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Diversity - How to Classify Organisms?

Grade 9CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Classification is the process of grouping organisms based on their similarities and differences. The primary aim is to make the study of a wide variety of organisms easy and systematic.

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The Five Kingdom Classification was proposed by Robert Whittaker in 19691969. The kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

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The criteria for Whittaker's classification include: (i) Complexity of cell structure (Prokaryotic vs Eukaryotic), (ii) Complexity of the organism's body (Unicellular vs Multicellular), and (iii) Mode of nutrition (Autotrophic vs Heterotrophic).

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The hierarchy of classification categories, from highest to lowest, is: Kingdom→Phylum (for animals) / Division (for plants)→Class→Order→Family→Genus→Species\text{Kingdom} \rightarrow \text{Phylum (for animals) / Division (for plants)} \rightarrow \text{Class} \rightarrow \text{Order} \rightarrow \text{Family} \rightarrow \text{Genus} \rightarrow \text{Species}.

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Binomial Nomenclature, introduced by Carolus Linnaeus, is the system of naming organisms using two components: the Genus name (capitalized) and the species name (lowercase). For example, the scientific name for humans is HomoHomo sapienssapiens.

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Evolutionary relationships, also known as phylogeny, play a crucial role in modern classification. Most organisms are classified based on their DNADNA sequences and ancestral traits.

📐Formulae

Organisms\text{Organisms} \begin{cases} \text{Prokaryotic} \rightarrow \text{Monera} \ \text{Eukaryotic} \begin{cases} \text{Unicellular} \rightarrow \text{Protista} \\ \text{Multicellular} \begin{cases} \text{With Cell Wall} \begin{cases} \text{Non-photosynthetic} \rightarrow \text{Fungi} \\ \text{Photosynthetic} \rightarrow \text{Plantae} \end{cases} \ \text{Without Cell Wall} \rightarrow \text{Animalia} \end{cases} \end{cases} \end{cases}

Scientific Name=Genus (Capitalized)+species (Lowercase)\text{Scientific Name} = \text{Genus (Capitalized)} + \text{species (Lowercase)}

💡Examples

Problem 1:

An organism is eukaryotic, multicellular, has a cell wall made of chitin, and follows a saprophytic mode of nutrition. Identify its Kingdom.

Solution:

The organism belongs to Kingdom Fungi.

Explanation:

The presence of a eukaryotic cell structure and a cell wall made of chitin (rather than cellulose) combined with a saprophytic (heterotrophic) mode of nutrition are the defining characteristics of Fungi.

Problem 2:

Arrange the following taxonomic groups in ascending order of similarity: Family, Genus, Kingdom, Species.

Solution:

Kingdom<Family<Genus<Species\text{Kingdom} < \text{Family} < \text{Genus} < \text{Species}

Explanation:

As we move from Kingdom down to Species, the number of shared characteristics between organisms increases. Therefore, the 'Species' level has the highest similarity among its members, while 'Kingdom' has the least similarity.

Problem 3:

Write the scientific name of a Tiger following the rules of Binomial Nomenclature if its Genus is PantheraPanthera and species is tigristigris.

Solution:

PantheraPanthera tigristigris (or Panthera‾\underline{Panthera} tigris‾\underline{tigris} when handwritten).

Explanation:

According to the rules, the Genus name starts with a capital letter (PP in PantheraPanthera) and the species name starts with a small letter (tt in tigristigris). Both must be italicized when printed or underlined separately when handwritten.