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Animal Kingdom

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Animal Kingdom Animal Kingdom 1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account? Solution: There are millions of animal species in this universe that show great variation. For the purpose of classification, various common fundamental characters are taken into account. This helps in grouping and organizing them effectively, to be picked when required for the purpose of study. If common fundamental features were not considered, the: • The picture of all life forms of animals at a glance could be not projected. • The inter-relationship among different animals could not be traced. • The development of other animal species could not be recognised, and hence, evolution could not be traced accurately. 2. If you are given a specimen, what are the steps that you would follow to classify it? Solution: To classify a given specimen, it first needs to be identified up to the phylum level. The steps to identify the given specimen are as follows: 1) Observation of the given specimen. 2) External features should be observed on the basis of: - level of organization (cellular, tissue, organ) -Body symmetry (radial, bilateral) - Body cavity (present, absent) - Coelom development [acoelom, pseudocoelom, eucoelom (true coelom)] - Body divisions (head, thorax, abdomen) and appendages (antennae, tentacles, legs) -Resemblance with any other known specimen - Vrtebrate or invertebrate nature -Presence of exoskeleton, i.e. scales, feathers, fins, hair, etc. Based on the above characters, we can conclude the phylum that the specimen belongs to. Once the phylum has been identified, other characteristics can be observed and classified following the standard dichotomous keys. 3. How useful is the study of the nature of body cavity and coelom in the classification of animals? Solution: The presence or absence of a cavity (coelom) between the body wall and the gut wall is a very important feature in the classification of animals. Based on the presence or absence of the coelom, animals are classified as a. Acoelomates: Animals in which the body cavity is absent are called “acoelomates,” e.g. Platyhelminthes. b. Pseudocoelomates: In some animals, the body cavity is not lined by the mesoderm. Instead, the mesoderm is present as scattered pouches between the ectoderm and the endoderm. Such type of body cavity is called pseudocoelom, and the animals possessing them are called “pseudocoelomates,” e.g. Aschelminthes. c. Coelomates: The body cavity that is lined by the mesoderm is called coelom, and the animals possessing it are called “coelomates”. Annelids, mollusks, arthropods, echinoderms, hemichordates and chordated are coelomates. Coelomates are advanced animals and occupy a higher position in the evolutionary tree. Hence, the study of coelom helps us to identify the position of an organism in the process of evolution. 4. Distinguish between intracellular and extracellular digestion? Solution: Intracellular digestion Extracellular digestion Digestion occurs in the Digestion occurs individual cell. outside the individual cell. Digestion occurs in lower Digestion occurs in organisms that are higher organisms that associated with the are associated with the microphagous mode of macrophagous mode of feeding. feeding. Immune cells like macrophages etc. in higher organisms show intracellular digestion. Comparatively less Comparatively more efficient. efficient. Only a few enzymes are A large number of associated with this digestive glands and digestion. enzymes are associated with this digestion. Example- Amoeba, Example- Hydra, human sponges and cell organelles beings. like lysosome. 5. What is the difference between direct and indirect development? Solution: Direct development Indirect development The young ones resemble The young ones do not the adult in all features, resemble the adult in except for size, colour and most of the features. sexual maturity. There is no larval stage in There can be one or the life cycle. more larval stages in the life cycle. The young one lives in the The larval line occupies same ecological niche as different ecological the adult. niches as compared to the adult. There is no reorganization Various systems are of the structural and reorganised during the functional features during transition from the larva the transition from young to the adult stage. to adult stage. Example: Development in Example: Development fish and humans. in sponges, arthropods, frogs. 6. What are the peculiar features that you find in parasitic platyhelminthes? Solution: The peculiar features of parasitic Platyhelminthes are: [A] Morphological features - Locomotory organs are absent, except when required for movement in search of a host. -Digestive organs are reduced or absent. They absorb nutrients directly through the body surface. -The nervous system and sense organs are poorly developed. - Suckers, hook or spines are present for attachment to host. - The cuticle shows resistance to the digestive enzymes and antitoxins of the hosts. - Circulatory and respiratory systems are absent. - Egg shells are resistant. This helps the contained young larvae to overcome unfavourable conditions of the environment as well as to provide safety from the host’s defence system. [B] Physiological features - Respiration is anaerobic. - Intestinal flatworms secrete anti-enzymes and mucus to neutralise the digestive enzymes of the host. - Osmotic adaptability to live in different media. - Hermaphroditism for ensuring reproduction and high rate of multiplication. 7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom? Solution: Arthropods constitute 82 of all animals and 63% of all organisms. - Animals of this kingdom are versatile and found distributed in all types of habitat such as aquatic (fresh water or marine), terrestrial and aerial. - They are omnivorous, i.e. they feed on plants and animals in various ways, and their mouth parts are highly specialised and modified. - A thick chitinous exoskeleton protects them from injury and desiccation. - Jointed appendages and jointed body increase manoeuvrability. - The presence of striated muscles allows the animal to move different parts at will. - There is a lot of variation and specialisation in the alimentary canal and respiratory structures. - The sense organs are well developed for quick response. - There is greater cephalisation. - They have a developed endocrine system for better coordination. - There is also an occurrence of primitive intelligence and instinct, including social instincts, in some groups. Because of the presence of all the above features, arthropods are better adapted to different conditions and are successful, and constitute the largest group of the animal kingdom. 8. Water vascular system is the characteristic of which group of the following: (a) Porifera (b)Ctenophora (c) Echinodermata (d) Chordata Solution: Water vascular system is a characteristic feature of the phylum Echinodermata. -The water vascular system in the phylum Echinodermata helps in locomotion, food capture and transport of food and respiration. E.g. Asterias (star fish), Antedon (sea lily). 9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement. Solution: All the diagnostic characteristics of chordates are present in vertebrates, viz. notochord, dorsal hollow nerve cord, pharyngeal gill slits and post anal tail. However, vertebrates have their own specific characteristics, like the differentiation of the nerve cord into brain and spinal cord, replacement of notochord with cranium and vertebral column, presence of paired appendages, etc. These characteristics are absent in other non-vertebrate chordates like tunicates and cephalochordates. Therefore, all vertebrates are chordates, but all chordates are not vertebrates. 10. How important is the presence of air bladder in Pisces? Solution: The important of the air bladder, swim bladder or air sac in Pisces is: • With the help of the air bladder, bony fishes can pass to various depths in water without being affected by the pressure of the overlaying water. • Bony fishes can also stay inside water by adjusting the amount of air in the air bladder without spending energy, as they need not swim constantly to stay there. • The air bladder is used to as a lung in certain groups of fishes. • In some fishes, the air bladder is used to produce sound during mating. 11. What are the modifications that are observed in birds that help them fly? Solution: The modifications in birds for flight adaptation are: • Occurrence of wings that are modified forelimbs. • Light and strong bones. • Pneumatic (air-filled) bones. • Fusion of bones in the skull, trunk and sacral region. • Development of the pectoral girdle. • Presence of keeled sternum for attachment of flight muscles. • Enlargement of the pelvic girdle for supporting body weight during rest. • Reduction in the size of the tail. • Absence of teeth and elongation of the jaw to form a beak to reduce the weight of the head. • Presence of a streamlined body to resist wind during flight. • Body covered by insulating feathers. • Absence of skin glands, except the preen or oil gland. • Presence of distensible air sacs attached to non-distensible lungs. • Excretion in the form of uric acid, and absence of the urinary bladder. 12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why? Solution: The number of eggs or young ones produced
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