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The main difference between chordates and non-chordates is that chordates are the animals with backbone whereas non-chordates are the animals without a backbone.
Chordates vs. Non-Chordates
Kingdom Animalia is divided into different phyla on the basis of the structure and cellular organization of the animals. Up till now, there are almost 30 animal phyla recognized. Animals like arthropods, mollusks, and annelids, etc. come under Non-chordate. The major and the last group of the animal kingdom is the phylum Chordata which includes pieces, Aves and mammals, etc. Chordates are the animals that have a notochord or backbone while non-chordates are the animals that are without a backbone. Chordates are the well-developed animals with the well-developed body systems whereas non-chordates are the less developed animals.
What are Chordates?
The word “Chordate” is derived from the Greek word, “chord” which means “ cord or string” and “ata” means “bearing.” They have 49,000 species up till now from which there are 2500 species of amphibian, 9000 birds, 4500 mammals, and around 6000 reptiles. They vary in size from medium to large, with exceptions of the gigantic blue whale and the smallest fish. They are considered as the most ecologically successful and largest group today. Chordates are able to occupy every type of habitat. They are found in the sea (marine), freshwater (aquatic), in the air (aerial) and on land (terrestrial), etc. from the poles to the equator. They have notochord or backbone and have well-developed body systems.
Subphyla of Chordates
- Urochordata: These are the chordates in which notochord is present only in their larval tail.
- Cephalochordata: In these chordates, notochord extends from head to tail region throughout their life.
- Vertebrata: In vertebrates, the notochord is present at their embryonic stage, which gets replaced by a bony vertebral column in the adult.
What are Non-Chordates?
Non-chordates also belongs to kingdom Animalia. They share many similarities and dissimilarities with chordates. They are less developed as compared to the chordates. They do not have well-developed body systems like the digestive system, reproductive system, etc. In non-chordates, the notochord is absent and pharynx not perforated by gill-slits. Their heart is also dorsal in position. They include the phyla like Porifera, Ctenophora, Platyhelminthes, Aschelminthes, Coelenterata (Cnidaria), Annelida, Arthropoda, Mollusca, and Echinodermata, etc.
- Animals that have a backbone are called chordates whereas animals that are without a backbone are called non-chordates.
- Chordates respire through gills or lungs, on the other hand, non-Chordates respire through the body surface, gills or tracheae.
- Chordates maybe both cold or warm-blooded conversely non-Chordates are always cold-blooded.
- The notochord is present at some stage in chordates or replaced by a backbone made of ring-like vertebrae on the flip side, notochord or backbone absent in non-Chordates.
- Chordates have hollow central dorsal nervous system whereas non-chordates have a solid central nervous system.
- Chordates are triploblastic while germ layers can be absent in non-chordates or they may be diploblastic or triploblastic.
- In chordates, hemoglobin is present in red corpuscles (RBC), but hemoglobin is present in plasma or absent in non-Chordates
- Chordates are truly coelomate, i.e., they have true body cavity whereas non-Chordates may be acoelomate (without body cavity), pseudocoelomate (false body cavity) or truly coelomate.
- Chordates have bilateral symmetry whereas non-chordates may be radial, biradial, bilateral or without any symmetry.
- Chordates have true metamerism, but non-chordates may have true or pseudo metamerism or without metamerism.
- The post-anal tail is usually present in chordates; on the other hand, the post-anal tail is absent in non-chordates.
- Chordates have a well-developed organ system whereas non-chordates may or may not have an organ system.
- The brain of chordates is dorsal to pharynx in the head while in the non-Chordates brain is absent or above pharynx (if present).
- Limbs are derived from several segments in chordates conversely limbs are derived from the same segment in non-chordates.
- The gut position is ventral to nerve cord in chordates whereas gut position is dorsal to nerve cord in non-chordates.
- In chordates, the anus is differentiated and opens before the last segment while in non-chordates, anus opens on the last segment or absent.
- Pharyngeal gill slits are present at some stage of life in chordates whereas pharyngeal gill slits are absent in non-Chordates.
- Chordates have a closed blood vascular system. While the blood vascular system is absent in non-chordates and if present it may be open or closed.
- The heart is ventrally placed in chordates but the heart is absent in non-chordates and if present it may be dorsal or lateral.
- In chordates, nerve cord is single, dorsal, and without ganglia on the other side in non-chordates, nerve cord is double, ventral, and usually bearing ganglia.
- Regeneration power is usually poor in chordates while regeneration power is usually good in non-chordates.
- Exoskeleton and endoskeleton both are present in chordates whereas the only exoskeleton is present in non-chordates.
- Hemichordata, Cyclostomata, Reptiles, Amphibia, Aves and Mammals are the examples of chordates whereas protozoa, Arthropods, Annelids, etc. are the examples of non-chordates.
From the above discussion, it is summarized that both chordates and non-chordates belong to Kingdom Animalia. Chordates are the well-developed animals with proper body systems and backbone or notochord present whereas non-chordates are less developed as compared to chordates and do not have a notochord.