Question

1. Address the following questions for the Cnidaria. Your answer for parts a-g combined must not be fewer than 150 words. (35 points)
   1. Describe the basic body plan of a cnidarian. Include any distinctive features. The better answers will not fail to mention basic body forms (polyp & medusa), cell layers, mesoglea, tentacles, mouth/anus, gastrovascular cavity. 5 pts

2. Do the Cnidaria have tissues? If so, what kind of tissues do they have? 5pts

3. How is an organ defined? Do the Cnidaria have organs ? If so, what organs ? 5pts

4. About how many species of Cnidaria are recognized? Sources may differ a bit so use a reasonable source and cite it. 5 pts

5. In what kind of habitat are they found? ? (g., Saltwater? Freshwater? Terrestrial ? Etc.). Are they equally common in all habitats where they are found? Where they do occur, are cnidarians free-swimming, attached to a substrate, crawling over a surface, burrowing, etc. ? 5 pts

6. Do cnidarians occur everywhere in the world that their habitat is found? Do any cnidaria occur here in Ohio? 5 pts

7. Dr. Rauschert talked about energy flow in ecosystems and trophic levels. Where do the Cnidaria fit it here? Describe the basic ecology of a cnidarian. How does the anatomy of a cnidarian reflect its basic ecology? Dr. Rauschert also talked about symbioses. Do any Cnidaria have interesting symbioses? (HINT: the answer here is “yes”, and it affects the answer about the trophic level of some cnidarians). 5 pts

8. According to the phylogenic tree (Fig. 1) below…3 bonus pts
   1. Is Chordata (represented by the mouse on the tree) more closely related to Porifera or to Cnidaria. Justify your answer.
   2. What feature(s) separates Porifera and Cnidaria from all other ‘higher’ groups?

You must write your answer in your own words. To do otherwise is plagiarism, which is one form of academic misconduct. You may not “cut & paste” any part of your answer. You may not “cut & paste” any material and then modify that material; to do so still is plagiarism. Write your answer in your own words.

Your answer to questions 1 & 2 each must be at least 150 words (for a total of at least 300 words for the entire report), and must be submitted as a single Word document through Turnitin.

Be certain that you fully acknowledge all of the sources of information that you use to answer these questions.

Answer 1

a. Cnidarians have two distinct body plans, the medusa and the polyp. All cnidarians have two membrane layers, with a jelly-like mesoglea between them. Polyp forms are sessile as adults, with a single opening to the digestive system (the mouth) facing up with tentacles surrounding it. The body wall of a cnidarian consists of three layers, an outer layer known as the epidermis, a middle layer called the mesoglea, and an inner layer referred to as the gastrodermis. The epidermis contains a collection of different types of cells.

b. Although they have specialized cells for particular functions, they lack true tissues in which specialized cells are organized into functional groups. All cnidarians have two tissue layers. The outer layer is called the epidermis, whereas the inner layer is called the gastrodermis and lines the digestive cavity.

c. Group of similar tissues that have a similar origin and perform a similar function is called organ. Cnidarians do not have true organs.

d. The phylum Cnidaria contains about 10,000 described species divided into four classes: Anthozoa, Scyphozoa, Cubozoa, and Hydrozoa.

e. Cnidarians live in aquatic environments and inhabit all depths, from the sandy substrate up to the surface. They can be found from the Great Barrier Reef rising off the coast of northeastern Australia to the continental shelves of bone-chilling arctic oceans, and just about every saltwater marine habitat in between.

f. With thousands of species, cnidarians are diverse in their habitat and are distributed in all the world's oceans, in polar, temperate, and tropical waters. Ohio is decidedly short on cnidarians.

g.  it is cnidarians, in particular corals, that are the builders of some of the richest and most complex ecosystems on the planet, coral reefs. Other cnidarians are important as predators in the open ocean.

The relationship between cnidarians and dinoflagellate algae is termed as "symbiotic" because both the animal host and the algae are benefiting from the association. It is a mutualistic interaction. They are primary consumers.