Samacheer Class 11 Bio Zoology - Organ and Organ Systems in Animals

• Earthworms are classified as epigeics, anecics and endogeics based on their ecological strategies.
• Epigeics are the surface dwellers e.g., Perionyx excavaus and Eudrilus eugeniae.
• Anecics are found in the upper layers of the soil e.g., Lampiro mauritii, Lumbricus terrestris.
• Endogeics are found in deeper layers of the soil e.g., Octochaetona thursoni.

The body wall of the earthworm is very moist, thin, soft, skinny, elastic and consists of the cuticle, epidermis, muscles and coelomic epithelium. The epidermis consists of supporting cells, gland cells, basal cells and sensory cells.

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A spacious body cavity called the coelom is seen between the alimentary canal and the body wall. The coelom contains the coelomic fluid and serves as a hydrostatic skeleton, in which the coelomocytes are known to play a major role in regeneration. immunity and wound healing. The coelomic fluid of the earthworm is milky and alkaline, which consists of granulocytes or cicocytes. amoebocytes, mucocytes and leucocytes.

In gardens, earthworms can be traced by their fecal deposits known as worm castings on the soil surface. The earthworms can be identified using the following characteristics:
* Long and cylindrical narrow body.
* Bilateral symmetry
* It is light brown in colour with purple tinge at the anterior end.
* The division of body into many segments or metameres.
* The dorsal surface of the body is marked by a dark mid-dorsal line.
* In mature worms, segments 14-17 may be found swollen with a glandular thickening of the skin called the clitellum.

Digestion of food takes place by the action of hydrochloric acid and gastric juices secreted from the walls of the stomach. This partially digested food is called as chyme.

In earthworms, respiration takes place through the body wall by the moist skin diffusion, oxygen diffuses through the skin into the blood while carbon dioxide from the blood diffuses out.

Cockroaches destroy food and contaminate it with their offensive odour. They are carriers of a number of bacterial diseases. The cockroach allergen can cause asthma in sensitive people.

• The photoreceptors of the cockroach consist of a pair of compound eye on the dorsal surface of the head.
• Each eye is formed of about 2000 simple eyes called the ommatidia.

Male frog has a pair of vocal sacs and a nuptial pad on the ventral side of the first digit of each forelimb. Vocal sacs assist in amplifying the croaking sound of frog. It makes a characteristic sound and attracts the female.

Frog respires on land and in the water by two different methods. In water, skin acts as aquatic respiratory organ (cutaneous respiration). Dissolved oxygen in the water gets exchanged through the skin by diffusion. On land, the buccal cavity, skin and lungs act as the respiratory organs. In buccal respiration on land, the mouth remains permanently closed while the nostrils remain open.
The floor of the buccal cavity is alternately raised and lowered, so air is drawn into and expelled out of the buccal cavity repeatedly through the open nostrils. Respiration by lungs is called pulmonary respiration. The lungs are a pair of elongated, pink coloured sac-like structures present in the upper part of the trunk region (thorax). Air enters through the nostrils into the buccal cavity and then to the lungs. During aestivation and hibernation, gaseous exchange takes place through skin.

• The dorsal wall of the intestine of earthworm is folded into the cavity as the typhiosole.
• This fold contains blood vessels and increases the absorptive area of the intestine.

Peristomium
Prostomium
1. The mouth is present in the centre of the first segment of the body called peristomium
Overhanging the mouth is a small flap called the upperlip or prostomium.

In mature earthworms, 14 – 17th segments are swollen with a glandular thickening of the skin called the clitellum. Permathecal openings are three pairs of small ventrolateral apertures lying intersegmental between the grooves of the segment 6 / 7, 7 / 8 and 8 / 9.

In mature worms 14 – 17 segments may be found swollen with a glandular thickening of the skin called the clitellum. This helps in the formation of cocoon.

The mouthparts of the cockroach are directed downwards. The head is small, triangular lies at a right angle to the longitudinal body axis. Hence it is called hypognathous.

• The two sex organs of earthworm mature at different times and hence self fertilisation are prevented.
• The sperm develops earlier than the production of ova. This process is known as protandrous.
• It transmits the diseases like cholera, dysentery, and tuberculosis hence it is known as vectors.

The head of the cockroach bears a pair of large sessile and reniform compound eyes. Each eye is formed of about 2000 simple eyes called the ommatidia and the vision caused by the ommatidia is mosaic vision.

Cockroach has two pairs of wing. The first pair of wings protects the hind wings when the rest is called elytra or tegmina. The second pair of wings used in flight.

There are 10 segments in the abdomen. The sclerites of the dorsal side are called tergites.
The sclerites on the ventral side are called sternites and the sclerites on the lateral sides are called pleurites.

In the respiratory system of cockroach there are spiracles and trachea. Each spiracles can open and close. During inspiration spiracles open. This oxygen enters into the haemocoel through spiracles and exchange of gases taking place.

A cockroach can live for a week without its head. There is no connection between head and respiration. There are no nostrils and lungs.
The abdomen has 10 pairs of spiracles. These spiracles are communicated with the tracheoles and hemolymph and exchange of gases taking place.

The unit of the compound eye is ommatidium. There are hundreds of ommatidia. Each ommatidium forms an image. Each image formed in all the ommatidia forms a vision. This image is a mosaic vision.

Compound eye
Simple eye
1. Formed of hundreds of small units
Single eye
2. Each ommatidium contains lens cornea retina and optic nerve
Only one lens cornea retina and optic nerve
3. Each ommatidium forms a separate image and forms an unclear mosaic vision
A single image informed. The image is clear

• The heart of birds and mammals have four chambers. The oxygenated and deoxygenated blood is carried by separate blood vessels and transports to body parts and the purifying organ.
• The frog has a three-chambered heart. The oxygenated and deoxygenated blood mixes here. This mixed blood is reaching all the parts.

• In the elasmobranhs amphibians, reptiles egg laying mammals the faeces and urine pass through this opening.
• This passage is also a genital passage for the deposition of sperm. This is called cloacal aperature.

• Earthworm have setae which are small hair like bristles. They are not composed of the same material as human hair.
• They will be helpful in feeding mating and locomotion.

In 26th segment of metaphire posthuma a pair of cone shaped bulging is seen. It is known as intestinal caecum. This secretes amylolytic enzymes. This helps in starch digestion.
( 3 marks)
III. Short Questions

Ecological strata
Earthworm type
1. Epigeics – up on the earth
Perionyx excavatus
2. Anecics – out of the earth
Lampito mauritii
3. Endogeics – with in the earth
Octohaetona thurstoni

• Micro chaetus rappi is an African giant earthworm can reach a length of 6.7 meter (22 feet)
• Drawida nilamburansis is a species of earthworm in Kerala reaches a maximum length upto 1 meter (3 feet).

• Photo receptors – Found on the dorsal surface of the body.
• Gustatory – Sense of taste are found in the buccal cavity.
• Tactile receptors Sense of touch
• Chemo receptors Seen in the prostomium and the bodywall.
• Thermo receptors

This statement is correct.
Reason:
* A cockroach can live for a week without its head.
* Due to their open circulatory system they breath through little holes on each of their body segment hence they are not dependent on the mouth or head to breath.

• Brain or supra oesophageal ganglion or brain.
• It acts as a sensory and an endocrine centre.
• Sub – oesophageal ganglion
• It acts as a motor centre controls the movements of the mouthparts legs and wings.

• The photoreceptors of the cockroach consist of a pair of compound eyes at the dorsal surface of the head.
• Each eye is formed of about 2000 simple eyes called ommatidia.

• During breeding the sexual dimorphism is seen clearly.
• The male frog has a pair of vocal sac and a; nuptial pad on the ventral side of the first digit i of each fore limb.
• Vocal sacs assist in amplifying the croaking sound of frog.

• Epigeics – Surface living (Eg.) Eudrilus eugeniae
• Anecics-Found in upper layers of the soil. (Eg.) Lampito mauritii.
• Endogeics – Found in deeper layers of the soil. (Eg.) Octochaetona thurstoni.

• Earthworm has no special respiratory organ like lungs or gills.
• Respiration takes place through the body wall.
• The outer surface of the skin is richly supplied with blood capillaries which helps in the diffusion of gases.
• Oxygen diffuses through the skin into the blood.
• Carbondi-oxide from the blood diffuses out.
• The skin is kept moist by mucous and coelomic j fluid and facilitates exchange of gases.

• The brain composed of bilobed mass of supra-pharyngeal ganglia. On the third segment j supra-pharyngeal nerve ganglion and on the 4th segment sub-pharyngeal nerve ganglion is seen.
• The brain and the sub-pharyngeal ganglia are connected by a pair of cirum-pharyngeal connectives.
• The double ventral nerve cord runs backward from the sub-pharyngeal ganglion.

The nephridia is the excretory organ of the earthworm
They are three types.
* Pharyngeal or tufted nephridia seen in 5-9 segments
* Micro nephridia or Integumentary nephridia seen 14 – 19th -segment.
* Mega nephridia or septal nephridia seen from 19th – last segment.

• Vermi wash is a liquid manure or plant tonic obtained from an earthworm.
• It is used as a foliar spray and helps to induce plant growth.
• It is a collection of excretory products, mucus secretion micronutrients from the soil organic molecules.

An earthworm can be used for recycling of waste food leaf litter and biomass to prepare a good fertilizer in container is known as wormery or worm bin. It makes superior compost.

Receptors
Organs
1. Thigmo receptor
Antenna, maxillary paips and anal cerci
2. Olfactory
Antennae
3. Gustatory
Maxillary paips labium
4. Thermo receptors
Tarsal segments on the legs.
5. Chordotonal which responds to air or earth borne vibrations
Anal cerci

• The entire body is covered by a hard chitinous exoskeleton.
• In each segment exoskeleton has hardened plates called sclerites which are joined together by a delicate and elastic articular membrane.
• The sclerites of the dorsal side are called tergites. Ventral side are called sternites lateral side are called pleurites.

* The appendages from the mouthparts are of biting and chewing type.
* These are mandibulate or orthopterus.
Mouthparts
* Labrum – Upper lip
* A pair of mandibles
* Pair of maxillae.
* Labium-Lower lip
* Tongue – Hypopharynx.

• The wide mouth opens into the buccal cavity.
• On the floor of the buccal cavity lies a large muscular sticky tongue.
• The tongue is attached in front and free behind.
• The free edge of the tongue is forked.
• A row of small and maxillary teeth is found on the inner region of the upper jaw.
• Vomerine teeth are present one on each side of the internal nosteils.

60% of frog’s blood is plasma and 40% is red blood cells. The blood cells composed of red blood cells, white blood cells and platelets.
White blood cells
* Neutrophil
* Basophil
* Eosinophils
* Lymphocytes
* Monocytes
(5 marks)
IV. Essay Questions

• Earthworm has along and cylindrical body.
• It is 80-210 mm in length. It is light brown in colour.
• The body is encircled by a large number of grooves which divides it into a number of compartments called segments ormetameres.
• The mouth is found in the centre of the first segment of the body called the peristomium.
• Overhanging the mouth is a small flab called prostomium.
• The 14 – 17th segments become swollen called clitellum.
• There are pair of female genital opening in the 14th segment and pair of male genital opening in the 18th segment.
• In the segments 6/7, 7/8, 8/9 lies the spermatheca.
• In all the segments of the body except the first last and clitellum there is ring of chitinous body setae. They all involved in locomotion.
• The last segments bear anus.

1. The alimentary canal runs as a straight tube throughout the length of the body from the mouth to anus.
2. The mouth opens into the buccal cavity which occupies the 1st and 2nd segments.
3. The thick muscular pharynx lies in the 3rd and 4th segments and is surrounded by the pharyngeal glands.
4. A small narrow oesophagus lies in the 5th segment and the 6th segment contains muscular gizzards. Which helps in grinding the soil and decaying leaves.
5. The intestine starts from the 7th segment and ’ continues upto the last segment.
6. The dorsal wall of the intestine is folded into the vascular cavity called typhlosole.

* In earthworm closed type of blood vascular system is seen which contains blood vessels, capillaries and lateral hearts.
* Two median longitudinal vessels run above and below the alimentary canal as dorsal and ventral vessels of the earthworm.
* There are paired valves in the dorsal vessels which prevent the backward flow of the blood.
* From 6 to 13 segments with the 8 pairs of commissural vessels which connects the dorsal and the ventral vessel called lateral hearts.
* The blood is pumped from the dorsal vessel to the ventral vessel.
The blood glands present in the anterior segments of the earthworm produce blood cells and haemoglobin and gives red colour to the blood.

The earthworm is a hermaphrodite organism the male and female reproductive organs are found in the same individual.
Male reproductive system:
* Two pairs of testes are present in the 10th and 11th segments. The testes give rise to the germ cellor spermatogonia.
* Two pairs of seminal funnels called ciliary rosettes are situated in the same segments as the testes. Three pairs of spermathecalies in the 7,8,9 segments.
* The vas deferens arise from the ciliary rosettes run upto the 18th segment and open exterior through the male genital aperture which contains two pairs of penial setae.
* A pair of prostate glands lie in the 18th and 19th segments.
* The secretion of the prostate cement the spermatozoa into a bundle of spermatophores.
Female reproductive system:
* A pair of ovaries lying in the 13th segment. Ovarian funnels are present beneath the ovaries continue as an oviduct and opens in the 14th segment as a female genital opening.
* There are three pairs of spermathecae lie in the 7th, 8th and 9th segment.
* They receive spermatozoa during copulation.
* The two earthworms mate juxtaposition opposite gonadal openings and exchanging sperms mature egg cells in the nutritive fluid are deposited in the cocoons produced by the glands cells of the citellum which also collects the partner’s sperm from the spermathecae.
* Fertilization and developments occurs in the cocoon.
* After 3 weeks baby earthworm are released.

• The earthworm normally crawls with the help of their body muscles setae and buccal chamber. The outer circular and inner longitudinal muscle layers lies below the epidermis of the body wall.
• The contraction of circular muscles make the body long and narrow while the longitudinal muscles make the body short and broad and hence due to the contraction of longitudinal muscle the earthworm moves.
• The alternate waves of extensions and contractions are aided by the leverage afforded by the buccal chamber and setae.

• A cockroach is a bilaterally symmetrical segmented animal which is divisible into head thorax and abdomen.
• The entire body is covered with a chitinous exoskeleton.
• Each segment consists of sclerites. The head is small and triangular and the mouthparts are directed downwards hence known as hypognathous. The head bears a pair of compound eye. Each compound eye is composed of unit of ommatidia.
• The mouthparts are of mandibulate type. It consists of labrum pair of mandibles a pair of maxillae labium and a tongue.
• The thorax consists of prothorax mesothorax and metathorax. Each thoracic segment bears a pair of walking legs.
• Due to the presence of 3 pairs of leg, they are called Hexapoda. Each leg consists of five segments they are coxa, trochanter femur tibia, and tarsus.
• It has two pairs of wings. It is called tegmina or elytra. The wings arise from the mesothorax protect the hind wings when at rest. The second pair of wings arise from metathorax and used inflight.

The alimentary canal is divided into three regions namely foregut midgut and hindgut.
Foregut:
* It includes pre-oral cavity mouth pharynx oesophagus and the posterior region contains crop.
* The food is stored in the crop. The crop is followed by gizzard which have chitinous teeth helps in the grinding of the food particles.
Midgut:
* At the junctional region of the gizzard are eight finger like tubular blind processes called the hepatic caecae or enteric caecae.
* At the junction of midgut and hind gut lies 100 – 150 yellow coloured malphigian tubules. It excretes the nitrogenous wastes from the haemolymph.
Hindgut:
* The hind gut is broader than the midgut.
* It consists of ileum colon andrectum. The rectum opens out through anus.
* Digestive glands
* Salivary glands
* Hepatic caeca

Cockroach has an open type of circulatory system.
The coelom is filled with haemolymph. Heart is an elongated tube with muscular wall lying mid dorsally beneath the thorax.
The heart consists of 13 chambers with ostia on either side.
The blood from the sinuses enter the heart through the ostia and is pumped anteriorilly to sinuses again. In each segment there is triangular muscle called alary muscles are seen. It is responsible for blood circulation.
There is a pulsatile vesicle lies at the base of each antenna also pumps blood.

• The malphighian tubules are the main excretory organs of cockroach which help in eliminating the nitrogenous wastes from the body in the form of uric acid. Excretion is uricotelic.
• In addition fat body, nephrocytes cuticle and urecose glands are also excretory in function. The malpighian tubules are attached at the junction of midgut and hindgut. There are about 100-150 in number present in 6 – 9 bundles.
• Each tubule is lined by glandular and ciliated cells and the waste is excreted out through the hindgut.
• The glandular cells of malpighian tubules absorb water salts and nitrogenous wastes. The cells of the tubules reabsorb water and inorganic salts.
• By the contraction of the tubules nitrogenous waste is pushed in to the ileum. The remaining waste with solid uric acid is exceeded along with the faecal matter.

• The male reproductive system consists of a pair of testes vasa deferentia an ejaculatory duct utricular gland phallic gland and the external genitalia.
• A pair of 3 lobed testes lies on the 4th and 6th abdominal segments. The vas deferens opens into the male gonopore which lies ventral to anus.
• The mushroom-shaped gland is a large reproductive gland which opens into the anterior part of the ejaculatory duet.
• The sperms are stored in the seminal vesicles as bundles of spermatophores. Surrounding the male genital opening are few chitinous structures called phallometric or gonopophyses which help in copulation.

• The female reproductive system consists of a pair of ovaries vagina genital pouch collaterial glands speromthecae and the external genitalia.
• A pair of ovaries lie in the segmetn of 2nd and 6th abdominal segment. Each ovary is formed of eight ovarian tubules. Oviducts of each ovary unite into a common oviduct known as vagina which opens into the genital chamber.
• A pair of spermathecae is present in the 6th segment and opens in to the genital pouch.
• During copulation the ova descend to the genital chamber and fertilised by the sperm. The collateral gland secreta a hard case called ootheeca around the egg.
• The ootheca is dropped to a crack or crevice of high relative humidity near a food source. The nymphs are released from this ootheca and they grows by moulting about 13 times to reach the adult form.

The body of frog is streamlined to help in swimming. Body is divided into head and trunk.
Head:
* The head is triangular and has an apex which forms the snout.
* The mouth is at the anterior end on the head contains pair of external nostrils, pair of eyes with unmovable upper eyelid movable lower eye lid which protects the eye.
* The nictitating membrane protects the eye when the frog is underwater.
* A pair of ear drum lies behind the eyes. There is no external ear neck and tail.
Trunk:
* It bears a pair of fore limbs and a pair of hind limbs. The hind limbs are longer than the forelimbs. At the posterior end between the hind limbs is the cloacal aperture.
* Forelimbs help to bear the weight of the body. It consists of upper arm forearm and a hand. The hind limbs consist of thigh shank and foot.
* Foot bears five long webbed toes and one small spot called the sixth toe cloacal aperture.
* Forelimbs help to bear the weight of the body. It consists of upper arm forearm anda hand.
* The hind limbs consist of thigh shank and foot. Foot bears five long webbed toes and one small spot called the sixth toe.

In hymenopteran insects such as honeybees, ants and wasps, a mechanism of sex determination called haplodiploidy mechanism of sex determination is common. In this system, the sex of the offspring is determined by the number of sets of chromosomes it receives. Fertilized eggs develop into females (Queen or Worker) and unfertilized eggs develop into males (drones) by parthenogenesis. It means that the males have half the number of chromosomes (haploid) and the females have double the number (diploid), hence the name haplodiplody for this system of sex determination.
This mode of sex determination facilitates the evolution of sociality in which only one diploid female becomes a queen and lays the eggs for the colony. All other females which are diploid having developed from fertilized eggs help to raise the queen’s eggs and so contribute to the queen’s reproductive success and indirectly to their own, a phenomenon known as Kin Selection. The queen constructs their social environment by releasing a hormone that suppresses fertility of the workers.

• The heart consists of three-chamber. Two auricle and one ventricle. Heart is covered by pericardium. On the dorsal side of the heart is a triangular chamber called sinus venosus.
• Truncus arteriosus is a thick-walled structure which is obliquely placed on the ventral surface of the heart.
• It divides into right and left aortic trunk. Each divides into carotid systemic and pulmocutaneous arteries.
• The systemic trunk of each side is joined posteriorly to form the dorsal aorta. They supply blood to the posterior part of the body. The pulmo-cutaneous trunk supplies blood to lungs and skin.
• The sinus venosus receives the deoxygenated blood from the pre and post venacava and delivers the blood to the right auricle.
• The left auricle receives oxygenated blood through the pulmonary vein.

Eugenics refers to the study of the possibility of improving the qualities of the human population.
Methods of Eugenics:
* Sex education in school and public forums.
* Promoting the uses of contraception.
* Compulsory sterilization for mentally retarded and criminals.
* Egg donation.
* Artificial insemination by donors.
* Prenatal diagnosis of genetic disorders and performing MTP
* Gene therapy
* Cloning
* Egg/sperm donation of healthy individuals.

• The nervous system is divided into the central nervous system, peripheral nervous system and the autonomous nervous system.
• Peripheral nervous system consists of 10 pairs of cranial nerves and 10 pairs of spinal nerves. The autonomous nervous system is divided into sympathetic and parasympathetic nervous system.
• CNS consists of brain and spinal cord. Brain is covered with pia mater and dura mater. The brain is divided into the forebrain mid-brain and hindbrain.
• Forebrain Consists of a pair of olfactory lobes and cerebral hemisphere and diencephalon. The olfactory lobes contain a small cavity called the olfactory ventricle.
• The midbrain includes two large optic lobes and has cavities called optic ventricles.
• Hindbrain consists of the cerebellum and medulla oblongata. The medulla oblongata passes out through the foramen magnum and continues as spinal cord.

• The earthworm normally crawl with the help of their body muscles setae and buccal chamber.
• The outer circular and inner longitudinal muscle layers lies below the epidermis of the body wall.
• The contraction of circular muscles make the body long and narrow while the longitudinal muscle make the body short and broad and hence due to the contraction of longitudinal muscle the earthworm moves.
• The alternate waves of extensions and contractions are aided by the leverage afforded by the buccal chamber and setae.

Characters
Lampito mauritii
Metaphor Posthuma
1. Shape and size
Cylindrical
80 mm – 210 mm in length 3.5mm – 5.0 mm in width
Cylindrical
115 – 130 mm in length 5 mm in width
2. Colouration
Light Brown
Dark Brown
3. Segmentation
165-190 Segments
About 140 Segments
4. Clitellum
14th – 17th Segments (4)
14th – 16th Segments (3)
5. Intestinal caeca
Absent
Present in 26th segment
6. Male genital pore
18th segment
18th segment
7. Female genital pore
14th segment
14th segment

Characters
Lampito mauritii
Metaphire posthuma
1. Sperma thecal opening
Three pairs 6/7, 7/8 and 8/9
Four pairs 5/6, 6/7, 7/8 and 8/9
2. Pharynx
3rd – 4th segment
Runs up to 4th Segment
3. Oesophagus
5th segment
8th segment
4. Gizzard
6th segment
8th – 9th segment
5. Intestine
7th segment to anus
15th segment to anus
6. Lateral hearts
8 pairs from 6 th to 13 th segments
3 pairs from 7 th to 9 th segments
7. Pharyngeal nephridia
5th _ 9th segment
4th – 6th segment
8. Micronephridia
14th to last segment
7th to last segment
9. Meganephridia
19th to last segment
15th to last segment

Characters
Male cockroach
Female cockroach
1. Abdomen
Long and narrow
Short and broad
2. Segments
In the abdomen, nine segments are visible
In the abdomen, seven segments are visible
3. Anal styles
Present
Absent
4. Terga
7th ter gum covers 8 th tergum
7th ter gum covers 8 th and 9th terga
5. Brood pouch
Absent
Present
6. Antenna
Longer in length
Shorter in length
7. Wings
Extends beyond the tip of abdomen
Extends up to the end of abdomen
23. Draw the life cycle of lampito mauritii.

Characters
Frog
Toad
1. Family
Ranidae
Buforudae
2. Body shape
Slender
Bulkier
3. Legs
Longer
Shorter
4. Webbed feet
present
Absent
5. Skin
Smooth and moist skin
Dry skin covered with wart-like glands
6. Teeth
Maxillary and vomerine teeth.
Teeth absent
7. Egg formation
Lays eggs in clusters
Lays eggs in strings