Marine Chapter 7 Worksheet

Generally describe the Class Polychaeta, including the general body plan of its members, and name at least one representative type of polychaete.

Almost all marine annelids are in the Class Polychaeta. Each segment of a polychaete has a pair of flattened extensions, called parapodia, which contain stiff and sometime sharp bristles or setae. Polychaete worms are typically 2 to 4 inches long. They have a variety of life styles and habitats. Some crawl on the bottom, others burrow into the sediment, while others live in tubes that they construct. Some are even planktonic. Many crawling polychaetes are carnivores. Tube-dwelling polychaetes are usually passive suspension feeders. Burrowing polychaetes often are deposit feeders—they ingest soft sediment, extract the organic matter in it, and then expel the indigestible part.

Briefly describe the diversity of types of sponges in the ocean. Include encrusting sponges, glass sponges, boring sponges, and coralline sponges.

Almost all of the 9,000 species of sponges are marine. They can be found in shallow and deep water, tropical and polar water, and everything in between. Sponges may be branching, tubular, round, volcano‐like, and any other shape. Encrusting sponges form thin, sometimes brightly colored growths on rocks or other hard surfaces. Glass sponges live in deep water and have a lace‐like skeleton of fused siliceous spicules (they are very pretty). Boring sponges create thin channels through calcium carbonate, such as oyster shells and corals, in which they live. Coralline sponges have a calcium carbonate skeleton beneath the body of the sponge and may also have siliceous spicules and spongin.

Describe the structural support of sponges.

As sponges get larger, they need structural support (or they'd just be mush). Most sponges have spicules, which are supporting structures of different shapes and sizes that are embedded in a gelatinous layer between the outer and inner layers of cells in the sponge. Spicules may be siliceous or calcareous. Many sponges also have tough, elastic fibers made up of the protein spongin for support.

Compare the abundance of invertebrate vs. vertebrate animal species.

At least 97% of all species of animals are invertebrates. All major groups of invertebrates have marine representatives, and many are exclusively marine.

Describe the economic significance of sponges.

Bath sponges are of limited commercial importance—they are the spongin fibers remaining after cells and debris are washed away. Some sponges produce chemicals that are potentially of medicinal importance.

What is bilateral symmetry? What are its advantages and disadvantages compared to radial symmetry?

Bilateral symmetry is the arrangement of body parts in such a way that there is only one way to cut the body and get two identical halves. Bilaterally symmetrical animals, including you, have a front or anterior end and a rear or posterior end. At the anterior end is a head with a brain (or at least a collection of nerve cells). Bilaterally symmetrical organisms also have dorsal or back surface that is different front the front or ventral surface. Radial symmetry works well for organisms that drift in currents or are attached to surfaces. Animals that are more active and crawl or swim in one direction tend to be bilaterally symmetrical (although this is not always true!). Bilaterally symmetrical animals tend to have more sophisticated behaviors than those of radially symmetrical animal (because they have more highly developed nervous systems].

Describe the cnidarian body plan.

Both polyp and medusa forms of cnidarians have a similar body plan. There is a centrally located mouth that is surrounded by tentacles, which are used to capture and handle food. The mouth opens into a blind gut where digestion occurs. The blind gut has only one opening—the mouth—and wastes are spit out from the mouth. Cnidarian tentacles are armed with nematocysts, which are stinging structures used to capture small prey. Cnidarian are carnivores, which are heterotrophs that feed on other heterotrophs. Cnidarians have two layers of cells—an inner gastrodermis that lines the gut and an outer epidermis. The mesoglea is the layer between these two cell layers; in the jellies it is expanded and gelatinous.

Generally describe cnidarians, including their level of organization, body shapes and symmetry, and life styles.

Cnidarians include sea anemones, jellies, and corals. They have a tissue level of organization and are radially symmetrical. Cnidarians have two basic forms: polyp and medusa. A polyp is a sac‐like attached stage, and a medusa is a bell‐like, upside down polyp adapted for swimming. Cnidarians may spend part of their life history as a medusa and part as a polyp; some cnidarians are only one or the other for their entire lives.

Briefly describe the tissues of cnidarians.

Cnidarians lack organ systems, so they don't have a true nervous system with a brain or nerves. However, they do have specialized nerve cells that connect together to form a nerve net. This relatively simple nerve net can distinguish between prey and other cnidarians. Some medusae have primitive eyes, and they also have statocysts—small calcareous "stones" in fluid-filled chambers surrounded by sensitive hairs. These allow medusae to distinguish "up" from "down."

Generally describe comb jellies, including their level of organization, body plan and symmetry, and life styles.

Comb jellies are all in the Phylum Ctenophora and are exclusively marine. Ctenophores have a tissue level of organization. They are radially symmetrical and have gelatinous bodies that resemble medusae. Eight rows of ciliary combs, long cilia fused at the base like combs, beat in waves and are used in swimming. Comb jellies species vary in size from a few millimeters to several feet in length. Comb jellies are common carnivores of plankton in surface waters of the ocean. They often occur in swarms. They capture their prey using two long tentacles armed with sticky cells named colloblasts. Comb jellies lack nematocysts.

Generally describe flatworms, including their level of organization, body shape and symmetry, and life styles.

Flatworms are in the Phylum Platyhelminthes, are bilaterally symmetrical, and are noted for their dorsoventrally flattened shapes. Flatworms are the simplest animals in which tissues are organized in to organs and organ systems.

Briefly describe the organ systems of flatworms.

Flatworms have a central nervous system in which information is stored and processed. In flatworms it typically consists of a simple brain, which is an aggregation of nerve cells in the head. There are also nerve cords that run the length of the body. The nervous system coordinates the muscular system and, therefore, motion. The flatworms have a blind gut, similar to cnidarians and ctenophores. They also have a middle tissue layer called the mesoderm, which gives rise to the muscles, reproductive system, and other organs.

Generally describe the Class Hydrozoa, including the general body plan of its members.

Hydrozoans have a wide range of forms and life histories. Many are feathery or bushy colonies of tiny polyps. They typically produce planktonic gametes and larvae. The larvae settle on the bottom to produce a new colony of hydrozoans.

Briefly describe the organ systems of ribbon worms.

In addition to a central nervous system, ribbon worms have a complete digestive tract, with a gut that includes a mouth and an anus. They also have a circulatory system that transports blood with nutrients and oxygen to the tissues. Ribbons worms have a very distinctive proboscis, which is a long, fleshy tube used to entangle prey. It superficially resembles a tongue, but a tongue that may be several feet longer than the body!

Describe the Kingdom Animalia.

Members of the Kingdom Animalia are multicellular and cannot manufacture their own food—They are heterotrophs. The need to obtain food (energy) from others has resulted in a diverse array of feeding styles in animals (carnivores, herbivores, scavengers, omnivores, etc.)

What is metamorphosis?

Metamorphosis refers to the dramatic change in body style and/or life style from the larval to adult stages of a marine organism. For example, larval sponges are microscopic and planktonic; adult sponges are sessile and macroscopic.

Generally describe nematodes, including their level of organization, body shape and symmetry, and life styles.

Nematodes are in the Phylum Nematoda. They are bilaterally symmetrical and have an organ system level of organization. Some nematodes are known as roundworms, because they are small, slender, and cylindrical in shape. Nematodes are rarely seen but they are very, very common in sediments, where they feed on bacteria and organic matter. Many other nematodes are parasites—some of which can be passed on to humans when they are consumed along with their host fish.

Briefly describe the organ systems and bodies of nematode worms.

Nematodes pretty much have the full complement of organ systems: central nervous system, muscular system, digestive system, etc. They have a hydrostatic skeleton, which is a system that uses water pressure against the body wall to maintain body shape and to aid in locomotion.

Describe radial symmetry.

Organisms with radial symmetry have similar parts of the body arranged and repeated around a central axis (sort of like slices of pizza or spokes on a bicycle wheel). Animals with radial symmetry look the same from all sides and have no head, front, or back. They do have an oral surface, where the mouth is, and an aboral surface on the opposite side.

Name the 9 phyla of invertebrates about which you are responsible for learning in this unit. List at least one representative type of organism from each phylum.

Phylum Porifera: the sponges Phylum Cnidaria: the sea anemones, jellies, corals, and their relatives Phylum Ctenophora: the comb jellies Phylum Rotifera: rotifers Phylum Sipuncula: Peanut worms Phylum Platyhelminthes: the flatworms Phylum Nemertea: the ribbon worms Phylum Nematoda: the roundworms Phylum Annelida: the segmented worms (earthworms)

Briefly describe the organ systems and bodies of polychaete worms.

Polychaete worms have a closed circulatory system with the circulating blood in distinct blood vessels. To bring enough oxygen into the body, polychaete worms cannot rely on simple diffusion across their surface. Instead they have gills on the parapodia that have many small blood vessels, called capillaries, which allow for the easy absorption of oxygen and release of carbon dioxide.

Briefly describe feeding and digestion in cnidarians.

Pretty much all cnidarians are carnivores and use their nematocysts to capture prey. Nematocysts are a fluid-filled capsule that contains a thread that can be quickly ejected. The thread may be sticky or armed with spines. Some nematocysts contain toxins (which is why they "sting"). Nematocysts work like little harpoons—when the nematocysts are touched (by prey or by an unsuspecting swimmer), they shoot out the thread, which sticks to the prey. They then "reel" the prey into the tentacles and then the mouth. Food passes into the gut where it is digested.

Generally describe ribbon worms, including their level of organization, body shape and symmetry, and life styles.

Ribbon worms are in the Phylum Nemertea and are more complex in their organization than the flatworms. They are long, thin worms that are carnivores and eat worms and crustaceans. They have bilateral symmetry and an organ system level of organization. Almost all of the 900 species of ribbon worms are marine. They are found in all oceans and are more common in shallow water than in deep water. They range from several inches to many feet in length. Some are very brightly colored.

Generally describe the Class Scyphozoa, including the general body plan of its members, and name at least one representative type of scyphozoan.

Scyphozoans include the common larger jellies in the ocean. (NOTE: biologists are trying to avoid calling them jellyfish because they aren't fish at all! So, jellies is now the preferred term.) The medusa is the dominant stage of scyphozoans. The rounded body or bell of jellies is contracted rhythmically to aid jellies in swimming. However, their swimming abilities are weak, and currents easily move them. As a result they are considered to be part of the zooplankton—the heterotrophic plankton. The nematocysts of scyphozoans can give extremely painful and sometimes fatal stings.

Generally describe segmented worms, including their level of organization, body shape and symmetry, and life styles

Segmented worms are in the Phylum Annelida, which includes earthworms as well as many marine worms. They are bilaterally symmetrical and have an organ system level of organization. Their body consists of a series of similar compartments or segments, a condition known as segmentation. [Each ring of an earthworm is a segment.] The gut goes through all of the segments and lies in a cavity that is lined with tissue from the mesoderm and which is filled with fluid. This cavity, called the coelom, allows the segments to act as a hydrostatic skeleton. Segmented worms are very flexible because of their segments and are efficient crawlers and burrowers.

Define the terms sessile and mobile.

Sessile refers to organisms that live attached to the bottom or a surface. Generally, these organisms are not mobile (they can't move)

What is siliceous? What is calcareous?

Siliceous is an adjective that refers to things made up of silica (SiO2). Calcareous is an adjective that refers to things made up of calcium carbonate (CaCO3).

Name and describe at least one representative type of hydrozoan.

Siphonophores are drifting colonies of hydrozoan polyps. Often, some of the polyps are specialized as gas-filled floats that buoy the entire colony. Other polyps are specialized tentacles for capturing food. The Portuguese man-of-war is a siphonophore that is famous for its painful stinging tentacles

Generally describe sponges, including their level of organization, body plan and symmetry, and life styles.

Sponges are members of the Phylum Porifera, which means "pore bearers." They are among the structurally simplest of the invertebrates and are complex aggregations of specialized cells. They have a cellular level of organization. They do not have tissues, organs, or organ systems. Sponges have a relatively simple body plan and no symmetry. Water enters the sponge through numerous tiny pores or ostia and circulates through a series of canals where plankton and organic particles are filtered out and eaten. The network of canals and relatively flexible skeletal framework give sponges their characteristic "spongy" texture. Nearly all sponges are sessile and live attached to the bottom (or any surface).

Describe reproduction in sponges.

Sponges reproduce both sexually and asexually. Asexual reproduction occurs when branches or buds break off of the parent sponge and grow into separate sponges that are identical to the parent. Sexual reproduction occurs when special collar cells in a sponge develop into male (sperm) and female (egg) gametes. The male gametes are typically released in to the water—this is called spawning. The sperm are drawn into the sponge, which is where fertilization takes place and the early stages of development take place. Eventually a planktonic larva is released by the sponge and drifts in the water until it settles on the bottom and grows into a new sponge.

What is suspension feeding? What is filter feeding? What is passive suspension feeding?

Suspension feeding is a feeding style in which animals eat food particles suspended in the water. Organisms that actively filter food particles from the water by pumping water through their bodies or using filtering structures to sweep up food particles are known as filter feeders. Passive suspension feeding occurs when water is not actively pumped (but passively flows by the animal) and the animal uses cilia and mucus to move food particles to the mouth.

Generally describe the Class Anthozoa, including the general body plan of its members, and name and describe at least one representative type of anthozoan.

The anthozoans are solitary or colonial polyps that lack a medusa stage and have more complex polyps than do the hydrozoans or scyphozoans. Most cnidarians are anthozoans. Anthozoans occur in a variety of sizes, shapes, and types. Some anthozoans are fleshy and do not have a hard skeleton: Sea anemones are common and colorful "fleshy" anthozoans that may be solitary or colonial. Soft corals, sea pens, and sea pansies are colonial "fleshy" anthozoans. Several types of anthozoans secrete hard skeletons: Colonial stony corals secrete calcium carbonate skeletons that may form coral reefs in tropical waters. Gorgonians, such as sea fans (Fig. 7.11), are colonial anthozoans that secrete a protein, branching skeleton.

Name at least one representative type of polychaete.

The fireworm is a carnivorous polychaete worm that is well known for the causing irritation to human skin when it is touched (its setae break off and embed themselves in our skin).

Briefly describe how sponges feed, using collar cells and oscula.

The outer surface of a sponge is covered with pores, through which water is pumped into feeding chambers that are lined with special feeding cells called Choanocytes (collar cells). Choanocytes have flagella that create currents and a thin collar that traps food particles, which are then ingested. Water leaves the sponge though a large openings called oscula (singular = osculum).

Name and describe at least one representative type of scyphozoans.

The sea nettle is an example of a scyphozoan jelly

What are the four classes in the Phylum Cnidaria about which you are responsible for learning?

The three classes in the Phylum Cnidaria are Class Hydrozoa, Class Cubazoa, Class Scyphozoa, and Class Anthozoa.

What are the two major types of animals?

The two major types of animals are the vertebrates and the invertebrates. Vertebrates are animals that possess a backbone (a row of bones called vertebrae), and invertebrates are animals without backbones

Name the most commonly seen type of marine flatworms.

There are approximately 20,000 species of flatworms, and the most commonly seen marine flatworms are the turbellarians. Turbellarians are free-living carnivores that often have striking color patterns (Fig. 7.14). Other types of flatworms include the parasitic flukes or trematodes and the parasitic tapeworms or cestodes.

What are tissues? What are organs? What are organ systems?

Tissues are specialized, coordinated groups of cells in an organism. Organs are structures consisting of several types of tissues, grouped together to carry out particular functions. Organ systems are groups of organs that work together to perform a particular function in an organism.