Question

Which of the following is not a characteristic feature of cnidarians? (1)They exhibit tissue level of organisation 2)They may be aquatic or terrestrial (3)They may be sessile or free-swimming (4)They are diploblastic animals

Answer 1

Answer:

All Cnidaria are aquatic, mostly marine, organisms. They all have tentacles with stinging cells called nematocysts that they use to capture food. Cnidarians only have two body layers, the ectoderm and endoderm, separated by a jelly-like layer called the mesoglea. Most Cnidarians have radial symmetry

Answer 2

Answer:

hey mate ur ans.. with explaination

Explanation:

Cnidarians share several basic characteristics. All Cnidaria are aquatic, mostly marine, organisms. They all have tentacles with stinging cells called nematocysts that they use to capture food. Cnidarians only have two body layers, the ectoderm and endoderm, separated by a jelly-like layer called the mesoglea. Most Cnidarians have radial symmetry. Most Cnidarians have complicated reproductive cycles that include an asexual stage and a sexual stage. Some Cnidarians are completely mobile while others are completely sessile, but most have both mobile medusa and sessile polyp stages in their life cycles.

Classes of Cnidarians

The four recognized classes of Cnidaria are: Hydrozoa, Cubozoa, Scyphozoa and Anthozoa. Class Hydrozoa contains tiny predatory animals which live in fresh water (hydras) or marine environments. Most Hydrozoa make calcite shells. Some Hydrozoa live singularly while others live in colonies. Class Scyphozoa contains jellyfish, All Scyphozoa live in the ocean. Scyphozoa have a short polyp phase but live most of their lives in their medusae form. Class Anthozoa includes sea pens, sea anemones and corals. Anthozoa have no medusae stage and all live in marine environments. Many fossil Cnidaria are members of Anthozoa. Class Cubozoa contains box jellyfish, which differ from true jellyfish in that they have a primitive nervous system and eyes. Among the most venomous animals on Earth, box jellyfish stings can be fatal to humans, especially children. While all Cnidarians share many characteristics, each class displays some unique characteristics as well.

Body Symmetry

The majority of Cnidarians share the characteristic of radial symmetry. Radial symmetry means symmetry around a center point such that any line drawn through the center of the organism divides the body into mirror images. A jellyfish, for example, viewed from above has radial symmetry. Many Cnidarians also exhibit a second axis of bilateral symmetry, and some Cnidarians only exhibit bilateral symmetry. Bilateral symmetry means a single plane drawn through the middle of the organism will show mirror images across the plane. More complex, "higher" order organisms all share the characteristic of bilateral symmetry. The class Cnidarian contains members with radial symmetry and members with bilateral symmetry as well as members that exhibit both symmetries. Cnidarians therefore may provide clues and insights into the development of more complex body sturcture

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