Marine Bio: Unit 1B Test

acoelomates

Triploblastic animals, such as flatworms, do not have an open space between the gut and the outer body wall.

class Scyphozoa (Cnidaria)

True jellyfish, with approximately 200 described species. Medusa

Cnidaria: sessile polyp

Typical sea anemone and coral, are cylindrical in form and most are sessile.

asymmetry

when there isn't any type of symmetry, and the organism cannot be "split" into equal parts. Only sponges display asymmetry, and are not able to be divided into equal sections.

cnidocytes

which are specialized cells that serve to catch prey and defend the animal from predation. Each cnidocyt contains a stinging capsule called a nematocyst, which contains an inverted harpoon on a thread.

coelomates

Animals with a true coelom, a cavity between the gut and outer body wall that is lined on all sides by tissue from the mesoderm are called.

Hydrozoans (Cnidaria)

There are over 3,000 hydrozoans, most of which are marine. Hydra, one of the few members found in fresh water, only exist as a colonial polyp. Most of the members of Hydrozoa are colonial, relying on multiple members, or zooids, of the colony to work together. One example is the Portuguese man o' war.

coelom

main body cavity to hold and protect any major organs.

Cnidaria: floating medusa

Jellyfish is a familiar example of the medusa body form, which is a flattened, mouth-down version of the polyp. The medusa body plan is capable of moving through the water via weak contractions of the bell-shaped body. Some cnidarians only exist in the polyp or medusa form, while others display both throughout their life cycle, something that is unique to this phylum.

mesoderm

Middle cell layer. forms the muscles and blood vessels and many of the other organs.

Sessile

Sponges are filter feeders. They cannot move to find food, so they generate a current that brings water inward through incurrent pores and outward through the excurrent opening called the osculum. This flow of water is generated by collar cells, flagellated choanocytes that line the inside of the body. The current is maintained through coordinated beating of the flagella.

phylum Porifera

Sponges. 10,000 species, only 100 are found in freshwater.

pseudocoelomate

When an animal has a gut that is separated from the body wall by a fluid filled cavity, but the cavity is not lined on all sides by the mesoderm.

radial symmetry

meaning the organism can be "cut" in half anywhere along a central axis, like slicing a pizza into several equal parts. Jellyfish, sea stars and sea anemones display radial symmetry. Radial animals have a top and bottom or an oral and an aboral side, but no front and back and no left and right.

ectoderm

outermost layer of the gastrula. develops into the outer covering of the animal and, in some phyla, the nervous system.

Mollusca to Echinodermata, and including Chordata, the vertebrates.

are all coelomates

bilateral symmetry

having two equal halves, the organism can be "sliced" down a central line into two equal parts. Bristle worms, lobster, clams, whales, sea otters and sea urchins display bilateral symmetry. Bilateral animals have a top, or dorsal side, and a bottom, or ventral side, as well as a head, or anterior end, and a tail, or posterior end, and a left and a right side.

phylum Cnidaria

include 10,000 species of radially symmetric animals such as jellyfish, coral, and sea anemones. The basic body plan of the cnidarians is a sac, called the gastrovascular cavity, with a single opening that functions as both mouth and anus. Cnidarians only have two tissue layers, an inner gastrodermis responsible for digestion and reproduction and an outer layer, the epidermis, responsible for capturing prey and defense. The two layers are held together by the mesoglea, which can vary in thickness from class to class, giving members of this phylum their distinguished jelly-filled look.

Class Anthozoa (Cnidaria)

includes the corals and sea anemones. These animals display only the polyp body form throughout their life cycle. There are more than 6,000 species of anthozoans, and all are marine. Sea anemones burrow into or attach to the substrate with a sticky basal disc. Some species are able to slowly slide along the floor, like a snail, on their basal disc, while others are able to detach it and tumble away in the water. Corals, on the other hand, are completely sessile due to the secretion of an external skeleton of hard calcium carbonate or softer protein-based secretions.

endoderm

innermost layer. becomes the lining of the digestive tract and respiratory system (if present)