MORPHOLOGY

Morphology is the study of general appearance and structure of an organism or its parts. External Morphology deals with external features of an organism without dissecting it. Internal Morphology deals with internal structure of an organism seen after dissecting it. Animals are grouped as chordates and non - chordates. Earthworm & Cockroach are non - chordates. Frog and Rat are chordates. 1.1 EARTHWORM:-  Earthworms belong to phylum Annelida, Genus - Pheretima and species - Posthuma. There are about 500 sps. out of which 13 are found in India (a) Habitat:- These are found in moist soil, living in upper layer to a depth of about 30 - 45 cm In dry climate, they come out on the ground (b) Habit:- These are nocturnal, feed upon decaying organic matter in the soil, leave their faecal deposit as 'Warm Castings', dig their burrows and move by muscular contractions. (c) External morphology:-  Shape:- Cylinderical, elongated, pointed arteriorly and slightly rounded posteriorly. Size:- full grown worm is about 150 mm long and 3 - 5 mm wide Colour:- Reddish brown. Dorsal surface is darker than ventral surface and has a dark median line Segmentation:- Entire body has 100 - 120 segments / metameres Externally the segments are separated / divided by annuli & internally by Septa. Each annuli corresponds to a septa except the first four. This type of segmentation, which is both, external and internal is called 'Metameric Segmentation' or 'Metamerism'. Mouth:- It is present at the anterior end of first segment 'Peristomium'. A small fleshy 'Prostomium' hangs over mouth. Anus:- It is slit like opening in the last segment 'Anal segment' (Pygidium). Female genital pore:- It is a small opening on ventral side of 14th segment. Eggs pass out of this Male genital pores:- A pair of openings present on ventral side of 18th segment. Male reproductive fluid and sperms come out of this. Nephridiopores:- These are numerous, very fine openings of excretory organs, scattered irregularly over all the segments except the first two. Clitellum:- A band of glandular skin called 'clitellum' covers the segments 14, 15, 16. It secretes mucus and albumen which helps in fertilization. On the basis of clitellum, body of earthworm is divisible into preclitellar, clitellar and post - clitellar regions Setae:- In all the segments, except first, last and clitellum, there is a ring of s - shaped setae which are made of chitin. These help in holding the substratum and during copulation. (d) Internal Morphology:-  (1) The body wall comprises of cuticle, Epidermis Muscular layer and Peritoneum - Cuticle is thin, non - cellular membrane covering the entire body. - Epidermis is made of single layer of columar epithelial cells and contains other cells also like secretory gland cells - Muscle layer has circular & longitudinal muscle fibres - Peritoneum lines the body cavity and secretes coelomic fluid. It is also called 'Parietal Peritoneum'. (2) Digestive System:- It includes alimentary canal (tube like, runs from 1st to last segment), mouth (1st segment), buccal cavity (1 - 3rd segments), pharynx (4th segment), oesophagus (5 - 7th segment), gizzard (8 - 9th segment), Stomach (9 - 14th segment), intestine (15 - last segment) and anus (last segment). Gizzard grinds the food, stomach has calciferous glands which neutrilize humic acid. Dorsal wall of intestine has folds known as 'Typhlosole'. (3) Circulatory System:- It is closed type. Blood is red. Blood glands are present on 4th, 5th and 6th segments. Haemoglobin remains dissolved in blood plasma. (4) Nervous System:- Not very well developed. It is represented by ganglia (mass of nerve cells) arranged segment wise on ventral nerve cord. Nerve cord, in the region of 3rd & 4th segment bifureates to form Nerve ring. Nerve ring and central ganglia together form brain. (5) Excretory System:- Main excretory organs are Nephridia. These can be septal nephridia (present on both sides of septa & opening into intestine), integumentary nephridia (attached on body wall living and opening on body surface) or pharyngeal nephridia (found in 4, 5, 6 segments as three paired tufts) (6) Sense organs:- Poorly developed and represented by epidermal, buccal and photoreceptors. (7) Reproductive System:- Earthworm is hermaphrodite. There are 2 pairs of testes (in 10th & 11th segments) and one pair of ovary (present at septum of 12th & 13th segments). Duct of testes ie vas deferens runs upto 18th segment. 4 pairs of sac like structures - sepermathecae are found, one in each - 6, 7, 8 & 9th segments. These receive and store sperms during copulation Development is direct.  Interaction with Mankind:- (1) Earthworms make soil porous, enrich the soil and facilitate respiration and penetration of developing plant roots. So they are known as 'Friends of farmers'. The digested and decayed vegetation and fine soil is deposited by earthworm as 'worm castings'. The nitrogenous waste of the earthworm as added to soil. The process of increasing soil fertility by earthworm is called 'Vermicomposting'. (2) These are used to cure piles, Jaundice, diarrhoea, bladder stones etc. (3) Used as food (4) Used as fishing bait (5) Damage the land by making burrows & thus causing seepage and erosion. 1.2 COCKROACH:- (Periplaneta ammericana) It belongs to class - Insecta, phylum - Arthropoda, genus - Periplaneta and species - americana There are about 2600 sps in world (a) Habitat:- Found in warm and damp places like sewage, pipes, kitchens, restaurants, bakeries, warehouses. (b) Habit:- They are nocturnal & become active during night. These are cursorial ie run very fast. They feed on almost everything food, paper, leather, cloth, dead remains of other cockroaches (c) External Morphology:-  Shape:- elongated, dorso - ventrally flat and bilaterally symmetrical body. Size:- Males - 35 - 40mm long and about 10 - 12 mm wide females are slightly smaller Colour:- Reddish brown Exoskeleton:- It is formed of hard, brown chitinous plates called 'Sclerites'. Adjacent sclerites are joined by thin, flexible and soft 'Articular Membrane'. Body division:- body is segmented externally and divided into three parts - head, thorax & abdomen. (i) Head:- It is triangular and lies at right angle to long axis. It is formed by fusion of six segments. It can move due to flexible neck. It has mouth with appendages, sessile eyes, a pair of antenna. Mouthparts consists of mandibles and maxillae, labium (forms lower lip). Hypopharynx acts like tongue. (ii) Thorax:- It has 3 ssegments - prothorax, mesothorax and metathorax. Neck connects head with thorax. Sclerites are present on thorax. There are 3 pairs of walking legs (one pair on each segment) . Each leg has 5 segments-coxa, trochanter, femur, tibia and tarsus. First pair of wings (Tegmina) arise from mesothorax. Second pair of wings (Tegmina) arise from metathorax. Tegmina are dark & leathery and cover the hind wings. Hindwings are transparent and are used in flight. (iii) Abdomen: - Made up of 10 segments: In females, sclerite of 7th segment overlaps the sclerite of 8th & 9th segment. 7th sternum is boat-like and along with 8th & 9th sternum, it forms 'brood/genital pouch'. Inmales: -7th segment overlaps 8th. 10th segment has a pair of jointed filamentous structures-Cerci. 9th segment has anal styles which is absent in females. (d) Internal Morphology: - (i) The body wall has cuticle (made up of chitin), epidermis (made up of single layer of columnar cells) and basement membrane (made of flat cells). (ii) Body cavity is not lined by peritoneum and is filled with blood. So it is called 'Haemocoel'. (iii) Digestive system is well developed. Alementary canal has 3 regions-foregut, midgut & hindgut. Mouth opens into pharynx which leads into oesophagus. Oesophagus opens into crop which is followed by Gizzard (Proventriculus) . Gizzard grinds the hard food particles. Mouth to gizzard form foregut. Midgut is tube like. Hepatic caeca which secretes digestive juices is present at junction of foregut & midgut. 150 malphigian tubules are present at junction of midgut and hindgut. Hindgut opens out by anus. (iv) Respiration occurs by system of branching tubes the 'tracheae' which deliver oxygen directly to tissues. Tracheae open out by 10 pairs of spiracles (2 pairs lie in meso and metathorax, 8 pairs in abdomen). (v) Circulatory system is open. There are no blood vessels. Heart is tubular and 13-chambered. Blood is colourless and called Haemolymph. It contains irregular, colourless corpuscles called Haemocytes. (vi) Excretion is performed by Malphigian Tubules. Each tubule is lined by glandular, ciliated cells. They absorb nitrogenous waste product and convert it into uric acid which is excreted through hindgut. (vii) Nervous system consists of series of fused ganglia joined by paired longitudinal connectives on the ventral sides. 3 ganglia lie in thorax and 6 in abdomen. Brain is represented by supra-oesophageal ganglion. (viii) Sense organs are antenna, eyes, maxillary palps, labial palps and anal cirri etc. Antennae, palps and cirri are sensitive to touch. Compound eye consists of about 200 hexagonal ommatidia covered externally by transparent cornea. These receive several images of an object. This kind of vision is known as Mosaic Vision. (ix) Reproductive System: -Males have a pair of testes lying one of each lateral side in 4-5th segment. Vas deferens arises from testes and opens into ejaculating duct through seminal vesicle. An accessory reproductive gland is present in 6-7th abdominal segments. Male gonapophysis/phallomere is the external genitalia. Sperms are stored in seminal vesicle as bundles called Spermatophores. Female have 2 large ovaries lying in 4,5,6th segments. Each ovary has 8 ovarian tubules which contain chain of ova. Vagina opens into genital chamber. Interaction with mankind: - (1) Causes damage to household materials. (2) Destroy the foodstuffs. (3) Carries harmful germs of cholera, diarrhoea, T.B, typhoid. (4) Serves as food. (5) Used in experiments in laboratories. 1.3 FROG: -(Rana tigrina) Frog belongs to phylum-chordata, sub-phylum vertebrata class Amphibia. Genus-Rana and species-tigrina. The most common frog found in India is Indian bull frog. Scientific name of common toad is Bufo melanostictus. (a) Habitat: - Found in fresh water marshes, ditches, pounds and shallow lakes. Frog is called amphibious because it can live on land as well as in water. (b) Habit: -They rest in squatting posture, are carnivorous, poikilothermous (body temp. changes with environment), swim, leap, make croaking sound for mating, breed in rainy season, undergo hibernation in winter and aestivation in summer. (c) External Morphology: - Form: -Frog has ovoid, slightly flattened body, streamlined for swimming in water. Size: -Generally 18-20 cm long and 5-8 cms wide. Colour: -dorsal skin is olive green with dark irregular lines and spots. Ventral side is pale yellow. Body divisions: -Body is divided into head and trunk. Neck is absent. (i) Head: -It is triangular, has mouth, external naris for breathing, eyes with eyelids, nictitating membrane for protecting eyes, Brow spot (light coloured spot in the median lines between eyes.) (ii) Trunk: -It is flat and has a bulge called 'hump'. Trunk is divided into anterior small thorax and posterior large abdomen. Forelimbs and hindlimbs are present on the trunk. At the posterior end of trunk there is a small opening called 'Cloacal aperture' for eliminating faeces. (d) Internal Morphology: - (i) Skin: - It is olive green with pigments in it. (ii) Body cavity is True coelom. It is lined by parietal peritoneum externally and visceral peritoneum internally. (iii) Digestive system includes alimentary canal and digestive glands. Mouth opens into buccopharyngeal cavity which has many teeth. Eustachian tube, vocalsac and glottis open into buccopharyngeal cavity. Tongue is bilobed. Oesophagus is short. Stomach is tubular and is followed by small intestine (with folds called 'villi'). Intenstine continues into rectum which opens out by cloaca. `Digestive glands are Gastric glands (present in stomach, secrete intestinal juice), liver (secrets bile) and Pancreas (secretes pancreatic juice). (iv) Respiration is pulmonary (by lungs), cutaneous (through skin) and buccopharyngeal. (v) Circulatory system is closed and consists of Blood vascular system and Lymphatic system. Blood vascular system comprises of Heart, blood vessels and blood, hymphatic system consists of lymph, lymph channels and lymph nodes. Heart is 3-chamibered and comprises of sinus venosus, two auricles, single ventricle and truncus arteriosus. RBCs, WBCs and leucocyctes and seen in the blood. Red-coloured pigment Haemoglobin is also present. (vi) Nervous system has 3 divisions: Central Nervous system (brain & spinal cord), Peripheral nervous system (cranial & spinal nerves), Autonomic nervous system (sympathetic & parasympathetic system). There are 10 pairs of cranial nerves. Brain is enclosed in cranium. Brain is divided into Forebrain (olfactory lobes, cerebral hemispheres, diencephalon), Midbrain(pair of optic lobes) and Hind brain (includes cerebellum and Medulla oblongata). (vii) Excretion occurs by a pair of bean shaped, red coloured kidneys. Each kidney has several uriniferous tubules/nephrons. Frog exeretes urea. Ureters coming out from kidneys open into cloaca. (viii) Frog has 5 types of sense organs: - organs of Touch (sensory papillae), organs of Taste (Taste buds), organs of smell (nasal epitheluim), organs of vision (Eyes) and organs of Hearing (Tympanum and Internal ears). (ix) Sexes are separate. Males have vocal sacs and nuptial pads which help in mating. Males have a pair of testes attached to upper part of kidney by mesorchium. 10-12 vasa efferentia arise from testes and open into Bidder's canals present in the kidneys. Bidder's canals open into urinogenital duct which opens into cloaca and release sperms outside. Females have a pair of ovaries which have their oviducts opening into cloaca. 2500-3000 ova are produced at a time. Fertilization is external. Development is indirect and has larval stage-'Tadpole'. Interaction with mankind: - 1. Used as an experimental material for teaching & research. 2. Muscular legs of frog are used as food. 3. Small froglets are used as fish-bait. 4. It maintains ecological balance because it serves as food-link in ecosystem.  1.4 RAT: -(Rattus rattus) It belongs to phylum-chordata, sub-phylum-vertebrata super class-Gnathostomata and class-Mammalia. There are about 137 species of rat. (a) Habitat: -Almost everywhere. It is found in holes and burrows in fields, indoors, hills, plains, rivers etc. (b) Habit: -Rats are herbivorous, fossorial (live in burrows), nocturnal and undergo hibernation. (c) External Morphology: -  Shape: -Body is elongated and covered with hair, tapered head, neck, slender trunk and long tail. Size: -Adult rat is about 20 cms long. Colour: -Colour varies. Rats living in open have bright colour coat whereas those living indoors have dull coat. Body division: -Their body is divided into head, neck, Trunk and tail. (1) Head: - It has nares (for respiration), mouth, eyes (with cyclids & reduced nictitating membrane), teeth, ears and tactile hairs called 'Pili tactiles' or 'Vibrissae' on both sides of nostrils. (2) Neck : -It is short and connects head with trunk. (3) Trunk: -Trunk has 2 forelimbs and 2 hindlimbs, anus & sex organs. Each limb is made up of stylopoduim, Zeugopoduim and autopoduim. Walking pads are present in palm. Anus is outlet situated at the base of tail. In females, urinary & genital apertures are located beneath anus & open separately into vulva. In males , urinary & genital apertures open through urethra into penis. In females, six pairs of nipples are present on the ventral surface of trunk. (d) Internal Morphology: -  (i) Skin/Integument: - It has multilayered epidermis and a dermis. Outermost layer of epidermis is Stratum corneum & lowermost layer is Stratum germinativum. Dermis contains blood vessels, nerve fibres, receptors etc Glands like sweat glands, mammary glands are present in the skin. (ii) Body cavity is true coelom. (iii) Digestive system includes mouth which opens into buccal cavity. Food passes into pharynx. Oesophagus is short tube like and opens into sac-shaped. Stomach which leads into small intestine, S.Intestine has 3 parts-duodenum, jejunum & ileum. Ileum opens into caecum which opens into large intestine (colon). Colon leads into rectum which opens out through anus. There are 4 pair of salivary glands. Other glands are liver and pancreas. (iv) Circulatory system is closed. Heart has 2 auricles and 2 ventricles. There is double circulation i.e. Oxygenated & deoxygenated blood circulates separately. Blood has RBCs (6-7 lac/cubic micro litre), WBCs (6-10 thousands/cubic micro litre) & platelets. (v) Respiration is pulmonary. Lungs are spongy, lie in thoracic cavity and are lined by visceral pleura. Trachea is long. (vi) Nervous system comprises of central Nervous system (Brain + Spinal cord) and Peripheral Nervous system. There are 12 pairs of cranial nerve and 33 pairs of spinal nerve. Brain is inside cranium. Autonomic nervous system comprises of chains of sympathetic & parasympathetic ganglia. Brain has large cerebral hemispheres and cerebellum. (vii) Urinary system includes a pair of kidneys, ureters and a urinary bladder. Urine from kidneys passes through ureters and is stored in urinary bladder. Finally, it is carried out through urethra. In Males, urethra is common urino-genital passage. In females, urinary & genital tracts are separate. (viii) Sense organs are Cutaneous (found in skin like tangorcceptors for touch, thermoreceptors for temperature, vibroreceptors for vibrations etc), Olfactory (for smell, present in epithelium of nasal chambers, jacobsons organs), Gustatoreceptors (for taste, found in tongue), Photoreceptors (eyes). Eye has cornea, iris, pupil, lens, eyeball, retina. Single image is formed on retina. Ear has 3 parts-pinna, middle ear & internal ear. (ix) Male reproductive organs are pair of testes, epididymis, vasa deferens, urethra, penis & spermatic cord. Five glands-Ampullary, vesicular, prostate, preputial and cowper's are associated with male reproductive system. Sperms are produced in seminiferous tubules. Female reproductive organs are -pair of ovaries, fallopian tubes, uterus, vagina and clitoris. Three accessory glands - uterine, vestibular bartholins and preputial glands arer associated with reproductive system. Fertilization is internal, placenta is present and parental care is shown Interaction with mankind:- (i) Rat destroys fields by making burrows and tunnels (ii) They damage 20% crop every year (iii) They damage household goods also like books, clothes, food, vegetables etc. (iv) It is a carrier of flea which spreads plague (v) It is important component in food chain (vi) Used in teaching & research (vii) Used as an experimental animal to test drugs