HSEB zoology notes | General characteristics of mollusa

1. Habitat : Mollusca are widely distributed all over the world. They are mostly freshwater or marine and few are terrestial found in damp places.

2. Body form : They are triploblastic animals. They have organ system of body organization. Their body is soft, unsegmented without appendeges and body divided into head, mantle, foot and vesciral mass.

3. Coelom : They are haemocoelomate animals. Their true coelom is reduced.

4.Symmetry : They are billaterally symmetrical but except gastropods which are asymmetrical due to coiling or torion during growth.

5. Respiration in mollusca take place with the help of feathers like fins or ctenidia in aquatic form and lungs or pulmunary sac in terrestrial form.

6. Excretion takes place with the help of paired metanephridia or kidney.

7. Sensory organs are eyes , tentacles, osphradium , statocysts.

HSEB notes | Classification and character of phyllum platyhelminthes

The general character of platyhelminthis are as follows :

1. Habit and habitat : They are moatly parasitic which live in the blood, intestine and liver of human. Some like planaria are freeliving found in freshwater, pond seawater and damp places on land. Parasitic form have suckers or hooks or  other connective device for the attachment on the host.

2. Level of organization : Tapeworms are the first metozoan group having developed body organs.

3. Symmetry : They are radiaaly symmetrical and triploblastic animals.

4. Coelom : They are acoelomate animals. The space betwwen the body wall and internal organ are filled with parenchyma.

5. Respiratory organs are absent in them and they perform aerobic type of respiration. Their exretory organ is called flame cell or protonephridia.

6. Reproduction : They reproduce sexally but some of the freshwater turbellarians reproduce asexually by regeneration and fission.

The classification of phyllum platyhelminthes are as follows :

1. Turbellarian

Planaria

a. They are in free-living aquatic form found in fresh water stream, pond, seawater and moist places.

b. They have unsegmeted body.

c. Sucker and hooks are absent in them.

d. Their lifecycle is simple and regeneration is common in them.

eg : bipalium, planaria etc

2. Trematoda

Liver-fluke

a. The are exclusively parasite (ecto or endo)

b. They have usually elongated and unsegmented body.

c. Sucker are present in them but hooks and spines are absent in them.

d. Their life cycle is complex. They require one or more host to complete their lifecycle.

eg :  Fasciola hepatica (liver fluke) , Schistosome (blood fluke) etc

3. Cestoda

a. They are exlusively endoparasite living in the small intestine of vertebrate animals.

b. They have segmented body like tape.

c. Sucker and hooks are present in them for the attacment in the host.

d. Their life cycle is also complex. They also require one or more host.

eg : Taenia solenia (tapeworm) etc

HSEB notes | Classification and character of phyllum Coelenterata

The general characteristic of Coelenterata are as follows :

1. Habitat : They are aquatic, most of them are marine and some are fresh-water. They are mostly sessile and some are free living. Few are active swimming or free floating like Aurelia.
2. Body organization : They are multicellular organism with tissue grade of organizarion.
3. Symmetry : They are bilaterally or radially symmetrical with central gastovascular cavity.
4. Locomotion : Their locomotion is bought about by smmoth muscle fibre. Some like corals and metridium remain fixed on substratum.
5. Excrerition and repiration takes place through general body surface.
6. Reproduction : They reproduce asexually by budding, fission, and fragmentation.
7. They exhibit polymorphism :
polyp     : asexuall form
medusa : sexuall form
Sexuall form is monoecious and dioecious.
The classification of phyllum Coelenterata is given below :


1. Hydrozoa

Hyrda

a. They are mostly marine , few are freshwater form.
b. Both poly and medusa form is present in them.
c. Mesogloea is simple and non-cellular.
eg : hydra, obelia , physalia etc.

2. Scyphozoa

Aurelia

a. They are exclusively marine.
b. Medusa form is dominant and polyp form is either reduced or absent.
c. Mesogloea is cellular.
eg : aurelia (jelly fish) , rhizostome

3. Anthozoa

Corals

a. They are also exclusively marine.
b. Only polyp form is present and mwdusa form is absent in them.
c. Mesogloea has fibrous connective and amoeboid cells.
eg : metridium (sea-anemone) , corals etc