BSc 1st Year Distinctions Question Answers Sample Practice Papers Sets
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1. Asconoid and Syconoid Canal System
The Asconoid canal system is the simplest. The body is vase-shaped with a thin body wall formed of an outer layer of pinacocytes (pinacoderm or dermal epithelium) and an inner layer of choanocytes (choanoderm). The spongocoel is lined with choanoderm also known as the gastral epithelium. The mesenchyme is thin and the body wall of the sponge is unfolded.
In syconoid canal system, the body wall is folded and produced into Ginger-like projections, called radial canals. The choanocytes underline the radial canals. The radial canals alternate with the incurrent canal and communicate through prosopyle.
2. Autogamy and Syngamy
Autogamy is a type of nuclear reorganization in Paramecium and other ciliates, where two micronuclei of the same individual fuse to form synakaryon, or the gametes produced inside a single cell are fused together to accomplish sexual reproduction.
Syngamy is the process of union of sex cells or gametes. The fusing gametes may be similar or dissimilar, and may come from the same parent or from different parents of the same species.
3. Bilateral and Radial Symmetry
Symmetry means the plan of arrangement of the body parts. In some animals, the arrangement is such that the organism is divisible into similar halves through one plane. This is called bilateral symmetry, e.g. higher non-chordates and chordates, but in some animals, it is possible to get two similar halves by any of the vertical planes passing through the centre, e.g. Hydra. This is radial symmetry.
4. Bladderworm and Roundworm
Bladderworm is the larval stage of Taenia which develops from hexacanth. A central cavity enlarges and becomes filled with a fluid consisting mainly of blood plasma of the host. The fluid-filled vesicle or bladder has a thin wall consisting of an outer layer of thick syncytial protoplasmic mass and an inner mesenchymal layer. At the anterior end, the wall thickens and invaginates.
The invagination differentiates into an inverted scolex possessing suckers, hooks and rostellum. The embryo at this stage is called the bladderworm. It develops into adult tapeworm only when ingested by the human host.
The roundworm or Ascaris is an endoparasite of man. Its body is cylindrical, tapering at both the ends, the anterior end being more slender than the posterior end. The cuticle bounding the body is non-ciliated and bears minute transverse striations all along the length. The female measures 20-40 cm in length and 4-6 mm in diameter, while the male is more slender and smaller. The posterior end of male is recurved ventrally.
5. Blastula and Amphiblastula
Blastula is a stage in the embryonic development of almost all the living beings except protozoans and sponges. It is seen in coelenterates for the first time. In coelenterates, it is a hollow ball of cells. The central space is known as blastocoel and the cells surrounding the blastocoel are called blastomeres. These are arranged in a single layer.
Amphiblastula is the larva of Sycon. Its anterior half is formed of flagellated micromeres and posterior half with large glandular macromeres. The flagella of micromeres are directed outward and help in swimming. The central space between the micro and macromeres is called blastocoel.
BSc Lower Non-chordates Distinctions Question Answers
6. Body Cavity and Coelom
Body cavity is the internal cavity in most triploblastic animals in which many body organs are suspended, allowing their mutual displacement. The body cavity is bounded externally by body wall. It may develop embryo logically in several ways, e.g. from coelom (earthworm and vertebrates), from blood system (Arthopoda) or as intercellular spaces (Nematodes).
The coelom is the main body cavity of many triploblastic animals in which organs are suspended. It is derived from mesoderm, and is lined by epithelium. It contains fluid which, unlike blood, is not circulated by muscular walls. Germ cells mature in its wall or in a specialized part of it (the gonads); and when they are ripe they are often shed into the coelom, and are then usually transported to exterior by coelomoducts. In many animals it plays an imported part in collecting excretory products which are removed from it by nephridia or coelomoducts.
The coelom is spacious in Echinodermata, Vertebrata, Polychaetes and Oligochaetes, where it forms the perivisceral cavity. In Arthropoda and Mollusca it forms only the cavity of gonads and excretory organs and not the penvisceral cavity, which is haemocoel.
7. Budding and Fission
Budding is an unequal division of the parent body in which one or more buds may separate from the parent and the nucleus of the bud is a part of the parent nucleus. Bud formation is common in Arcella, Ephelota, and Hydra.
Fission is a form of asexual reproduction in which the organism splits into two equal parts (binary fission) as in protozoans and Hydra and some corals. Multiple fission occurs in course of spore formation in Protozoa.
8. Canal System and Water Vascular System
Canal system is a system of radial and inter-radial canals found in the body wall of sponges. Through this system water circulates in the body of the sponge and provides food and oxygen to various cells of the sponge body. Water reaching the spongocoel comes out through the osculum.
Water vascular system is found in echinoderms and helps mainly in locomotion. It is a modified part of coelom consisting of a system of canals containing sea water and amoeboid corpuscles.
9. Cercaria and Cysticercus
Cercaria is one of the larval forms of flukes (Trematoda). These are produced asexually within redia larvae which are parasitic in snails. The cercariae are infective to a new host to which they gain access either in food (sheep liver-fluke) or by penetrating skin (Schistosoma). The new host may be definitive one in which cercariae become sexually mature flukes or in some species it may be second intermediate host, where they live for some time before being swallowed by definitive host and becoming sexually mature.
Cysticercus is the larval form of some tapeworms, consisting of scolex tacked into a large bladder. It occurs in intermediate host. It grows into mature tapeworm on being swallowed by definitive host.
10. Choanocytes and Amebocytes
Choanocytes and amoebocytes are found in sponges. Choanocytes are collared cells having oval body, contractile collar and a long flagellum. These line the radial canals or flagellated chambers and cause water current to flow inside the sponge’s body.
The amoebocytes are amoeboid cells present in the mesenchyme. These have pseudopodia and can wander freely in the mesenchyme. These carry out different functions and are named accordingly as archeocytes, myocytes, scleroblasts, etc.
BSc Lower Non-chordates Distinctions Question Answers
11. Choanocytes and Solenocytes
Choanocytes or collar cells line the flagellated chambers of sponges. These are rounded or ovoid cells. Each has a collar-like structure that surrounds the base of flagellum. The choanocytes help sponges in feeding, excretion and reproduction. The collective movement of flagella of choanocytes produces water current in the spongocoel.
Solenocytes are found in the nephridia of Amphioxus. Every solenocyte is a long tubular cell. Its basal part is swollen and contains a nucleus. The cavity of solenocyte encloses a long flagellum which shows a flickering movement.
Solenocytes hang in the body fluid and collect excretory material from it.
12. Coelom and Haemocoel
Coelom is the wide space between the gut and internal body wall. It is lined by coelmic epithelium of mesoderm externally by parietal layer of coelomic epithelium (parietal peritoneum) and internally by the visceral layer of coelmic epithelium (visceral peritoneum).
Haemocoel is the space around visceral organs which is filled with a blood-like fluid or haemolymph. It is found in arthropods and mouse
13. Cysticercus and Cysticercoid
Cysticercus is the bladderworm stage of Taenia in the voluntary muscles of secondary host. It has a fluid-filled bladder, a long neck and a scolex.
Cysticercoid is the laws of Hymenolepiana. It develops in the villi or host from the hexacanth larva. It is without a neck and bladder
14. Dactylozooid and Gastrozooid
Dactylozooid and gastrozooids are found in Hydrozoa. These are Individuals of a hydrozoan colony modified to carry different functions. Dactylozooids are protective in nature. These are for defence and for obtaining food. These are tubular zooids without mouth but with long tentacles armed with batteries of nematocysts.
Gastrozooids are nutritive zooids of the colony. These have mouth and carry out ingestion and digestion of food
15. Digenea and Monogenea
Both Digenea and Monogenea are orders of class Trematoda of phylum Platyhelminthes, Monogenea includes ectoderm and endoparasitic helminth worms found in vertebrates. These have only the posterior sucker which is present at the posterior end and is in the form of an adhesive disc. These are without oral sucker. Their anterior end has a pair of adhesive structures. These have a pair of excretory pores.
Digenea includes endoparasitic forms having two suckers-an anterior or oral sucker and a posterior sucker or acetabulum. The excretory pore is unpaired.
BSc Lower Non-chordates Distinctions Question Answers
16. Diploblastic and Triploblastic
In Diploblastic organisms the body is made up of two cellular layers only (ectoderm and endoderm). The coelenterates are diploblastic, and all other metazoa are triploblastic i.e, their body is made up of three layers (ectoderm, endoderm and mesoderm). In diploblastic animals, however, unlike triploblastic, no organs develop from the middle layer, but only from the ectoderm and endoderm.
17. Excretion and Secretion
Excretion is the process of getting rid of products of metabolism in animals it applies to products of protein metabolism, the organs mainly concerned being kidney of vertebrates, Malpighian tubules of insects, and probably nephridia in many other invertebrates
The secretion is the process of passage of material elaborated by a cell from inside to the outside of its plasma membrane. The secreted material has a special function in an organism. Secretion is probably an activity of most cells but is specialised in gland cells.
18. Exonephric and Enteronephric Nephridia
Exonephric and Enteronephric nephridia are found in annelids. The nephridia which open into the alimentary canal are called enteronephric nephridia while the nephridia which open to the outside directly are called exonephric nephridia.
19. Flame cells and Lasso cells
The flame cells are excretory in function. These are found in the individuals of phylum Platyhelminthes. A flame cell is hollow bulb-like structure. A bunch of cilia or flagella hang down into its lumen. The flagella move continuously like the flickering of a candle flame (flame cell).
The lasso cells are the endoblasts or nematoblasts or the stinging cells, found in phylum Coelenterata. A lasso cell contains a pyriform sac or bladder, and the nematocyst, a layer of cytoplasm and a large crescentic nucleus. The nematocyst is filled with a proteinous fluid, the hypotoxin. Hypotoxin is poisonous. The outer end of capsule (nematocyst) is vaginated into a long hollow filament.
It lies coiled in the cavity of nematocyst. Its swollen basal port is known as shaft or butt. The opening of nematocyst is covered by operculum. A restraining thread, called lasso is attached to the base of nematoblast (hence lasso cells). This prevents the nematocyst from being thrown out of the body.
The nematoblasts are organs of offence and defence. These also help in food capture, locomotion and anchorage.
20. Gonotheca and Hydrotheca
In Obelia colony and other Hydrozoans the colony has a tough chitinous protective covering called perisarc. The perisacral covering around the plastosyle or gonozooid is known as gonotheca and around polyp or hydranth is called hydrotheca.
BSc Lower Non-chordates Distinctions Question Answers
21. Holozoic and Holophytic Nutrition
Holozoic nutrition feeding in animal-like fashion i.e. eating other organisms. These require a supply of organic food material from its environment. All herbivores and carnivores are holozoic. These obtain food from other plants and animals.
Holophytic nutrition is plant like. These organisms (some animals and all greenplants) synthesise their food (i.e. carbohydrates) from carbon dioxide and water in presence of sunlight and with the help of chlorophyll.
22. Hydated cyst and Tentaculocyst
Hydated cyst is the infective stage of dog tapeworm Echinococcus granulosus. It encloses a watery bladder or hydated vesicle. It is surrounded by an ectocyst and endocyst. The bladder along with cyst is called hydated cyst. It is formed in the tissue of intermediate host in heart, lung, bone, brain, etc.
Tentaculocysts are sensory structures found in Aurelia and other scyphozoans. Each is a club-shaped structure situated between two marginal lappets. It is a specialised hollow-tentacle. Tentaculocysts control equilibrium of umbrella while swimming.
23. Intracellular Digestion and Extracellular Digestion
In unicellular organisms like Amoeba, the food is digested inside the food vacuole by the enzymes secreted by the cell. This is known as intracellular digestion.
In higher organisms there are special organs for the digestion of food. The food in these organisms passes through the alimentary canal. Here several digestive enzymes are secreted to break the complex food materials into similar substances. This takes place outside the cell and is called extracellular digestion.
24. Leucosolenia and Sycon
Leucosolenia is the most primitive calcareous sponge having asconoid type of canal system. Its colony consists of numerous white or yellowish white vertical tubes connected at the base by a horizontal stolon. Each tube represents one individual with a terminal osculum, is a central par gastric cavity and numerous ostia in its wall: Path of water current is:
Ostia – Spongocoel – Osculum
Sycon or Scypha possesses syconoid canal system. The colony is branched with several cylindrical or vase-like branches arising vertically from the stolon. Each vertical hollow cylinder represents one individual whose wall is thick and is permeated by incurrent and radial canal. The path of water current is
Ostia – Incurrent canals Radial canals or flagelleted chambers – excurrent canal – Paragastric cavity – osculum- exterior
25. Micronucleus and Macronucleus
Members of Ciliophora have two kinds of nuclei, one is the large macronucleus, which divides amitotically and is concerned with the ordinary protein synthesis of the organism. The outer smaller micronucleus divides meiotically and provides gametes during conjugation. The macronucleus appears during conjugation, and is reconstituted from the zygote nucleus. More than one micronucleus may occur in some organisms.
26. Miracidium and Cercaria
Miracidium is the first larval stage in the life cycle of liver-fluke which hatches out of the egg. It is ciliated and swims freely in the pond water to reach the secondary host-snail. It is roughly triangular with an apical papilla.
Cercaria is the last larval stage in the life-cycle of liver fluke which comes out of snail (the secondary host) and adheres to the leaf blades of aquatic plants. Here it changes into metacercaria to be picked up by the final host sheep. It has an oval body and a long tail. It has rudimentary organs of the adult and a distinct mouth, oral sucker and posterior sucker, etc.
27. Miracidium and Hexacanth
Miracidium is ciliated larva of fluke. It emerges from egg, which is released from vertebrate host in excreta, and parasitines a snail, in which it reproduces asexually. The hexacanth is the six-hooked embryo of tapeworm. It develops from egg. On getting into a suitable host, it grows into a cysticerous larva
28. Monogenetic and Digenetic life-cycle
Monogenetic life cycle is completed within one host. There is no intermediate host. Infection of primary host occurs through contaminated water or food or by other means.
In Digenetic life cycle two hosts are required. One host acts as primary or definitive host and the other one as intermediate or secondary host. The secondary host also acts as a vector and helps in transmission of parasite to new hosts.
29. Nematocyst and Trichocyst
Nematocysts are stinging cells found in the epidermis of Coelenterates. These help in paralysing and capturing the prey and act as organs of offence and defence.
Trichocysts are spindle-shaped bags embedded in the ectoplasm of Paramecium. These help in adhesion or act as organs of offence and defence.
30. Parazoa and Metazoa
Parazoa is a grade of organization exemplified only by Porifera. These are multicellular animals with poorly defined tissues and no organs. These are mostly irregular with a system of water canals and openings. Internal surface is lined with choanocytes. These are sessile, marine and a few fresh-water. They are solitary or colonial.
Metazoa is the subkingdom which comprises of multicellular animals. They have a complex structure with strongly marked cellular differentiation. The grade of organisation may be cellular, cell tissues, tissue organ or organ system. The physiological division is well marked and all reproduce sexually.
31. Pinacocytes and Choanocytes
Pinacocytes are thin polygonal scale-like cells which lie with their edges touching and thus form a continuous layer. These are endodermal in origin and form a protective covering over sponge body and line the incurrent canals and spongocoel.
The choanocytes are collared cells which line the radial canals. These are oval cells, each with a contractile collar and a long flagellum.
32. Proscolex and Scolex
During the development of cysticerous larva from bladder in Taenia, the invagination of bladderworm develops books and suckers and forms an inverted scolex. This inverted scolex called prescolex. The prescolex remains inside the bladder of cysticerous.
When prescolex evaginates, the suckers and hooks exposed to the exterior. This structure is now called scolex. It is present in the fully formed cysticerous or bladderworm and also in the adult cestodes.
33. Redia and Cercaria
Both redia and cercaria are larva in the life-cycle of liver fluke.
Redia larva develops parthenogenetically from the germ cells present in the sporocyst inside the muscles of snail. It has a pair of ventral processes near the posterior end, precrusculum, a birth pore and thick muscular collar.
Cercaria larva is free swimming larval stage with a long tail that helps in swimming. It has rudimentary organs of adult. It develops from germ cells of redia.
34. Sexual reproduction and Conjugation
Sexual reproduction is the reproduction involving fusion of haploid nuclei, usually free swimming gametes.
Conjugation is the temporary union of complete organisms so as to exchange nuclei. It is the process by which sexual reproduction is effected in most ciliates. In the simplest case two individuals partially fuse. Macronuclei disintegrate and micronuclei undergo changes, including meiosis, resulting in production of gametic nuclei. One gametic nucleus from each organism passes into the other organism and there fuses with the stationary gamete nucleus, so that a zygote results in each individual. The organisms then separate, the zygote nucleus undergoes further divisions and ultimately gives rise to a micronucleus and a macronucleus.
35. Spicule and Gemmule
Spicules are skeletal elements found in the body of sponges. These are formed of crystalline calcium carbonate which remains embedded in the mesenchyma.
Gemmules are also found in sponges. These develop in the form of a bud formed internally as a group of cells which may become free by the decay of parent and form a new individual. These also tide over the unfavourable conditions.
36. Spicules and Spongin fibres
Both spicules and spongin fibres constitute skeleton in sponges. The spicules are formed either of CaCO3 or of silica. These are of different shapes and sizes.
The spongin fibres are fibres of halogenated termed as spongin B. These fibres are horny being related to collagen protein and form a meshwork in the mesenchyme of sponge body. The spongin fibres are secreted by spongioblases.
37. Spongocoel and Coelenteron
The central space in sponge body is called spongocoel. In asconoid sponges it is lined with choanocytes while in all other sponges, it is lined with pinacocytes. It is not a digestive cavity, but serves for egress of water current.
The coelenteron or the gastrovascular cavity is the central space in the body of all coelenterates. It is lined with gastrodermis (or endoderm) and serves for gastric (digestive) cavity and also as a body cavity.
38. Spongocoel and Pseudocoel
Spongocoel is the cavity of sponge surrounded by body will consisting of two cellular layers, the pinacoderm and choanoderm with non-cellular mesenchyme in between.
Pseudocoel is the body cavity between the body wall and the visceral organs as found in Ascaris. The cavity is not the true coelom as (1) it is not lined by coelomic epithelium, (2) it has no relation with the reproductive and excretory organs, and (3) it develops from the blastocoel i.e. between mesoderm and endoderm of the embryo.
39. Sporocyst and Redia
Sporocyst is the second larval stage of Fasciola hepatica. It is formed from miracidium larva inside the digestive gland of secondary host snail. It in the form of an elongated sac. It contains protonephridia and germ cells. Its germ cells divide and form redia larva.
Redia is the third larval stage of Fasciola hepatica passed inside the digestive gland of secondary host. It develops inside the sporocyst and inside this develops next larval form, the cercaria. Redia is in the form of a cylindrical sac with mouth, pharynx and a small blind gut. It contains protonephridia and germ cells which give rise to either second generation of redia or the next larval form cercaria. There is a muscular collar slightly behind the pharynx and a pair of conical projections the procruscula near the posterior end.
40. Testicular and Pretesticular nephridia
In leech, nephridia are of two types-pretesticular and testicular nephridia.
Testicular nephridia are present in segments from 12th to 22nd in which testis sacs are also present. These are eleven pairs. The initial lobe of each testicular nephridium ends blindly over the testis sac of its side close to the perinephrostomial ampulla.
The pretesticular nephridia are present in segments from the 6th to 11th. These are six pairs. The initial lobe of pretesticular nephridium ends loosely in the general connective tissue.
41. Trichocyst and Tentacuolcyst
Trichocysts are rod-like or oval organelles present in the ectoplasm underneath the pellicle in Paramecium. These discharge and anchor the animal to a firm substratum.
Tentacuolcysts are sense organs found in Aurelia. These are club-shaped structures present between two marginal lappets. These control equilibrium of the umbrella during swimming.
BSc 1st Year Distinctions Question Answers Sample Practice Papers Sets