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Phylum Aschelminthes (Roundworms): Characteristics, Classification & NEET Important MCQs

Introduction of Aschelminthes
  • Aschelminthes are  Pseudocoelomate , Triploblastic, bilateral symmetrical roud worms with  organ level of organisation . 

Table of Contents

  • ​Introduction to Aschelminthes
  • ​General Characteristics (The Pseudocoelomate Concept)
  • ​Body Systems (Digestive, Excretory & Nervous)
  • ​Sexual Dimorphism in Roundworms
  • ​Key Examples: Ascaris, Wuchereria, & Ancylostoma
  • ​Economic Importance & Diseases
  • ​NEET Previous Year Questions (PYQs) & Practice Test

General features 
  • The body of the aschelminthes is circular in cross-section, hence, the name roundworm. 
  • They may be free living, aquatic and terrestrial or parasitic in plants and animals. 
  • Roundworms have organ-system level of body organisation. 
  • They are bilaterally symmetrical, triploblastic and pseudocoelomate animals. 
  • Digestive system is developed Alimentary canal is complete with a well- developed muscular pharynx. 
  • Excretory system contain an excretory tube to removes body wastes from the body cavity through the excretory pore. 
  • Sexual dimorphism is seen .Sexes are separate (dioecious), i.e., males and females are distinct. Often females are longer than males.
  • Fertilisation is internal and development may be direct or indirect. the young ones resemble the adult. 
  • Body of Round worms are covered by the syncytial cuticle to protect the body from digestive enzyme in body of host.
  • They have  nervous system including nerve ring around the Oesophagus and branches nerves through out the body.
  • Respiratory system is absent . They Respire through their body surface.
Key points of Aschelminthes 
  • Aschelminthes are the first Pseudocoelomates in animal evolution.
  • ​They exhibit a Tube-within-a-tube body plan with a complete alimentary canal.
  • ​The body is covered by a tough, resistant Cuticle.
  • ​Excretion occurs through Renette cells or H-shaped excretory systems.
Watch my detail video lecture on Aschelminthes



Examples of Aschelminthes  

 Ascaris (Round worm)

  • Ascaris is long round worm which can be up to more than 30 cm but female is always longer than male. 
  •  Ascaris show sexual dimorphism. Male is usually shorter with folded end at one side.
  • Ascaris has non cellular cuticle covering on body to get protection from digestive enzyme of host

  • Digestive system is well developed in with various digestive organs.
  • Nervous system include nerve ring with numerous nerve cords.
  •  Embryonated egg is infective stage of Ascaris. These eggs are passed out with the stool of infective person and make contaminated the soil.
  • Egg is ingested by host when it comes contact with contaminated soil into host body. 
  • Egg is developed into Rhabditiform larva and than into adult Ascaris.

Comparison table of male and female 


Feature

Male Ascaris

Female Ascaris

Size

Chota (Short)

Lambi (Long)

Tail

Curved (Mudi hui)

Straight (Seedha)

Pineal Setae

Present

Absent

Cloaca

Present

Absent


Read also notes and MCQs of Phylum Coelenterata

Wuchereria ( Filaria worm)

  • It is commonly called as Filaria worm.
  • It show sexual dimorphism. Adult female is usually longer  with rounded  ends and male is shorter than female. The tail of male is centrally curved.
  • Wuchereria has 15 pairs of sensory organs.
Wuchereria 

  • It resides in lymphatic system of Human but may also found in blood.
  • Alimentary canal include Muscular pharynx oesophagus intestine and anus. The mouth is present without oral lips.
  • Female genital pore is present as vulva whereas male has cloaca.
  • Penial setae or copulatory Spicules are present in male.
  • Microfilareae is larval stage of wuchereria found in blood of human.

Ancylostoma ( Hook Worm )

  • It is commonly called as Hook worm.
  • Adult female is usually longer  with rounded  ends and male is shorter than female.
  • Hook worm is small cylinder and white or pinkish in color.
  • It has sharp teeth or cutting plate in their buccal capsule.
Ancylostoma 
  • Male Hook worm has bursa with two Spicules.
  • Female Hook worm has vulva. It lay 10000 to 30000 eggs per day.
  • It create various health complex like anemia , Malnutrition and protein loss.

Diseases and Causative Agents (Quick Revision Table)

Common Name

Scientific Name

Disease Caused

Roundworm

Ascaris lumbricoides

Ascariasis

Filarial Worm

Wuchereria bancrofti

Elephantiasis (Filariasis)

Hookworm

Ancylostoma duodenale

Ancylostomiasis (Iron deficiency)



1. Consider the following statement and select the correct code:

1.  Members of Aschelminthes have dorso flattened body.  
2. Members of Platyhelminthes have round body in cross section area. fl
A. Only 1   
B. Only 2
C. Neither 1 nor 2 
D. Both 1 and 2 
Answer : C  

2. Which of the following pairs of feature are present in members of Aschelminthes.
A. Organ system level of organisation and Pseudocoelom.
B. Acoelomate condition and Radial symmetry
C. Flame cells and Protonephridia. 
D. Diploblastic condition and Coelomate
Answer : A  

3. Alimentary canal of round worm is complete with well developed 
A. Radula  
B. Muscular Pharynx 
C. Gastric Cecae 
D. Syrinx 
Answer : B  

4. Which one of following is Excretory organ in members of Aschelminthes.
A. Malpighian tubules  
B. Flame cells
C. Protonephiredia 
D. Excretory pore 
Answer : D 

5. Which of the following statement is not correct with respect to Aschelminthes.
A. Development is direct or indirect  
B. Larva resemble with the adult.
C. Fertilization is external.
D. Saxes are Separate. 
Answer : C  

6. Which of the following statement is correct for the round worms.
A. Alimentary canal is incomplete.
B. They remove their nitrogenous waste through body surface.
C. Fertilization is external.
D. Saxes are Separate 
Answer : B  

7. Match the list 
A. Enterobius  1. Pin worm
B. Ascaris       2.Round worm 
C.Wucheteria 3.Filaria worm                   D.Ancyclostoma 4.Hook worm                                                                                                                     

             A       B       C      D
A.         1        2        3      4
B.         1        2        4      3
C.         2        1        3      4
D.         3        1       4       2
Answer : A  

8. Which of the following statement is correct with respect to round worm.
A. Development is indirect without larval stage.
B. Female individual is often longer than male.
C. Fertilization is external.
D. They are mostly hermaphrodite. 
Answer : B  

9. Consider the following characteristics of Aschelminthes and select the correct code:
1. Aquatic 
2. Terrestrial 
3. Free living
4. Parasite in animals 
5. Parasite in Plants
A. 1, 2, 3 and 4
B. 1, 2, 3 and 5
C. 2, 3, 4 and 5
D. 1,2,3,4 and 5
Answer : D 

10. In which of the following animals, mesoderm is present as scattered pouches In between the ectoderm and endoderm.
A. Round worm
B. Flat worm
C. Earth worm
D. All of the above.
Answer : A  



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