What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

What features are used as the basis of animal classification?

Levels of organisation, symmetry, number of germ layers, presence and nature of coelom, segmentation and presence or absence of a notochord.

Distinguish between coelomate, pseudocoelomate and acoelomate animals.

Coelomates have a body cavity lined by mesoderm, pseudocoelomates have a cavity not fully lined by mesoderm, and acoelomates have no body cavity.

Which phylum is characterised by a water vascular system?

Echinodermata, whose members use the water vascular system in locomotion, food capture and respiration.

Why are arthropods the largest group of the animal kingdom?

Their jointed appendages, chitinous exoskeleton, varied respiratory and sensory organs and adaptability let them occupy nearly every habitat, so over two-thirds of named species are arthropods.

Name the distinguishing features of phylum Chordata.

Presence of a notochord, a dorsal hollow nerve cord, paired pharyngeal gill slits and a post-anal tail.

What are the peculiar features of parasitic platyhelminthes?

They have a dorsoventrally flattened body with hooks and suckers, absorb nutrients through the body surface and have flame cells for excretion.

Differentiate between intracellular and extracellular digestion.

Intracellular digestion occurs within cells (as in sponges), while extracellular digestion occurs outside cells in a cavity or gut (as in higher animals).

In which phylum is body segmentation first observed?

True metameric segmentation is first observed in phylum Annelida.

CBSE · Senior secondary

CBSE Class 11 — Notes, Chapters & Practice Quizzes

Q: Justify the statement that all vertebrates are chordates but not all chordates are vertebrates.

All vertebrates possess a notochord, dorsal nerve cord and gill slits (chordate features), but protochordates also have these features without a vertebral column, so they are chordates yet not vertebrates.

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Chapter 4: Animal Kingdom — Class 11 Biology

Biology · 19 chapters

Summary, key terms, important questions and a practice quiz with AI diagnosis for each.

Chapter 4: Animal Kingdom

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A body cavity lined by mesoderm is called a:

Summary

This chapter explains how the animal kingdom is classified using fundamental features shared across diverse forms, then surveys the major phyla. The basis of classification includes levels of organisation (cellular, tissue, organ and organ-system), body symmetry (asymmetrical, radial or bilateral), the number of germ layers (diploblastic or triploblastic), the nature of the body cavity or coelom (coelomate, pseudocoelomate or acoelomate), segmentation and the presence of a notochord. Using these, the chapter describes Porifera (sponges with choanocytes), Coelenterata or Cnidaria (with cnidoblasts and polyp and medusa forms), Ctenophora (comb jellies), Platyhelminthes (flatworms), Aschelminthes (roundworms), Annelida (segmented worms), Arthropoda (the largest phylum, with jointed appendages), Mollusca (soft-bodied with a calcareous shell), Echinodermata (spiny-skinned with a water vascular system) and Hemichordata. Phylum Chordata is defined by a notochord, dorsal hollow nerve cord and pharyngeal gill slits; it includes protochordates and the vertebrates, which are further divided into Cyclostomata, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves and Mammalia. The chapter notes which classes are cold-blooded and which are warm-blooded, and contrasts oviparous and viviparous reproduction. A key point is that all vertebrates are chordates but not all chordates are vertebrates.

Basis of classification: levels, symmetry, coelomDiploblastic and triploblastic organisationNon-chordate phyla from Porifera to HemichordataPhylum Chordata and its featuresVertebrate classes: fishes to mammalsComparison of chordates and non-chordates

Key terms

Coelom

A body cavity lined by mesoderm; animals with it are coelomates, those without are acoelomates, and those with a partly lined cavity are pseudocoelomates.

Notochord

A mesodermally derived rod-like structure on the dorsal side; animals with it are chordates.

Diploblastic

Having cells arranged in two germ layers, ectoderm and endoderm, as in coelenterates.

Triploblastic

Having three germ layers, ectoderm, mesoderm and endoderm, as in platyhelminthes to chordates.

Metamerism

The serial repetition of body segments with at least some organs repeated, as in earthworm.

Choanocytes

Collar cells lining the canal system of sponges that help in food gathering and water flow.

Important questions

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Coelom

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A body cavity lined by mesoderm; animals with it are coelomates, those without are acoelomates, and those with a partly lined cavity are pseudocoelomates.

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Practice quiz · Animal Kingdom

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