The Living World Test - 84

Taxon represents a group of many organisms, not individual organism.

The taxonomic hierarchy was introduced by Linnaeus. It is also known as a Linnaean hierarchy. It is used to classify organisms into different categories. It includes the sequence of categories in a decreasing or increasing order from kingdom to species and vice versa. The domain is the highest rank in the hierarchy followed by kingdom, division or phylum, class, order, family, genus, and species in the ascending order. The ascending order will be species, genus, family, order, class, phylum and kingdom. Species is the lowest rank in the hierarchy. 

A. Correct option - A

Holotype is a single specimen along with the description. On this holotype the name of the genus, species are mentioned and the description is also given. This is done by a single team or a person. The duplicate of the nomenclatural type is called isotype 

• Ernst Mayr proposed the concept of biospecies. 
• According to this concept of Mayr, all the members that can interbreed among themselves and can produce fertile offspring are the member of same species. 
  
• According to Mayr, the words 'reproductively isolated' are the key words of the biological species. 
  

Subphylum Vertebrata is divided Into two divisions. They are agnatha (jawless) and gnathostomata (with jaw). Agnatha are further divided into two classes-Ostracodermi, which is extinct and Cyclostomata (e.g., hag fish). Jawed vertebrates are divided into two superclasses-Pisces (true fish) and Tetrapoda (four limbs).

$$\textbf{Correct answer: C}$$ 

$$\textbf{Option (A):}$$ 

$$\bullet$$ Based on the taxonomic hierarchy, the phylum is close to kingdom and class. Multiple phyla form a given kingdom and multiple classes form a single phylum.

$$\textbf{Option (B):}$$ 

$$\bullet$$ Class is close to order and phylum. Multiple orders together form a class and multiple classes together form a phylum.

$$\textbf{Option (C):}$$ 

$$\bullet$$ The closest categories to family are order and genus. This is because multiple families together form an order.

$$\bullet$$ This is why an order will be the closest of all the taxonomic hierarchies.

$$\textbf{Option (D):}$$ 

$$\bullet$$ Species is the lowest rank in the taxonomic hierarchy and the only close category with it is the genus.

Hence, the correct answer is option (C).

A nematocyst is a specialized cell in the tentacles of a jellyfish or other coelenterate, containing a barbed or venomous coiled thread that can be projected in self-defence or to capture prey. These, minute, elongated, or spherical capsule produced exclusively by members of the phylum Cnidaria also called Coelenterata (e.g., jellyfish, corals, sea anemones). Several such capsules occur on the body surface.

Keys help in identification of plants and animals by comparing similarities and dissimilarities. In a key there are two opposite terms that form a couplet. If one is selected the other automatically is rejected. The key follows this pattern till a set sequence of taxa is reached.

The correct hierarchical order of taxonomical classification is: