Phylum Aschelminths, general character of Phylum Aschelminths, function, example, Objective question of Aschelminths,

 Phylum Aschelminths

There are several groups of animals in which the space inside the body is a pseudocoel. It is not a true coelom because it is not lined with mesodermal epithelium and represents a persistent embryonic blastocoel. These groups of animals are known as pseudocoelomates (presence of a cavity, the pseudocoel, between the gut and body wall), and they are often placed within a single super phylum aschelminths. Gegenbaur (1859) created a group nemathelminth to place some pseudocoelomates animal. The name aschelminths was proposed by grobben (1910), in place of the older name 

nemathelminths. It has been derived from two Greek words: askes - cavity + helmins – worm.

GENERAL CHARACTERS: -

• Mostly aquatic, free living or parasitic.
• Usually small, even microscopic. Some reach a meter or more in length.
• Body slender, vermiform, unsegmented, flatter cylindrical, bilaterally symmetrical and triploblastic.
• Organ system grade of body organization.
• Head not distinctly formed with well-defined sense organs.
• Body wall with a syncytial or cellular epidermis externally covered with thick cuticle of scleroprotein. 
• Cilia absent except anterior cilia of rotifers.
• Musculature includes mostly longitudinal fibers.
• Body cavity pseudocoel not lined by mesoderm.
• Digestive canals complete with mouth, specialized pharynx, straight non-muscular intestine and posterior or anus.
• No circulatory and respiratory systems.
• Excretory system is of protonephridia and canals. 
• Cloaca is present in some species.
• Nervous system of cerebral ganglia, or of circumenteric nerve ring with anterior and posterior nerves.
• Mostly dioecious. Male usually smaller than female.
• Gonads and ducts single or double. 
• Eggs with chitinous shell. Cleavage is determinate and spiral.
• Development usually direct with no larval stages, or indirect with a complicated life history.

Important notes: -

The name aschelminths was proposed by grobben (1910), in place of the older name nemathelminths. It has been derived from two Greek words: askes - cavity + helmins – worm. Mostly aquatic, free living or parasitic. Usually small, even microscopic. Some reach a meter or more in length. Body slender, vermiform, unsegmented, flat or cylindrical, bilaterally symmetrical and triploblastic. Body cavity pseudocoel not lined by mesoderm. Digestive canals complete with mouth, specialized pharynx, straight non-muscular intestine and posterior anus. No circulatory and respiratory systems. Excretory system of protonephridia and canals. Nervous system of cerebral ganglia, or of circumenteric nerve ring with anterior and posterior nerves. Mostly dioecious. Male usually smaller than female. Gonads and ducts single or double. Eggs with chitinous shell. Cleavage determines and spiral. Development usually direct with no larval stages, or indirect with a complicated life history

Aschelminths includes one very large group (nematode) and four smaller groups (rotifer, gastrotricha, kinorhyncha and nematomorpha). According to some zoologists such as Hyman (1951), aschelminths is regarded as a distinct phylum, and the various groups included in it as classes. However, others treat different groups as separate phyla and the name of aschelminths as a superphylum or without any taxonomic rank. Modified classification was proposed by storer and Usinger (1971).

Ascaris lumbricoides, commonly known as round worm. It is largest nematode parasite in the human intestine. It is found more commonly in children than in adults. It is a large size nematode showing sexual dimorphism. The female length measures 20-40 cm in length and 6-8 mm to width. Fresh specimens are pale pink or flesh colored body. The body wall is formed of following three layers: a). Cuticle b). Epidermis c). Muscle layer. There are no respiratory organs in Ascaris. The parasites carry on anaerobic respiration as the oxygen content in the intestine of host is very poor. The excretory system is in the shape of H. Ascaris excretes more urea when water is scarce. A female Ascaris is recorded to lay as many as 27,000,000 eggs. Eggs of Ascaris are about 40-75 (microns) in size and elongated elliptical or oval in form. The eggs become stained yellowish or brown in the intestine. No secondary host in the life history of Ascaris. The Ascaris larvae inside the lungs cause inflammation and produce severe and fatal pneumonia. Sometimes their presence causes fever, anaemia, leukocytosis and eosinophiles. Piperazine salt is the ideal drug administered for Ascaris.

👉Objective question of Platyhelminthes: -

1)Pseudocoelom is present in: -

(a)Aschelminths (b) Platyhelminthes (c)Coelenterates (d) Annelida 

2)Organ system of body organization presents in: -

(a) Porifera (b) Platyhelminthes (c)Aschelminths (d) Coelenterate 

3)In Rotifer the sense organs are: -

(a) eye spot (b) antennae (c) statocyst and eye spot (d) eye spot and antennae 

4)Development of Gastrotricha  is: -

(a) Direct (b) indirect (c) parthenogenetic (d) regenerative 

5)One of these known as hair worms: -

(a) Rotifer (b) Kinorhyncha (c) Nematomorpha (d) Nematoda

6)Juvenile parasite in grasshopper and other insects: -

(a) Rotifera (b) Kinorhyncha (c) Nematomorpha (d) Nematoda

7)Digestive system present complete with muscular pharynx and glands: -

(a)Nematoda (b) Nematomorpha (c) kinorhyncha (d) Gastrotricha 

8)digestive system with a grinding mastax in animal of phylum: -

(a) Rotifers (b) Gastrotricha (c)Kinorhyncha (d) Nematomorpha 

9) Which type of body is found in Ascaris?

(a) Gastrovascular (b) Pseudocoelom (c) Coelom (d) none of these

10)In life cycle of Ascaris, the juvenile hatches out of egg in: -

(a) Lung (b) Liver (c) Intestine (d) None of these

11)The mouth of Ascaris lumbricoides is bound by three lips of which: -

(a)One is median and two are lateral (b) One is dorsal and two are ventral (c) Two are dorsal and one is ventral (d) One is median and dorsal and two are ventrolateral. 

12)Normal life span of Ascaris is: -

(a) 9-12 weeks (b) 9-12 months (c)9-12 years (d) 3-4 months 

13)Ascaris has well developed: -

(a) Nervous system (b) Reproductive system (c)Receptors (d) Digestive system 

14)Ascaris is not: -

(a)Endoparasite (b)Monogenetic (c) free living (d) Dioecious 

15)Respiration in Ascaris is: -

(a)Aerobic Reproduction (b) Anaerobic Reproduction (c)Both (d)none of these 

16)Ascaris, being a parasite possesses reduced sense organs called: -

(a)Amphids (b) Penial setae (c) Penial papillae (d)post-anal papillae 

17)Infection of Ascaris usually occurs by: -

(a)Contaminated water and vegetable (b)Tse-Tse fly (c)Both (d)none of these

18) The space between alimentary canal and body wall in Ascaris is: -

(a) Parasole (b) haemocoel (c) Pseudocoel (d)Gastrocoel 

19)Special feature of sperms of Ascaris is: -

(a)With tail (b) more than one tail (c) Without tail (d) Largest 

20)In Ascaris, how many juveniles are formed from fertilized egg up to adult: -

(a)1 (b)2 (c)3 (d) 4

21)Female Ascaris can be differentiated from male Ascaris by: -

(a)Straight posterior end (b) Curved posterior end (c)Smaller size (d)Genital papillae. 

22)During development, Ascaris needs: -

(a)One intermediate host (b) Two definite hosts (c) No intermediate host (d) No definite host 

23)From the egg of Ascaris, first larva hatches in 

(a) Uterus of female Ascaris (b) outside the body of host (c) Stomach of Host (d)Intestine of host 

24)The first juvenile larva of Ascaris is known as: -

(a)Miracidium larva (b) Microfilariae (c) rhabditiform larva (d) filiform larva 

25)Which type of excretory canal system is present in Ascaris: -

(a) C-shaped (b)J- shaped (c) H-shaped (d) W-shaped 

26)In Ascaris, the reserve food is stored as glycogen and fats in: -

(a) Intestine (b) muscles (c)Hypodermis or epidermis (d) all of these 

27)In which of the animals, the syncytial epidermis follows the cuticle?

(a)Fasciola (b) Ascaris (c)taenia (d) Earthworm 

28)Excretory organ in Ascaris is: -

(a)nephridia (b)Kidneys (c) Flame cells (d) None of these   

29)Two sexes of Ascaris can be identified as: -

(a)Posterior end of female is straight (b)Anal papillae are found in male (c)female has vulva (d) all of these. 

30)Penial setae arise from; - 

(a) Cloaca of male (b) Anus of female (c)Vulva of female (d) none of these

31)In Ascaris, egg is fertilized in: -

(a)Oviduct (b)Uterus (c) Vagina (d) Outside human body 

32) Egg of Ascaris passed out of host's body are: -

(a)Unfertilized (b) fertilized (c) Fertilized and shelled (d) With a larva. 

Answer Key: -

(1) a (2) c (3) d (4) a (5) c (6) d (7) a (8) a (9) b (10) c (11) d (12) b (13) b (14) c (15) b (16)a (17) a (18) c (19) c (20) d (21) a (22) c (23) d (24) c (25) c (26) c (27) b (28) d (29) d (30) c (31) c (32) d

Phylum Platyhelminthes |general characters of Platyhelminthes| classification| Objective question of Platyhelminthes|

 Phylum Platyhelminthes

The phylum Platyhelminthes was coined by Gegenbaur in 1859. It includes the simplest animals that are bilaterally symmetrical and triploblastic (composed of three fundamentals 

cell layers). These are also known as the flatworms. Flatworms have no body cavity other than the gut and lack an anus; the same pharyngeal opening both takes in food and expels 

waste. Because of the lack of any other body cavity, in larger flatworms the gut is often very highly branched in order to transport food to all parts of the body. The lack of a cavity also constrains flatworms to be flat; they must respire by diffusion, and no cell can be too far from the outside, making a flattened shape necessary.

Flatworms are once divided into three groups. The free-living Turbellaria include the 

planarian dugesia, shown above; these are found in the oceans, in fresh water, and in moist terrestrial habitats, and a few are parasitic. The Trematoda, or flukes, are all parasitic, and have complex life cycles specialized for parasitism in animal tissues. Members of one major taxon of flukes, the Digenea -- which includes the human lung fluke which pass through a number of juvenile stages that are parasitic in one, two, or more intermediate hosts before reaching adulthood, at which time they parasitize a definitive host. The Cestoda, or tapeworms, are intestinal parasites in vertebrates, and they also show anatomical and life history modifications for parasitism. Platyhelminths have practically no fossil record. A few trace fossils have been reported (Alessandrello et al., 1988), and fossil trematode eggs have been found in Egyptian mummies and in the dried dung of Pleistocene ground sloth.

General Characters of Platyhelminthes 

• Bilaterally symmetrical with definite polarity of anterior (head) and posterior (tail) ends
• Triploblastic, i.e., body derived from three embryonic germ layers: ectoderm, mesoderm and endoderm.
• Dorso – ventrally flattened. 
• Usually with a well- defined ventral surface bearing mouth and gonophores. 
• Free- living commensal or parasitic forms. 
• Tissue- organ grade of organization, i.e., body cells aggregate into definite tissues and tissues make up organs. 
• Body unsegmented (except in class Cestoda). 
• Acoelomate, i.e., without any body cavity or true coelom. 
• Spaces between various organs filled with special mesodermal tissue, the mesenchyme or parenchyma. 

• Adhesive structures like hooks, spines and suckers, and adhesive secretions common in parasitic forms. 
• Epidermis cellular or syncytial, frequently ciliated. Absent in some. 
• Muscular system of mesodermal origin. 
• Longitudinal, circular and oblique muscle layers beneath epidermis. 
• Digestive system branched and incomplete without anus. Altogether absent in Acoela and Cestoda.
• Skeletal, respiratory and circulatory system are wanting. 
• Excretory system includes lateral canals and proto-nephridial (flame cells). Absent in some primitive form. 
• Nervous system primitive, ladder- like. Comprises a pair of anterior ganglia with longitudinal nerve cords connected by transverse nerves. 
• Sense organs simple. Eye- spots or photo receptors in free living forms. 
• Mostly monoecious (hermaphrodite) with complex reproductive system. 
• Well- developed gonads, gonoducts and accessory organs. 
• Eggs mostly devoid of yolk. 
• Yolk produced separately in yolk or vitelline glands. 
• Fertilization internal may be cross or self. 
• Development direct or indirect. 
• Usually indirect in endoparasites with a complicated life cycle involving many larvae and hosts.

Cercaria larva: - 

A fully formed cercaria larva possesses a flattened heart-shaped body with a long contractile tail. Its body surface covered with thin cuticle with backwardly directed spines. The anterior end bears mouth, muscular pharynx, esophagus and bifid intestine. The mouth is surrounded by oral sucker. A ventral sucker or acetabulum is also present between the two limbs of the intestine. There are numerous flame cells. A small excretory duct arises from the bladder and opens to the exterior by excretory pore situated at the base of the tail. A number of unicellular cystogenous glands are situated below the large body wall.

Their secretion forms the cyst around the larva when it is converted into metacercaria. Groups of germ cells are also present. When mature the cercaria leaves the Redia through birth pore it also wriggles out of the snail body. It swims in water for some time and finally settles down on the blade of some aquatic weed. It sheds off the tail and a cyst are formed by the secretion of cystogenous gland. Thus, a metacercaria is formed. 

Metacercaria: -

The metacercaria is somewhat rounded with thick outer covering of cuticle in the form of 

cyst. The Cystogrenous cells of the cercaria disappear and the flame cells increase in number.

Important point: -

• The phylum name was coined by Gegenbaur in 1859. The simplest animals that are bilaterally symmetrical and triploblastic (composed of three fundamental cell layers) are the Platyhelminthes, the flatworms. Flatworms were once divided into three groups. 
• A. Class - Turbellaria B. Class- Trematoda C. Class- Cestoda.The class -Turbellaria includes all free-living members of the phylum, as well as a few parasites. It includes many marine forms, whose beautiful colors serve as a warning of their toxicity to would be predators, as well as the more drab freshwater planarians. 
• The class-Trematoda, commonly called flukes, are unsegmented parasitic flatworms that usually parasitize a snail as an intermediate host (in which they reproduce asexually) and a human or other vertebrate as a definitive host (in which the worm's mate and lay eggs).
• The class-Cestoda, commonly called tapeworms, are segmented, ribbon like parasites usually found as adults in the small intestines of vertebrate animals. 
• Platyhelminths have practically no fossil record. A few trace fossils have been reported that were probably made by platyhelminths (Alessandrello et al., 1988), and fossiltrematode eggs have been found in Egyptian mummies and in the dried dung of Pleistocene ground sloth. 
• Fasciola hepatica is a common liver fluke. 
• Main species of Fasciola like Fasciola hepatica (Liver fluke- Sheep) and Fasciola gigantica (Liver fluke – Cattal). 

• Fasciola hepatica is a digenetic trematode.
• It is endo-parasite in the bill passage and liver of sheep and cattle and completes part of its life cycle in snail. 
• Its primary host is sheep and secondary host is freshwater snail.
• Shape: - Body is soft and fleshly. It is Dor-ventrally flattened and leaf like, somewhat oval in appearance. 
• Size: - It is about 18-30mm long and 4-15mm broad. 
• Colour: - The colour is slightly pinkish and the margins appear to be brownish or blackish. Internal organs are roughly visible because of transparent body wall.
• The eggs are fertilized in the uterus or in ootype. Fasciola is a hermaphrodite animal, but cross fertilization occurs. 
• The fully formed fertilized capsulated eggs are inside the uterus. The first cleavage is complete but unequal and produced: -
• (i) a small granular propagatory cell and 
• (ii) a large somatic or ectoderm of larva. Segmentation and cleavage start even when the eggs are inside the uterus.
• The first cleavage is complete but unequal and produces: - (i) a small granular propagatory cell and (ii) a large somatic or ecto-dermal cell. Repeated division of the somatic cell further from ectoderm of larva.

Larval stage of Fasciola hepatica: - 

Miracidium larva: - 

• It is the first larval stage in the life cycle of Fasciola hepatica. 
• It swims actively in water in search of secondary host, the snail of genus, Limnaea. 
• Miracidium larva does not feed. It swims actively in search of its secondary host. 
• In case it fails to reach the host, it dies within 24 hours. 

Sporocyst larva: - 

• Miracidium lose its apical gland, penetrated gland, brain, eyespot and change into a sac-like sporocyst larva. 
• It looks like an elongated sac about 0.7mm long. 

Redia larva: -

• It is an elongated and cylindrical sac. 
• It comes out by the rapture of sporocyst. 

Cercaria larva: - 

• A fully formed cercaria larva possesses a flattened heart-shaped body with a long contractile tail. 
• Its body surface covered with thin cuticle with backwardly directed spines. 
• The anterior end bears mouth, muscular pharynx, esophagus and bifid intestine. 
• The mouth is surrounded by oral sucker. 

Metacercaria: - 

• The metacercaria is somewhat rounded with thick outer covering of cuticle in the from of cyst. 
• The Cystogrenous cells of the cercaria disappear and the flame cells increase in number.

Infection to the final host: - 

• The metacercaria enters the final host, the sheep, when it grazes on the aquatic weeds and reaches the intestine. 

Infection: - 

• The vertebrate host (sheep, goat, etc.) gets the infection by grazing on grass, leaves and other vegetation to which metacercaria cysts are attached. 
• The invertebrate host (snail) acquires infection when a miracidium, at random, established contact with a suitable part of its body. 

Pathogenesis or Symptoms: - 

• Infection of invertebrate host (snail) result in a partial or complete destruction of the affected site, which is preferably the digestive gland (liver) or gonad. 
• In case of heavy infection, snail considerably increases in size. 
• Significant economic important is the effect of F. hepatica on its vertebrate, host whose bile ducts as well as liver may be damaged. 

Treatment: - 

 Anti-Helminthes drugs such as hexachloroethane, carbon tetrachloride, filcin, emetine hydrochloride, phenothiazine and tetrachloroethane are being employed or treating case of liver-rot. 

Prophylaxis or Prevention: - 

• Killing heavily infected sheep. 
• Destroying eggs and manure of infected sheep. 
• Feeding infected sheep with salt and little dry food. 
• Killing or checking snail population. 

Parasitic Adaptation of Fasciola: -

1. Liver fluke has undergone great modification, morphologically as well as physiologically, to suit its existence as an end parasite in the bile ducts of sheep. 
2. Locomotory organs are absent as not required by adult. However, free swimming larvae, such as miracidium have cilia and cercaria has a locomotory tail. 
3. Adult lacks circulatory, respiratory and sensory organs as they are not needed. 
4. Nervous system is poorly developed for the same reason. However, free swimming miracidia has sensory eye sport.
5. Reproductive system is highly developed. 
6. Number of eggs produced is enormous (about 200,000 eggs per fluke).
7. Hermaphroditism ensures self-fertilization even in the absence of another for copulation. It is necessary of the species. 

Objective question of Platyhelminthes: -

1) Liver flukes belong to class: -

(a)Cestoda (b) Nematoda (c) Trematoda (d) Turbellaria 

2) Fasciola hepatica is found in: -

(a)Intestine of sheep (b) Stomach of Sheep (c) Liver of sheep (d) None of them 

3)Fasciola hepatica is: - 

(a)Free living (b) Ectoparasite (c) Endoparasite (d) Ecto and Endoparasite 

4) Which of the following infects the snail in life cycle of Fasciola?

(a)Cercaria (b) Miracidium (c)Redia (d) Metacercaria 

5) Which of the following stage in the life cycle of Fasciola is infective stage for sheep?

 (a)Cercaria (b) Miracidium (c)Redia (d) Metacercaria 

6) The intermediate host in the case of liver fluke of is: -

(a) Snail (b) Man (c)Pig (d) fly 

7) The correct sequence of various larva in liver fluke is: -

(a)Miradium ,sporocyst, redia ,cercaria, metacercaria 

(b)Miracidium, sporocyst, cercaria, metacercaria, redia

(c)Cercaria, sporocyst, redia, metacercaria, miracidium 

(d)Sporocyst ,redia , metacercaria, miracidium 

8)Larva of Fasciola hepatica that bores into snail is: -

(a)Cercaria (b) Hexacanth (c) miracidium (d) Redia 

9)The aperture presents at posterior end of Fasciola hepatica: -

(a) Anus (b) Excretory pore (c)Genital aperture (d) Cloacal aperture 

10)Laurer's canal is present is: -

(a)Fasciola (b) Taenia (c) Ascaris (d) Cockroach 

11)During its life cycle, Fasciola hepatica infects its intermediate host and primary host at the following larval stages respectively: -

(a)Redia and miracidium 

(b) Metacercaria and cercaria 

(c)Cercaria and redia 

(d) Miracidium and metacercaria 

12)In Fasciola, miracidium develops into the next stage inside: -

(a)Bulinus (b) Limnaea truncatula (c)Pila globosa (d) Planorobis

13) Planorbis and Limnaea are the intermediate of Fasciola?

(a)Faciola (b) Schistosoma (c) Trichinella (d) Echinococcus 

14)Which of the infective stage to the primary host of Fasciola?

(a)Miracidium (b) Sporocyst (c) Metacercaria (d)Cercaria 

15)Whichof the following larval stage of Fasciola does not produce several larva?

(a)Sporocyst (b) Secondary redial (c) Primary Redial (d)Cercaria

16)Which layer of Dugesia contains rhabditids?

(a) Epidermis (b) Circular muscle (c)Parenchyma (d)Cuticle

17) Fasciola hepatica (b) Taenia solium (c) Ascaris lumbricoides (d)Planaria 

18) In Fasciola, the region where the shell gland opens into is the: -

(a)Oviduct (b) Ovovitelline duct (c) Uterus (d) Oocyte 

19) Fasciola hepatica is a parasite that lives in the: -

(a)Intestine of sheep (b) Liver of sheep (c)Spleen of sheep (d)Pancreas of sheep

20)In Fasciola ,the germ cells of redia gives rise to: -

(a)Daughter Cercaria (b) Daughter Sporocyst  (c) Daughter Redia (d)Daughter Metacercaria  

21) Liver fluke is not affected by enzymes of host because of: -

(a)Cuticle (b) Suckers (c) Sporocyst (d) Cysticercus 

22)The stage of life history the liver fluke when it infects the primary host is: -

(a)Redia (b)Cercaria (c) Sporocyst (d) Cysticercus 

23)Which stage of Liver fluke infects the intermediate host?

(a)Redia (b)Cercaria (c) Sporocyst (d) Cysticercus

24)Primary host of Fasciola is: -

(a)Man (b) Pig (c) Sheep (d) Dog 

25)For Attachment, fasciola has: -

(a)Four suckers and hook (b) Two suckers (c) Two suckers and hooks (d) Hooks only 

26)Correct sequence of larval stages during development of fasciola is: -

(a)Miracidium, Redia, Sporocyst, and Metacercaria 

(b)cercaria, Miracidium, Sporocyst and Metacercaria 

(c)Miracidium, Sporocyst, Redia, Cercaria and Metacercaria 

(d)Miracidium, Sporocyst, Redia, Cercaria and Metacercaria 

27)In Fasciola, germ ball of Redia give rise to: -

(a)Daughter sporocyst (b) Daughter Cercaria (c) Daughter Redia (d) Metacercaria 

28)Which is the first stage of larva of Fasciola?

(a)Miracidium (b) Sporocyst (c)Redia (d)Cercaria 

29)Fasciola has: -

(a)Salivary gland (b)Pharyngeal gland (c) Gastric Gland (d) Intestinal gland 

30)The cause of 'liver rot ' in sheep: -

(a) Dugesia (b) Fasciola (c) Taenia (d) Schistosoma 

👉 Answer Key: - 

1.(c)2.(c)3.(c)4.(b)5.(d)6.(a)7.(a)8.(c)9.(b)10.(a)11.(d)12.(b)13.(a)14.(d)15.(d)16.(a)17.(a)18.(b)19.(b)20.(c)21.(a)22.(b)23.(b)24.(b)25.(b)26.(c)27.(c)28.(a)29.(b)30.(b)

👇Terminal Question 👇

1.Give an account of the life cycle of Fasciola hepatica.

2.What are adaptations? Explain with reference to the structure of Fasciola hepatica.

3.Where is Fasciola hepatica occurrence? Give an account of its structure.

4.Describe reproduction organ of Fasciola hepatica? (Only Diagram).

5.Describe the various larval form of Fasciola hepatica.

6.What is the infective stage of Fasciola hepatica for sheep?

7.Which organism is the secondary host of Fasciola?

8.What is miracidium?

9.To which larva does miracidium larva give rise to? 

10.What are flame cells?

11.Where can you located flame cells?

Phylum Coelenterate, general characteristic of coelenterate, Function of coelenterate, Objective question of Coelenterate, Terminal question of Coelenterate,

 Phylum Coelenterates 

Phylum Cnidaria (formally known as coelenterate) includes about 9000 species. Some are found in fresh water, but the greater numbers are marines. Coelenterates (Gr. koilos- hollow + enteron- gut) are the simplest of eumetazoans. This interesting group of animals takes its name from the large cavity in the body that serves as the intestine. They include the hydra, jellyfish, sea anemones and corals. 

General Characters: -

✔Coelenterate are metazoan or multicellular animals with tissue grade of organization. 

✔2Body radial or bi-radially symmetrical with oral-aboral axis. 

✔3They are diploblastic animals. 

✔Coelenterate animals are represented by two morphologically different types of individuals, polyps and medusa. 

✔Polyps are sessile (attached to the substratum) with a tubular body (e.g., Hydra). Whereas medusas are free-swimming with an umbrella or bell-shaped body, e.g., Aurelia, Metridium. 

✔They are all aquatic, mostly marine and some freshwater (e.g., Hydra). 

✔They may exhibit solitary or colonial habitat. 

✔One of the most characteristic structures of all coelenterates is the stinging cells, called nematocysts. 

✔Nematocysts serve for adhesion, food capture and offence and defence. 

✔They have a single gastro-vascular cavity, into which mouth opens. 

✔Short and slender tentacles encircle the mouth in one or more whorls. 

✔Coelenterate animals are usually carnivorous. 

✔The coelom, excretory, circulatory and respiratory organs are absent

✔ Anus is absent. 

✔ Locomotion is brought about by smooth muscle fiber.

✔Nervous system consists of one or more networks or nerve cells and neurites located in the ectoderm and endoderm. 

✔Sense organs are ocelli and statocysts. 

✔Skeleton either calcareous or horny and external or internal but absent in few. 

✔Reproduction is both asexual and sexual methods. 

✔Asexual reproduction occurs by budding and sexual reproduction by the formation of gametes. 

✔The Planula larva present in the life history of Coelenterata. 

✔The life history exhibits the phenomena of alternation of generations or metagenesis in which the asexual polypoid, sessile generation alternates with sexual medusoid, free-swimming generation.

Alternation of Generation: - 

Life history of Aurelia exhibits the phenomenon of “alternation of generation” since the sexual medusoid form always alternates with the asexual polypoid from. The fee-swimming adults Aurelia (medusoid form) represents sexual generation and reproduces by the formation of gametes. The fertilized ovum develops into a fixed polypoid scyphi stoma through a free-swimming planula larva. The polypoid scyphi stoma represents asexual generation and reproduces asexual by budding.

A brief account of coral and coral reefs and their importance: - 

Corals: - 

Meaning of coral: - 

Coral animals or corals are marine, mostly colonial, polypoid coelenterates, looking like miniature sea anemones and living in a secreted skeleton of their own. Their calcareous or horny skeleton is also commonly known as coral. Some corals grow into massive, solid structures; others form large, branched colonies. Most of the corals belong to the class Anthozoa and the few to class Hydrozoa of phylum coelenterate. 

Structure of coral polyp 

1.  Soft structure A typical coral polyp from a colony is a small organism about 10 mm long and 1 to 3 mm in diameter. A basal disc is absent because the basal region of polyp is surrounded by a calcareous exoskeleton. Oral disc bears numerous tentacles, in several rows around an elongated, oval or circular mouth. Pharynx or stomodaeum is short and without siphonoglyphs. Mesenteries are restricted to the upper part of coelenteron and mesenterial filaments contain only one glandular lobe bearing nematocysts. Body wall is without cinclids and nematocyst bearing structures (acontia). Muscles are poorly developed while little is known about nervous system. Living polyps are found only on surface layers of coral masses. They feed at night both by raptorial and suspension feeding. When not feeding, they withdraw into cup-like cavities of skeleton.
2. Structure of coral skeleton: - Skeleton of solitary coral is known as corallite. It is a calcareous exoskeleton secreted by epidermis. In a colonial coral, corallites of individual polyps fuse together to form a skeletal mass, called Corallium. Each corallite is like a stony cup with a basal part or basal plate, and a cup wall or theca, enclosing the aboral portion of polyp. Cavity of cup contains a number of vertical radiating ridges called sclerosepta, proceeding from theca towards the center of cup. Inner ends of sclerosepta are fused to form an irregular central skeletal mass or columella. 

Types of corals in different groups: - 

1. Hydrozoan corals: -Order hydrocorallina includes few genera, like millepora, stylaster and distichopora, which are colonial and secrete massive branched calcareous exoskeletons. These are found in coral reefs with other corals. Skeleton is secreted by a modified epidermis, called calicoblastic layer. Living within the skeleton occur two types of polyps, large feeding gastrozooids and defensive dactylozooids. 
2. Octocorallian corals: - (a)Order alcyonaceaincludes marine, colonial and soft corals. A well-known genus is alcyonium, popular as “dead man’s fingers” because of its resemblance to a human hand. It has an endoskeleton of separate calcareous spicules embedded in a massive mesoglea or coenenchyma. 

(b)Order stolonifera includes the organ pipe coral, tubipora musica, widely distributed on coral reefs in warm waters. Skeleton is made of mesogloeal calcareous spicules forming parallel and vertical tubes, each occupied by one polyp, and connected together by lateral platforms. Skeleton is dull red in colour due to presence of iron salts. 

(c)Order coenothecalia includes a single genus heliopora, commonly known as blue coral. Its massive calcareous, skeleton or Corallium is secreted by polyps living in large, erect, cylindrical solenialtubes on the surface of skeleton. 

3. Hexacorallian corals: -

Order madrepora includes stony corals, which are the principal builders of coral reefs. While 

some of them are solitary, most are colonial, assuming a great variety of forms.

(a) Solitary corals: - Fungia, flabellum, etc., are the solitary corals or cup corals. The corallite is disc-like or mushroom shaped in form and measures 5 mm to 25 cm across. 

(b) Colonial corals: -Most of stony corals are colonial with plate –like, cup-like, spherical, or vase-shaped skeleton. Typical examples of colonial medreporarian corals are acropora, oculina, favia, madrepora, etc. Some of the colonies are branched. 

Coral Reefs 

Coral colonies grow continuously in size by budding of polyps and often form extensive masses, known as coral reefs. According to T.Wayland Vaughan (1917), a coral reef is a ridge or mound of limestone, the upper surface of which is near the surface of sea, and which is formed chiefly of CaCO3 secreted by coral polyps. Principal builders of coral reefs are stony corals (madreporians), but other important contributors are the hydrocorallines and alcyonarians. Coralline algae and foraminiferan protozoa also take part in the formation of coral reefs.Reef building corals require warm shallow waters (normally above 20C). They are therefore limited to the Indo-pacific, the central western pacific, and the carabian regions north of Bermuda. About 50 species of corals contribute in the formation of reefs along the Florida Keys and in the West Indies. 

Kinds of coral reefs 

The coral reefs are of three kinds, depending on how they are formed: -

1.)Fringing reefs: - Coral reefs lying close to the shores of some volcanic islands or pert of some continents are termed fringing reefs. Fringing reefs may extend out to a distance of a quarter mile from the shore with the most active zone of the coral growth facing the sea. This seaward zone is commonly called the edge or front. A shallow water channel, 50 to 100 meters broad, lies between the reef-edge and shore at low tide, water of channel recedes at quickly exposing a flatbottom surface, called reef flat. It is largely composed of coral sand, mud dead and living coral colonies and other animals. 

2). Barrier reefs: - Barrier reefs are like fringing reefs, but they are located some distance away from the shore. The stretch of water, separating the barrier reef from land, may be half a mile to 10 miles or 

more in width. It is called a lagoon. It is 10 to 50 fathoms deep and suitable for navigation. Most notable example of barrier reefs is the Great Barrier Reef along the north- eastern coast of Australia. It is about 2000 km long and up to 150 km from shore.

3.) Atoll: -An atoll is also termed a coral island or lagoon island. It is a ring-like or horse-shoe shaped reef that encircles a lagoon but not an island. The lagoon varies from a few to about 90 km across. It may be complete or broken by a number of channels, of which only a few are navigable. Outer side of the reef slopes off rather steeply into the depth of ocean. The atoll of Bikine, famous for atomic and hydrogen bomb tests, lies in the Pacific Ocean.

Economic importance of coral reefs: - 

Corals of the remote geological past formed reef structures. They were highly favorable sites for 

accumulation of petroleum deposits. Thus, coral reefs are of much importance to oil industry. Large quantities of corals are shipped every year for the curio trade. The coral reefs serve as habitats for many plants and animals like sponges, molluscs, echinoderms, fishes, etc. Some coral reefs are used for habitations by man as well. Some corals are highly prized for their decorative value. Corallium rubrum is considered to be a precious coral stone in India and china and treated as auspicious. The red coral and organ pipe coral are used in some indigenous system of medicine in India Chunks of coral skeleton belonging to species Porites are used as building materials. Coral skeletons serve as raw material for the preparation of lime, mortar and cement because of their calcium carbonate and magnesium carbonate content. Coral reefs serve as good nursery grounds for commercially important fishes. Reef fish varieties are more colourful than others. 

💥Objective question of Phylum Coelenterata :--

1)Nematocysts are found in: - 

(a)Porifera (b) Coelenterata (c) Platyhelminthes (d) Annelida 

2)The mesenteries attached to the stomodeum are known as: -

(a)Primary (b) secondary (c) tertiary (d) directives 

3)The function of a dactylozooid in polymorphic colony is: -

(a)nutrition (b) reproduction (c) locomotion (d) offence & defence 

4)Polymorphism is found in: -

(a)Halistemma (b) Leucernaria (c) Zoanthus (d)Alcyonium 

5)Pneumatophore is absent in: -

(a)Diphyes (b)Halistemma (c) Physalia (d) Porpita 

6)Gonozooid with a mouth is found in: -

(a)Physalia (b) Velella (c) Porpita (d) all of these 

7)Hypnotoxin is a poisonous fluid produced by: -

(a)parasitic protozoa (b)nematocysts (c) Ascaris (d)sponges 

8)Gastric filaments occur in: - 

(a)Hormiphora (b) Aurelia (c)Obelia (d) Ctenophores 

9)Which of the following inhabit freshwater bodies?

(a)Scyphozoans (b)anthozoans (c)Hydrozoans (d)Ctenophores 

10)The animal without sexual medusa: -

(a)Hydra (b)Millepora (c)Velella (d) Halistemma

11)The function of a tentaculocyst in Aurelia: -

(a)photoreception (b)chemoreception (c)balancing (d)reproduction 

12)Float is not found in: -

(a)Physalia (b) Velella (c)Porpita (d) Obelia 

13)An example of a soft coral: -

(a)Tubipora (b)Heliopora (c)Alcyonium (d)Gorgonia 

14)Which of the following is connected with Coral formation: -

(a)  Halistemma (b)Millepora (c)Adamsia (d)Rhizostoma

15)The scientific name of precious red coral: -

(a)Tubipora (b)Fungia (c)Heliopora (d) Corallia

16)A sea anemone was found growing on a Costopodia shell occupied by a hermit crab: -

(a)symbiosis (b)commensalism (c)competition (d)neutralism

17)Which of the following is the probable reason or such association?

(a)Sea anemone cannot live without the hermit crab (b) Hermit crab benefits by being protected by the Sea anemone (c) Both of them (d) All of them 

18)Fringing reef is usually located: -

(a)very near the shore (b) away from the shore (c)in the deep sea (d)in the Island 

19)The larva of Physalia is: -

(a)a Planula (b)an ephyra (c)a cydippid larva (d)a scyphistoma

20)Example for a permanently sessile Scyphozooa is: -

(a)Aurelia (b)Lucemaria (c) Pelagia (d)Pilema

21)'Hedgehog hydroid commonly known as: -

(a)Tubularia (b)Hydructinin (c)Pennaria (d)Physalia  

22)'Fire coral ' is known as: -

(a)Tubularia (b)Pennaria (c)Millepora (d) Physalia    

23)The nature of Hydra is: -

(a)herbivorous (b)carnivorous (c) omnivorous (d)none of these 

24)Mesogloea secreted by: -

(a)ectoderm (b) Endoderm (c)Both of theme (d)All of them 

25)Most sensitive region of the body of Hydra: -

(a)Mouth (b)tentacle (c)basal disc (d)bud 

26)Peanatula region of the body of Hydra: -

(a)sea fun (b)sea fish (c)sea disc (d)sea pen 

27)Which is known as mushroom coral: -

(a)Fungia (b)Tubipora (c)Adamsia (d)Aurelia

28)Dead man's finger is: -

(a)Fungia (b)Alcyonium (c)Corallium (d)Heliopora

29)Prototheen is a: -

(a)Nutritive secretion (b)Skeleton rudiments (c)All of these (d)None of these 

30)Most important example of barrier reef is: -

(a)Florida keys (b)West Indies (c)Great Barrier Reef (d)None of these 

💥Answer key: -

(1) a (2) a (3) d (4) a (5) a (6) d (7) b (8) b (9) c (10) a (11) c (12) d (13) c (14) b (15) d (16) b (17) c (18) a (19) a (20) b (21) b (22) c (23)b (24) c (25) a (26) d (27) a (28) b (29) b (30) c

Terminal Questions: -

1.Write short notes on: -

(a)Coral reefs.

(b)Fringing reef.

(c)Barrier reef.

2.What is corallite? Discuss coral reefs, in brief?

3.Write notes on:

(a)Generalised polyp and medusa.

(b)Corallite.

(c)Types of coral reefs.

4.How are coral reefs formed?

5.Differentiate between atoll, barrier reef and fringing reef?

6.Write the outline classification of Phylum Coelenterates?

Phylum Porifera| general characteristics| Diagram| MCQ of Porifera| Terminal question of porifera|

 Phylum Porifera 

 Members of phylum Porifera or sponges are most primitive of metazoans or multicellular animals. It includes more than 5,000 species. They appear to be quite life-less and plant like. 

Porifera are a conspicuous and colorful component of many seascapes. 

General characters: -

1. Porifera is multicellular organisms. 
2. All are marine with few exceptions (A single family of freshwater species. e.g., Spongilla). 
3. Its shape some time cylindrical, branching, globular, brightly or dull in colour, they are orange, red, yellow or green colour.
4. Solitary or colonial. 
5. The body is perforated by pores and canals but lack other organs (mouth or nervous system).
6. Body is asymmetrical or radially symmetrical. Body surface has numerous pores, the ostia, serving for inflow of water. 
7. The water current passes through ostia into the chambers and the central cavity and finally comes out of the body through terminal aperture, the osculum. 
8. Body wall has outer pinacoderm (dermal epithelium), inner choanoderm (gastral epithelium) and gelatinous non-cellular mesenchyma in between. 
9. No definite organ for feeding and digestion. 
10. Digestion is intracellular. 
11. The water current serves to bring food organisms and oxygen in the body and carry away the excretory and reproductive products. 
12. Cells are loosely arranged and do not form definite layers. Thus are not truly diploblastic
13. Choanocytes (flagellated collar cells) usually line special chambers.
14. Choanocytes are present only in sponges. 
15. Sensory and nerve cells absent. 
16. Each cell is directly stimulated and transmits sensations to other cells also. 
17. Development is indirect through free swimming ciliated larva, the amphiblastula or parenchyma.
18. All sponges are hermaphrodite. 
19. The sexual reproduction occurs by the sperms and ova but asexual reproduction by buds or gemmules.
20. Sponges have great power of regeneration. 
21. Sponges are cultivated for commercial purposes.
22. About 10,000 species of sponges are known in the world.

 Scypha or Sycon

Classification: 

PHYLUM - PORIFERA 

CLASS - CALCAREA 

ORDER - HETEROCOELA 

GENUS - SCYPHA 

Habit and Habitat: -

Scyphy or Sycon is commonly called as ‘urn sponge or crown sponge’ because of its 

typical shape. Scyphy or Sycon is marine sponge.This has been found widely in nature. It 

is found attached to submerged rocks in shallow water near coast. It occurs solitary or as 

branching colonial form. Several species of Scyphy are S. elegans, S.ciliatum, 

S.lingua and S. gelatinosum etc.

Structure: -

External morphology: -

Shape- The colony has the appearance of a branching tree. It consists of two to several cylindrical branches connected together to a stolon at their bases. The latter is attached to substratum. Each cylinder is vase like.

Size- The size of a cylinder varies from 2-8cms. 

Colour- The sponge presents various shades of grey or light brown colour. 

Osculum and oscular fringe: The free distal end of each cylinder has wide opening, the osculum or exhalent pore. It is surrounded by numerous straight needles like calcareous spicules arranged in a circle. 

Dermal pores or ostia: - 

Body surface of Sycon has regularly arranged polygonal elevations separated lines or furrows. In furrows present numerous apertures, the ostia or inhalant pores and open into current canals. 

Entire body surface has spicules protruding out from it. 

Canal System in Sycon: -

Sycon, like all other sponges, possesses the characteristic peculiarity-the canal system. The body wall of sponges is folded to produce complex system of pores and canals for entrance of water current. Scypha or Sycon represents Sycon type of canal system. 

Its components are: -

• Ostia or dermal pores- The external body surface is covered by thin pore membrane.  It bears two or more openings, the ostia or the dermal pores. The pores are surrounded by myocytes. These can reduce the diameter of dermal pores and thus reduce amount of incoming water. These open into incurrent canals.
• In current cannels- These are narrow spaces placed radially between adjacent radial canals. These are lined with pinacocytes and opens outside by ostia.
• Prosopyles- Incurrent canals communicate with radial canals by prosopyles.
• Radial or flagellated canals- The body of Sycon invaginates to form thimble-shaped chambers. Chambers are lined by flagellated choanocytes and called flagellated chambers or radial canals. The radial canals and incurrent canals lie parallel and alternate to each other and are separated by mesenchyme. Radial canals end at their outer ends but open into spongocoel.
• Apopyles- The openings of radial canals into spongocoel are called apopyles or gastric ostia.
• Spongocoel- It’s the large central cavity into which radial canals open through apopyles. The choanocytes line radial canals and spongocoel is lined by flattened pinacocytes. Spongocoel is central space all along the length of body. 
• Osculum- The spongocoel opens to outside by a terminal opening, the osculum. Osculum is surrounded is surrounded by a contractile myocyte. These form a sphincter which regulates the rate of water flow.

Mechanism of water circulation: 

 The water current is produced, and water is pumped into the body by beating of flagella of choanocytes which line the radial canals. A wave of spiral undulations passes from base to tip of each flagellum and water is pushed in. Water enters the body by ostia into incurrent canals, from there by prosopyles into radial canals and then by apopyles it reaches spongocoel and discharge into exterior by osculum. In other way, the path of water into the canal system can be represented as following: -

Step 1) Water from outside 

Step 2) Dermal ostium 

Step 3) In current canal 

Step4) Prosopyle 

Step 5) Radial canal 

Step 6) Apopyle

Step 7) Excurrent canal 

Step 8) Gastic ostium 

Step 9) Para gastric cavity

Step 10) Psculum 

Step 11) Exterior

Importance of water circulation of canal system: - 

Water current plays a very important role in the physiology of the sponges. The water circulation system helps the sponges in nutrition, digestion, respiration, excretion and reproduction. The water current brings in food and oxygen and it takes away waste products.

1. Nutrition: -Scypha feeds on particles of organic matter and small living organisms, like a diatoms, bacteria and protozoa; they are drawn in the water current. 
2. Digestion- It is entirely intracellular, as in protozoa. Partly digested food is taken up by amoebocytes in which digestion is completed, the amoebocytes transport and supply the digested food to all parts of the body. 
3. Respiration- The Gaseous exchange occurs by simple diffusion, between the cells of sponge and the current of water. Water entering body is rich in oxygen and facilities exchange of gases. The rate of consumption of Scypha was found to range from 0.16 ml.of oxygen per gram of fresh weight per hour in the smaller specimens to 0.04ml. in the larger ones.
4. Excretion- While outgoing, water current removes CO2 and nitrogenous products.
5. Reproduction-The spermatozoa enters body of other sponges along water current.

Reproduction in Sycon: -

The sponges reproduce both asexually and sexually. 

Asexual Reproduction –

Asexual reproduction occurs throughout the Porifera. The asexual reproduction takes place by budding, regeneration and gemmule formation. 

a) By budding - During favorable conditions Sycon reproduces by budding. The buds arise basally near its attachment and then constrict off after some time to lead independent existence. 

b) By regeneration - Sponges have a great power of regeneration. They not only replace parts lost during injury, but any piece of body can grow into complete sponge. The process is however very slow and is completed in months or years. The regeneration power is used for cultivation of bath sponge industrially.

Sexual Reproduction -

Both male and female gametes are formed inside body of same animal (hermaphrodite) Gametes 

develop specialized amoeboid cells, called archeocytes found in mesenchyme. 

• Spermatogenesis-sperms are produced from amoebocyte or spermatogenesis and get surrounded by one or more flattened cells cover cells. The spermatocyte divides two to three times and cells develop into sperms. Mature sperm has round head with nucleus and long tail.
• Oogenesis- Oocyte is differentiated into an enlarged amoebocyte with nucleus. It increases in size, stores food material, is nourished by choanocytes called trophocytes or nurse cells. Its nucleus undergoes two maturation divisions (meiosis) to form ovum. 
• Fertilization- The fertilization is internal and cross fertilization occurs. The sperm does not enter directly in the ovum but reaches a radial canal and is dispersed by the water currents. Sperm cell enters the nurse cells or choanocyte adjacent to mature oocytes, which becomes amoeboid and fuses with ovum liberating the sperm. The nuclei of ovum and sperm fuse and form zygote.

Development of Sycon: -

1. Cleavage- The divisions are holoblastic and development occurs inside the body of sponge. The 1st three divisions are vertical and produce pyramidal plate of 8 cells. The 4th division is horizontal and divides blastomeres unequally into 8 micromeres and 8 macromers. A cavity develops in between, and embryo enters into the blastula phase. Micromeres divide more rapidly and develop flagella at their free ends, while macromere becomes rounded and represents the Stom blastula.
2. Stom blastula- One side of Stom blastula is composed of many small, elongated, flagellated micromeres, while other side composed of 8 rounded, non-flagellated macromeres. Inner cavity (blastocoel) opens outside through the mouth. It is used to engulf the surrounding amoebocytes for nutrition.
3. Amphiblastula- The Stom blastula undergoes inversion and flagellated ends of flagellated cells comes to lie to the exterior. The flagellated Stom blastula is called amphiblastula larva. The fully formed amphiblastula is set free into radial canal. It escapes by osculum along the water current and leads free swimming existence and undergoes gastrulation by invagination and emboly. The flagellated cell invagination into blastocoel and macromere grows over them by rapid multiplication. Thus, gastrula is formed.
4. Gastrula- Gastrula has two-layer bodies. Outer layer is granular, ectoderm and inner are non-granular flagellated cells, endoderm. The central cavity opens outside by opening called blastopore.
5. Metamorphosis (Post embryonic development) - The gastrula adheres to substratum like rock, sea weeds, etc., by its blastoporal end and undergoes metamorphosis to form adult Sycon.

• The larva lengthens into a cylinder and develops osculum at free distal end. 
• The non-granular flagellated cells of endoderm form choanocytes. 
• The granular non-flagellated cells of ectoderm give rise to pinacocytes of dermal epithelium. 
• The body wall gets perforated by Ostia and Olynthus stage is attained by Sycon. The choanocytes are shifted in these radial canals and the body wall increase in thickness, the adult Scypha is formed and its colony develops. 

Objective Question of Phylum Porifera: -

1) Most primitive group of animals, which are multicellular is: -

(a) Coelenterata  (b) Sponge (c) Nemertine (d) None of these 

2) In case Demospongiae, leucon type of canal system is derived from: -

(a) Ascon type of canal system of larva (b) Rhagon type of canal system of larva (c) None of these (d) Both a and b

3)Animal of phylum Porifera are characterized by: -

(a) Gland cell (b) Choanocytes (c) Amoeboid cell (d) All of these 

4)Ascon type of canal system is formed in: -

(a) Euspongia (b) Leucosolenia (c) Amoeboid cell (d) None of these 

5) Which one of the sponges is harmful to the oyster industry?

(a) Cliona (b) Euspongia  (c) Spongilla (d) All of these 

6) Venus Flower Basket is the name of the dried skeleton of: -

(a) Euspongia (b) Spongilla (c) Euplectella (d) all of these 

7)Which of the following is a freshwater sponge?

(a) Spongilla (b) Euplectella (c) Euspongia (d) None of these 

8)The simplest type of canal system in Porifera: -

(a) Leucon type (b) Radial type (c) Ascontype  (d) All of these 

9)Porifera is characterized by the presence of: -

(a)Para gastric cavity (b) Coelenteron (c) Coelom (d) None of these 

10)In Poriferan skeleton secreting cell are: -

(a) Amoebocytes (b) Thyrocytes (c)Archeocytes (d) All of these 

11)Correct sequence of evolution of canal system if sponges are: -

(a) Sycon - Ascon - Leucon (b) Ascon - sycon - Leucon (c) Sycon - Leucon - Ascon (d) Ascon - Leucon - Sycon 

12)Member of phylum Porifera are: -

(a) Mostly marine animal, few being freshwater (b) Exclusively marine animal (c) Mostly fresh water few being marine (d) Exclusively freshwater animals.

Answer Key: -

(1) b (2) b (3) b (4) b (5) a (6)c(7) a (8) c (9) a (10) b (11) b (12)a

Terminal Question: - 

1. Write the outline classification of Phylum Porifera?

2. Into how many classes is Phylum porifera divided? Write their names and important characters?

3. What is the characteristic feature of phylum Porifera based? 

4. On basis of which characters is the classification of Porifera based?

Phylum protozoa, characteristic of protozoa, 26 MCQ of Protozoa, bsc sem-1 zoology objective question,

 Phylum Protozoa 

The Protozoa are heterogeneous assemblage of some 50,000 cellular or single- cell organism. 

found worldwide in most habitats. Protozoa means ‘first animal’ the simplest form of animal life. 

Protozoa are unicellular microorganisms (eukaryotes) that lack cell walls. They are found in 

marine habitat or soil, in freshwater bodies, symbiotic, some forms are parasites in other. 

organisms. Protozoa depends on nutrition, temperature, pH, and some depends on sunlight. 

Protozoa were defined as unicellular protists with animal-like behavior, such as movement. 

Protozoa were regarded as the partner group of protists to Protophyta, which have plant-like 

behavior, e.g., photosynthesis. The term protozoan has become highly problematic due to the 

introduction of modern ultra structural, biochemical, and genetic techniques, which have showed 

that the group does not form a clade as required by modern classifications.

Modern unicellular clades within Eukaryotes which may be viewed as approximately collectively. 

replacing the class of protozoa include: Excavata, Amoeba, Chromalveolata and Rhizaria. 

Protozoans are usually single-celled heterotrophic eukaryotes containing non-filamentous 

structures that belong to any of the major lineages of protists. They are restricted to moist or 

aquatic habitats (i.e., they are obligate aquatic organisms). Many protozoan species are 

symbionts, some are parasites, and some are predators of feces bacteria and algae. There are an 

estimated 50,000 protozoan species. 

The Protozoa are considered to be a subkingdom of the kingdom Protista, although in the 

classical system they were placed in the kingdom Animalia. More than 50,000 species have been 

described, most of which are free-living organisms; protozoa are found in almost every possible 

habitat. The fossil record in the form of shells in sedimentary rocks shows that protozoa were 

present in the Pre-Cambrian era. Anton van Leeuwenhoek was the first person to see protozoa, 

using microscopes he constructed with simple lenses. Between 1674 and 1716, he described, in 

addition to free-living protozoa, several parasitic species from animals, and Giardia 

lamblia from his own stools.

General Characters of protozoa: - 

• They are aquatic (fresh and salt water) free living parasitic, symbiotic or commensally. Usually microscopic with oval, elongated, spherical or ever-changing shape.
• They show cellular level of organization, where all the activities of the body are performed by a single cell.
• The protozoan cell body is either naked or surrounded by a non rigid pellicle. Cellulose is absent in the pellicle. 
• Some protozoans secrete shells of various inorganic compounds as external covers.
• They possess different types of locomotory organs. 
• They may bear flagella (flagellates), cilia (ciliates) or pseudopodia (scorodines). 
• Locomotory organs are absent in the parasitic forms.
• They are holozoic (animal-like) and feed largely on bacteria, microscopic algae and minute animals such as rotifers or on other protozoan’s including members of their own species. 
• Some are holophytic (plant-like); they contain chlorophyll and prepare their own food by photosynthesis (Euglena). 
• The parasitic protozoans devour on materials obtained from the hosts (Monocytes). 
• Some are saprozoic (subsisting on dead organic matter) and saprophytic (feeding on liquid food).
• The osmotic concentration of cell body (Osmoregulation) is maintained by one or more contractile vacuoles and these contractile vacuoles are help in excretion. 
• The excretory product is ammonia. 
• Asexual reproduction takes place by binary fission or budding. 
• Sexual reproduction is performed by the fusion of gametes or by conjugation. 

Examples: 

Free living- Euglena, Amoeba, Noctiluca, Paramecium, Elphidium (Polystomella) Parasitic Monocystis, Entamoeba, Giardia, Plasmodium, Trypanosome, etc 

• The single cell of the body performs all the vital activities. 
• Encystment occurs to tide over the unfavorable conditions and to help in the dispersal of race. 
• In certain animalcules, the life cycle is complicated and exhibits alternation of generations.

Habit and habitat: - 

Paramecium is occurrence in freshwater ponds, lakes, rivers and streams. It is also found in abundance in stagnant water bodies. 

Objective Question of Protozoa: - 

1) Coprozoic nutrition is found in: -

(a)Balantidium (b)Euglena (c) Noctiluca (d) Copromonas 

2)Holozoic nutrition is found in: -

(a) Paramecium (b)Balantidium (c) Euglena (d) Nyctotherus 

3)Saprophytic nutrition is found in: -

(a) Euglena (b) Leishmania (c) Amoeba (d) Monocystis 

4) Photoreceptor organ of euglena is: - 

(a) Stigma near reservoir (b) Stigma and Paraflagella Body (c) Chromatophore 

5) Lactoflavin (sensitizer) found in: -

(a) Eye spot (b) Paraflagella body (c) Golgi body (d) Mitochondria

6) Euglena is green in colour which is due to: -

(a) Chromatophores (b) Leucoplast (c) Carotene (d) Pyrenoid 

7) Euglenas belong to class: - 

(a)Phyto mastigophore (b) Zoo mastigophore (c) Rhizophore (d) None of these

8) Connecting link between plank and animal kingdom: - 

(a) Amoeba (b) Paramecium (c) Euglena (d) Opalina 

9)Which is oldest one of the animals: -

(a) Amoeba (b) Euglena (c) Opalina (d) Paramecium 

10)Osmoregulation in euglena Occur with the help of: -

(a) Vacuole (b) food vacuole (c) Contractile vacuole (d) none

11)Main Function of contractile vacuole is: -

(a) Nutrition (b) Excretion (c) Osmoregulation (d) Locomotion 

12)Digestion in protozoa is: -

(a) Intercellular (b) Intracellular (c) extracellular (d) all of these

13)Cytopyge is found in 

(a) Amoeba (b) Paramecium (c) Euglena (d) Trypanosome 

14) Tentacles are found in: - 

(a) Stylonychna (b) Ephelota (c) Euglypha (d) Trypanosome 

15)The presence of a long Flagellum and a short tentacle is the characteristic feature of: -

(a) Copromonas  (b) Chlamydomonas (c) Noctiluca (d) Euglena 

16) One of the characteristic features of Telosporea is: -

(a) Unicellular trophozoites (b) Multicellular trophozoites (c) Presence of shell (d) Presence of an eye spot 

17) Class sporozoan includes parasites protozoa in which locomotory organelles are: -

(a) flagella (b) absent (c) Both cilia and pseudopodia (d) of various type 

18)Locomotion in young sporozoan is by 

(a) Glidding (b) ciliary (c) amoeboid (d) euglenoid 

19) An example of sporozoan is: - 

(a) Elphidium (b) Monocystis (c) Difflugia (d) Vorticells 

20) Contractile vacuole is present in: -

(a) in marine protozoa (b) in parasitic protozoa (c) in fresh water (d) none of these

21) Which of the following do not have locomotory organelles: -

(a) Rhizopoda (b) Flagella (c) Ciliata (d) sporozoan 

22)Trichocysts are found in: - 

(a)ectoplasm of euglena (b) ectoplasm of paramecium (c) Both (d) none of these 

23)The mononucleate form is: -

(a) Balantidium (b) Chrysamoeba (c) stylonychia (d) Pelomyxa 

24) Trichomonas belongs to: - 

(a) protomonadia (b) dinoflagellate (c) schistoflagellata (d) polymastigina 

25)The characteristic feature of class Sporozoa is the presence of: - 

(a) flagella (b) parasitism (c) chlorophyll (d) none

26)The primary grouping of the protozoan is based on their: - 

(a) mode of feeding (b) locomotory organells  (c) both (d) none 

27) Class mastigophore include the protozoan in which locomotory organells is: -

(a)Lobo podium (b) flagella (c) cilia (d) absent 

28) The phylum protozoa is divided into sub-phylum on the basis of their: -

(a) nuclear structure (b) locomotory organ (c) Both (d) none of these 

29)The presence of slender pseudopodia with interlacing branch to form a network in the characteristic feature of the order: -

(a)Radiolaria (b) lobosoa (c) foraminifera (d) Mycetozoa 

30) Oder lobosa include: - 

(a) Pelomyxa (b) elphidium (c) globigerina (d) euglypha 

31) Chilomonas belong to the order: -

(a) chrysomonadina (b) euglenodina (c) Crypdomomadina (d) all of these 

32) Order Suctorida included: - 

(a) Trichonympha (b) Giardia (c) lophantonas (d) all of these 

33)Protenospongia is included in order: -

(a) Euglena (b) Rhizomastinoida (c) Choanoflagellida (d) all of these 

34)Volvox is included in order: - 

(a) Phytomonadida (b) euglenida (c) Chrysomonadida (d) none of these 

35) Ceratium is included in order: -

(a) Mastigophora (b) Dinoflagellata (c) Euglena (d) all of these 

36)Karyosome consist of two materials, what is the achromatic substance present in it?

(a)Plastin (b) Chromosome (c) Paramylum (d) None of these 

37) The shell of polystomella is made up of: -

(a) calcium carbonate (b) Silicon (c) all of these (d) None of these 

38) Cytopyge is found in: -

(a) Amoeba (b) Trypanosoma (c) Euglena (d) All of these 

39) The locomotory organelle of foraminifera are: -

(a) lobopodian (b) filopodia (c) axopodia (d) all of these 

40)which of the following protozoans is unlikely to have a contractile vacuole?

(a) Paramecium (b) Plasmodium vivax (c) Euglena (O all of these 

41)Grand old man of the intestine is 

(a) Amoeba (b) Giardia (c)Entamoeba (d) None of these 

42) The disease caused by the infection of Trichomonas :-

(a) amoebiosis (b) Kala-azar (c) Trichomoniasis (d) None of these 

43) 'Tripali stone ' is characterise presence of :- 

(a) Foramaniferian (b) Radiolarian (c) Actinosphaerium (d) None of these 

44)Which show endocommensal form in large intestine of anura :- 

(a) Opalina (b) Monocystis (c) Trypanosoma (d) none of these 

45)Balantidium in Housing the intestine of: - 

(a) Man (b) Pig (c) Sheep (d) fish (e) all 

Answer key: -

(1)d (2)c(3)a(4)c(5)b(6)a(7)a(8)c(9)b(10)c(11)c(12)b(13)b(14)b(15)c(16)a(17)b(18)a(19)b(20)c(21)d(22)b(23)b(24)d(25)b(26)b(27)b(28)b(29)c(30)d(31)c(32)a(33)c(34)a(35)b(36)a(37)b(38)b(39)b(40)a(41)b(42)c(43)b(44)a(45)e