Chapter 7 Exercise

Q1. What are the advantages of classifying organisms?

Ans:

Listed below are the advantages of classification of organisms:

  • When organisms are classified, their common features can easily be studied.
  • The study of scientific experiments is simplified.
  • The interrelation of humans with other entities can be interpreted. Their dependence and interactions can be studied.
  • When entities are crossbred and modified genetically, it paves the way for commercial applications.

Q2. How would you choose between two characteristics to be used for developing a hierarchy in classification?

Ans:

The basis of the start of the hierarchy will be formed by the Gross character while the basis of steps further will be taken care of by the fine character.

For instance:

  • Human beings are categorized under vertebrates as they possess the vertebral column
  • For categorization of tetrapods
  • For Tetrapods, the existence of four limbs is taken into consideration
  • In the case of mammals, the mammary gland is the required part

Q3. Explain the basis for grouping organisms into five kingdoms.

Ans:

The following factors govern the basis of grouping organisms into five kingdoms

  • The number of cells present forms the first criteria.
  • Next is the arrangement and the number of layers present.
  • Another important factor for classification is the existence of cell wall.
  • Classification of complex organisms is also based on the mode of intake of nutrition.
  • To classify, we consider the organization level too.

Q4. What are the major divisions in the Plantae? What is the basis of these divisions?

Ans:

The following table depicts plant division and the basis of classification for each division.

DivisionBasis of Classification
Thallophyta or AlgaeLike body
BryophytaThe body is divided into leaf and stem
PteridophytaThe body is separated into root, stem and leaf
GymnospermSeed-bearing, naked seeds
AngiospermSeed bearings covered seeds

Q5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

Ans:

  • One of the major specifications to categorize plants into Thallophytes and Bryophytes is the basic cell structure.
  • Gymnosperms and Angiosperms are classified on the basis of visibility of seeds.

Hence, morphological characteristics play a key role in plant classification. In animal classification, cytology is considered primarily as more minute structural variations are taken into account.

  • The cell layers, cytology, morphology are significant features to be considered in the classification of animals.
  • The presence and absence of various features decide the classification of higher hierarchies.

Q6. Explain how animals in Vertebrata are classified into further subgroups.

Ans:

Vertebrata has two subclasses namely

  • Pisces
  • Tetrapod

Wherein, organisms belonging to Pisces subclass have a streamlined body with tails and fins which help them in their movement (swim) whereas, the Tetrapoda species have four limbs for their movement.

Furthermore, The tetrapod animals are classified as:

1. Amphibia: The animals belonging to this group are adaptive in nature. They dwell both in the land as well as in water. They show the presence of specialized organs, which allows them to breathe underwater.

2. Reptilia: The animals belonging to this class crawl. Their skin is very thick and withstands extreme temperatures.

3. Aves: The forelimbs of these organisms are modified which help them in their flight. They lack teeth and instead have a beak and feathers that cover up their body.

4. Mammalia: The animals belonging to this group show nurturing skills as they contain mammary glands to support them. Their skin is covered with hair and most of them are viviparous in nature.

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