STRUCTURAL ORGANISATION IN ANIMALS

 

Blood vascular system :

• Blood vascular system is closed type.
• Blood vascular system consists of:
  • Blood vessels
  • Capillaries
  • Heart.
  
  
• Blood glands present on 4th, 5th and 6th segments.
• Blood glands produce blood cells and haemoglobin.
• Haemoglobin dissolved in plasma instead of embedded in corpuscles.
• Blood cells are Phagocytic in nature.

Respiration:

• Earthworm lack specialized breathing devices.
• Gaseous exchange takes place through moist surface of skin.
• Transport of respiratory gases takes place in haemoglobin.

Excretory system:

• Excretory organs are segmentally arranged coiled tubules called nephridia.
• There are three types of nephridia:


• Septal nephridia:
  • Present on both side of intersegmental septa of segment 15 to last segment.
  • They opened into the intestine.
  
  
• Integumentary nephridia.
  • Attached to the lining of the body wall from 3th to last segment.
  • Opened into the body surface.
  
  
• Pharyngeal nephridia:
  • Present in three pairs in 4th, 5th and 6th segment.
  
  
• Nephridia regulate the volume and composition of body fluids.
• A nephridium starts with a ciliated funnel like structure called nephrostome, connected with a tubular part.

Nervous system :

• Represented by ganglia arranged segmentally on the ventral paired nerve cord.
• Nerve cord in the anterior region (3rd and 4th segments) bifurcates, laterally encircling the pharynx and joins the cerebral ganglia dorsally to form nerve ring.
• Segmental ganglia give rise to nerve fibres to the body organs.

Sensory organs :

• Possesses light and touch sensitive organs (receptor cells)
• Have specialized chemoreceptor, which reacts to chemical stimuli.
• Sense organs located in the anterior part of the body.

Reproductive system :

• Earthworm is hermaphrodite
• Two pairs of testes present in the 10th and 11th segments.
• Their vasa deferentia run upto 18th segment and joins with prostatic duct.
• Two pairs of accessory glands present one pair each in the 17th and 19th segment.
• The prostrate and spermatic duct (vasa dererentia) opens to exterior by a pair of male genital pore on the ventro-lateral side of the 18th segment.
• Four pairs of spermathecae are located in 6th – 9th segments.
• They receive and store spermatozoa during copulation.
• One pair of ovaries is attached at the inter-segmental septum of 12th and 13th segment.
• Ovarian funnel continued as oviduct, join together and open by a single female genital aperture on the 14th segment.
• Mutual exchange of sperm occurs between two worms during mating.
• Mature sperms and egg cells and nutritive fluid are deposited in the cocoons produced by gland cells of clitellum.
• Fertilization takes place inside the cocoon which deposited in soil,
• After three weeks each cocoon produces two to twenty baby worms.
• Development is direct without larval stage.

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
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