THE RADIATE ANIMALS PHYLUM CNIDARIA PHYLUM CTENOPHORA

PHYLUM CNIDARIA Over 10,000 species of Cnidarians All are aquatic; almost all are marine Do have nerves and muscles Single opening for mouth/anus, with tentacles around the mouth Mainly carnivorous Two body types: polyp and medusa

All cnidarians have radial symmetry All are diploblastic. They possess an epidermis and a gastrodermis, separated by a nonliving mesoglea Cnidocytes with nematocysts are a unique characteristic of the phylum

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TWO BODY FORMS Cnidarians show dimorphism (two body forms); the polyp and the medusa Polyp: sessile, tubular body with a mouth at one end surrounded by tentacles Medusa: the jellyfish-form. The medusa form is adapted for a floating or free- swimming lifestyle

Examples of Cnidarians jellyfish

Sea anemones

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Distinguish between the 2 body plans Handout: Label the 2 body forms label and define the following: –Mouth –Tentacle –Gastrovascular cavity –Nematocyst –cnidocytes

Stings from jellyfish

REPRODUCTION Most Cnidarians are dioecious, with external fertilization The embryo will develop into a free- swimming planula larva Most Cnidarians also reproduce asexually by budding (polyp form only)

THE RADIATE ANIMALS12 Obelia

Describe digestion in Cnidarians Nemataocysts sting prey. Prey is taken in for digestion. 1. Internal extracelluar digestion. Digestion takes place within a gut cavity, rather than within individual cells 2. Digestive enzymes are released from cells lining the walls of the cavity and partiallbreakdown food.

1.The digestion is not completely extracelluar 2.Food is fragmented extracellulary into small bits that are engulfed by the cells lining the gut (phagocytosis) 3.Digestion is completed. 4.Any food particles that cannot be digested are released out eh same opening through which they were pulled into the animal originally.

What is the advantage of extracellular fragmentation

Describe the nerve net

Name and give examples of the classes of cnidarians

Class Hydrozoa: Most are marine and are colonial with a medusa (sexual reproduction) and a polyp (asexual reproduction) form. Examples: Obelia (colonial), Hydra (polyp form only; not colonial; freshwater), and Physalia (Portuguese-man-of-war, a colonial hydrozoan)

THE RADIATE ANIMALS19 Hydra, with bud

THE RADIATE ANIMALS20 Portuguese Man-of-War

Class Scyphozoa the true jellyfish, which have a thick mesoglea. Polyp stage reduced or absent. Solitary (not colonial), dioecious animals that are active swimmers. Example: Aurelia

THE RADIATE ANIMALS22 Aurelia

THE RADIATE ANIMALS23 Aurelia

Class Cubozoa the box jellyfishes. Solitary, marine animals with a reduced polyp stage. Strong swimmers and excellent predators. Contains the sea wasps, which have a toxin potentially fatal even to humans

THE RADIATE ANIMALS25 SEA WASP

Class Anthozoa: No medusa stage. Larger, heavier polyps than the hydrozoans. Can be solitary or colonial. Examples: the sea anemones (Metridium), stony and soft corals, sea fans, sea pens, and sea pansies

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CORALS Many corals secrete an exoskeleton of calcium carbonate to form a cup that the animal resides in. These are called stony corals Other corals have an endoskeleton. This group includes the soft corals as well as some that are very tough

THE RADIATE ANIMALS30 A CUP CORAL

THE RADIATE ANIMALS31 POLYPS WITHDRAWN POLYPS EXTENDED

THE RADIATE ANIMALS32 CORALS

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THE RADIATE ANIMALS34 SEA FAN

THE RADIATE ANIMALS35 SEA FAN

PHYLUM CTENOPHORA (THE COMB JELLIES OR SEA WALNUTS The only other phylum showing primary radial symmetry. All marine, found free-swimming in warm waters. No nematocysts. Less than 100 species. Have eight rows of comb-like plates that contain cilia for locomotion. Each individual has both an ovary and a testis, so they are monoecious (hermaphroditic). Example: Pleurobrachia

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THE RADIATE ANIMALS38 Comb Jelly

Phylum Platyhelminthes: Flatworms

Give the general characteristics of Platyhelminthes Marine flatworm

Describe digestion in flatworms

Describe excretion in flatworms

Describe circulation in flatworms

Describe nervous control in flatworms Compare their nervous system with that of the cnidarians.

Describe reproduction in flatworms

Define regeneration

What is the important evolutionary trend exhibited by flatworms

List the classes of flatworms and examples

tapeworms Parasitic Can grow up to 10 meters or larger Body made up of head and repeating sections called proglottids Head is knob shaped and called a scolex Each proglottid may contain up to eggs and may have 2000 prglottids Handout

Tapeworm scolex

Life cycle of liver fluke

Roundworm Both free living and parasitic Unlike the other worms, they have 2 openings to the gut (mouth and anus)

Types of parasitic roundworms Ascaris – infects children who swallow eggs when they put soiled hands into their mouths or vegetables that have not been washed.

Hookworms Commonly infect humans in warm climates where people walk on contaminated soil in bare feet. Feel weak and tired due to blood loss.

Pinworms Most common parasite in children Enter intestinal tract when children eat something that has come in contact with contaminated soil Pinworms lay eggs near the anus and reinfection is common because the worms cause itching.

Prevention Good personal hygiene such as washing hands, clothing, and bedding

Trichinella Worms enter the body in undercooked pork Controlled by cooking pork long enough to kill any worms that my be present Not as common in US as it once was due to stricter meat inspections standards. It embeds within muscle tissue of host