কর্ডাটা

উইকিপিডিয়া, মুক্ত বিশ্বকোষ থেকে
Chordata
সময়গত রেঞ্জ: Early Cambrian – Recent, ৫৪০–০Ma
The X-ray tetra (Pristella maxillaris) is one of the few chordates with a visible backbone. The spinal cord is housed within its backbone.
বৈজ্ঞানিক শ্রেণীবিন্যাস
Classes

See below

কর্ডাটা বা ( কর্ডাটা পর্ব ) মেরুদন্ডী বা ভার্টিব্রেটা (Vertibrata) এবং অমেরুদন্ডী বা ইনভার্টিব্রেটা (Invertibrata) উভয়শ্রেণীর প্রাণীদেরকে বোঝায়। গ্রিকশব্দ chorde যার মানে দড়ি বা বাদ্যযন্ত্রের তন্ত্রী বা এই পর্বভুক্ত প্রাণীদের নোটোকর্ড নামক একটি স্থিতিশীল অঙ্গ থাকে তাই এই পর্বের নাম কর্ডাটা। এই পর্বে প্রজাতির সংখ্যা প্রায় ৪৫ হাজার।

সংজ্ঞা[সম্পাদনা]

1 = bulge in spinal cord ("brain")
4 = post-anal tail
5 = anus
9 = space above pharynx
11 = pharynx
13 = oral cirri
14 = mouth opening
16 = light sensor
17 = nerves
19 = hepatic caecum (liver-like sack)
Anatomy of the cephalochordate Amphioxus. Bolded items are components of all chordates at some point in their lifetime, and distinguish them from other phyla.

Chordates form a phylum of creatures that are based on a bilateral body plan[১], and is defined by having at some stage in their lives all of the following:[২]

  • A notochord, in other words a fairly stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail.
  • A dorsal neural tube. In fish and other vertebrates this develops into the spinal cord, the main communications trunk of the nervous system.
  • Pharyngeal slits. The pharynx is the part of the throat immediately behind the mouth. In fish the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live.
  • A muscular tail that extends backwards behind the anus.
  • An endostyle. This is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.[৩] It also stores iodine, and may be a precursor of the vertebrate thyroid gland.[২]

তথ্যসূত্র[সম্পাদনা]

  1. Valentine, J.W. (2004)। On the Origin of Phyla। Chicago: University Of Chicago Press। পৃ: 7। আইএসবিএন 0226845486 "Classifications of organisms in hierarchical systems were in use by the seventeenth and eighteenth centuries. Usually organisms were grouped according to their morphological similarities as perceived by those early workers, and those groups were then grouped according to their similarities, and so on, to form a hierarchy."
  2. ২.০ ২.১ Rychel, A.L., Smith, S.E., Shimamoto, H.T., and Swalla, B.J. (2006)। "Evolution and Development of the Chordates: Collagen and Pharyngeal Cartilage"। Molecular Biology and Evolution 23 (3): 541–549। ডিওআই:10.1093/molbev/msj055পিএমআইডি 16280542 
  3. Ruppert, E. (2005)। "Key characters uniting hemichordates and chordates: homologies or homoplasies?"Canadian Journal of Zoology 83: 8–23। ডিওআই:10.1139/Z04-158। সংগৃহীত 2008-09-22 

বহিঃসংযোগ[সম্পাদনা]