will regroup into sponges of the original two species.
Reproduction of Sponges
Sponges reproduce both sexually and asexually. Most speciesare hermaphrodites (huhr maf run dyts)—that is, an individualsponge can produce both eggs and sperm, though at differenttimes. Sperm cells produced by one sponge are carried to another sponge by water currents. Once inside the sponge, spermcells are captured by carrier cells, which are modified collarcells. The carrier cells take the sperm to the egg. The fertilizedegg develops into a larva(lahr vuh), an immature form.Sponge larvae have flagella and swim about. They soon attachthemselves to objects in the water and develop into adult sponges.
Fragmentation is a common method of asexual reproductionamong sponges. Even a small branch that breaks off from the parent sponge can develop into a full-grown animal. Spongesalso reproduce asexually by producing gemmules(jehm yoolz)—special food-filled balls of amoebocytes surrounded by protective coats. Generally only freshwater sponges produce gemmules. The gemmules can survive harsh conditions, such asextreme cold or periods of dry weather. When conditions arefavorable for growth, sponge cells emerge through an openingin the gemmules and grow into new sponges.
Coelenterates
Coelenterates(sih LEHN tuh rayts) are animals with saclike bodies and long, flexible appendages called tentacles. Most coelenterates live in sea water. One group, the hydras, lives in freshwater. The 9,000 species of coelenterates also include jellyfish,sea anemones, and corals. Although corals are one of the simpler forms of animal life, they have had profound effects on thegeography of continents and islands. Millions of tiny coralskeletons massed together over centuries have formed entireislands and offshore reefs. These islands and reefs are found primarily in the South Pacific Ocean, in the Caribbean Sea, andalong the Florida coast.
Characteristics of Coelenterates
Coelenterates get their name from their coelenteron, or "hollowgut." The coelenteron is a digestive cavity with only one opening. Coelenterates also have special stinging cells calledcnidocytes(nyduh syts). For this reason, they are also knownas cnidarians(nydairee uhnz).
Coelenterates generally exhibit radial symmetry. Theyhave two body plans: vase-shaped and bell-shaped.Hydras andsome other coelenterates develop only a vase-shaped body,called a polyp. Jellyfish and some other coelenterates go through a polyp stage but spend most of their lives as a bell-shaped medusa (muh doo suh).
Coelenterates live singly or in colonies. Individual animalswithin a coelenterate colony may have specialized functions.The Portuguese man-of-war is an example of a colonial coelenterate. Some of the individual animals specialize in reproduction or feeding, others in gathering food.
The bodies of both polyps and medusae consist of two layers of cells, the endoderm and the ectoderm, separated by ajellylike substance called mesoglea (mehz uh glee uh). Themesoglea of a polyp is thin. In a medusa, however, the mesoglea often makes up the major part of the body substance.
The tentacles of most coelenterates circle the mouth of theanimal, and the cnidocytes are in the tentacles. Inside eachcnidocyte is a sac containing a coiled stinger, called a nematocyst(neh MAT uh sihst). When discharged, the stinger can paralyze or lasso small prey. New cnidocytes replace those whosenematocysts have been discharged. The tentacles draw thefood up to the mouth. Enzymes inside the digestive cavity break down the food, and the food particles are absorbed by thecells that line the cavity. Undigested waste products are expelledthrough the animal's mouth. Individual cells carry out respiration directly, taking in oxygen from the surrounding water bydiffusion.
Hydras
Hydras and related animals make up the class Hydrozoa (hydruh zoh uh). Hydras are the most extensively studied coelenterates, but they are not typical of hydrozoans in some ways.For example, hydras have only the polyp form, while most hydrozoans go through a medusa stage as well.
Hydras are only about 1 cm (0.4 in.) long. Most hydras areorange, brown, white, or gray in color, but some are green dueto algae that grow in the cells of their endoderm. Hydras live infreshwater streams and ponds. They attach themselves to leavesand other debris in the water by means of a flattened adhesivebase called the basal disc. Hydras move by floating, gliding, orsomersaulting.
Although primitive animals, hydras show a great degree ofspecialization in their nematocysts. Four distinct types havebeen identified. One type of nematocyst anchors the tentacleswhen the animal moves, and another repels animals other thanprey. A third holds the prey by winding around the animal,while a fourth nematocyst stings the prey, paralyzing it.
Like other coelenterates, hydras have no brain or centralnervous system.Anetwork of nerves, the nerve net, permitssome coordination of responses and some simple movements.Hydras also have sensory cells that respond to chemical andmechanical stimuli. The animals have little control in their responses to stimuli. If touched with a probe on one part of the body, for example, the whole body will contract.
When a hydra catches a shrimp or a water flea in its tentacles, a feeding response begins. The tentacles move the preytowards the mouth, the mouth opens in response to a chemicalgiven off by the prey, and the prey is pushed in whole. Enzymesare released that digest the food, and the undigested remains areexpelled through the mouth.
Hydras reproduce asexually by forming small buds on theoutside of their bodies. These buds grow, and within two orthree days they fall off and begin life as independent animals. Hydras also reproduce sexually, usually in autumn. When thewater temperature drops, individual hydras begin to develop either egg-producing ovaries or sperm-producing testes. Thesperm swims to the egg, which remains attached to the body ofthe hydra. After fertilization has occurred, the egg begins todivide and falls off the adult female. The young hydra emergesin the spring.
Hydras live individually and independently. Most otherhydrozoans, however, live in colonies. Most hydrozoans alsohave both polyp and medusa forms at different times in their lifecycle. Certain species, for example, spend most of their lives as colonial polyps. A single polyp multiplies by budding, forminga colony. Within the colony, the polyps become specialized.Some are feeding polyps, and some are reproductive polyps.Tiny medusae bud off the reproductive polyps. These medusae produce eggs or sperm. Thus, colonial polyps exhibit a divisionof function between feeding and reproductive forms. Other colonial coelenterates also show specialization of individuals.
Jellyfish
From a distance, jellyfish resemble inflated plastic bags. Observed more closely, jellyfish can be seen swimming by rhythmically contracting and relaxing their "bells." Jellyfish belongto the class Scyphozoa (sy fuh zoh uh), which means "cupanimals." The tentacles of jellyfish with their stingers may reach up to 70 m (230 ft.) in length. Their central discs may range from 4 cm (1.5 in.) to a meter (3.3 ft.) in diameter, though one observer has recorded a central disc3.6m(12ft.)indiameter.
In the life cycle of a jellyfish, the medusa reproduces sexually, and the polyp reproduces asexually.The male medusa releases sperm cells through its mouth, and the female releaseseggs. The eggs lodge in pockets on the tentacles of the femaleand are fertilized. The eggs grow and develop into small, free-swimming larvae.
The larvae swim away and attach themselves to the seafloor. There they develop into a polyp stage that resembles thehydra. The jellyfish polyp grows and eventually produces buds. This development is the asexual phase of its reproductive cycle.The buds grow and eventually begin to form medusae, which, as they build up, resemble a stack of plates. These medusae bud offone by one and begin the cycle again. The polyp may repeat the process the following year.
Sea Anemones and Corals
The sea anemones (uh nehm uh neez) and corals belong to theclass Anthozoa (an thuh ZOH uh). Anthozoa means "flower animals." These coelenterates are often beautifully colored andhave varied forms.
Sea anemones are marine polyps that inhabit coastal areas. A sea anemone has a basal disc like that of the hydra, by whichthe anemone attaches itself to rocks or other objects. Sea anemones are solitary. They feed on fish and crabs that swim withinreach of their tentacles. Sea anemones digest their food in much the same way as hydras do.
Corals resemble sea anemones but have skeletons and livein colonies. Soft coral species have flexible skeletons. The stonycoral has an external skeleton that is almost pure limestone. Theskeletons of some corals are used to make jewelry. The skeletons of dead corals accumulate and form the reefs often seenrising above the surface of tropical waters.
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