Every living organism is made up of tiny building blocks called cells — the fundamental units of life. Chapter 4 of Class 11 Biology, Animal Kingdom, unravels the vast diversity of animals by classifying them based on their structural and functional features. From the simplest sponges to complex mammals, this chapter explores how animals are organized, how their body systems evolve, and how different phyla exhibit increasing levels of complexity in body design, symmetry, and organization. It also provides insight into the distinguishing characteristics of each phylum, helping students understand evolutionary relationships and adaptations in the animal world.
The NCERT Solutions for Animal Kingdom provided here include detailed, step-by-step answers to all textbook questions, making even intricate classifications and examples easy to remember. These solutions help students strengthen their conceptual clarity, improve answer-writing skills, and prepare confidently for both school exams and competitive tests like NEET.
NCERT Solutions for Class 11 Biology Chapter 4- All Exercise Questions
Q.
What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
Q.
If you are given a specimen, what are the steps that you would follow to classify it?
Q.
How useful is the study of the nature of the body cavity and coelom in the classification of animals?
Q.
Distinguish between intracellular and extracellular digestion?
Q.
What is the difference between direct and indirect development?
Q.
What are the peculiar features that you find in parasitic platyhelminthes?
Q.
What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
Q.
Water vascular system is the characteristic of which group of the following:
(a) Porifera
(b) Ctenophora
(c) Echinodermata
(d) Chordata
Q.
“All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.
Q.
How important is the presence of air bladder in Pisces?
Q.
What are the modifications that are observed in birds that help them fly?
Q.
Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
Q.
Segmentation in the body is first observed in which of the following:
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda
Q.
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 ) Hairs (vi) Cyclostomata and Chondrichthyes
(g) Choanocytes (vii) Mammalia
(h) Gill slits (viii) Osteichthyes
Q.
Prepare a list of some animals that are found parasitic on human beings.
Class 11 Biology Chapter 4 Questions and Answers PDF
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Animal Kingdom NCERT Solutions: Class 11 Biology Chapter 4 Question and Answers
Q.1 What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
For classification of animals, various common features such as the arrangement of cells, body symmetry, nature of coelom, circulatory system, the pattern of digestive system or reproductive system are taken into consideration. If these common features are not considered, the classification of each organism would become very difficult and chaotic. Classification of animals also helps in comparing different organisms. So, if only a single characteristic is considered while classifying the living organisms then the main objective would not be fulfilled. Thus, to study the classification of animals then it has to be based on various common basic features. This process also helps in the addition of new discovery into the respective group.
Q.2 If you are given a specimen, what are the steps that you would follow to classify it?
Taxonomy is the study of principles and procedures of classification. Classification is the arrangement of living things according to their similarities and differences which bring order in the vast assemblage of living things in the world. A specimen can be classified in a stepwise process using the following classification categories:
(i) Classify level of organization: Classify the arrangement of cells in the cellular and tissue-level organization.
(ii) Symmetry: Classify the organism according to radial or bilateral symmetry.
(iii) Classify Diploblastic or triploblastic organization
(iv) Presence or absence of body cavity
(v) Type of coelom development
(vi) Classify segmentation
(vii) Differentiate the presence or absence of notochord.
Q.3 How useful is the study of the nature of the body cavity and coelom in the classification of animals?
Coelom is a fluid-filled cavity formed between the gut wall and the body wall lined by the mesodermal cells. Presence or absence of coelom is an important criterion for animal classification. The animals with bilateral symmetry are further classified into three types of groups based on the presence or absence of coelom. They are as follows:
- Coelomates: In these animals, true coelom lined by mesoderm is present. E.g. Annelids, Arthropoda, Mollusca, Echinodermata, Hemichordata, Chordata
- Pseudocoelomates: In these animals, the body cavity is not lined by mesoderm instead the mesoderm is present in scattered pouches between the ectoderm and the endoderm. E.g. Aschelminthes
- Acoelomates: In these animals, body cavity is absent. E.g. Platyhelminthes
Q.4 Distinguish between intracellular and extracellular digestion?
| Intracellular Digestion |
Extracellular Digestion |
| It occurs in lower organisms |
Occurs in multicellular organisms |
| Occurs within cells |
Occurs within the cavity of the alimentary canal, outside the cell |
| It is less efficient with no regional differentiation |
Highly efficient with regional differentiation |
| Enzymes associated are very few |
Large number of digestive glands and enzymes are required |
Q.5 What is the difference between direct and indirect development?
| Direct development |
Indirect development |
| Direct development has a larval stage that is morphologically distinct from the adult. |
In indirect development, larval stage is absent, the embryo develops into a mature organism (looks like a miniature adult) without entering into the larval stage. |
| A process called metamorphosis transforms the larva into a mature adult. |
In indirect development, metamorphosis is absent. |
| It is found in invertebrates and amphibians. |
It is found in fishes, reptiles and mammals. |
Q.6 What are the peculiar features that you find in parasitic platyhelminthes?
The peculiar features of parasitic platyhelminthes are as follows:
- Hooks and suckers are present to attach to the wall of the gut.
- They have an extra coating (of glycocalyx) to protect themselves from being digested in the gut.
- They absorb nutrients from the host directly through their body surface. Their digestive systems are less evolved as compared to the free-living platyhelminthes.
- Locomotory organs like cilia and sensory organs like the primitive eye are absent in the parasitic forms of flatworms.
- Parasitic flatworms are mostly hermaphrodite ensuring reproduction in the host. The reproductive capacity is enhanced with most of their body lumen packed with testes and eggs.
Q.7 What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
Arthropoda is the largest phylum of animal kingdom. Over two-thirds of all known species on earth are arthropods. The following are the reasons for arthropods to constitute the largest group of the animal kingdom:
- Arthropods are very diverse in structure and form.
- Their diversity in form is responsible for their dispersion into varied habitats. Arthropods are known to inhabit the ocean depths to the tallest mountain peaks.
- Their hard exoskeleton made of chitin is tough and protects the animal from extreme dryness. The exoskeleton is also insoluble in water, weak alkaline and acidic solutions.
- They have joint appendages that allow for efficient and precise movements. Many appendages are modified to meet the need of the arthropod for a specific foraging behaviour or a habitat.
- Their reproductive cycle is short and the female lays numerous eggs at one time.
Q.8 Water vascular system is the characteristic of which group of the following:
(a) Porifera
(b) Ctenophora
(c) Echinodermata
(d) Chordata
Water vascular system is the characteristic of Echinodermata.
Q.9 “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.
To understand the above statement, one needs to define the two words – notochord and vertebra – from which the terms chordates and vertebrates are derived.
Notochord: The notochord is a flexible rod-shaped structure found in embryos of all chordates.
Vertebral column: The vertebral column, also known as backbone or spine, is a bony structure found in vertebrates. It is formed from individual bones called vertebrae.
Chordata is a phylum which is divided into three subphyla – Urochordata, Cephalochordata and Vertebrata. All the chordates at some point of their lives possess a notochord. However, in vertebrates, this notochord is replaced by the vertebral column in the adult stage. Hence, it is right to state that “All vertebrates are chordates but all chordates are not vertebrates”.
Q.10 How important is the presence of air bladder in Pisces?
Air bladder or swim bladder is a sac filled with air that regulates buoyancy in fishes. It plays a very important role in Pisces. The fishes (like Osteichthyes) where air bladder is present, it plays the following roles:
- The air bladder controls the buoyancy by enabling the fish to stay at a particular water depth without having to waste energy in swimming continuously.
- It acts as a resonating chamber to produce or receive sound.
In another kind of fishes (like Chondrichthyes), the air bladder is absent. Therefore these fishes have to swim constantly to avoid sinking resulting in the consumption of a lot of energy.
Q.11 What are the modifications that are observed in birds that help them fly?
Some of the modifications that help birds to fly are listed below:
- The forelimbs are modified into wings.
- Birds have feathers that help them fly, steer and balance.
- Long bones are hollow with air cavities making their body weight light.
- Birds have air sacs that connect to the lungs and provide them with additional oxygen which is essential for flying.
- Birds have well-developed eyesight and brains that help them gauge any approaching danger as well as to forage for food.
Q.12 Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
An oviparous mother lays more eggs at one time as compared to the number of offspring a viviparous mother gives birth to at any given time. This is because of the following reasons:
- In oviparous mother, the eggs are laid soon after fertilisation, or eggs are externally fertilised. Therefore many eggs can be laid at one time. This also provides an evolutionary advantage as many eggs are liable to be eaten, destroyed during the period of development.
- In the case of the viviparous mother, she has to house the embryo in the uterus till the full term of development. The embryo also draws nutrition from its mother. The mother thus is constrained by space in the uterus.
Q.13 Segmentation in the body is first observed in which of the following:
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda
(c) Annelida
Q.14 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 ) Hairs (vi) Cyclostomata and Chondrichthyes
(g) Choanocytes (vii) Mammalia
(h) Gill slits (viii) Osteichthyes
| (a) Operculum |
(viii) Osteichthyes |
| (b) Parapodia |
(v) Annelida |
| (c) Scales |
(iv) Reptilia |
| (d) Comb plates |
(i) Ctenophora |
| (e) Radula |
(ii) Mollusca |
| (f) Hair |
(vii) Mammalia |
| (g) Choanocytes |
(iii) Porifera |
| (h) Gill slits |
(vi) Cyclostomata and Chondrichtyes |
Q.15 Prepare a list of some animals that are found parasitic on human beings.
| Endoparasite –
Cause infection inside the body |
Worms |
| Taenia(Tapeworm), |
Parasitic worms can cause a number of problems, including diarrhoea, fatigue, skin rash, nervousness, asthma and anaemia. |
| Fasciola(Liver fluke). |
| Ascaris(Round Worm) |
| Wuchereria(Filaria worm) |
| Ancylostoma(Hookworm) |
| Protozoa |
| Plasmodium |
Malaria |
| Entameoba |
Amoebiasis |
| Trypanosomabrucei |
African sleeping sickness |
| Ectoparasites – Cause infection within the skin |
Pediculushumanuscapitis |
Head lice |
| Phthitus pubis |
Pubic lice |
NCERT Solutions for Class 11 Biology Chapter 4 – FAQs
Q1. What are the difficulties you would face in classification of animals if common fundamental features are not taken into account?
Without common features like symmetry, body cavity, germ layers, levels of organization, and organ systems, it becomes chaotic to group organisms — each organism would seem unique; evolutionary relationships would be lost; adding new species would be unmanageable.
Q2. What steps would you follow to classify a specimen?
The typical steps include:
- Determine level of organization (cellular, tissue, organ)
- Check body symmetry (asymmetry / radial / bilateral)
- Check germ layers (diploblastic / triploblastic)
- Assess presence/absence and type of body cavity (coelom)
- Look for segmentation
- Check for notochord or other features, and match with known phyla
Q3. How useful is studying the nature of the body cavity (coelom) in animal classification?
The presence, absence, or nature (true coelom, pseudocoelom, acoelom) of body cavity is a major structural criterion. It helps distinguish levels of complexity and the arrangement of internal organs in different animal groups.
Q4. What are the peculiar features of parasitic Platyhelminthes?
Parasitic flatworms (e.g. tapeworms, flukes) typically have: hooks or suckers for host attachment; absence of digestive tract (or highly reduced); a tegument that resists host digestion; nutrient absorption across body surface; flame cells for excretion; and often hermaphroditism.