Ncert Questions
Question 1. If you are given a specimen, what are the steps that you would follow to classify it?
Answer: Steps used for animal classification are,(i) arrangement of cells, (ii) body symmetry, (iii) nature of coelom, patterns of digestive, circulatory or reproductive systems.
Question 2. How useful is the study of the nature of body cavity and coelom in the classification of animals?
Answer: Presence or absence of a cavity between the body wall and the gut wall is very important in classification. 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 patches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g.,aschelminthes. The animals in which the body cavity is absent are calledacoelomates, e.g., platyhelminthes.
Question 3. Distinguish between intracellular and extracellular digestion.
Answer:
Question 4. What are the peculiar features that you find in parasitic platyhelminthes?
Answer: Platyhelminthes have dorso-ventrally flattened body, hence are called flatworms. These are mostly endoparasites found in animals including human beings. Flatworms are bilaterally symmetrical, triploblastic and acoelomate animals with organlevel of organisation. Hooks and suckers are present in the parasitic forms. Some of them absorb nutrients from the host directly through their body surface. Specialized cells called flame cells help in osmoregulation and excretion. Sexes are notseparate. Fertilisation is internal and development is through many larval stages. Some members like Planaria possess high regeneration capacity.
Question 5. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
Answer: Arthropoda is the largest phylum of Animalia, which includes insects. Over two-thirds of all named species on earth are arthropods. They have organ-system level of organisation. They are bilaterally symmetrical, triploblastic, segmented and coelomate animals. The body of arthropods is covered by chitinous exoskeleton. The body consists of head, thorax and abdomen. They have jointed appendages (arthros-joint, poda-appendages). Respiratory organs are gills, book lungs or tracheal system. Circulatory system is of open type. Sensory organs like antennae, eyes (compound and simple), statocysts or balance organs are present. Excretion takes place through malpighian tubules. They are mostly dioecious. Fertilisation is usually internal. They are mostly oviparous. Development maybe direct or indirect.
Question 6. How important is the presence of air bladder in Pisces?
Answer: The presence of air bladder in Pisces is important because it regulates buoyancy.
Question 7. What are the modifications that are observed in birds that help them fly?
Answer: The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds (e.g., Ostrich). The forelimbs are modified into wings. The hind limbs generally have scales and are modified for walking, swimming or clasping the tree branches. Skin is dry without glands except the oil gland at the base of the tail. Endoskeleton is fully classified (bony) and the long bones are hollow with air cavities (pneumatic).
Question 8. In which of the following is Segmentation in the body first observed:(a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda.
Answer: The segmentation in the body is first observed in annelidas.
Question 9. Match the following:
Answer:
Question 10. List some parasitic animals that are found on human beings.
Answer: Tape worm, liver fluke, round worm, hook worm, are some animals parasitic that are found on human beings.