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Animal Kingdom - Salient features and classification of Chordates

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Chordates are characterized by the presence of a notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits. They exhibit bilateral symmetry, are triploblastic, and have a coelomate level of organization with an organ-system level of body plan.

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Subphylum Urochordata (Tunicata): The notochord is present only in the larval tail, for example, AscidiaAscidia and SalpaSalpa.

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Subphylum Cephalochordata: The notochord extends from the head to the tail region and is persistent throughout their life, for example, BranchiostomaBranchiostoma (Amphioxus).

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Subphylum Vertebrata: Members possess a notochord during the embryonic period, which is later replaced by a cartilaginous or bony vertebral column in the adult. Thus, 'all vertebrates are chordates, but all chordates are not vertebrates.'

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Vertebrata is divided into Agnatha (lacks jaw, e.g., Class Cyclostomata) and Gnathostomata (bears jaw). Gnathostomata is further divided into Super-classes Pisces (fins) and Tetrapoda (limbs).

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Class Chondrichthyes (Cartilaginous fishes) possess a ventral mouth, placoid scales, and lack an operculum (gill cover), whereas Class Osteichthyes (Bony fishes) have a terminal mouth, cycloid/ctenoid scales, and possess an operculum.

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Tetrapods include Classes Amphibia, Reptilia, Aves, and Mammalia. Transition from 33-chambered hearts in Amphibians and most Reptiles to 44-chambered hearts in Crocodiles, Birds, and Mammals is a key evolutionary feature.

📐Formulae

Chordate Characteristics=Notochord+Dorsal Hollow Nerve Cord+Pharyngeal Gill Slits+Post-anal Tail\text{Chordate Characteristics} = \text{Notochord} + \text{Dorsal Hollow Nerve Cord} + \text{Pharyngeal Gill Slits} + \text{Post-anal Tail}

Vertebrata⊂Chordata\text{Vertebrata} \subset \text{Chordata}

Heart Chambers (Amphibia/Reptilia)=2 Atria+1 Ventricle=3\text{Heart Chambers (Amphibia/Reptilia)} = 2 \text{ Atria} + 1 \text{ Ventricle} = 3

Heart Chambers (Aves/Mammalia)=2 Atria+2 Ventricles=4\text{Heart Chambers (Aves/Mammalia)} = 2 \text{ Atria} + 2 \text{ Ventricles} = 4

Respiration (Aquatic)∝Gills/Skin, Respiration (Terrestrial)∝Lungs\text{Respiration (Aquatic)} \propto \text{Gills/Skin}, \text{ Respiration (Terrestrial)} \propto \text{Lungs}

💡Examples

Problem 1:

Distinguish between the circulatory systems of a ChameleonChameleon (Reptile) and a ColumbaColumba (Pigeon/Aves).

Solution:

The ChameleonChameleon typically possesses a 33-chambered heart (incomplete 44-chambered), whereas ColumbaColumba possesses a complete 44-chambered heart.

Explanation:

In Reptiles (except crocodiles), the ventricle is incompletely divided, leading to some mixing of oxygenated (O2O_2) and deoxygenated (CO2CO_2) blood. In Aves, the separation is complete, ensuring high efficiency for flight.

Problem 2:

Identify the unique feature of CyclostomataCyclostomata regarding their mouth and feeding habit.

Solution:

They have a sucking and circular mouth without jaws (AgnathaAgnatha).

Explanation:

Cyclostomes like PetromyzonPetromyzon (Lamprey) are ectoparasites on some fishes. Their jawless, circular mouth allows them to attach to the host's body.

Problem 3:

A fish is found with an air bladder that regulates buoyancy. To which class does it likely belong?

Solution:

Class Osteichthyes (Bony fishes).

Explanation:

The presence of an air bladder is a salient feature of bony fishes (OsteichthyesOsteichthyes), allowing them to maintain buoyancy without constant swimming, unlike ChondrichthyesChondrichthyes (Cartilaginous fishes) which lack an air bladder and must swim constantly to avoid sinking.