1. Phylum
    2. 1. Classification of Animals
    2. Protozoa
    3. Porifera
    4. Coelenterata
    5. Platyhelminthes
    6. Nemathelminthes
    7. Annelida
    8. Earthworm
    9. Arthropoda
    10. Cockroach
    11. Mosquito
    12. Honey bee and Silk moth
    13. Mollusca
    14. Echinodermata
    15. Hemichordata
    16. Chordata
    17. Pisces
    18. Amphibia
    19. Frog
    20. Reptile
    21. Aves
    22. Mammalia
    23. Rabbit bone
  2. Animal Behaviour and Adaptation
    3. 24. Animal behaviour
    25. Animal adaptation
    26. Migration
  3. Developmental Biology
    4. 27. Development of Animals
    28. Development of Frog
  4. Human Biology
    5. 29. Tissues
    30. Sense organs
    31. Digestive system
    32. Circulatory system
    33. Respiratory system
    34. Nervous system
    35. Endocrine system
    36. Reproductive system
    37. Excretory system
    38. Skeletal system
    39. Basic concept of Immunology
    40. Human diseases
  5. Evolutionary Biology
    6. 41. Origin of Life
    42. Organic Evolution
    43. Theories of Evolution
    44. Evolution of Human beings
    45. Horse Evolution
Phylum
8. Earthworm
GENERAL
▢ Introduction:
Image 1
❖ Genera:
  1. Pheretima posthuma
  2. Megascolex (South-Indian Earthworm)
  3. Lumbricus (European Earthworm)
  4. Metaphire
❖ Habitat: Burrowing (Fossorial)
❖ Habit: Nocturnal
▢ Features:
❖ Symmetry: Bilaterally symmetrical
❖ Body structure: Elongated with Metameric segmentation
❖ Segmentation:
◉ External: Annuli or Grooves
◉ Internal: Septa
▢ Morphology:
❖ Colour:
◉ Description: Brown/ Clay-coloured
◉ Pigment:
◈ Name: Porphyrin
◈ Location: Circular muscle layer of body wall
◈ Origin: From chlorophyll in decaying vegetable matter
◈ Function: Protects the body from harmful sunlight radiation
❖ Segments: 100-120
❖ Setae per segment: 80-100
❖ Head and sense organs: Lacks distinct head, eyes, cirri, and tentacles
Image 1
❖ Body shape: Cylindrical
❖ Setae:
Image 1
Image 2
◉ Parts:
◈ Neck: Projects outside the body
◈ Nodulus:
◈ Base: Embedded inside the body
◉ Embedded in: Setal Sac
◉ Formed by: Formative/ Generative/ Seta-forming cells
◉ Arrangement:
◈ Perichaetine: Setae arranged in a ring (Pheretima)
◈ Lumbricine/Otochaetine: 2 pairs on each lateral side (Lumbricus)
◉ Composition: Made of Chitin (Insoluble in KOH)
◉ KOH Treatment: Section with setae kept in 40% KOH to separate them
◉ Muscles:
◈ Protractor: Contraction causes extension of setae (out)
◈ Retractor: Contraction causes withdrawal of setae (in)
◉ Functions:
◈ Ventral setae: Crawling on ground
◈ Lateral setae: Movement in burrows
Image 1
❖ Anus:
◉ Location: Last segment
◉ Note: Postanal tail absent
❖ Dorsal pores:
◉ Location: Mid-dorsally behind 12th segment (except last)
◉ Function: Exude body fluid to keep wall moist
◉ Connection: Communicates with coelom
◉ Response: Ejects white milky coelomic fluid when disturbed
❖ Nephridiopores:
◉ Type: Integumentary nephridia
◉ Location: All segments except first six
◉ Count:
◈ General: 200–250 per segment
◈ Clitellar: 2000 per segment — Forest of Nephridia
▢ Body wall:
Image 1
❖ Layers:
◉ Cuticle:
◈ Type: Thin, transparent, flexible, non-cellular, non-chitinous double layered
◈ Made of: Collagen fibres
◈ Secreted by: Epidermis (Supporting cells)
◈ Function: Protection from mechanical and chemical injury
◉ Epidermis:
◈ Structure: Cellular, single-layered
◈ Cells:
■ Supporting: Main bulk of epidermis
■ Glandular:
● Mucous: Secretes mucus (moist/slippery surface)
● Albumen: Secretes albumen (nutrition to embryo)
■ Basal: Replacement cell
■ Sensory: Receives external stimulus
◉ Muscular layer:
◈ Circular muscle: Contraction causes elongation
◈ Longitudinal muscle: Contraction causes shortening
◉ Coelomic peritoneum: Also called Parietal peritoneum
▢ Body cavity:
❖ Type: True coelom (Schizocoel)
❖ Coelomic fluid:
◉ Nature: Milky white, alkaline
◉ Components:
◈ Water: true
◈ Salts: true
◈ Minerals: true
◈ Corpuscles:
Image 1
■ Amoebocytes:
● Also called:
  1. Phagocytes
  2. Granulocytes
  3. Electrocytes
● Size: Largest
● Function: Engulf harmful microorganisms
■ Chloragogen cells:
● Also called:
  1. Chloro cells
  2. Yellow cells
● Shape: Small, star-shaped
● Function:
  1. Storage of reserve food (fats & glycogen)
  2. Urea formation and excretion
  3. Silica elimination (analogous to vertebrate liver)
■ Leucocytes:
● Also called: Circular cells
● Function: Circulate digested food
■ Mucocytes:
● Shape: Fan shaped
● Function: Produce mucus
◉ Functions:
  1. Acts as Hydraulic Skeleton
  2. Aids in locomotion
  3. Bioluminosity in some species due to bioluminous cells
◉ Other facts:
◈ Haemoglobin: Absent in coelomic fluid
◈ Secreted by: Parietal peritoneum
◈ Production: Continuously produced and lost
❖ Lining:
◉ Outer: Parietal peritoneum / Somatic peritoneum
◉ Inner: Visceral peritoneum / Splanchnic peritoneum
▢ Septa:
❖ Absence:
◉ First 4 segments: No septa
◉ 9/10 segment: No septa (due to large gizzard)
❖ Structure:
◉ 4/5 segment: Thin and membranous
◉ 5/6 to 10/11: Thick, muscular, and oblique
◉ 11/12 onwards: Thin, membranous, and transverse
❖ Completeness:
◉ First nine (up to 13/14): Complete (no apertures)
◉ 14/15 onwards: Incomplete (perforated)
DIGESTIVE SYSTEM
Image 1
a
Parts
Segments
b
Peristomium (Mouth)
1
c
▢ Buccal chamber:
  1. Buccal receptors = Gustato-receptor and Olfactoreceptor
  2. Helps in attachment and catching of prey.
2-3
d
▢ Pharynx:
    ◉ i. Dorsal salivary chamber:
    1. Chromophil cell/ Saliva secreting gland cell
    2. Produces saliva (Mucus and Proteases)
    ◉ ii. Ventral Conducting chamber:
    1. Helps in conduction of saliva to food
3-4
e
Oesophagus
5-7
f
▢ Gizzard:
  1. Thick walled muscular organ
  2. Lined by thick cuticle covered with thick circular muscle layer
  3. Longitudinal muscle is absent
8
g
▢ Stomach:
  1. Located in segments 9–14
  2. Contains Calciferous glands (lime-secreting glands)
  3. Neutralize acidic soil content
9-14
h
▢ Intestine:
❖ Intestinal caeca:
  1. Arises from 26th segment and extends forward to 22/23
  2. Secretes amylolytic ferment (amylase)
❖ Typhlosole:
  1. Highly glandular, vascular, longitudinal ridge
  2. Blind and folded structure
  3. Increases absorption area for digested food
15 onwards
Region
Segments
Details
Pre-typhlosolar region
15–25
Typhlosolar region
27–23/25 segments in front of anus
Post-typhlosolar region (Rectum)
Last 23/25 segments
Absorption of H₂O from waste food and elimination of waste; also known as Rectum
CIRCULATORY SYSTEM
▢ Blood:
  1. Red in colour
  2. Respiratory pigment = Haemoglobin is dissolved in the blood plasma.
  3. So, the blood is red in colour.
  4. No Red Blood Cells
  5. Oxygen carrying capacity of the blood in earthworm is less than that of vertebrate blood.
▢ Blood Vessels:
Image 1
Image 2
❖ Longitudinal blood vessels:
S.N.
Dorsal Blood Vessel
Ventral Blood Vessel
Lateral Oesophageal Blood Vessels
Subneural Blood Vessel
Supra-oesophageal Blood Vessel
Location
1st to last segment
1st to last segment
1st to 13th segment on both sides of alimentary canal
14th to last segment below the ventral nerve cord
9th to 13th segment
Features
  1. Largest blood vessel in the earthworm
  2. Bears a pair of valves in each segment
  1. Found below alimentary canal
  2. Single
  3. No valves
  1. After 13th segment, they unite to form a single sub-neural vessel
  2. Single
    Smallest lateral blood vessel
    Flow of Blood
    Posterior to Anterior direction
    Anterior to Posterior direction
    Type
    1. Distributing type = 1st to 13th segment
    2. Collecting type = 14th onwards
      1. Collects from Dorso-intestinals and Sub-neurals through Commissural vessel
    1. Main distributing blood vessel
    2. Gives off paired tegumentary vessels in each segment to supply blood to segmental organs
    1. Collects blood from seminal vesicles present in 11th and 12th segments
    1. Receives blood from latero-oesophageal vessel through anterior loops
    2. Also receives from stomach and gizzard through ring vessel
    3. 1 segment bears about 12 ring vessels
      ◉ One pair of Commissural vessel is present in each segment. It transfers blood from sub-neural to dorsal vessel. It gives a branch called Septo-intestinal to intestine.
      ❖ Transverse blood vessels:
      S.N.
      Lateral Hearts
      Anterior Loops
      Lateral Oesophageal Hearts
      Location
      7th and 9th segments
      10th and 11th segments
      12th and 13th segments
      Features
      1. One pair in each segment
      2. Sends blood from dorsal vessel to ventral vessel
      3. Each vessel with 4 pairs of valves
      1. One pair in each segment
      2. Sends blood from lateral oesophageal vessel to supra-oesophageal vessel
      1. One pair in each segment
      2. Sends blood from supra-oesophageal and dorsal vessel to ventral vessel
      3. Each vessel with 3 pairs of valves
      ▢ Hearts:
      ❖ Description: Heart of earthworm is muscular, thick-walled, valvular, and pulsating.
      ▢ Blood Glands:
      ❖ Location: Segments 4, 5, and 6 above the pharyngeal mass
      ❖ Association: Blood glands are associated with pharyngeal nephridia
      ❖ Function: Manufacture of blood corpuscles and haemoglobin
      ▢ Lymph Glands:
      ❖ Location: Both sides of dorsal blood vessel from 26th segment onwards
      ❖ Number: 1 pair per segment
      ❖ Shape:
      ◉ Size: Small
      ◉ Color: Whitish
      ❖ Function: Supposed to produce certain phagocytic cells (Amoebocytes)
      RESPIRATORY SYSTEM
      1. Cutaneous respiration
        1. No respiratory organs
        2. Exchange of gases takes place through moist skin
          1. The absorptive area of earthworm is more than its volume. So, earthworm doesn't require any respiratory organ.
          2. The cutaneous blood supply of the animal is more which is helpful in the process of gaseous exchange.
          3. If the skin of the earthworm dries, it cannot respire. It is due to asphyxia.
      2. 100 cc of blood carries 10 cc of oxygen.
      3. Note: Vertebrate blood carries 20 cc of oxygen per 100 cc.
      EXCRETORY SYSTEM
      Image 1
      S.N.
      Septal nephridia / Typical nephridia
      Pharyngeal nephridia
      Integumentary nephridia
      Image 1
      Image 2
      1. Location
      Attached to both faces of each intersegmental septum behind 15th segment.
      4th, 5th and 6th segments on either side of alimentary canal.
      Scattered in the ventral body wall in all segments except first 2 or 3. Absent in anterior 14 segments.
      2. Number
      Each septum has 2 rows with 80–100 nephridia per septum.
      In the form of paired tufts — 3 pairs of tufts, each containing numerous nephridia.
      200–250 per segment. 10× more in clitellar region = 'Forest of nephridia'. No. of nephridiopores = No. of nephridia.
      3. Type
      Enteronephric nephridia
      Enteronephric nephridia
      Exonephric nephridia
      4. Parts of Nephridia
      a. Nephrostome (with upper & lower lips)
      b. Neck (ciliated duct)
      c. Main body (twisted & straight loop)
      d. Terminal duct (ciliated)
      e. Nephridial tube (single coiled tubule with 4 ciliated regions)
      Without nephrostome
      Paired tufts with common pharyngeal duct.
      Without nephrostome
      Smallest nephridia
      5. Flow of Wastes
      Nephrostome → Neck → Main body → Terminal duct → Septal excretory canal → Two supra-intestinal excretory canals → Intestine
      Terminal ducts of tufts open into a common pharyngeal nephridial duct (common excretory duct)
      -
      6. Features
      a. Largest nephridia
      b. Only type with nephrostome
      Ducts from 4th & 5th segments open into pharynx; 6th into buccal cavity.
      a. Smallest nephridia
      b. Most numerous
      c. V-shaped
      REPRODUCTIVE SYSTEM
      ▢ Male reproductive system:
      Male Reproductive Parts
      Number
      Location
      Features
      Function in Development of Sperm
      1. Testes
      2 pairs
      10th and 11th segments
      1. i. Small white structure enclosed within testis sac.
      2. ii. Segmental septa of testes are 9/10th and 10/11th segments.
      3. iii. Each testis consists of 4–8 finger-like projections, containing spermatogonia at different stages of development.
      4. iv. Testes remain well developed in young earthworm but degenerate in mature earthworm.
      i. Produce spermatogonia.
      2. Testes sacs
      2 pairs
      10th and 11th segments
      1. i. Thin-walled fluid-filled membranous bag, encloses the testes.
      2. ii. Each testis sac is ventro-lateral in position and bilobed in front.
      3. iii. Also encloses spermiducal funnel.
      4. iv. The testis sac of 10th and 11th segment communicate with the respective seminal vesicles of 11th and 12th segment.
      i. The spermatogonia are shed into the testis sac, from where they enter into seminal vesicles for maturation.
      3. Spermiducal funnels
      2 pairs
      10th and 11th segments
      1. i. Funnel-like structure with folded and ciliated margin.
      2. ii. Lies behind the testis, enclosed within testis sac.
      3. iii. Each spermatic funnel leads to vas deferens.
      i. Collects sperms.
      4. Seminal vesicles
      2 pairs
      11th and 12th segments
      1. i. Oval sacs, found on both sides of stomach.
      2. ii. Developed from septa as outgrowth, so called septal pouches.
      3. iii. 12th segment seminal vesicles are larger than 11th segment ones.
      4. iv. Seminal fluid with fructose, the chief food for sperm.
      1. i. Play role in maturation of spermatozoa from spermatogonia.
      2. 1. Produce sperms.
      3. 2. Sperms rest here until copulation.
      5. Vasa deferentia
      2 pairs
      Extends from 10th/11th to 18th segment
      1. i. Narrow elongated ducts, run on either side of alimentary canal piercing through inter-segmental septa.
      2. ii. In 18th segment, they incorporate with prostatic duct forming common prostatic and spermatic duct, which opens outside through male genital aperture on the ventral wall.
      i. Conduct sperms.
      6. Prostate gland
      1 pair
      Extends from 16th/17th to 20th/21st segment
      1. i. Large, elongated white coloured and irregularly-shaped lobulated gland.
      2. ii. The prostatic secretion is useful for the activation of sperms.
      i. Provides nourishment to the sperm.
      7. Accessory glands and Genital Papillae
      2 pairs
      17th and 19th segments
      1. i. Found on either side of the nerve cord, attached to the floor of body cavity.
      2. ii. Secretes the sticky substance which helps in attachment of two worms during copulation.
      3. iii. Opens out through genital papillae.
      ▢ Female reproductive system:
      Female Reproductive Parts
      Number
      Location
      Features
      1. Ovaries
      1 pair
      13th segment
      1. i. Small whitish masses on either side of ventral nerve cord.
      2. ii. Consist of finger-like projections called ovarioles, which contain eggs of different developmental stages.
      3. iii. The eggs at the apices are the matured ones.
      2. Oviducal funnel
      1 pair
      13th segment just beneath ovaries
        3. Oviducts
        1 pair
        Extending from 13th to 14th segment
        1. i. Starts from 13th segment as oviducal funnel, meant for receiving ova from the ovary.
        2. ii. In 14th segment, they converge and open outside ventrally through female genital pore.
        4. Spermathecae
        4 pairs
        6th, 7th, 8th, and 9th segments ventrolaterally
        1. i. Spermathecae (seminal receptacles) are for receiving sperm from another worm during copulation and temporary storage of sperms.
        2. ii. Each spermatheca is flask-shaped, consisting of a pear-shaped ampulla and a short elongated diverticulum.
        3. 1. Diverticulum = Storage of sperms received from another worm during copulation.
        4. 2. Ampulla = Provides nourishment to the stored sperms.
        5. iii. Spermathecal openings are in the intersegmental grooves of 5/6th, 6/7th, 7/8th, and 8/9th segments.
        NERVOUS SYSTEM
        ▢ Central Nervous System:
        Image 1
        S.N.
        Parts of CNS
        Number
        Location (Segment)
        Gives rise to
        Features
        a.
        Cerebral ganglia / Supra-pharyngeal ganglia (Brain)
        1 pair
        3rd segment dorsally
        6-8 nerves
        1. a. White in color
        2. b. Pear-shaped bilobed mass
        b.
        Circum-pharyngeal connective / Peri-pharyngeal connectives
        1 pair
          c.
          Sub-pharyngeal ganglia
          1 pair
          Beneath the pharynx in 4th segment
          2-3 pairs of nerves
            d.
            Ventral nerve cord with Segmental ganglia
            3 pairs of nerves
            1. a. In each segment from the 5th to the last, the nerve cord has a swollen structure known as a Segmental ganglion.
            2. b. Nerve cords of *Pheretima* are ventral, double, and solid.
            3. c. Actually formed by fusion of 2 longitudinal cords.
            4. d. Coverings:
            5. 1. The nerve cord is surrounded by a common sheath of connective tissue called *Epineurium*.
            6. 2. Outside Epineurium, a layer of longitudinal muscle fibres is present.
            7. 3. This is ultimately surrounded by a layer of visceral peritoneum called *Perineurium*.
            ▢ Peripheral Nervous System:
            ▢ Autonomic Nervous System:
            ▢ Receptors:
            Epidermal receptor
            Buccal receptor
            Photo-receptor
            Image 1
            Image 1
            Image 1
            1.
            2.
            3.
            4.
            5.
            6.
            7.
            8.
            9.
            10.
            11.
            12.
            13.
            14.
            15.
            16.
            17.
            18.
            19.
            20.
            21.
            22.
            23.
            24.
            25.
            26.
            27.
            28.
            29.
            30.
            31.
            32.
            33.
            34.