Animal Kingdom - Exercises

Subject: Biology
Chapter: 4 - Animal Kingdom

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Exercises

1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account? Answer: Without common fundamental features (like level of organisation, symmetry, coelom, patterns of digestive, circulatory or reproductive systems), classification would be arbitrary and inconsistent. It would be difficult to assign a systematic position to newly described species, and we wouldn't be able to establish a clear understanding of the evolutionary relationships and commonalities between different groups of animals.

2. If you are given a specimen, what are the steps that you would follow to classify it? Answer: To classify a given animal specimen, the following steps are generally followed:

1. Level of Organisation: Determine if it has cellular, tissue, organ, or organ system level of organisation.
2. Symmetry: Check if the body is asymmetrical, radially symmetrical, or bilaterally symmetrical.
3. Germ Layers: Identify if it is diploblastic or triploblastic.
4. Coelom: Check for the presence or absence of a body cavity (acoelomate, pseudocoelomate, or coelomate).
5. Segmentation: Observe if the body shows metameric segmentation.
6. Notochord: Check for the presence of a notochord.
7. Specific Phylum Features: Look for unique characteristics like pores/canals (Porifera), cnidoblasts (Cnidaria), comb plates (Ctenophora), flame cells (Platyhelminthes), water vascular system (Echinodermata), etc.

3. How useful is the study of the nature of body cavity and coelom in the classification of animals? Answer: The nature of the body cavity (coelom) is a fundamental criterion for classification. It allows scientists to group animals into three broad categories:

• Acoelomates: Animals without a body cavity (e.g., Platyhelminthes).
• Pseudocoelomates: Animals where the body cavity is not lined by mesoderm, but exists as scattered pouches (e.g., Aschelminthes).
• Coelomates: Animals with a true body cavity lined by mesoderm (e.g., Annelids, Arthropods, Molluscs, Echinoderms, Hemichordates, and Chordates).

4. Distinguish between intracellular and extracellular digestion? Answer:

• Intracellular Digestion: Occurs within the cells. Food particles are taken into the cell (usually in vacuoles) and broken down by enzymes. This is seen in primitive animals like sponges (Porifera).
• Extracellular Digestion: Occurs in a cavity outside the cells, such as the gastro-vascular cavity or the alimentary canal. Enzymes are secreted into the cavity to break down food. This is found in most higher animals, including Cnidarians, Ctenophores, and all triploblastic animals.

5. What is the difference between direct and indirect development? Answer:

• Direct Development: The young ones hatched or born resemble the adult form in almost all aspects except size and sexual maturity. There is no intermediate larval stage (e.g., mammals, birds, reptiles).
• Indirect Development: The development includes one or more larval stages that are morphologically very different from the adult form. The larva must undergo metamorphosis to become an adult (e.g., frogs, butterflies, sponges).

6. What are the peculiar features that you find in parasitic platyhelminthes? Answer: Parasitic flatworms (Platyhelminthes) exhibit several specialized features:

• Dorso-ventrally flattened body.
• Presence of hooks and suckers for attachment to the host's body.
• Absorption of nutrients directly through the body surface.
• Specialized cells called flame cells for osmoregulation and excretion.
• Complex life cycles often involving multiple larval stages.

7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom? Answer: Arthropods are successful due to several key adaptations:

• Chitinous Exoskeleton: Provides protection against predators and prevents desiccation.
• Jointed Appendages: Allow for highly versatile and efficient locomotion (crawling, swimming, flying).
• Efficient Respiratory Systems: Diverse organs like gills, book gills, book lungs, and tracheal systems adapted to various habitats.
• Well-developed Sensory Organs: Antennae, compound/simple eyes, and statocysts provide excellent environmental awareness.
• High Reproductive Potential: Many arthropods produce a large number of offspring.

8. Water vascular system is the characteristic of which group of the following: (a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata Answer: (c) Echinodermata

9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement. Answer: All vertebrates belong to the phylum Chordata as they possess a notochord, dorsal hollow nerve cord, and pharyngeal gill slits at some stage of their life. However, in vertebrates, the notochord is replaced by a cartilaginous or bony vertebral column in the adult. On the other hand, protochordates (Urochordata and Cephalochordata) possess a notochord but never develop a vertebral column. Therefore, while all vertebrates are chordates, the chordates that lack a vertebral column are not vertebrates.

10. How important is the presence of air bladder in Pisces? Answer: In the class Osteichthyes (bony fishes), the air bladder is a vital organ that regulates buoyancy. It allows the fish to maintain a certain depth in the water without expending energy on constant swimming. In contrast, Chondrichthyes (cartilaginous fishes) lack an air bladder and must swim continuously to avoid sinking.

11. What are the modifications that are observed in birds that help them fly? Answer: Birds (Aves) have several flight adaptations:

• Forelimbs are modified into wings.
• Presence of feathers for lift and insulation.
• Pneumatic bones: Long bones are hollow with air cavities to reduce body weight.
• Air sacs connected to lungs to supplement respiration and provide additional buoyancy.
• Streamlined body and powerful flight muscles.

12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why? Answer: No, the number is generally not equal. Oviparous mothers usually produce a much larger number of eggs because the eggs are laid externally and are highly vulnerable to predators and environmental changes. A large quantity ensures that at least some survive. Viviparous mothers produce fewer young ones because the offspring are protected and nourished inside the mother's body, leading to a much higher survival rate for each individual.

13. Segmentation in the body is first observed in which of the following: (a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda Answer: (c) Annelida

14. Match the following: (a) Operculum -- (viii) Osteichthyes (b) Parapodia -- (v) Annelida (c) Scales -- (iv) Reptilia (d) Comb plates -- (i) Ctenophora (e) Radula -- (ii) Mollusca (f) Hairs -- (vii) Mammalia (g) Choanocytes -- (iii) Porifera (h) Gill slits -- (vi) Cyclostomata and Chondrichthyes

15. Prepare a list of some animals that are found parasitic on human beings. Answer:

• Taenia (Tapeworm)
• Fasciola (Liver fluke)
• Ascaris (Roundworm)
• Wuchereria (Filaria worm)
• Ancylostoma (Hookworm)
• Plasmodium (Malarial parasite)
• Entamoeba histolytica (Amoebic dysentery parasite)