This chapter is highly factual and contains many technical terms. These solutions provide the specific NCERT-aligned definitions and examples that are critical for scoring well in subjective and objective exams.
NEET consistently features high-weightage questions from this chapter, particularly on the unique features of different phyla. These solutions provide the exact keywords and "exception-based" facts that are frequently tested.
Yes, they are fully updated. They are useful because they simplify the vast diversity of the animal kingdom into a logical, hierarchical structure, making it much easier for students to retain and recall information.
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NCERT Solutions Class 11 Biology Chapter 4 - Animal Kingdom
NCERT Solutions for Class 11 Biology Chapter 4 (Animal Kingdom) explore the vast diversity of the animal world, ranging from microscopic sponges to the blue whale. This chapter provides a systematic framework for classification based on common fundamental features like cell arrangement, body symmetry, and the nature of the coelom.
NCERT Solutions for Class 11 Biology Chapter 4 by ALLEN are developed by expert faculty to help students memorize the distinguishing features of various phyla. The solutions focus on the unique "identifying characters" of each group—such as the water vascular system in Echinoderms or the presence of a notochord in Chordates—making it easier to handle "Match the following" and "Identify the organism" type questions. For NEET aspirants, this is one of the most important chapters in the Diversity unit. These solutions provide the conceptual clarity needed to navigate the transition from Non-Chordates to Chordates and understand the specialized adaptations of different classes like Cyclostomata, Chondrichthyes, and Osteichthyes.
What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
Ans. The common fundamental features used for classifying animals include arrangement of cells, nature of coelom, level of organisation, symmetry of body, patterns of digestive, circulatory and reproductive systems. If these fundamental features are not taken into account, animal classification would become very confusing and difficult.
If you are given a specimen, what are the steps that you would follow to classify it?
Ans. Various steps considered to classify a specimen are:
Level of organisation : Cellular, tissue, organ or organ-system level.
Body symmetry : Asmmetrical, radical or bilateral symmetry.
Germ layers : Diploblastic of triploblastic.
Body cavity (coelom) : Acoelomate, pseudocoelomate or coelomate.
Segmentation : Presence or absence of segmentation.
Presence or absence of notochord : Used particularly for distinguishing chordates from non-chordates.
How useful is the study of the nature of body cavity and coelom in the classification of animals?
Ans. Organisms can be classified according to presence or absence of the coelom. The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates. In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity iscalled pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes. In pseudocoelomates, body cavity is derived from blastocoel of the embryo. The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes.
Distinguish between intracellular and extracellular digestion.
Ans. Differences between intracellular and extracellular digestion are:
Intracellular digestion
Extracellular digestion
(i)
It occurs inside the cell.
It occurs outside the cell in the cavity of the alimentary canal.
(ii)
Digestive enzymes are secreted by surrounding cytoplasm into the food vacuoles.
Digestive enzymes secreted by special cells into the cavity of alimentary canal by ducts.
(iii)
The products of digestion diffuse into the cytoplasm.
The products of digestion are absorbed the intestinal wall.
What is the difference between direct and indirect development?
Ans. Differences between direct development and indirect development are :
Direct development
Indirect development
(i)
Young ones may resemble the adult.
In this young hatchlings (larvae) do not resemble the adult.
(ii)
Intermediate stages are absent.
Intermediate stages are present.
(iii)
Metamorphosis is absent.
Metamorphosis is seen in indirect development.
E.g., Hydra, man
E.g., Frog, cockroach
What are the peculiar features that you find in parasitic platyhelminthes?
Ans. Following are the peculiar features of parasitic platyhelminthes:
(i) The thick tegument (body covering) resistant to the host's digestive enzymes and antitoxins.
(ii) Adhesive organs like suckers in flukes and the hooks and suckers in tapeworms provide a firm grip on or in the host's body.
(iii) Loss of locomotory organs.
(iv) Digestive organs are absent in tapeworms because digested and semidigested food of the host is directly absorbed' through the body surface.
What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
Ans. Arthropods are most successful animals and constitute the largest group of the animal kingdom because :
The have conquered land, sea and air and occupy a wide range of habitats. They have a thick, tough and non-living chitinous cuticle, which forms an exoskeleton and protects them from predators.
The exoskeleton also provides support and prevents water loss, helping them survive on land. They possess jointed appendages, which are modified for different functions such as walking, swimming, feeding and sensing.
They have well-develolped organ systems and highly specialised body structures.
Hence, their adaptability, protective exoskeleton and specialised appendages make arthropoda the largest and most successful animal phylum.
Water vascular system is the characteristic of which group among the following ?
"All vertebrates are chordates but all chordates are not vertebrates". Justify the statement.
Ans. Chordates are the animals that possess notochord (a stiff, supporting rod like structure present on the dorsal side) at some stage of their lives. Phylum Chordata is divided into three Subphyla: Urochordata or tunicata, Cephalochordata and Vertebrata. Subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marine. In urochordata, notochord is present only in tail of larva and disappears in adults, while in cephalochordata, it extends from head to tail region and persists throughout the life.
The members of Subphylum Vertebrata a possess notochord during the embryonic period and is replaced by a cartilaginous or bony vertebral column in the adult. Thus all vertebrates are chordates but all chordates are not vertebrates.
How important is the presence of air bladder in Pisces?
Ans. Bony fishes have a sac-like outgrowth, the swim bladder also called air bladder, which arises from the dorsal wall of oesophagus. It is hydrostatic in function. It regulates buoyancy and helps them to swim up and down, thus preventing them from sinking. In some species air bladder also helps in respiration. It also serves as resonating chamber to produce or receive sound.
What are the modifications that are observed in birds that help them fly?
Ans. Birds have adapted to aerial mode of life through the following modifications:
(i) Body is streamlined and spindle shaped which minimise resistance to the wind.
(ii) Body is covered with feathers. It reduces the friction, prevent loss of heat and help to maintain constant temperature.
(iii) Forelimbs are modified into wings, which help during flight.
(iv) Flight muscles are greatly developed
(v) Most of the bones are pneumatic, hollow and filled with air which makes the body lighter and helps in flight.
Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
Ans. No, the number of eggs or young ones produced by an oviparous and viviparous mother respectively cannot be equal. Oviparous mother lays large number of eggs, as the eggs are laid outside the body, so they are not protected from predators and harsh environmental conditions, and therefore destroyed. However in viviparous mother, eggs are not laid outside, but the embryos develop inside the mother and thus are protected from the outside harsh environment, thus, the number of eggs produced are less. Therefore, the number of eggs or young ones produced by an oviparous and viviparous mother respectively cannot be equal.
Segmentation in the body is first observed in which of the following?
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda
Ans. (c) Annelida
Match the following:
(a) Operculum (i) Ctenophora
(b) Parapodia (ii) Mollusca
(c) Scales (iii) Porifera
(d) Comb plates (iv) Reptilia
(e) Radula (v) Annelida
(f) Hair (vi) Cyclostomata and Chondrichthyes
(g) Choanocytes (vii) Mammalia
(h) Gill slits (viii) Osteichthyes
Prepare a list of some animals that are found parasitic on human beings.
Ans. List of some animals that are found parasitic on human beings :
Parasite
Direct development
Indirect development
Taenia solium (Pork Tapeworm)
Endoparasites
Small intestine
Schistosoma (Blood fluke)
Endoparasites
Hepatic portal system and mesenteric blood vessels.
Ancylostoma duodenale (Hook worm)
Endoparasites
Small intestine
Wuchereria (Filarial worm)
Endoparasites
Lymph nodes and lymphatic vessels.
Enterobius (Pin worm)
Endoparasites
Colon, caecum or vermiform appendix
3.0Key Features of NCERT Solutions for Class 11 Biology Chapter 4
Criterion-Based Differentiation: The solutions clearly explain the fundamental differences between various groups (e.g., Diploblastic vs. Triploblastic), which is essential for understanding evolutionary complexity.
Unique Character Highlights: Expertly curated points that highlight "exclusive characters" (e.g., comb plates in Ctenophora or radula in Mollusca) that are frequently tested in NEET.
Comparative Chordate Tables: Detailed comparison tables for Chondrichthyes and Osteichthyes, as well as the differences between Chordates and Non-Chordates.
Morphological and Anatomical Logic: Step-by-step breakdown of why certain animals are placed in specific phyla despite looking similar, such as the difference between a Silverfish (Arthropod) and a Jellyfish (Cnidarian).
Prepared by Expert Faculty: Prepared by ALLEN subject experts, ensuring that the terminology and classifications are biologically accurate and aligned with the latest NCERT syllabus.
Example-Rich Explanations: The solutions provide multiple scientific and common names for each phylum to help students build the vocabulary required for competitive exams.