Question

Porifera and Cnidaria

1. What level of organization do sponges have?                      _____________________
2. What is the function of spicules?                                         _____________________
3. What level of organization do cnidarians have?       
4. What kind of symmetry do cnidarians have?                       
5. Which body type dominates the hydrozoan life cycle?                
6. Which body type dominates the hydrozoan life cycle?                
7. What are the examples of hydrozoans?
8. Which class does jellyfish belong?                                        
9. Which body type dominates the jellyfish life cycle?             
10. Which class is the largest of cnidarians?
11. What are the examples of this largest class of cnidarians?
12. Observe the preserved specimens of corals.   What chemical compound composes the remains of corals?

Answer 1

Ans 1) Sponges have cellular level of organisation.
There body is composed of cells, it does not have any specialised structures which can be described as organs.

Ans 2) Spicules are specialised structures which are mainly found in sponges. They functions in providing the structural support to sponges. There are two types of spicules . Larger spicules which can be seen through a naked eye is megascleres
Smaller spicules which can be seen under the microscope are microscleres.

Ans 3) Cnidarians have tissue level of organisation.
In this, various cells are grouped together to form tissues but they lack true organs.

Ans 4) Cindarians which are mostly called as coelentrates, includes jelly fish, Hydra and sea anemone are radially symmetrical.

Ans 5) Hydrozoans life cycle have two stages: asexual Polyp stage and other is free swimming, sexual medusae stage. Medusae is the dominant stage of life cycle.

Ans 6) Hydrozoans are mostly found in saltwater. It includes predator, small animals. They can be found in colony or are solo that is solitary.
Example of Hydrozoans are : 1. Hydra- found in freshwater and have radial symmetry.
2. Obelia : they live in freshwater and marinewater. It has both medusae and polyp stage in their life cycle.

Ans 7) Jellyfish belongs to class scyphozoa
These are planktonic
Found in marine water

Ans 8) Jellyfish life cycle is dominated by Medusa stage and the other stage which is polyp has reduced time and size.

Ans 9 ) Anthozoa is the largest class of cnidarians. It have species more than 6000. Presence of septa, will increase surface area for absorption and digestion.

Ans 10)Examples of Anthozoa are sea pens, anemones and True corals.

Ans 11) Corals are made of calcium carbonate compound.