#Kingdom Animalia

Animal Classification

Kingdom Animalia is considered monophyletic because

Kingdom Animalia recognized as monophyletic because all metazoan phyla trace to single common ancestor, a colonial choanoflagellate-like protoctist, confirmed through phylogenomic concatenation of hundreds of nuclear genes, 18S rRNA, homeobox Hox clusters, Wnt signaling and mitochondrial genome arrangement. Monophyly supported by exclusive shared derived characters: multicellular heterotrophy with ingestion, collagen type IV basal lamina, cadherin mediated adhesion, tight junctions, blastula stage and regulated apoptosis. Polyphyletic hypothesis requiring independent origins refuted by robust molecular trees and embryonic homology, thus all animals share exclusive common ancestry not convergent similarity.

Ref: Campbell Biology 12th ed. Chapter 32 Animal Phylogeny Overview; NCERT Class 11 Chapter 4 Animal Kingdom

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Biological Classification

A prominent evolutionary feature seen in higher forms of Kingdom Animalia is the development of a complex:

As animals evolved to actively search for food, avoid predators, and find mates, they required advanced bodily coordination. The NCERT textbook notes that higher forms of Kingdom Animalia show extraordinary elaboration and development of complex 'sensory and neuromotor mechanisms'. This encompasses everything from simple nerve nets in lower animals to the highly advanced brain and sensory organs found in vertebrates.

Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.5 Kingdom Animalia

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Biological Classification

The general mode of nutrition in Kingdom Animalia, characterized by the ingestion of food, is biologically termed:

According to the NCERT textbook, animals are strict heterotrophs that must consume organic matter. Their specific mode of nutrition involves directly taking in solid or liquid food particles into an internal digestive cavity where enzymes break it down. This specific process of ingestion-based nutrition is biologically termed 'holozoic' nutrition, distinct from the absorptive nutrition seen in fungi.

Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.5 Kingdom Animalia

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Biological Classification

Which fundamental cellular structure is completely absent in the members of Kingdom Animalia?

Kingdom Animalia comprises heterotrophic, multicellular eukaryotic organisms. A major, defining structural characteristic that distinguishes animal cells from plant and fungal cells is the complete absence of a 'cell wall'. The NCERT textbook emphasizes this structural deficit, meaning animal cells are bound only by a flexible plasma membrane, which allows for highly varied cell shapes and the development of complex tissues like muscles and nerves.

Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.5 Kingdom Animalia

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