Category: Essays

Important external features of fasciola hepatica are given below: 1. Shape and Size: Fasciola is a dorso-ventrally flattened, soft, leaf like oval shaped endoparasite. It is about 1.8 to 3.0 cm long, with a maximum width of 0.4 to 1.5 cm. which is a little in front of the middle region of body. Anterior end is somewhat broad and rounded, while posterior end is bluntly pointed. Image Source: biologiklaten.files.wordpress.com ADVERTISEMENTS: 2. Colour of the body: Transparent body wall makes all the body organs to be visible. Due to this, the colour of the fluke appears pinkish. 3. Oral cone: ADVERTISEMENTS: Anterior end of body is drawn out into a prominent conical projection, termed the oral cone or head lobe. At the apex of cone, a triangular mouth is found. 4.…

Male and female reproductive system of fasciola hepatica Fasciola is monoecious and hermaphrodite. Gonads are well developed and open into a common chamber, genital atrium. It opens outside through gonopore. 1. Male Reproductive System ADVERTISEMENTS: (a) Testes: A pair of testes, tandemly arranged lie in the middle and posterior part of the body. Epithelium lining of testes gives rise to sperms. Image Source: studydroid.com (b) Vasa deferentia and seminal vesicles: ADVERTISEMENTS: Testes lead into sperm duct or vasa deferens. The two vasa diferentia run side-by-side anteriorly upto the level of acetabulum. Here they unite to form a large seminal vesicle for storage of sperms. (c) Cirrus sac: Anteriorly from seminal vesicle, arises a narrow and somewhat twisted, tube, the ejaculatory duct, which extends forward and enters a stout muscular and…

Alimentary canal:Ascaris has a straight alimentary canal from mouth to anus, consisting of mouth, pharynx, intestine and rectum. Image Source: siera104.com ADVERTISEMENTS: Important parts consist in the digestive system of ascaris1. Mouth:It is a triradiate aperture, guarded by three lips.2. Pharynx: ADVERTISEMENTS: This is short, cylindrical, thick walled and muscular pharynx. The wall of pharynx consists of a syncytial epithelium traversed by radial muscles and containing glands.Mouth and pharynx are lined internally by cuticle and ectoderm derived from embryonic stomodeum, and represents the foregut.The lumen of pharynx is triradiate, each ray is a deep groove divide the pharynx into three sectors- dorsal and two subventral.All the three sectors contain branched pharyngeal glands. Radial fibers of pharynx wall help in its expansion and marginal fibers help in preserving the triradiate form…

Important parts in the water vascular system or ambulacral system of asterias are listed below: (1) Madreporite: ADVERTISEMENTS: It is a thick sieve like calcareous plate situated on the aboral surface of the central disc. It bears as many as 250 minute pores on the surface and they lead into pore canals. All pore canals unite to form collecting canals within the substance of madreporite. Below the madreporite, collecting canal communicates with stone canal through ampulla. Image Source: 1.bp.blogspot.com (2) Stone canal: It is S-shaped tube, which opens on the oral side into a ring canal around the mouth. It is also known as madreporite canal. Its walls are supported by a series of calcareous rings, hence the name stone canal. Inner lining of the wall bears cilia or flagella,…

External features of palaemon or prawn of phylum arthropoda Phylum Arthropoda is the largest phylum of the animal kingdom and crustacea is a large and important class of the phylum Arthropoda. It includes prawns, crabs, lobesters, shrimps, barnacles, water fleas and related forms. Image Source: 185.26.182.219 ADVERTISEMENTS: Habits and habitat : Palaemon or prawn, found in fresh water ponds, rivers and lakes. It is a nocturnal animal. It comes out at the water surface in the night in search of food. It is an omnivorous. It is an active swimmer and swims with the help of pleopods. It breeds from May to July. Shape and Size: ADVERTISEMENTS: Palaemon has elongated, spindle shaped, bilaterally symmetrical body. Different species have different sizes. P. malcomsonii (Macrobrachium malcomsonii) the giant prawn found in Tamilnadu,…

Shape size and colouration: The body is laterally compressed and somewhat oblong or rectangular in shape with the attached end slightly narrower than the free end. It measures about 9.5 cm long, 7.0 cm broad and 4.0 cm thick. The foot, when present, measures, 3.0 to 4.0 cm long. Fresh specimens are pinkish in colour. Image Source: cdn.shopify.com ADVERTISEMENTS: Division of Body: The body is covered by the test and is divisible into two parts, body proper and foot. (1) Body Proper: ADVERTISEMENTS: The distal free part of the animal is body proper. Two short cylindrical projections called the branchial and atrial siphons or funnels arise from the anterior and the dorsal end respectively. Both the siphons are situated at the same level. The branchial or oral siphon is smaller,…

Important parts of digestive system in herdmania are mentioned below: In Herdmania it is coiled and complete and contains the following parts. ADVERTISEMENTS: (1) Mouth: It forms the opening of branchial siphon marking the anterior end of the body. It is guarded by four lobes derived from the test. Image Source: wp4.cdn.brainsins.com (2) Buccal Cavity: Mouth leads into a laterally compressed cavity of branchial siphon, called buccal cavity or stomodaeum. ADVERTISEMENTS: A strong branchial sphincter present at the base of siphon which regulates the opening of mouth. A circlet of highly branched delicate branchial tentacles, richly supplied by nerves is also found at the base of siphon. These are 64 in number and of four different sizes like 8 large (5 mm) 8 medium (2.5 mm) 16 small (1.5 mm)…

Important types of circulatory system in herdmania are given below: The circulatory system is well developed and closed type. It includes (1) heart and pericardium (2) blood vessels and (3) Blood (1) Heart and Pericardium: ADVERTISEMENTS: It is a non contractile, elongated and transparent tube about 7.0 cm long and 3.0 mm wide running obliquely below the right gonad. It is closed at both the ends and is filled with a colourless pericardial fluid with corpuscles similar to those of blood. Its wall is thick, made of connective tissue and contains blood sinuses and is internally lined by squamous epithelium. Image Source: s3.amazonaws.com ADVERTISEMENTS: The heart is enclosed within the pericardium and is attached to its wall along its entire length by a thin mesentery like connective tissue flap. It…

The origin and ancestory of modern chordates is not very clear and remains obscure. Because their early ancestors most liably were soft bodied and left no definite fossils. The earliest known fossils of truly vertebrate animals were, freshwater forms abundant during the late Silurian and middle devonian periods. Their fossils are collectively known as ostracoderms. They are placed in the group of jawless animals called Agnatha. Image Source: 3.bp.blogspot.com ADVERTISEMENTS: The oldest fragmentary fossils belonging to ostracoderms occur in the late cambrian and middle ordovician. About the place of origin of chordates an American geologist Chamberlain gave the idea of fresh-water origin of chordates in 1900. This idea was supported by Romer and Homer Smith also. Theories of Invertebrate ancestory of chordates: ADVERTISEMENTS: The invertebrate ancestory of chordates is now…

Important body features of scoliodon are given below: 1. Mouth: It is situated a little behind the apex on the ventral side of the anterior region of the body. Mouth is bounded by upper and lower jaws each bearing 1 or 2 rows of sharply, pointed and backwardly directed teeth. Teeth are adapted for holding and tearing of the prey. Image Source: d.fastcompany.net ADVERTISEMENTS: 2. Nares: Two crescentic apertures, the nares or nostrils are present ventro-laterally and anterior to mouth. They are exclusively olfactory, have no role in respiration, as they are not connected to mouth cavity by internal nostrils. ADVERTISEMENTS: 3. External gill slits: Anterior to each pectoral fin, on either side of the body vertically elongated external gill slits or branchial clefts are present in a series of…