Class 10 Science - TAMILNADU
Structural Organization of Animals
The chapter 'Structural Organization of Animals' in Tamil Nadu Class 10 Science explores the complexity of living organisms, focusing primarily on the anatomy and physiology of the leech (Hirudinaria granulosa) as a representative invertebrate. Students learn about the external morphology, organ systems such as digestive, excretory, nervous, and reproductive systems, along with economic importance. Understanding this chapter is crucial for board exams as it features frequently in both objective and descriptive questions, testing students' knowledge of biological systems and technical scientific terminology.
Start Learning FreeKey Concepts
Habit and Habitat of Leech
Leeches are mostly ectoparasitic, sanguivorous (blood-sucking) freshwater organisms found in ponds, swamps, and sluggish streams.
External Morphology
The body of a leech is elongated, segmented into 33 rings called annuli, and possesses two suckers: an anterior sucker and a posterior sucker for locomotion and attachment.
Digestive System
The digestive tract features a muscular pharynx, crop for storing blood, and a caecum that allows the leech to store large amounts of blood for prolonged digestion.
Locomotion in Leech
Leeches move primarily by looping or crawling using their two suckers, and they can also swim gracefully in water.
Hirudin Secretion
Leeches secrete an anticoagulant called hirudin from their salivary glands to prevent host blood from clotting during feeding.
Important Formulas
Board Exam Info
In the Tamil Nadu (Samacheer Kalvi) Class 10 Science board examination, this chapter typically carries around 4 to 7 marks. Questions commonly include 1-mark objective questions, 2-mark or 4-mark short answers focusing on the leech's organ systems, locomotory structures, or the role of hirudin.
Frequently Asked Questions
What is the function of the posterior sucker in a leech?
The posterior sucker is used mainly for attachment to the host during feeding and acts as a primary anchor during locomotion.
Why does a leech's blood meal not clot inside its body?
The salivary glands of the leech secrete a natural anticoagulant called hirudin, which prevents blood from clotting.
How many segments are present in the body of a leech?
A leech's body is externally divided into 33 segments, though internally the segmentation is slightly different.
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