SAMACHEER CLASS 10 UNIT 13 NOTES

 

UNIT 13

    SAMACHEER SCIENCE
CLASS 10

BIOLOGY

STRUCTURAL ORGANISATION OF ANIMALS

 

INTRODUCTION

·        Kingdom Animalia – 2 groups

·        Invertebrates

·        Vertebrates

·        Structural morphology & anatomy of an Invertebrate (Leech) & a Vertebrate (Rabbit)

 

LEECH

·        Hirudinaria granulosa

·        Phylum – Annelida

·        Annelids – metamerically segmented worms

·        Well developed organ system 

 

RABBIT

·        Oryctolagus cuniculus

·        Phylum – Chordata

·        Class – Mammalia

·        Mammals – highest group in animal kingdom – shows advancements over other group

·        Warm blooded

·        Body covered by hair

·        Females – mammary gland – important feature

 

THE INDIAN CATTLE LEECH (Hirudinaria granulosa)

HABIT & HABITAT

·        Found in – India, Bangladesh, Pakistan, Myanmmar & Srilanka

·        Lives in – Fresh water ponds, lakes, swamps & slow streams

·        They are Ectoparasitic – lives on or in the skin but not within the body

·        Feed on blood of fishes, frogs, cattle & human

·        Sanguivorous in nature – Blood sucking

 

EXTERNAL MORPHOLOGY

SHAPE & SIZE

·        Body – soft, vermiform, elongated & segmented

·        Ribbon shaped – extended; Cylindrical – contracted

·        Grow to a length of 35cm

COLOURATION

·        Dorsal surface – Olive green

·        Ventral surface – Orange yellow

SEGMENTATION

·        Segmentation – metamerism (linear series of body segment)

·        Body – metamerically divided into 33 segments

·        Segments – arranged one behind the other

·        Each segment – further superficially subdivided into rings or annuli

·        Temporary Clitellum – segments 9 to 11 – to produce cocoon during breeding season

RECEPTORS

·        Dorsal side – 5 pairs of eyes – on first 5 segments

·        Each segment – bears number of sensory projections – receptors

·        Annular receptors – located in each annulus

·        Segmental receptors – located on the first annulus of each segment

SUCKERS

·        Have 2 suckers

·        Sucker at anterior end – anterior sucker or oral sucker – ventral in position – occupy 1^st five segments

·        Posterior sucker – formed by – fusion of last 7 segments

·        Anterior sucker – helps in feeding

·        Both suckers – helps in attachment & locomotion

 

EXTERNAL APERTURES

·        MOUTH – located in the middle of anterior sucker

·        ANUS – a small aperture – opens on mid-dorsal of 26^th segment

·        NEPHRIDIOPORES – Nephridia – open to exterior – by 17 pairs of Nephridiopores – lie ventrically on the last annulus of each segment – 6 to 22

·        MALE GENITAL PORE – mid-ventral opening – between 2^nd & 3^rd annuli of 10^th segment

·        FEMALE GENITAL PORE – mid-ventrally – between 2^nd & 3^rd annuli of 11^th segment

 

DIVISIONS OF THE BODY

BODY WALL

·        Body wall – 5 layers

·        Cuticle – Outermost layer

·        Epidermis – lies below cuticle

·        Dermis – lies below epidermis – formed of connective tissue

·        Muscular layer – formed of circular & longitudinal muscles

·        Botryoidal tissue – lies below longitudinal muscles – fills entire coelom around the gut

 

LOCOMOTION

·        Locomotion takes place by

·        Looping or crawling movement

·        Swimming movement

LOOPING/ CRAWLING MOVEMENT

·        By contraction & relaxation of muscles

·        2 suckers – for attachment – during movement on substratum

SWIMMING MOVEMENT

·        Swim actively

·        Perform undulating movements

 

DIGESTIVE SYSTEM

·        Includes long alimentary canal & digestive glands

ALIMENTARY CANAL

·        Straight tube – mouth to anus

·        Mouth – triradiate aperture – middle of anterior sucker – leads into small buccal cavity

·        Wall of buccal cavity – 3 jaws – single row of minute teeth

·        Jaws – have papillae – bear openings of salivary glands

·        Mouth & buccal cavity – occupy first 5 segments

·        Buccal cavity – leads into muscular pharynx

·        Surrounded by salivary glands

·        Saliva – contains hirudin – prevents coagulation of blood

·        Pharynx – leads to crop – through short & narrow oesophagus

·        Crop – largest portion of alimentary canal

·        Divided into – series of 10 chambers

·        Chambers – communicate with one another – through circular apertures – surrounded by sphincters

·        Each chamber – pair of lateral, backwardly directed caecae arises – as blind outgrowth – Caeca or Diverticula

·        Crop & diverticula – store large amount of blood – which can be slowly digested

·        Last chamber of crop – opens into stomach

·        Stomach – leads into intestine – small straight tube – opens into rectum

·        Rectum – opens to the exterior – by Anus

 

FOOD FEEDING & DIGESTION

·        Leech – feeds by sucking blood – cattle &n domestic animals

·        While feeding – attaches to victim strongly – by posterior sucker

·        Leech – triradiate or Y shaped incision – in skin of host – by jaws – protruded through mouth

·        Blood sucked – by muscular pharynx – salivary secretion poured in

·        Ingested blood – stored in crop & diverticulum

·        Blood passes – from crop into stomach

·        Digestion – takes place in stomach – by action of proteolytic enzyme

·        Digested blood – absorbed slowly by the intestine

·        Undigested food – stored in rectum – egested through anus

·        Leeches prevent blood clotting – secretes protein – hirudin

·        They inject an anaesthetic substance – prevent host from feeling their bite

 

DIGESTIVE SYSTEM

 

MORE TO KNOW

·        Leeches – no ear – sense vibrations through their skin

·        Have 2 to 10 tiny eyes – helps to locate food

·        Suck blood – 5 times more than their body weight

·        May take more than a year – for complete digestion & absorption of a full meal

 

SEGMENTATION OF LEECH

 

RESPIRATORY SYSTEM

·        Respiration – through skin

·        Dense network of capillaries (tiny blood vessels) – containing haemocoelic fluid – extends between epidermal cells

·        Exchange of gases – through diffusion

·        O₂ dissolved in water – diffuses through skin – into haemocoelic fluid – CO₂ diffuses out

·        Skin – kept moist & slimy – by mucus secretion – prevents from drying 

 

CIRCULATORY SYSTEM

·        In Leech – circulation – through haemocoelic system

·        No true blood vessels

·        Blood vessels – replaced by channels – haemocoelic channels or canals – filled with blood like fluid

·        Coelomic fluid – contains haemoglobin

·        There are 4 longitudinal channels

·        1 lies above alimentary canal (dorsal)

·        1 below alimentary canal (ventral)

·        Other 2 – lie on either side of alimentary canal (lateral) – serve as heart & have inner valves

·        All 4 channels – connected together – posteriorly – in 26^th segment 

 

NERVOUS SYSTEM

·        CNS of Leech – consists of

·        A Nerve ring

·        a paired ventral nerve cord

·        Nerve ring – surrounds pharynx – formed of

·        Suprapharyngeal ganglion (Brain)

·        Circumpharyngeal connective &

·        Subpharyngeal ganglion

·        Subpharyngeal ganglion – lies below pharynx – formed by – fusion of 4 pairs of ganglia

 

EXCRETORY SYSTEM

·        Excretion – through Nephridia – 17 pairs

·        Segmentally arranged – 6^th to 22^nd segments

·        Nephridia – opens out by Nephridiopores

 

REPRODUCTIVE SYSTEM

·        Leech – Hermaphrodite – both male & female reproductive organs – present in same animal

 

MALE REPRODUCTIVE SYSTEM

·        11 pairs of testes – arranged segmentally – 12 to 22 segments

·        Form spherical sacs – called Testes sacs

·        From Testes – arise a short duct – Vas efferens – joins with Vas deferens

·        Vas deferens – becomes convoluted – to form Epididymis or Sperm vesicle – stores spermatozoa

·        Epididymis – leads to – short duct – ejaculatory duct

·        Ejaculatory ducts on both sides – join to form – genital atrium

·        Atrium – 2 regions

·        Coiled Prostate gland

·        Penial sac – consisting Penis – opens through the male genital pore

 

FEMALE REPRODUCTIVE SYSTEM

·        Consists of – Ovaries, Oviducts & Vagina

·        Single pair of Ovary – 11^th segment – ventral side

·        Ovary – ribbon-shaped structure

·        Ova – budded off from ovary

·        From each ovary – a short oviduct arises

·        Oviducts – from both sides – joins together – form common oviduct

·        Common Oviduct – opens into Vagina – pear-shaped – lies mid-ventrally – in the posterior part of 11^th segment

 

DEVELOPMENT

·        Internal Fertilization

·        Followed by – Cocoon formation

·        Cocoon / egg case – formed around 9^th , 10^th & 11^th  segments

·        Development – direct

·        Takes place in cocoon

·        Cocoon – has 1 to 24 embryos

·        Young leech – resembling adults emerges

 

MORE TO KNOW – MEDICINAL VALUE OF LEECH

·        Leeches – effective – increasing blood circulation & breaking blood clots

·        Used to treat Cardiovascular diseases

·        Leech saliva – biochemical substances – used for preparation of drugs – treat hypertension (High BP)

 

PARASITIC ADAPTATIONS OF LEECH

·        Leech – parasitic mode of life – by sucking blood of vertebrates – shows several important adaptations in their structure

·        Blood – sucked by pharynx

·        Anterior & posterior suckers – helps them to attach to the host

·        3 jaws – inside mouth – causes painless Y shaped wound – in the host’s skin

·        Salivary gland – hirudin – does not allow blood clot – maintains continuous flow of blood

·        Parapodia & Setae – completely absent

·        Blood – stored in Crop – gives nourishment for several months – therefore no secretion of digestive juices & enzymes

 

RABBIT (Oryctolagus cuniculus)

HABIT & HABITAT

·        Rabbits – gentle & timid animals

·        Leaping movements; Live in burrows

·        Distributed throughout the world

·        Herbivorous – feeds on – grass & vegetables – turnips, carrots & lettuce

·        Rabbits – gregarious animals (moving in groups)

 

EXTERNAL MORPHOLOGY

SHAPE, SIZE & COLOURATION

·        Elongated & cylindrical body

·        Males & females – same size

·        Adults – 45 cm in length; 2.25 kg in weight

·        Colour – varies – white to black & white

·        Body – covered with fur – keeps it warm

BODY – DIVISION

·        Body – divisible into – Head, Neck, trunk & tail

HEAD

·        Head – ovoid, flattened & bears a truncate snout

·        Contains – mouth, external nares, eyes, ears & vibrissae

·        Mouth – transverse slit-like – bounded by upper lip & lower lip

·        Above mouth – 2 oblique openings – Nostrils

·        From each side of the upper lip – tactile hairs or Vibrissae (Whiskers) – projects outwards

·        A pair of large, movable external ear / pinnae – on top of the head

NECK

·        Connects head & trunk

·        Helps to turn the head

TRUNK

·        Divisible into

·        Anterior thorax

·        Posterior abdomen

·        Females – between ventral side of thorax & abdomen – 4 or 5 teats or nipples are present

·        Bears – 2 pairs of pentadactyl limbs

·        Forelimbs – shorter than hindlimbs

·        All the digits – have claws

·        Anus – present at – posterior end of the abdomen – base of the tail

·        Females – ventral side – slit like – vulva present

·        Males – ventral side of anus – penis present

·        Males – pair of testes – enclosed by – Scrotal sacs

TAIL

·        Tail – short

·        Give signals to other rabbits – during danger

 

INTEGUMENT (SKIN)

·        Forms outer covering of the body

·        Structures derived from it – hairs, claws, nails & glands (sweat, sebaceous & mammary glands)

·        Mammary glands – modified glands of the skin – secrete milk – nourishes young ones

·        Sweat glands & sebaceous glands – embedded in the skin – regulates body temperature

 

COELOM (BODY CAVITY)

·        Rabbit – Coelomate animal

·        Body – divided into – thoracic cavity & abdominal cavity – separated by diaphragm (transverse partition)

·        Diaphragm – characteristic feature of mammals

·        Breathing movements – brought by – movement of diaphragm

·        Lungs & heart – thoracic cavity

·        Digestive & Urinogenital system – abdominal cavity

 

DIGESTIVE SYSTEM

·        Includes – alimentary canal & associated digestive glands

·        Alimentary canal – consists of – Mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, caecum, large intestine & anus

·        Mouth – transverse slit – bounded by upper & lower lips

·        Mouth – leads to buccal cavity

·        Floor of buccal cavity – muscular tongu

·        Jaws – bears teeth

·        Buccal cavity – leads to – Oesophagus – through pharynx

·        Oesophagus – opens into stomach – followed by small intestine

·        Caecum – thin walled sac – present at the junction of small intestine & large intestine

·        Caecum – contains bacteria – helps in digestion of cellulose

·        Small intestine – opens into large intestine – has colon & rectum

·        Rectum – opens outside – by anus

DIGESTIVE SYSTEM

 

DIGESTIVE GLANDS

·        Digestive glands – salivary glands, gastric glands, liver, pancreas & intestinal glands

·        Digestive gland secretions – helps digestion of food – in alimentary canal

 

DENTITION IN RABBIT

·        Teeth – hard bone-like structure – used to – cut, tear & grind – food materials

·        2 sets of teeth – existence of 2 sets of teeth in the life of an animal – called Diphyodont dentition

·        2 types of teeth – milk teeth (young ones) & permanent teeth (Adults)

·        Rabbit – different types of teeth – Hence, dentition – called heterodont

·        4 kinds of teeth in mammals – viz., Incisors (I), Canines (C), Premolars (PM) & Molars (M)

·        Expressed – in Dental formula

·        Dental formula – simple method of representing the teeth of a mammal

·        Number of each kind of tooth – in upper & lower jaw – on one side is counted

·        Dental formula –

·        Rabbit – Dental formula 

·        Canines absent

·        Gap between Incisors & premolar – called diastema

·        Diastema – helps in mastication & chewing of food – in herbivorous animals

 

RESPIRATORY SYSTEM

·        Respiration – takes place by – pair of lungs – light spongy tissues – in thoracic cavity

·        Thoracic cavity – bound dorsally by – Vertebral column; ventrally – sternum; laterally – ribs

·        Lower side of thoracic cavity – diaphragm – dome shaped

·        Each lung – double membrane – pleura

·        Atmospheric air à External nostril à Nasal passage  Pharynx  glottis  wind pipe

·        Anterior part of wind pipe – enlarged – form larynx / voice box – its wall supported by 4 cartilagenous plates

·        Inside larynx – vocal cord – its vibrations – produces sound

·        Larynx – leads to Trachea / Wind pipe

·        Tracheal walls – supported by – rings of cartilage – helps in free passage of air

·        Epiglottis – prevents entry of food – into trachea through glottis

·        Trachea – divides into 2 branches – Bronchi – enters lungs – divides into further branches – Bronchioles – end in alveoli

·        Respiratory events – Inspiration (breathing in) & Expiration (breathing out) – allows exchange of gases (O₂ & CO₂)

·        Inspiration – active process; Expiration – passive process

 

RESPIRATORY SYSTEM

 

CIRCULATORY SYSTEM

·        Circulatory system – formed by – blood, blood vessels & heart

·        Heart – pear shaped – lies in thoracic cavity – between lungs

·        Heart – enclosed by Pericardium (double layered membrane)

·        Heart – 4 chambers – 2 auricles; 2 ventricles

·        Right & left auricles – separated by – Interauricular septum

·        Right & left ventricles – separated by – Interventricular septum

·        Right auricle à opens into – right ventricle – by right auriculoventricular aperture – guarded by tricuspid valve

·        Left auricle à opens into – left ventricle – by left auriculoventricular aperture – guarded by bicuspid valve / mitral valve

·        Opening of pulmonary artery & aorta – guarded by 3 semilunar valves

·        Right auricle – receives deoxygenated blood – through 2 precaval (superior Vena cava) & post caval (inferior venacava) veins – from all parts of the body

·        Left auricle – receives oxygenated blood – from pulmonary veins – from lungs

·        From right ventricle – pulmonary trunk arises – carries deoxygenated blood – to lungs

·        From Left ventricle – Aorta (systematic arch) arises – supplies oxygenated blood – to all parts of the body

CIRCULATORY SYSTEM

 

NERVOUS SYSTEM

·        Nervous system – formed of

·        CNS – Central Nervous System

·        PNS – Peripheral Nervous System

·        ANS – Autonomic Nervous System

·        CNS – Brain & Spinal cord

·        PNS – 12 pairs of cranial nerves & 37 pairs of spinal nerves

·        ANS – Sympathetic & Parasympathetic nerves

·        Brain – in cranial cavity – covered by 3 membranes

·        Outer Duramater

·        Inner Piamater &

·        Middle Arachnoid membrane

·        Brain – divided into

·        Forebrain (Prosencephalon)

·        Midbrain (Mesencephalon) &

·        Hindbrain (Rhombencephalon)

·        Forebrain – pair of olfactory lobes, cerebral hemispheres & diencephalon

·        Right & left Cerebral hemisphere – connected – Corpus callosum (transverse band of nerve tissue)

·        Mid brain – optic lobes

·        Hind brain – Cerebellum, Pons Varolii & Medulla Oblongata

 

URINOGENITAL SYSTEM

·        Comprises – Urinary / Excretory system & genital / reproductive system – hence described as Urinogenital system – in Vertebrates

 

EXCRETORY SYSTEM

·        Kidney – made of several Nephrons

·        Nephrons – separates nitrogenous wastes – from blood – excretes as urea

·        Kidneys – dark red, bean shaped – in abdominal cavity

·        From each kidney – arises ureters – opens posteriorly into urinary bladder – leads into urethra (muscular duct)

REPRODUCTIVE SYSTEM

·        Sexual dimorphism – seen in Rabbits – male & female sexes – separate & morphologically different

 

MALE REPRODUCTIVE SYSTEM

·        Male Reproductive system – consists of – pair of testes – ovoid shape

·        Testes – enclosed by scrotal sacs – in abdominal cavity

·        Testes – has many fine tubules – seminiferous tubules – this tubule network – lead into – epididymis (coiled tubule) – lead into Vas deferens (Sperm duct) – joins in Urethra (below urinary bladder) – runs backwards – passes into Penis

·        3 accessory glands – prostrate gland, cowper’s gland & perineal gland – secretions involved in – Reproduction

FEMALE REPRODUCTIVE SYSTEM

·        Consists of – pair of ovaries – small ovoid – behind the kidneys – in abdominal cavity

·        Oviduct arises from each ovary – through a funnel shaped opening

·        Anterior part of oviduct – fallopian tube – leads to wider tube – called Uterus – joins together – form median tube – Vagina

·        Common tube formed – union of urinary bladder & vagina – urinogenital canal or vestibule – runs backwards – opens out by slit like aperture – Vulva

·        Accessory glands – pair of cowper’s gland & perineal gland – present