Phylum annelida, Biology

Assignment Help:

PHYLUM ANNELIDA

Definition  and Introduction

Bilateral and  protosomial  eucoelomate  eumetazoans  whose  long   narrow and  wormlike body  is division  into  ring like  true  or metameric segments (Gr. Annelus= little  ring) and the skin  usually bears  enjointed  chitinous appendages , termed setae.

Commonly  known as segmented worms. About 9,000 species known.

Brief History

Linnaeus (1758) included all  soft  bodied worms  in Vermes  Lamarck (1801)  established phylum  Annelida for higher types   or worms.

Important Characters

1.       Annelids  occur  widely in water  or moist soil. Some  free living  some  burrowing  and  a few parasitic.

2.       Body  usually long , slender and  distinctly segmented. Body  cavity ( coelom and many internal organs also exhibit  metameric segmentation .

3.       Soft  and extensile body  triploblastic  and bilateral.

4.       Muscular and  contractile  body wall  covered  by a thin moist cuticle containing secreted unjointed  chitinous  setae. A distinct columnar epidermis  and both  longitudinal and circular muscle layers  present.

5.       Body  cavity is true coelom lined  by sesodermal epithelium ( peritoneum)  phylogentically,  annelids are, perhaps, the  first animals to acquire a ture  schizocoelic  coelom, In most  annelids ,it is divided into segmental  chambers  by inter segmental septa. Coelomic fluid  contains  cells ( corpuscles ) .

6.       Alimentary  canal  straight  with  anterior  mouth  and posterior  anus .Due to spacious, fluid  filled  body cavity  between  body  wall and  alimentary  canal, the  body  grossly  appears  like a tube within  a tube  in section.

7.       A distinct and    closed type  of blood vascular system present. Blood of red  colour with haemoglobin  dissolved in plasma. Free amoeboid  blood  corpuscles  present, but  no red  blood  corpuscles.

8.       Respiration  through moist skin some  possess gills.

9.       Excretion  by minute  and coiled paired tubules  of ectodermal  origin ,called  metanephridia.

10.      Nervous  system uncludes nerve ring  near anterior end. Two  ventral nerve  cords  extending throughout body length   from nerve ring, and  segmental ganglionic  swellings upon  nerve cords, representing true  metamerism. Several types  of sensory  cells  and organs found.

11.   Sexes  separate  or united .Reproductive  organs  develop  from  coelomic  epithelium.

12.   Development  mostly direct. When  present , the larval  stage is trochophore.


Related Discussions:- Phylum annelida

What is an analogy for microtubules, What is an analogy for microtubules? ...

What is an analogy for microtubules? Microtubules have two major functions in cells and in doing so act such as a skeleton as well as like railroad tracks. Microtubules are the

Define physical activity as a factor for obesity, Define Physical activity ...

Define Physical activity as a factor for obesity? Sedentary life style with lack of an exercise schedule tends to make one obese. As we approach middle age, our physical activi

Ecosystem degradation and wildlife, Ecosystem Degradation and Wildlife ...

Ecosystem Degradation and Wildlife Man is an animal with ecological requirements just like any other animal. It constantly needs a source of energy and.minera1 nutrients for i

Explain homologous and heterologous immunoglobulins, What is the difference...

What is the difference between homologous and heterologous immunoglobulins? Homologous immunoglobulin is the human (from the similar species) immunoglobulin. In case of inocula

Sympatric speciation, Sympatric speciation can be regarded as speciation wh...

Sympatric speciation can be regarded as speciation where parent species gives rise to a daughter species without the individuals of a species being separated by space or territory.

Explain the class reptilia perform gas, Do beings of the class Reptilia per...

Do beings of the class Reptilia perform gas exchange in the same way amphibians do? These beings do not have permeable skin so they do not make cutaneous respiration such as a

Explain about the probiotics, Explain about the Probiotics? A mono or m...

Explain about the Probiotics? A mono or mixed culture of living organisms, which when ingested in certain amounts, has a positive impact on host health, beyond conventional nut

What are colonies and societies, Q. What are colonies and societies? Th...

Q. What are colonies and societies? The Colonies are functional integrated aggregates formed by individuals of the similar species. The Colonies are often confused with a singl

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd