Answers
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.
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