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The main examination for the Indian Forest Service comprises: (A) The written examination consisting of the following papers:Paper I

General English

300 marks

Paper II

General Knowledge

300 marks

Paper Paper Paper Paper

Any two subjects to be selected from the list of the optional subjects. Each subject will have two papers.

200 Marks for each paper

III IV V VI

Interview for Personality Test —Maximum marks: 300 LIST OF OPTIONAL SUBJECTS 1. 3. 5. 7. 9. 11. 13.

Agriculture Animal Husbandry & Veterinary Science Chemistry Civil Engineering Geology Mechanical Engineering Statistics

2. 4. 6. 8. 10. 12. 14.

Agricultural Engineering Botany Chemical Engineering Forestry Mathematics Physics Zoology

Provided that the candidate will not be allowed to offer the following combination of subjects: Agriculture and Agricultural Engineering Agriculture and Animal Husbandry & Veterinary Science Agriculture and Forestry Chemistry and Chemical Engineering Mathematics and Statistics Of the Engineering subjects viz. Agricultural Engineering, Chemical Engineering, Civil Engineering and Mechanical Engineering not more than one subject.

GENERAL INSTRUCTIONS All the question papers for the examination will be of conventional (Essay) type. All question papers must be answered in English. Question papers will be set in English only. The duration of each of the papers referred to above will be 3 hours.

(iii)

Previous Previous Previous Previous Previous Previous Previous Previous

Years’ Years’ Years’ Years’ Years’ Years’ Years’ Years’

Papers, Papers, Papers, Papers, Papers, Papers, Papers, Papers,

2021 (Exam held on 02/03/2022) ....................................... 1-44 2020 (Exam held on 03/03/2021) ....................................... 1-52 2019 ............................................................................. 1-44 2018 ............................................................................. 1-32 2017 ............................................................................. 1-36 2016 ........................................................................... 37-68 2015 ......................................................................... 69-100 2014 ....................................................................... 101-136

PAPER–I SECTION–A 1. NON-CHORDATA & CHORDATA ............................................................. SECTION–B 1. 2. 3. 4. 5.

ECOLOGY ......................................................................................................... ETHOLOGY ..................................................................................................... ECONOMIC ZOOLOGY .................................................................................. BIOSTATISTICS .............................................................................................. INSTRUMENTAL METHODS .........................................................................

PAPER–II SECTION–A 1. CELL BIOLOGY .................................................................................................. 2. GENETICS ......................................................................................................... 3. EVOLUTION ......................................................................................................

SECTION–B 1. BIOCHEMISTRY ............................................................................................... 2. PHYSIOLOGY (WITH SPECIAL REFERENCE TO MAMMALS) .................. 3. DEVELOPMENTAL BIOLOGY ....................................................................... (iv)

Previous Years’1 Paper (Solved)

Indian Forest Service Main Exam, 2021

SUBJECT–ZOOLOGY (Exam held on 02-03-2022)

PAPER-I Explain how it is different from Metatheria with example.

INSTRUCTIONS: Question no. 1 and 5 are compulsory. Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and . All questions carry equal marks. Answers must be written in English only.

4. (a) Describe different patterns of fish migration and write about its significance. (b) Give an account of chemical nature and function of Neurohypophyseal hormones in mammals.

SECTION–A

(c) Describe the parental care in Amphibians with suitable examples.

Write a brief account about each of the following:

SECTION–B

a) Nutrition and Osmoregulation in Euglena.

5. Differentiate between the following:

b) Torsion in Gastropoda. c) Ambulacral system in Asterias.

(a) Indian major carps and Exotic carps.

d) Archaeopteryx.

(b) Mean and Mode.

e) Feeding mechanism of Branchiostoma.

(c) Natality and Mortality.

a) Describe morphological structures of Peripatus and discuss its affinities.

(d) Navigation and Orientation behaviour in birds.

b) What is polymorphism? Explain different polymorphic forms in Coelenterates.

(e) Hormones and Pheromones. 6. (a) Write an account of the mission “Project Tiger” and mention the conservation strategies.

c) Describe the life history of Taenia solium and its parasitic adaptation.

(b) What is the objective of courtship behaviour? Describe courtship in Drosophila and three-spined stickleback.

a) Give a comparative account of the aortic arches in Vertebrates. b) Describe the larval forms of Crustacea with suitable diagrams.

(c) What is phosphorus cycle? Describe the importance of phosphorus cycle as a component of Biogeochemical cycle.

c) Describe the salient features of Prototheria. 1

(1241) Zoology PP 2021—1

(1241) Zoology PP 2021—1-II

2 a) What are the different criteria for the selection of candidate species for aquaculture?

malarial parasite and its pathogenicity in man.

b) What is the working principle of Transmission Electron Microscope (TEM)? Describe its application with suitable diagram.

(b) What are independent and dependent variables? What is coefficient of correlation and how is it calculated? Illustrate with formula and range of values (r).

c) What is lac? Describe in detail about the lac culture. a) What are the common malaria causing species? Write an account of life cycle of

(c) Write an account of Tiger Prawn culture with emphasis on seed resources and transportation.

PAPER-II INSTRUCTIONS: Question no. 1 and 5 are compulsory. Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and . All questions carry equal marks. Answers must be written in English only.

SECTION–A a) Briefly explain the contributions of George Gamow, Har Gobind Khorana, Marshall Nirenberg and Severo Ochoa in deciphering the genetic code. b) How do proteins move through the Golgi apparatus? Explain. c) Explain synonymy and homonymy in context of the International Code of Zoological Nomenclature. d) Briefly discuss the role of geographical and reproductive isolations in speciation. e) Describe different types of intercellular junctions in animal cells. a) Explain molecular m echanism of chromosome movements in eukaryotes. b) What is an Operon? Explain how a polycistronic structural gene is regulated by a common promoter and a combination of regulatory genes in a zac-operon.

(c) Give an account of ancestry of Miocene and Pliocene proboscideans. 3. (a) Define Linkage. Give an illustrated account of complete, incomplete and sex linkages. (b) How does continental drift theory explain the discontinuous and restricted distribution of organisms? (c) Explain the phenomenon of endocytosis in organisms with suitable examples. 4. (a) Describe the principle, procedure and applications of DNA fingerprinting. (b) Define Mimicry. Enlist its causes. Explain different types of mimicry with suitable examples. (c) Give the structure and functions of nuclear envelope.

SECTION–B 5. (a) Explain quaternary haemoglobin.

structure

of

(b) What is Bohr’s effect? How does it promote gaseous exchange in the lungs and the tissues? (c) What are oligosaccharides? Give structural formulae and functions of biologically important maltose, sucrose and lactose.

3 d) Explain morphogenetic movements in gastrulation of frog.

coupling mechanism in oxidative phosphorylation using chemiosmotic model.

e) Briefly write about hormonal control of digestive secretions in humans.

(b) Enumerate different blood coagulation factors. Explain their role in the process of blood coagulation.

a) Describe structural differences among glycogen, starch and cellulose and elaborate their functions.

(c) Classify Vitamins. Discuss deficiency symptoms of fat soluble vitamins.

b) Explain countercurrent mechanism of urine concentration in the kidneys of higher vertebrates.

8. (a) Why do cells die? Discuss apoptosis, necrosis and autophagy. Add a note on “cell death proteins”.

c) What is invasive placenta? Discuss its types, causes and risk factors.

(b) Explain hormonal regulation of menstrual cycle in women.

a) Give schematic representation of electron transport chain. Describe the energy

(c) Describe the structure and functions of neutral fats.

ANSWERS PAPER-I a) Nutrition and Osmoregulation in Euglena Nutrition in Euglena: All unicellular eukaryotes, irrespective of their mode of nutrition, are included in the kingdom Protista in Whittaker’s system. Protista includes autotrophic or photosynthetic organisms, consumer-decomposer organisms and protozoans. Euglenoids are unicellular, flagellate protists found in water or damp soil. Majority of them are freshwater organisms found in stagnant water. Euglenoid body is spindle-shaped with a blunt anterior end and pointed posterior end. Euglenoids belong to a group of chlorophyllous and non-chlorophyllous flagellate protists, and the largest genera amongst them is the Euglena. Nutrition in Euglena is photoautotrophic. However, it is capable of getting nourishment from dead and decaying organic matter in the substrate by secreting digestive enzymes (saprophytic nutrition) in the absence of light. This dual-

mode of nutrition is absent in Euglena. Some forms are holozoic (Peranema) or saprobic (Rhabdomonas). So, Euglena is a type of protist (producer-decomposer). Osmoregulation in Euglena Euglena viridis has a semi-permeable pellicle and lives in water so that water continuously enters in its body by endosmosis. The removal of excess of water from the body is known as osmoregulation. The elimination of excess of water is done by the contractile vacuole. Elimination of excess water is done by the contractile vacuole and its tributaries. The radiating or associating smaller vacuoles collect surplus water from the endoplasm and liberate their contents into the main vacuole, which gradually increases in size and finally contracts to force the fluid into the reservoir. From the reservoir the fluid escapes through the gullet. Along with this, water soluble wastes are thrown out of the body.

4 b) Torsion in Gastropoda Torsion (twisting) is the rotation of visceral organs in anticlockwise direction through an angle of 180° on the rest of the body during larval development. The phenomenon takes place in the free-swimming (veliger) larva of gastropods and converts the symmetrical larva into an asymmetrical adult. Contraction of the larval retractor muscles and differential growth are possibly responsible for such rotation. Entire rotation results within few minutes. Asymmetry is encountered at the early stage in Veliger larva where the mesodermal bands develop asymmetrically. The mesodermal band on the right side is larger than its left counterpart. The right band is composed of five mesoderm cells which elongate to form muscle cells. With the transformation of the muscle cells the visceral hump is displaced to the left side. These cells on the right side converge and transform into the larval retractor muscles. The muscle cells are absent on the left side. Torsion of the visceral hump commences as soon as the larval muscle cells attain the power of contraction. c) Ambulacral system in asterias:

Fig. Ambulacral system in asterias

The water vascular system is a modified part of coelom and it consists of a system of seawater filled canals having certain corpuscles. It plays most vital role in the locomotion of the animal and comprises madreporite, stone canal, ring canal, radial canal, Tiedeman’s bodies, lateral canals, and tube feet. 1. (d) Archaeopteryx Archaeopteryx is a connecting link between reptiles and birds. Despite the presence of numerous avian features, Archaeopteryx had many non-avian tetrapod dinosaur characteristics. So, it is a connecting link between reptiles and birds. Archaeopteryx is known to have evolved from small carnivorous dinosaurs, as it retains many features such as teeth and a long tail. It also retains a wishbone, a breastbone, hollow thin-walled bones, air sacs in the backbones, and feathers, which are also found in the non-avian coelurosaurian relatives of birds. It was the first reptilian fossil found with clear evidence of feathers, a trait long considered the key distinction between birds and “non-birds.” Archaeopteryx is now a fossil and once lived in the Late Jurassic period around 150 million years ago, in present-day southern Germany and Portugal. In fact, Archaeopteryx is the first bird on earth considered to be about 150 million years old. These organisms were seen during the time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now. Two perfectly preserved specim ens of Archaeopteryx were found in Bavaria in the fine-grained lithographic limestone of the Upper Jurassic period. It was discovered by Andreas Wagner in 1861. Another fossil was found in 1877 and the third was also found in 1956 from the same place. Archaeopteryx is an example of Mosaic evolution (or modular evolution) which states that the evolutionary change only took place in some of body parts or systems w ithout simultaneous changes in other parts.

5 e) Feeding Mechanism of Branchistoma Amphioxus (Branchiostoma) obtains food by filtering the stream of waters that enters the pharyngeal cavity. The wheel organ produces a vortex. The buccal cirri become curved to form a sieve to prevent the entry of large particles. The sensory papillae in the buccal cirri and velar tentacles act as chemo receptors and taste the nature of the food particles and also estimate the size of food particles. If food particles are large in size or liable to cause toxicity, these are expelled by the forceful expulsion of the water from the pharyngeal cavity. The ingress of water into the pharyngeal cavity through the mouth is controlled by the velum. The pharynx plays the most important role in food collection. The major portion of the water passes out into the atrium through the gillslits. The cilia present on the gill-bars beat to drive the water out into the atrium and, thus, facilitate the inflow of fresh water current through the mouth. The food particles, due to their own weight, begin to fall on the floor of the pharyngeal cavity and are entangled by the sticky secretion of the mucus-secreting cells of the endostyle. The cilia in the endostyle and gill-bars beat to produce an upward current to push the mucus-entangled food particles towards the epipharyngeal groove. The cilia of the endostyle also beat to drive the food along the peripharyngeal-ciliated tracts to the epipharyngeal groove. The food is pushed backwards by the backward beating of the cilia of the epipharyngeal groove. The secretion of the glandular cells of the endostyle transforms the boluses of mucusentangled food particles into a cord-like structure, known as food cord. The food cord from the pharynx passes through the oesophagus into the hepatic diverticulum and midgut where this food cord is subjected to the action of digestive enzymes secreted

by the hepatic diverticulum. The food cord from the hepatic diverticulum is pushed backwards by the cilia present in its cavity. The mucus-entangled food cord is rotated by the ciliary action in the ileocolon ring. Digestion in Branchiostoma is both intracellular as well as extracellular. The intracellular digestion takes place inside the hepatic diverticulum while the extracellular digestion occurs inside the midgut. The secretory cells of the hepatic diverticulum contain zymogen granules and they show phagocytosis, i.e., the cells are able to engulf the food particles from the food cord and digest the food as seen in Amoeba and Hydra. The phenomenon of phagocytosis is attested by the fact that carmine particles, after ingestion into the diverticulum, are taken inside the cells. The digestive enzymes in Branchiostoma are amylase, lipase and protease. The digested food is absorbed in the hindgut and the undigested particles are expelled through the anus. The controlling mechanism of the ciliary mode of feeding in Branchiostoma is not clearly known. The afferent and efferent nerve fibres in the atrium presumably play the important role in feeding. The rate of water current is largely controlled by the intensity of beating of cilia and also the degree of contraction or dilatation of the Inhalant and exhalant apertures. The different receptors present on the velum and the atrium taste the nature of water current. If the water current contains any toxic substance, the atriopore closes and the water is regurgitated by sudden contraction of the pterygial muscles which form the floor of the atrium. 2. (a) Morphological Structure and Affinities of Peripatus Peripatus is a soft bodied worm like, bilaterally symmetrical animal. It shows tracheal mode of respiration. It is grouped in Phylum Arthropoda and Class Onychophora.

6 This class is the smallest and it includes only one genus, and seventy species. Class Onychopora includes primitive worm like, Arthropods. It is a connecting link between annelids and arthropods. Peripatus is seen in neotropical regions like West Indies, America, Congo, Australia, Tasmania, NewZealand, Malaya etc. It exhibits Peripatus is terrestrial animal. It lives under stones; bark of trees and in shady places. It is nocturnal in habit. During day time it remains in the dark place and in night time it comes out in search of food. It feeds on small insects, worms and termites.

Fig. Peripatus External Structure: It is a soft bodied, worm like animal. It grows up to 1 to 2" in length. The soft body shows deep black colour on the dorsal side and light red colour on the ventral side. The integument exhibits large number of wrinkles or ring like constructions which are superficial. The skin is soft and bears many minute papillae and bristles along the mid-dorsal line of the body. It produces slimy secretion which is protective and helps in capturing the food organisms. The body is divisible into two parts. 1. Head: Head is composed of three segments. They are fused. It has a pair of antennae. Each antenna shows a large number of segments. On the ventral side of the head mouth is seen. The mouth is surrounded by a lip which has ridges. A pair of jaws with teeth surrounds the mouth. A tongue is also seen in the mouth. A pair of oral papillae will be present. Each oral papilla contains the openings of slime glands. On the dorsal side of the head a pair of simple eyes will be seen.

Fig. Peripatus head ventral-view 2. Trunk: It contains 14-42 segments arranged serially. All the segments are alike. Each segment shows a pair of appendages. The anus is terminal and it is present at the posterior end of the body. On the ventral side below the anus the genital pore is present. Appendages: Each segment contains a pair of appendages. Each appendage shows 2 parts. (1) A conical proximal leg. (2) A short distal foot with a pair of horny claws. The leg shows 2 spiniferous pads at its distal end. The leg bears rings of papillae with bristles. The foot is attached to the distal end of the leg. All the appendages are hollow. Affinities of Peripatus: Peripatus is a unique organism. It forms a connecting link between Annelids and Arthropods. It exhibits several important Annelida characters and some Arthropodan characters. In addition to these, peripatus exhibits some peculiar characters not shown by either Annelids or Arthropods. Annelidan Characters:  Presence of worm like body with bilateral symmetry.  Presence of thin flexible cuticle.  Absence of distinct head region.  Presence of dermomuscular body wall with circular and longitudinal muscles.  Presence of a pair of simple eyes on the dorsal side of head.  Presence of hollow stumpy appendages in the trunk segments.  Presence of muscular pharynx.

7 Presence of short stom odaeum and proctodaeum regions of alimentary canal.  Presence of salivary glands which are modified Nephridia.  Presence of paired Nephridia in every segment.  Presence of segmentally-arranged coxal glands which are homologous with settiparous glands of chaetopods.  Presence of cilia in the reproductive ducts. Arthropodan Characters:  Presence of a chitinous cuticle.  Presence of jointed appendages arranged one pair in each segment.  Presence of jaws in the mouth which are modified appendages.  Presence of haemocoel.  Presence of colourless blood.  Presence of long, tubular and dorsal heart enclosed by pericardium. 

b) Polymorphism: Polymorphism, as related to genomics, refers to the presence of two or more variant forms of a specific DNA sequence that can occur among different individuals or populations. The most common type of polymorphism involves variation at a single nucleotide (also called a single-nucleotide polymorphism, or SNP).

Fig. Polymorphism in Coelenterata Polymorphic form in coelenterata: two types of zooids: Coelenterates which may be single or colonial, they exists in two forms-polyps and medusa.

1. Polyp:  In Hydrozoa, polyps has a tubular body with a mouth surrounded by tentacles at one end. Other end is blind and usually attached to pedal disc to the substratum  Polyps are generally sessile  They reproduce asexually 2. Medusa:  In Hydrozoa, medusa has a bowl or umbrella shaped body with marginal tentacles and mouth centrally located on a projection called manubrium of the lower concave surface.  Medusas are generally motile  They reproduce sexually Importance of polymorphism:  It is essential for division of labor among the individual zooids.  Different functions are assigned to different forms. For examples; polyps are concerned with feeding, protection and asexual reproduction whereas medusa are concerned with sexual reproduction. 2. (c) Life History of Taenia Solium Copulation and Fertilization: Selffertilisation occurs by the insertion of the cirrus of one proglottid into the vagina of the same proglottid and sperms are deposited there. From the vagina the sperms come to lie in the seminal receptacle from where they fertilize the eggs in oviduct. But crossfertilisation between different proglottids of the same tapeworm is very com mon. Actually, T. solium is protandrous, i.e., testes mature first. Hence, after copulation the sperms are stored temporarily in the seminal receptacle waiting for the maturity of the eggs and when such eggs come in the oviduct, fertilisation occurs. After fertilisation, the eggs are transformed into capsules and packed in the uterus. Later, the various reproductive organs degenerate and the uterus becomes distended and branched having more than 30,000-40,000 egg capsules.

8 Formation of Egg Capsules: Just after fertilisation, the zygote gets surrounded by yolk in the ootype received from the vitelline glands through the vitelline duct. The zygote and the yolk then become enclosed in a thin shell or chorionic membrane which is formed from the yolk material. The structure, thus,

formed, is called capsule which passes into the uterus. The secretion of Mehils’s gland facilitates the passage of capsule in the uterus. However, the gravid proglottid gets separated from the strobila and passes out with the faeces of the host.

Fig. T. solium, A—Zygote; B to E—Stages Illustrating the formation of onchospheres Development of Taenia: It starts when the eggs enter the uterus. The zygote first divides unequally to give rise a larger megamere and a smaller embryonic cell. The megamere divides a number of times to give rise several similar megameres. Similarly, the embryonic cell divides repeatedly to give rise two types of cells, larger mesomeres and smaller micromeres. Hence, from zygote, three types of cells are resulted. These are larger megameres, medium-sized mesomeres and smaller micromeres which are arranged in a characteristic sequence. In fact, the smaller micromeres form an inner ball of cell mass called morula; the mesomeres are placed as an envelope around the morula, while the megameres as an outer envelope around the mesomeres. The megameres fuse to form the outer embryonic membrane which finally disappears; the mesomeres form the inner embryonic membrane or embryophore which is thick, hard, cuticularised and striated. Below the embryophore, a thin basement membrane is also formed. The inner cell mass of morula forms an embryo which develops six chitinous hooks at its posterior side. The hooks are secreted by some differentiated

cells of morula called onchoblasts. This sixhooked embryo is called hexacanth which possesses a pair of penetration glands and is surrounded by two hexacanth membranes. The hexacanth embryo, hexacanth membranes, basement membrane, embryophore and the egg shell or chorionic membrane together is known as onchosphere. The gravid proglottids which pass out from the host body contain embryos in onchosphere stage. Transmission to Secondary Host: The gravid proglottids or sometimes when they disintegrate, the onchospheres are eaten up by the pigs with human faeces due to their coprophagous habit. After reaching in the stomach of a pig, the capsule shell and other membranes around the hexacanths are dissolved resulting into the liberation of hexacanths. Sometimes dogs, camels and monkeys may also become infected by these onchospheres. However, the hexacanth now starts boring through the intestinal wall with the help of a pair of unicellular penetration glands found in it between the hooks. The hooks do not play any role in boring the interstinal tissue but they help in anchoring it.

9

T. solium. Stages in the life cycle. A–Young onchosphere; B–Mature onchosphere; C–Free hexacanth; D–Bladderworm with invagination; E–Bladderworm with proscolex; F–Bladderworm with evaginated scolex and G–Cysticercus with neck budding off proglottids. Thus, the hexacanth enters the blood vessels of the intestine and passes through the heart and finally comes to lie in the striated muscles in any part of the body. But they usually settle in the muscles of the tongue, neck, heart and shoulder. After reaching in the muscles, they lose their hooks, increase in size and acquire a fluid filled central cavity then they become encysted in a cuticular covering to become cysticerci or bladderworms. The cysticercus of Taenia solium is called cysticercus cellulosae. The flesh of pig or pork containing these cysticerci appears white spotted resembling something like that of measles, hence, it is characteristically called measly pork. Thus, the pig becomes infected.

(1241) Zoology PP 2021—2

Cysticercus or Bladder-Worm: It is the larval stage of Taenia solium which has been formed by the transformation or modification of hexacanth stage. It is a bladder-like sac filled with a clear watery fluid having mostly blood plasma of the host. The wall of the bladder consists of an outer cuticle and inner mesenchyme. A thickening arises gradually on one side of the bladder which marks the anterior end of the larva. The thickened area invaginates as a hollow knob. The invaginated knob develops suckers on its inner surface and hooks are developed at its bottom. Now, this inverted knob is called proscolex which bears suckers, hooks and rostellum. In fact, the embryo at this stage is called cysticercus or bladderworm whose further development does not take place unless it reaches to the main host, the man. Transmission to Primary Host: When man, the main or primary host ingests raw or improperly cooked pork containing cysticerci or measly pork, the cysticerci become active in the intestine. Actually, their bladder is digested in the stomach of the host and the proscolex gets evaginated or turned inside out, so that the suckers and rostellum come to lie on the outer surface as in the adult. Thus, a scolex and a small neck is formed. The scolex anchors itself to the mucous membrane of the intestine and the neck proliferates a series of proglottids to form the strobila. It takes nearly ten to twelve weeks to a proscolex to be converted into an adult Taenia and the adult Taenia, thus, formed, starts producing gravid proglottids with onchospheres within eight to ten weeks. The life history of Taenia solium is not so complicated because it does not involve any asexual generation. However, the complete life history of Taenia solium may be represented with the help of the following flow-chart: Adult tapeworm in human gut  Fertilised eggs in mature proglottids  Egg capsules in gravid proglottids  Onchospheres in

10 gravid proglottids  Gravid proglottids or onchospheres in human faeces  Out from the human body with faeces  Onchosphere in the gut of pig due to coprophagy  Hexacanths in the gut  Hexacanth in the intestinal blood vessels  Hexacanth in the heart  Hexacanth in the muscles  Cysticercus in the striped muscles Measly pork  Cysticercus in the gut of human beings  Adult tapeworm in human gut.

Fig. Taenia solium. Diagrammatic life cycle Effect of Parasite on the Host: The infection of Taenia Solium causes a disease called taeniasis in human beings. The taeniasis is characterised by abdominal discomforts like pain, indigestion, vomiting, constipation, loss of appetite, diarrhoea and nervous disorder like nervousness, insomnia, nausea and epileptic fits, etc. Its infection may cause eosinophilia up to 13 per cent and obstruction in the passage of alimentary canal. Taeniasis is comparatively lesser dangerous than cysticercosis caused by the infection of bladder worm or cysticercus larva. Sometimes, it has been seen that if somehow man ingests onchospheres with contaminated food and drink or due to antiperistaltic movements of the intestine, then bladder worm enters through the intestinal circulation in different parts of the body. After reaching in the vital organs like liver, eyes and brain, the cysticerci get

encysted and cause serious even fatal diseases. Encystment in eyes may cause blindness and in brain develops epilepsy. Parasitic Adaptations of Taenia Solium: The tapeworm exhibits a number of adaptive features to live comfortably in the intestine of the human beings. Some of these include the following:  It has well developed four suckers and hooks to anchor with the intestinal wall of the host, which prevents it from being pushed out with food due to peristaltic movements of the intestine.  Its body is covered externally by tegument which protects it form hosts’ digestive juice.  Loss of alimentary canal is compensated by freely permeable tegument for water and nutrients from the digested food of the host intestine.  The power of anaerobic respiration enables it to live in an environment of intestinal contents which is oxygen-free.  The long-flattened body provides larger surface area for its saprozoic mode of nutrition.  The sense organs are altogether absent due to its sheltered habit.  Huge power of reproduction makes it able to ensure for the transference of at least a few embryos to pig and of larvae from pig to man, to maintain the continuity of the race.  A tapeworm can survive for more than thirty years and every year it sheds nearly 2500 gravid proglottids containing nearly 30,000-40,000 onchospheres in each of them.  The simplicity of its life cycle lowers the chances of hazards it has to face in transfer from man to pig and pig to man. The pigs being coprophagous in habit automatically approach the human faeces containing onchospheres and ingest them to become infective. Man, also feeds on pork and, hence, by ingesting measly pork it becomes infected.

11 a) Comparative Account of the Aortic Arches in Vertebrates Aortic arches are paired blood vessels that emerge from the ventricle of the heart. These are basically similar in number and disposition in different vertebrates during the embryonic stages. But in adult the condition of the arrangement is changed either being lost or modified considerably. The number of aortic arches is gradually reduced as the scale of evolution of vertebrates is ascended. Embryonic aortic arches: During the embryonic stages.  Six pairs of aortic arches develop in most gnathostomes and are named according to the name of the visceral clefts.  The first aortic arch named Mandibular, proceeds upwards on either side of the pharynx.  Mandibular aortic arch turns backwards as lateral aortae which both join mesially to form the common dorsal aorta.  The second aortic arch becomes hyoid arch.  The third, fourth, fifth & sixth are called branchial arches. Modification of aortic arches in different vertebrates:  The number of aortic arches is different in different adult vertebrates but they built on the same fundamental plan in embryonic life.  The differences in number of aortic arches are due to the complexity of heart circulation in the mode of living from aquaticto terrestrial respiration.  There is a progressive reduction of aortic arches in the vertebrate series during evolution. Aortic arches in primitive vertebrates: Branchiostoma (amphioxus) has about 60 pairs of aortic arches, but Petromyzon has only 7 pairs and Myxine has 6 pairs of aortic arches.

Cyclsotomes: In lampreys (Petromyzon) there are eight pairs of aortic arches and in hag fishes (Bdellostoma) there are fifteen pairs. The aortic arch is divided into afferent branchial artery and efferent branchial artery. In lampreys each aortic arch divides and sends branches to the posterior hemibranch and anterior hemibranch of the adjacent gill pouch. In hagfishes each arch supplies to the hemibranch of a single gill-pouch.

Fig. Schematic lateral view of the anterior part of the arterial arches of Petromyzon (after Jollie, 1962).

Fig. Schematic view of the anterior arterial arches of Eptatretus (after Jollie, 1962).

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