What is the difference between direct and indirect development?
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Direct development |
Indirect development |
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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. |
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Metamorphosis is absent. |
Metamorphosis is present. |
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It occurs in fishes, reptiles, birds, and mammals |
It occurs in most of the invertebrates and amphibians. |
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.
What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth. The reasons for the success of arthropods are as follows.
(i) Jointed legs that allow more mobility on land.
(ii) Hard exoskeleton made of chitin that protects the body from the harsh conditions.
(iii) The hard exoskeleton also reduces water loss from the body making them more adapted to terrestrial conditions.
(iv) The fertilisation is internal which provides protection to the progeny from the external harsh conditions.
Distinguish between intracellular and extracellular digestion?
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Intracellular digestion |
Extracellular digestion |
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Digestion takes place inside the cell. |
Digestion takes place outside the cell |
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Enzymes are secreted into the food vacuole |
Enzymes are secreted into the digestive cavity. |
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Less efficient |
More efficient |
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Found in unicellular animals |
Found in multicellular organisms |
What are the peculiar features that you find in parasitic platyhelminthes?
Parasitic platyhelminthes have the following peculiar features:
1. They have dorsiventrally flattened body and bear hooks and suckers to attach inside the body of the host. They can absorb nutrition from the host directly through the body surface.
2. Their body is covered with thick covering to protect them from the action of digestive juices of the host.
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