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Biology Class Eleven

Animal Kingdom

Question 1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?

Answer: Common fundamental features help grouping animals in certain categories or sub-categories. For the common fundamental feature of all the Arthropods is joined legs for locomotion. Higher animals, like mammals too have joined legs but the difference is the absence/presence of muscles to facilitate articulation. Similarly, all birds have fore-limbs modified to assist in flying. This gives us one clue to categorise a particular animal among aves.

Had we not used fundamental features we could not get a point to start with. Fundamental features help us further pin point the characteristics for classification and identification.

Question 2. If you are given a specimen, what are the steps that you would follow to classify it?

Answer: Steps to Follow for Classification:

1. Identify Levels of Organization: Identify if it is cellular level of organization or tissue level of organization.

2. Identify Body Symmetry: Find if the animal is having a radial body symmetry or a bilateral body symmetry.

3. Presence or Absence of Body Cavity: This will give a clue if the animal belongs to acoelomata or psudcoelomata or coelomata.

Once these steps have been followed a fair idea can be derived about the animal. It can be inferred if the animal is multicellular or unicellular. It can be known if the animal is a chordate or a non-chordate.

Question 3. How useful is the study of the nature of body cavity and coelom in the classification of animals?

Answer: The presence or absence of the body cavity gives a clue about a particular animal’s position in evolutionary ladder. The absence of coelom indicates that the animal is yet to develop a functional dividion of labour to carry out various activities. This indicates towards a simplicity of activities going on inside the body. The presence of coelom paves the way for evolution of a more complex and more efficient organ system for various activities.

Question 4. Distinguish between intracellular and extracellular digestion?

Answer: In smaller animals the food comprises of mainly basic molecules, like carbohydrates so need of elaborate digestive system is not there. Especially, in unicellular animals, the same cell is responsible for carrying out all the basic activities. The intracellular digestion is enough to take care of the nutrition needs of the animal in this case.

In animals with complicated systems the need for variety of food components increases manifold. The complexity of food substances necessitates a complex digestive system. So major steps of digestion take place outside the cell.

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

Answer:

Direct Development: In direct development the young animal resembles an adult. There is not intermediate stage.

Indirect Development: In indirect development there is intermediate stage, like larval stage. For example, frogs before being developed into adult pass through a tadpole stage. This is the case of indirect development.

Question 6. What are the peculiar features that you find in parasitic platyhelminthes?

Answer: In parasitic platyhelminthes hooks and suckers are present. Suckers help the parasite in sucking the blood from the host.

Question 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 the first phylum to have well developed systems to carry out different activities. There is distinct system for respiration, locomotion and reproduction. Their survival capacity is great because of elaborate system. This has helped them survive in diverse conditions. This can be one of the reasons why arthropods are the largest group among the animal kingdom.

Question 8. Water vascular system is the characteristic of which group of the following:

(a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata

Answer: (a) Porifera is having water vascular system. Food is gathered through movement of water and excretory products are expelled out of the body with the flow of water.

Question 9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.

Answer: All chordates have notochord present in some stage of life. The difference between vertebrates and non-vertebrates is as follows: In vertebrates the notochord is present in the embryonic stage. This is replaced by a vertebral column during the adult stages.

Question 10. How important is the presence of air bladder in Pisces?

Answer: Presence of air-bladder in Pisces helps in buoyancy. This means that members of pisces don’t have to keep on swimming to remain floating.

Question 11. What are the modifications that are observed in birds that help them fly?

Answer: Following modifications in birds help them fly:

1. Pneumatic or hollow bones makes for a lightweight skeleton.

2. Fore-limbs are modified into wings to assist in flight.

3. Excretion of urine and faeces is through single opening facilitating weight reduction.

4. Aerodynamic body helps in flying.

Question 12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?

Answer: Usually number of eggs produced by oviparous mothers is greater than number of young ones produced by viviparous mothers. The main reason for this is the need of resources required for development of the embryo. In viviparous the major part of development of the embryo takes place outside the uterus. This makes lesser burden on the mother. On the other hand in viviparous animals the development takes place inside the uterus so lesser number of young ones can be successfully incubated.

Question 13. Segmentation in the body is first observed in which of the following:

(a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda

Answer: (c) Annelida are the first group to show body segmentation.

Question14. Match the following:

(i) Operculum (a) Ctenophora

(ii) Parapodia (b) Mollusca

(iii) Scales (c) Porifera

(iv) Comb plates (d) Reptilia

(v) Radula (e) Annelida

(vi) Hairs (f) Cyclostomata and Chondrichthyes

(vii) Choanocytes (g) Mammalia

(viii) Gill slits (h) Osteichthyes