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Animal Kingdom

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What is the difference between direct and indirect development?

Direct development

Indirect development

In this the embryo develops into a mature individual without involving a larval stage.

Indirect development encompasses a larval stage that undergoes a metamorphic transition into a juvenile.

Metamorphosis is absent.

Metamorphosis is present.

It occurs in fishes, reptiles, birds, and mammals

It occurs in most of the invertebrates and amphibians.


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

Coelom is the body cavity which is lined by a mesoderm. The presence or absence of body cavity or coelom plays a very important role in the classification of animals.
Animals that having  a cavity between body wall and digestive tract are known as coelomates for eg. annelids, molluscs, arthropods, echinodermates, and chordates etc.
The animals in which the body cavity is not lined by mesoderm are known as pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates.
Animals in which the body cavity is absent  are known as acoelomates For e.g platyhelminthes.


Distinguish between intracellular and extracellular digestion? 

Intracellular digestion

Extracellular digestion

Digestion takes place inside the cell.

Digestion takes place outside the cell

Enzymes are secreted into the food vacuole

Enzymes are secreted into the digestive cavity.

Less efficient

More efficient

Found in unicellular animals

Found in multicellular organisms


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

The difficulties that one would face in classification of animals if common fundamental features are not taken into account are as following:

(i) Animal kingdom consists of a large number of organisms. If the common fundamental characteristics are not considered for classification, each organism will have to be placed in a different group. Thus, the study of the organisms would become nearly impossible and it would be very tough.

(ii) Without common fundamental features, it would be very difficult to segregate the organisms into groups.

(iii) Without segregation into groups, comparing different organisms and judging their individual evolutionary significance would be difficult. We would not be able to deduce the evolutionary relationship. 


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

The steps that we would follow to classify the given specimen will be
(i) First we would classify the specimen according to the level of organisation. The animals can be classified into Cellular and Tissue/Organ level.

(ii)  The second criteria for classification would be on the basis of the body symmetry i.e. whether the specimen is of radial symmetry of bilateral symmetry.

(iii) The third classification would be on the basis of the body cavity or coelom.  Wheteher the body cavity is present or absent. And whether the coelom  is acoelom, pseudocoelom or true coelom
(iv) The specimen would be classified on the basis of the arrangement or the number of the layers into diploblastic or triploblastic.

(v) The specimen would then be classified on the basis of the presence or the absence of notochord.