Phylum platyhelminthes, Biology

PHYLUM  PLATYHELMINTHES

Definition and Introduction

Bilateral and protostominal  organ  grade eumetazoans  without  a body cavity ( acoelomates)  platyhelminthes means flatworms  (Gr. Platys= flat; helmins  =  worms. )  their  body is  dorsoventrally  flattened. About  10,000 species  known.

Brief History

Aristotle mentioned tapeworms. But  scientific studies of flatworms began only  in the 18 th  century. It was  Gegenbaur  (1859)  who  placed these in a separate  group  and suggested  the  name of  the phylum.

Important Characters

1.       Mostly  parasitc , cheif  invertebrates  , including man. Some  pathogenic,  i.e.  disease producing .

2.        Differentiation  of head   ( cephalisation )  with  a brain and , in some  primitive  eye spots, at anterior  begins  in eumetazoans with  platyhelminths .

3.       In  many forms body  is divided into  segments,  but this  segmentation  is not  true  metamerism.

4.       Sukers, hooks  spines, etc. Often  developed  for  attachment to host tissue .

5.       Soft and  delicate,  dorso ventrally flattened  bilateral  body  is triploblastic,  both triploblastic  organization  and bilateral symmetry  also  begin  in eumetazoans  with these  animals .

6.       Similary , development  of distinct organs  and organ system  also  begins in eumetazoans  with platyhelminths .     Distinct digestive,  excretory , nervous and  anus. Reproductive  systems occur, but  no skeletal,  vascular and respiratory  system ,No  anus  some  have secondarily  lost  the digestive  system .

7.       No  body  cavity  ,Space  between  body  wall  internal organs  occupied by s loose  mesodermal  tissue  called  parenchyma.

8.        Units  of excretory  system  are peculiarly specialized  protonephridial    tubules  with terminal  flame  cells  or bulbs.

9.       As  an  adaptation to parasitic  mode of life , the  reproductive  system

Posted Date: 10/4/2012 2:56:54 AM | Location : United States







Related Discussions:- Phylum platyhelminthes, Assignment Help, Ask Question on Phylum platyhelminthes, Get Answer, Expert's Help, Phylum platyhelminthes Discussions

Write discussion on Phylum platyhelminthes
Your posts are moderated
Related Questions
What are the differences between blood retinal barrier and blood aqueous barrier? Blood Retinal Barrier: Blood retinal barrier is present in retina. In retina there are t

Hypotension, hyperkalemia, taste disturbance, angiedema, renal insufficiency. In the absence of any symptoms of hypotension, and normal renal function and K + levels, the dosage

Draw and describe the structure of amphibian,reptile mammal and bird

What are alleles of a gene? Diploid individuals have paired chromosomes. For instance in humans there are 23 pairs of chromosomes totalling 46 chromosomes. Each pair comprehend

Phosphorus deficiency Deficiency of phosphorus is usually primary and is widespread under natural conditions. It is characterized by pica, poor growth, infertility, and osteody

Wind pollinated flowers are: 1. Small, brightly coloured, producing large number of pollen grains 2. Small, producing large number of dry pollen grains 3. Large producing

Monosaccharide Sugar - carbohydrate consisting of a single sugar unit Have an aldehyde or a ketone group and 2-5 alcohol groups depending of the # of carbons

Standards of Psychiatric Nursing: By  1956, the Masters programme was extended  to two academic years. Some nurses established private practices with psychiatric patients. It

what is atp explain in detail?

Hypomagnesaemic tetany of calves Young calves in the age group of 2-8 weeks and fed whole milk or milk replacer are more likely to develop hypomagnesaemia due to inadequate ma