ORGAN SYSTEM
$\displaystyle \small \bullet$ Each organ in our body is made up of one or more type of tissues.
$\displaystyle \small \bullet$ Basic tissue types in the body organize into organs.
$\displaystyle \small \bullet$ Group of organs associate each other to form organ system.
$\displaystyle \small \bullet$ This helps in the better coordination of activities of millions of cells of an organism.
$\displaystyle \small \bullet$ Morphology refers to study of form or externally visible features.
$\displaystyle \small \bullet$ In case of animals this refers to the external appearance of the organs or parts of the body.
$\displaystyle \small \bullet$ Anatomy is the study of internal structure or morphology of internal organs in the animals.
EARTHWORM
Phylum—Annelida
Class— Oligocheata
Order – Terricolae
Genus— Pheretima
Species—posthuma
$\displaystyle \small \bullet$ Earthworm is a reddish brown terrestrial invertebrate that inhabits the upper layer of the moist soil.
$\displaystyle \small \bullet$ During day time, they live in burrows made by boring and swallowing the soil.
$\displaystyle \small \bullet$ The common Indian earthworms are Pheretima and Lumbricus.
External Morphology
$\displaystyle \small \bullet$ Earthworm has a long narrow, bilaterally symmetrical cylindrical body.
$\displaystyle \small \bullet$ Body is brown in colour due to pigment porphyrin.
$\displaystyle \small \bullet$ The body is segmented and has tapering at the anterior end.
$\displaystyle \small \bullet$ There is a dark median line on the dorsal surface, it represent the dorsal blood vessel. It has 100—120 segments.
$\displaystyle \small \bullet$ The ventral surface shows genital openings and papillae towards the anterior end.
$\displaystyle \small \bullet$ A prominent band of glandular tissue is called clitellum, surrounds 14-16 segments.
$\displaystyle \small \bullet$ Internal segments have septa, which is absent between 3-4 and 9-10.
$\displaystyle \small \bullet$ Body is metamerically segmented, external segments corresponds to internal segmentation.
$\displaystyle \small \bullet$ It has an anterior mouth with prostomium (pre oral segment). Prostomium is covered by crescent shaped structure called peristomium, which helps in burrowing of soil.
$\displaystyle \small \bullet$ Eyes and tentacles are absent.
$\displaystyle \small \bullet$ Locomotion is by setae. The setae are embedded in the epidermal pit at the middle of each segment.
$\displaystyle \small \bullet$ Body wall has outer circular and inner longitudinal muscle that helps in locomotion.
$\displaystyle \small \bullet$ Body keeps moist by mucus secretion.
$\displaystyle \small \bullet$ They are hermaphrodites having both male and female sex organs.
Anatomy
Body wall is externally covered by a thin non-cellular cuticle. Epidermis is present below the cuticle.
Two muscle layers are in the mesoderm, and innermost layer is coelomic epithelium.
Digestive System
$\displaystyle \small \bullet$ The alimentary canal is a straight tube and runs between first to last segment of the body.
$\displaystyle \small \bullet$ Prostomium is a preoral segment before the mouth of the worm.
$\displaystyle \small \bullet$ Mouth is present in the $\displaystyle \small 1^{st}$ segment (peristomium) and is terminal in position.
$\displaystyle \small \bullet$ A terminal mouth opens into the buccal cavity which leads into muscular pharynx (4-5 segments). Salivary glands are present in pharyngeal wall.
$\displaystyle \small \bullet$ A small narrow tube is the oesophagus (5-7 segments) that continues into a muscular gizzard (8-9segments). It helps in grinding the soil particles and decaying leaves, etc.
$\displaystyle \small \bullet$ The stomach extends from 9-14 segments. Calciferous glands present in the stomach, neutralise the humic acid present in humus.
$\displaystyle \small \bullet$ Intestine starts from the $\displaystyle \small 15^{th}$ segment and continues till the last segment.
$\displaystyle \small \bullet$ A pair of short and conical intestinal caecae project from the intestine on the $\displaystyle \small 26^{th}$ segment.
$\displaystyle \small \bullet$ The characteristic feature of the intestine between 26-35 segments is the presence of internal median fold of dorsal wall called typhlosole. This increases the effective area of absorption in the intestine.
$\displaystyle \small \bullet$ The alimentary canal opens to the exterior by a small rounded aperture called anus.
$\displaystyle \small \bullet$ The ingested organic rich soil passes through the digestive tract where digestive enzymes breakdown complex food into smaller absorbable units. These simpler molecules are absorbed through intestinal membranes.
Circulatory System
$\displaystyle \small \bullet$ Earthworm have a closed type of blood vascular system, consisting of blood vessels, capillaries and heart.
$\displaystyle \small \bullet$ The main blood vessels are dorsal blood vessel and ventral blood vessel. They are connected by five pairs of connecting tubes. They have branches in all segments.
$\displaystyle \small \bullet$ Contractions keep blood circulating in one direction.
$\displaystyle \small \bullet$ Smaller blood vessels supply blood to the gut, nerve cord and the body wall.
$\displaystyle \small \bullet$ Blood glands are present on the $\displaystyle \small 4^{th}$, $\displaystyle \small 5^{th}$ and $\displaystyle \small 6^{th}$ segments. They produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature.
Respiratory System
$\displaystyle \small \bullet$ Respiration occur through the general body surface.
$\displaystyle \small \bullet$ The cuticle is kept moist by a slimy mucous.
$\displaystyle \small \bullet$ Respiratory exchange occurs through moist body surface into their blood stream.
$\displaystyle \small \bullet$ Moist surface is necessary to take $\displaystyle \small O_{2}$ and give out $\displaystyle \small CO_{2}$.
Excretory System
$\displaystyle \small \bullet$ The excretory organs occur as segmentally arranged coiled tubules called nephridia.
$\displaystyle \small \bullet$ They are absent in first two segments and in last segment.
$\displaystyle \small \bullet$ They maintain water balance in body.
$\displaystyle \small \bullet$ Nephridia regulate the volume and composition of the body fluids.
$\displaystyle \small \bullet$ A nephridium starts out as a funnel that collects excess fluid from coelomic chamber.
$\displaystyle \small \bullet$ The funnel connects with a tubular part of the nephridium which delivers the wastes through a pore to the surface in the body wall into the digestive tube.
$\displaystyle \small \bullet$ Types of Nephridia
i) Septal nephridia, present on both the sides of intersegmental septa of segment 15 to the last that open into intestine.
ii) Integumentary nephridia, attached to lining of the body wall of $\displaystyle \small 3^{rd}$ segment to the last that open on the body surface.
iii) Pharyngeal nephridia, present as three paired tufts in the $\displaystyle \small 4^{th}$, $\displaystyle \small 5^{th}$ and $\displaystyle \small 6^{th}$ segments.
Nervous System
$\displaystyle \small \bullet$ Nervous system is represented by ganglia, arranged segment wise on the ventral paired nerve cord.
$\displaystyle \small \bullet$ The nerve cord in the anterior region bifurcates, laterally encircling the pharynx and joins the cerebral ganglia dorsally to form a nerve ring.
$\displaystyle \small \bullet$ The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular responses of the body.
$\displaystyle \small \bullet$ Sensory system does not have eyes but does possess light and touch sensitive organs (receptor cells), to distinguish the light intensities and to feel the vibrations in the ground.
$\displaystyle \small \bullet$ Worms have specialized chemoreceptors (taste receptors) which react to chemical stimuli.
$\displaystyle \small \bullet$ These sense organs are located on the anterior part of the worm.
Reproductive system
$\displaystyle \small \bullet$ Earthworm is hermaphrodite (bisexual) i.e., testes and ovaries are present in the same individual.
$\displaystyle \small \bullet$ There are two pairs of testes present in the $\displaystyle \small 10^{th}$ and $\displaystyle \small 11^{th}$ segments.
$\displaystyle \small \bullet$ Their vasa deferentia run up to the $\displaystyle \small 18^{th}$ segment where they join the prostatic duct.
$\displaystyle \small \bullet$ Two pairs of accessory glands are present, one pair each in the $\displaystyle \small 17^{th}$ and $\displaystyle \small 19^{th}$ segments.
$\displaystyle \small \bullet$ The common prostrate and spermatic duct (vary differential) opens to the exterior, by a pair of male genital pores on the ventro-lateral side of the $\displaystyle \small 18^{th}$ segment.
$\displaystyle \small \bullet$ Four pairs of spermathecae are located in $\displaystyle \small 6^{th}-9^{th}$ segments (one pair in each segment).
$\displaystyle \small \bullet$ They receive and store spermatozoa during copulation.
$\displaystyle \small \bullet$ One pair of ovaries is attached at the inter-segmental septum of the $\displaystyle \small 12^{th}$ and $\displaystyle \small 13^{th}$ segments.
$\displaystyle \small \bullet$ Ovarian funnels are present beneath the ovaries which continue into oviduct, join together and open on the ventral side as a single median female genital pore on the $\displaystyle \small 14^{th}$ segment.
$\displaystyle \small \bullet$ A mutual exchange of sperm occurs between two worms during mating. One worm has to find another worm and they mate juxtaposing opposite gonadal openings exchanging packets of sperms called spermatophores.
$\displaystyle \small \bullet$ Mature sperm and egg cells and nutritive fluid are deposited in cocoons produced by the gland cells of clitellum.
$\displaystyle \small \bullet$ Fertilization and development occur within the cocoons which are deposited in soil.
$\displaystyle \small \bullet$ The ova (eggs) are fertilized by the sperm cells within the cocoon which then slips off the worm and is deposited in or on the soil.
$\displaystyle \small \bullet$ The cocoon holds the worm embryos. After about 3 weeks, each cocoon produces two to twenty baby worms with an average of four.
$\displaystyle \small \bullet$ Earthworms development is direct.
Earthworm is ‘friend of farmers’
1. They make burrows and hence aerate the soil.
2. The faeces of the worms make a good manure.
3. They enrich the soil by decaying the dead organic matters.
4. They form a part of food chain as they are food for number of animals.
$\displaystyle \small \bullet$ Each organ in our body is made up of one or more type of tissues.
$\displaystyle \small \bullet$ Basic tissue types in the body organize into organs.
$\displaystyle \small \bullet$ Group of organs associate each other to form organ system.
$\displaystyle \small \bullet$ This helps in the better coordination of activities of millions of cells of an organism.
$\displaystyle \small \bullet$ Morphology refers to study of form or externally visible features.
$\displaystyle \small \bullet$ In case of animals this refers to the external appearance of the organs or parts of the body.
$\displaystyle \small \bullet$ Anatomy is the study of internal structure or morphology of internal organs in the animals.
EARTHWORM
Phylum—Annelida
Class— Oligocheata
Order – Terricolae
Genus— Pheretima
Species—posthuma
$\displaystyle \small \bullet$ Earthworm is a reddish brown terrestrial invertebrate that inhabits the upper layer of the moist soil.
$\displaystyle \small \bullet$ During day time, they live in burrows made by boring and swallowing the soil.
$\displaystyle \small \bullet$ The common Indian earthworms are Pheretima and Lumbricus.
External Morphology
$\displaystyle \small \bullet$ Earthworm has a long narrow, bilaterally symmetrical cylindrical body.
$\displaystyle \small \bullet$ Body is brown in colour due to pigment porphyrin.
$\displaystyle \small \bullet$ The body is segmented and has tapering at the anterior end.
$\displaystyle \small \bullet$ There is a dark median line on the dorsal surface, it represent the dorsal blood vessel. It has 100—120 segments.
$\displaystyle \small \bullet$ The ventral surface shows genital openings and papillae towards the anterior end.
$\displaystyle \small \bullet$ A prominent band of glandular tissue is called clitellum, surrounds 14-16 segments.
$\displaystyle \small \bullet$ Internal segments have septa, which is absent between 3-4 and 9-10.
$\displaystyle \small \bullet$ Body is metamerically segmented, external segments corresponds to internal segmentation.
$\displaystyle \small \bullet$ It has an anterior mouth with prostomium (pre oral segment). Prostomium is covered by crescent shaped structure called peristomium, which helps in burrowing of soil.
$\displaystyle \small \bullet$ Eyes and tentacles are absent.
$\displaystyle \small \bullet$ Locomotion is by setae. The setae are embedded in the epidermal pit at the middle of each segment.
$\displaystyle \small \bullet$ Body wall has outer circular and inner longitudinal muscle that helps in locomotion.
$\displaystyle \small \bullet$ Body keeps moist by mucus secretion.
$\displaystyle \small \bullet$ They are hermaphrodites having both male and female sex organs.
Anatomy
Body wall is externally covered by a thin non-cellular cuticle. Epidermis is present below the cuticle.
Two muscle layers are in the mesoderm, and innermost layer is coelomic epithelium.
Digestive System
$\displaystyle \small \bullet$ The alimentary canal is a straight tube and runs between first to last segment of the body.
$\displaystyle \small \bullet$ Prostomium is a preoral segment before the mouth of the worm.
$\displaystyle \small \bullet$ Mouth is present in the $\displaystyle \small 1^{st}$ segment (peristomium) and is terminal in position.
$\displaystyle \small \bullet$ A terminal mouth opens into the buccal cavity which leads into muscular pharynx (4-5 segments). Salivary glands are present in pharyngeal wall.
$\displaystyle \small \bullet$ A small narrow tube is the oesophagus (5-7 segments) that continues into a muscular gizzard (8-9segments). It helps in grinding the soil particles and decaying leaves, etc.
$\displaystyle \small \bullet$ The stomach extends from 9-14 segments. Calciferous glands present in the stomach, neutralise the humic acid present in humus.
$\displaystyle \small \bullet$ Intestine starts from the $\displaystyle \small 15^{th}$ segment and continues till the last segment.
$\displaystyle \small \bullet$ A pair of short and conical intestinal caecae project from the intestine on the $\displaystyle \small 26^{th}$ segment.
$\displaystyle \small \bullet$ The characteristic feature of the intestine between 26-35 segments is the presence of internal median fold of dorsal wall called typhlosole. This increases the effective area of absorption in the intestine.
$\displaystyle \small \bullet$ The alimentary canal opens to the exterior by a small rounded aperture called anus.
$\displaystyle \small \bullet$ The ingested organic rich soil passes through the digestive tract where digestive enzymes breakdown complex food into smaller absorbable units. These simpler molecules are absorbed through intestinal membranes.
Circulatory System
$\displaystyle \small \bullet$ Earthworm have a closed type of blood vascular system, consisting of blood vessels, capillaries and heart.
$\displaystyle \small \bullet$ The main blood vessels are dorsal blood vessel and ventral blood vessel. They are connected by five pairs of connecting tubes. They have branches in all segments.
$\displaystyle \small \bullet$ Contractions keep blood circulating in one direction.
$\displaystyle \small \bullet$ Smaller blood vessels supply blood to the gut, nerve cord and the body wall.
$\displaystyle \small \bullet$ Blood glands are present on the $\displaystyle \small 4^{th}$, $\displaystyle \small 5^{th}$ and $\displaystyle \small 6^{th}$ segments. They produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature.
Respiratory System
$\displaystyle \small \bullet$ Respiration occur through the general body surface.
$\displaystyle \small \bullet$ The cuticle is kept moist by a slimy mucous.
$\displaystyle \small \bullet$ Respiratory exchange occurs through moist body surface into their blood stream.
$\displaystyle \small \bullet$ Moist surface is necessary to take $\displaystyle \small O_{2}$ and give out $\displaystyle \small CO_{2}$.
Excretory System
$\displaystyle \small \bullet$ The excretory organs occur as segmentally arranged coiled tubules called nephridia.
$\displaystyle \small \bullet$ They are absent in first two segments and in last segment.
$\displaystyle \small \bullet$ They maintain water balance in body.
$\displaystyle \small \bullet$ Nephridia regulate the volume and composition of the body fluids.
$\displaystyle \small \bullet$ A nephridium starts out as a funnel that collects excess fluid from coelomic chamber.
$\displaystyle \small \bullet$ The funnel connects with a tubular part of the nephridium which delivers the wastes through a pore to the surface in the body wall into the digestive tube.
$\displaystyle \small \bullet$ Types of Nephridia
i) Septal nephridia, present on both the sides of intersegmental septa of segment 15 to the last that open into intestine.
ii) Integumentary nephridia, attached to lining of the body wall of $\displaystyle \small 3^{rd}$ segment to the last that open on the body surface.
iii) Pharyngeal nephridia, present as three paired tufts in the $\displaystyle \small 4^{th}$, $\displaystyle \small 5^{th}$ and $\displaystyle \small 6^{th}$ segments.
Nervous System
$\displaystyle \small \bullet$ Nervous system is represented by ganglia, arranged segment wise on the ventral paired nerve cord.
$\displaystyle \small \bullet$ The nerve cord in the anterior region bifurcates, laterally encircling the pharynx and joins the cerebral ganglia dorsally to form a nerve ring.
$\displaystyle \small \bullet$ The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular responses of the body.
$\displaystyle \small \bullet$ Sensory system does not have eyes but does possess light and touch sensitive organs (receptor cells), to distinguish the light intensities and to feel the vibrations in the ground.
$\displaystyle \small \bullet$ Worms have specialized chemoreceptors (taste receptors) which react to chemical stimuli.
$\displaystyle \small \bullet$ These sense organs are located on the anterior part of the worm.
Reproductive system
$\displaystyle \small \bullet$ Earthworm is hermaphrodite (bisexual) i.e., testes and ovaries are present in the same individual.
$\displaystyle \small \bullet$ There are two pairs of testes present in the $\displaystyle \small 10^{th}$ and $\displaystyle \small 11^{th}$ segments.
$\displaystyle \small \bullet$ Their vasa deferentia run up to the $\displaystyle \small 18^{th}$ segment where they join the prostatic duct.
$\displaystyle \small \bullet$ Two pairs of accessory glands are present, one pair each in the $\displaystyle \small 17^{th}$ and $\displaystyle \small 19^{th}$ segments.
$\displaystyle \small \bullet$ The common prostrate and spermatic duct (vary differential) opens to the exterior, by a pair of male genital pores on the ventro-lateral side of the $\displaystyle \small 18^{th}$ segment.
$\displaystyle \small \bullet$ Four pairs of spermathecae are located in $\displaystyle \small 6^{th}-9^{th}$ segments (one pair in each segment).
$\displaystyle \small \bullet$ They receive and store spermatozoa during copulation.
$\displaystyle \small \bullet$ One pair of ovaries is attached at the inter-segmental septum of the $\displaystyle \small 12^{th}$ and $\displaystyle \small 13^{th}$ segments.
$\displaystyle \small \bullet$ Ovarian funnels are present beneath the ovaries which continue into oviduct, join together and open on the ventral side as a single median female genital pore on the $\displaystyle \small 14^{th}$ segment.
$\displaystyle \small \bullet$ A mutual exchange of sperm occurs between two worms during mating. One worm has to find another worm and they mate juxtaposing opposite gonadal openings exchanging packets of sperms called spermatophores.
$\displaystyle \small \bullet$ Mature sperm and egg cells and nutritive fluid are deposited in cocoons produced by the gland cells of clitellum.
$\displaystyle \small \bullet$ Fertilization and development occur within the cocoons which are deposited in soil.
$\displaystyle \small \bullet$ The ova (eggs) are fertilized by the sperm cells within the cocoon which then slips off the worm and is deposited in or on the soil.
$\displaystyle \small \bullet$ The cocoon holds the worm embryos. After about 3 weeks, each cocoon produces two to twenty baby worms with an average of four.
$\displaystyle \small \bullet$ Earthworms development is direct.
Earthworm is ‘friend of farmers’
1. They make burrows and hence aerate the soil.
2. The faeces of the worms make a good manure.
3. They enrich the soil by decaying the dead organic matters.
4. They form a part of food chain as they are food for number of animals.
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