The name “Protozoa” was coined by Goldfuss (1817). The branch of their study is called Protozoology.
⚫ Salient Features
- Protozoans are the simple and primitive organisms
- free living or parasitic
- All the free living forms are aquatic
- Asymmetrical or radially symmetrical or bilaterally symmetrical
- They are unicellular (acellular)
- They have protoplasmic grade of organization.
- Locomotion is affected by flagella, cilia or pseudopodia.
- Nutrition is holophytic, holozoic, saprozoic or parasitic.
- Digestion is intracellular
- Excretion & Respiration occurs by diffusion
- In fresh water protozoans osmoregulation is carried out by the contractile vacuoles.
- Encystment is a common phenomenon
- Reproduction occurs by asexual and sexual methods.
⚫ Classification of Protozoa
Class 1. Flagellata or Mastigophora
- The body is covered by a thin pellicle or cuticle.
- The locomotory organs are flagella.
- The contractile vacuoles are present in fresh water forms with accessory vacuoles.
- Chloroplast is found in some forms.
- They may be free-living or parasitic.
- The class flagellata has been divided into eight orders.
- Examples: Chrysamoeba, Cryptomonas, Euglena, Volvox, etc.
- Euglena is a connecting link between Animal & Plant.
- Trychonymph (symbiotic) live in alimentary canal of termite that is digest to cellulose.
Class 2. Rhizopoda
- There is no definite cell wall or pellicle
- There is no definite shape
- The locomotory organs are pseudopodia
- There is no permanent mouth or anus.
- The contractile vacuoles are present in the fresh water forms.
Class 3. Ciliophora
- The body is covered by thin pellicle
- They have a fixed permanent shape
- The locomotory organs are cilia
- Tentacles are present
- The class ciliophora is divided into two sub-classes, namely Ciliata and Suctoria.
■ Sub-class 1 – Ciliata
- Cilia are present throughout life.
- Tentacles are absent
- Mouth and cytopharynx are usually present.
- Contractile vacuoles are present.
- Trichocysts, organs of offense and defense are present in certain forms.
- Examples: Paramecium, Stylonchia Vorticella, etc., Paramecium is filter feeder
- In a paramecium two contractile vacuoles are present. Posterior contractile vacuole is highly active.
■ Sub-class 2 – Suctoria
- Cilia are present only in the young conditions and adults are devoid of them.
- Tentacles are present in the adult
- One to many contractile vacuoles are present
- Examples: Acineta, Dendrocometes, Dendrosoma, etc.
Class 4 – Sporozoa
- They are exclusively endoparasitic
- The body is covered by pellicle.
- Reproduction takes place by spore formation
- The class is divided into two sub-classes, namely, Telosporidia and Neosporidia
■ Sub-class 1 – Telosporidia
- The spores do not contain polar capsules or filaments
- The life history ends with the formation of spores.
- The spore cases are simple and contain many spores
- Examples: Monocystis, Gregarina, Isopora, Eimeria, Plasmodium, Babesia, etc.
■ Sub class 2 – Neosporidia
- The trophozoite is amoeboid multinucleated
- Spore cases are complex usually having a single germ
- Examples: Nosema, Myxidium, Globidium, etc.
⚫ The word “Porifera” means pore bearers (Gr., porus = pore; ferre = to bear); their body wall has numerous minute pores, called ostia, through which a continuous current of outside water is drawn into the body.
⚫ Phylum porifera has the following salient features:
- All the sponges are Aquatic, Sedentary, Asymmetrical or Radially,
- They are diploblastic.
- The body is perforated by numerous minute pores called ostia.
- The ostia open into a large cavity called spongocoel.
- The spongocoel opens to the outside by a large opening called osculum.
- The sponges possess an endoskeleton in the form of calcareous spicules.
- Excretion and respiration occur by diffusion.
- They have greater power of regeneration.
- Reproduction takes place by asexual or sexual methods.
- Development is indirect or direct. The common larval are parenchymula, amphiblastula, etc.
Class 1. Calcarea
- Skeleton is formed of Calcareous spicules.
- Radially symmetrical.
- Choanocyte cells are large and conspicuous. Examples: Clathrina, Leucosolenia, Sycon, etc.
- Euplectela is the sponge which is given as a Gift in Japan.
- Leucosolenia is a smallest sponge.
- Ectorderm is formed by pinachocyte and endoderm is formed by choanocyte.
Class 2. Hexactinellida
- Skeleton is formed of six rayed triaxon, silicious spicules.
- Canal system is branched or unbranched.
- Radially symmetrical.
- These are also known as glass sponges.
- Examples: Pheronema, Hyalonema, etc.,
- Hylonema is a Glass rope sponge.
Class 3. Demospongia
- Skeleton either absent or present.
- The silicious spicules when present are never six rayed
- The canal system is complicated Rhagon type
- These sponges are of great economic importance
- Examples: Cliona, Spongilla, Chalina, Euspongia, Hippospongia, Oscarella, etc.
- Spongilla is a fresh water sponge.