Chapter 4: Animal Kingdom

Ans. Common fundamental features are taken into account in the classification of living organisms. But if we consider specific characteristics, then each organism will be placed in a separate group and the entire objective of classification would not be achieved.

Another difficulties are:

• In comparing different organisms and judging their evolutionary significance the classification of animals is also important.

• If only one character is considered, then this objective would not be achieved.

• The delicate balance between organisms will become harder to untangle.

• Increased obstacles for future studies on animal symbiosis.

• Development of new species of animals will become difficult.

Ans. To classify the given specimen we will consider a certain common fundamental feature that helps in the classification of living organisms. The features that can be used for classification are as follows: 

Based on the above-mentioned features, we can easily classify a specimen into its respective category.

Ans. The coelom is a fluid-filled space between the body wall and digestive tract that acts as a cavity for other organs. The presence or absence of body cavity or coelom plays a very important role in the classification of animals as it decides the complexity for any animal at the organ level. Based on the nature and presence of the body cavity the animals can be classified into:

1. Coelomates: These are the animals that possess a fluid-filled cavity between the body wall and digestive tract. Annelids, mollusks,  arthropods, echinoderms, and chordates are examples of coelomates. 

2. Pseudocoelomates: These are the animals in which the body cavity is not lined by the mesoderm and remains scattered in between the ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates. 

3. Acoelomates: These are the animals in which the body cavity is absent. Platyhelminthes is an example of acoelomates.

Ans. The differences between intracellular and extracellular digestions are as follows:

Ans. The difference between direct and indirect development are as follows:

Ans. The peculiar features that are found in parasitic platyhelminths are as follows:

1. They have dorsoventrally flattened bodies and bear hooks.

2. Their body is covered with thick tegument, which protects them from the action of the digestive juices of the host.

3. The tegument also helps in absorbing nutrients from the host’s body.

4. Mostly Hermaphrodites and free-living and have organ level of organisation.

5. Incomplete digestive tract or may be absent.

Examples include: Taenia (Tapeworm) and Fasciola (liver fluke)

Ans. The phylum, Arthropoda, which consists of more than two-thirds of the animal species on earth constitutes the largest group of the animal kingdom. The reasons for the success of arthropods are as follows: 

1.Presence of jointed legs that allow more mobility on land.

2.Hard exoskeleton is present which is made up of chitin that protects the body, 

3.The hard exoskeleton also reduces water loss from the body of arthropods making them more adapted to terrestrial conditions.

Ans. The water vascular system is a characteristic feature of the phylum Echinodermata. This system consists of an array of radiating channels, tube feet, and madreporite. It helps in locomotion, food capturing, and respiration. 

Ans. The presence of a notochord and paired pharyngeal gill slits are the characteristic features of the phylum Chordata. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. Thus, it is said that all vertebrates are chordates but all chordates are not vertebrates.

Ans. An air bladder is a gas-filled sac present in Pisces which helps in maintaining buoyancy. It is important as it helps fishes to ascend or descend and stay in the water current.