1. Earthworm (Phylum: Annelida)

General Characteristics

  1. Belongs to phylum Annelida and class Oligochaeta.
  2. Scientific name: Lumbricus terrestris (Indian earthworm: Pheretima posthuma).
  3. Found in moist soil, rich in organic matter.
  4. Body is elongated, cylindrical, and segmented (100-120 segments).
  5. Lacks limbs, eyes, and a distinct head.
  6. Exhibits bilateral symmetry and is triploblastic.
  7. Has a clitellum (thickened band) for reproduction.

Digestive System

  1. Food consists of decaying organic matter and soil.
  2. Digestive tract is straight, extending from mouth to anus.
  3. Main parts: Mouth → Buccal cavity → Pharynx → Esophagus → Crop → Gizzard → Intestine → Anus.
  4. Gizzard helps in grinding food.

Circulatory System

  1. Closed blood vascular system.
  2. Has 5 pairs of aortic arches (heart-like structures) for circulation.
  3. Blood contains hemoglobin but lacks RBCs.

Respiratory System

  1. Respiration occurs through moist skin by diffusion.

Nervous System

  1. Consists of a paired ventral nerve cord.
  2. Brain is a pair of cerebral ganglia.

Excretory System

  1. Excretion occurs through nephridia.
  2. Excretory waste includes urea and ammonia.

Reproductive System

  1. Earthworms are hermaphrodites (both male and female reproductive organs present).
  2. Fertilization is external and occurs in a cocoon formed by the clitellum.

2. Cockroach (Phylum: Arthropoda)

General Characteristics

  1. Belongs to phylum Arthropoda and class Insecta.
  2. Scientific name: Periplaneta americana.
  3. Body is bilaterally symmetrical and segmented.
  4. Body is divided into head, thorax, and abdomen.
  5. Covered by a hard chitinous exoskeleton.
  6. Exhibits sexual dimorphism (males have longer wings than females).

Digestive System

  1. Has a well-developed alimentary canal.
  2. Main parts: Mouth → Pharynx → Esophagus → Crop → Gizzard → Midgut → Hindgut → Anus.
  3. Crop stores food, and gizzard helps in grinding.

Circulatory System

  1. Has an open circulatory system.
  2. Blood is colorless (hemolymph) and lacks hemoglobin.
  3. Heart is a tubular structure with 13 chambers.

Respiratory System

  1. Respiration occurs through tracheal tubes.
  2. Oxygen enters through spiracles and reaches tissues via tracheae.

Nervous System

  1. Consists of a paired ventral nerve cord.
  2. Brain is made of supraesophageal ganglia.
  3. Possess antennae for sensory functions.

Excretory System

  1. Excretion occurs through Malpighian tubules.
  2. Excretory waste is mainly uric acid (uricotelic).

Reproductive System

  1. Reproduction is sexual with separate sexes.
  2. Internal fertilization occurs.
  3. Females lay eggs inside ootheca (egg case).

Additional Key Points

  1. Earthworm is beneficial for soil fertility and is known as the "farmer’s friend".
  2. Earthworms show regeneration to some extent.
  3. Cockroach is an omnivorous scavenger.
  4. Cockroaches can survive without their head for several days due to their open circulatory system.
  5. Both species have well-developed sensory organs adapted for survival.

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