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Classification of Living Things - Linnaean Taxonomy

Grade 6IB

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

🔑Concepts

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Taxonomy is the branch of science concerned with the classification of living organisms. It was founded by Carl Linnaeus in the 18th18^{th} century.

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The Linnaean Hierarchy consists of eight main levels (taxa), moving from the most general to the most specific: Domain →\rightarrow Kingdom →\rightarrow Phylum →\rightarrow Class →\rightarrow Order →\rightarrow Family →\rightarrow Genus →\rightarrow Species.

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Binomial Nomenclature is a two-part naming system where every organism is assigned a scientific name consisting of its Genus and species. The Genus is always capitalized, and the species is lowercase, e.g., PantheraPanthera leoleo.

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Classification is based on shared physical characteristics and evolutionary relationships. Organisms in the same species can interbreed to produce fertile offspring.

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The Five Kingdom System classifies organisms into: Animalia (multicellular heterotrophs), Plantae (autotrophs that use CO2CO_2 and sunlight), Fungi (decomposers), Protista (mostly unicellular eukaryotes), and Monera (prokaryotes).

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A Dichotomous Key is a tool used by scientists to identify unknown organisms through a series of choices between two characteristics.

📐Formulae

Scientific Name=Genus+species\text{Scientific Name} = \text{Genus} + \text{species}

Species Richness (S)=∑number of individual species identified\text{Species Richness (S)} = \sum \text{number of individual species identified}

Hierarchy Order: D>K>P>C>O>F>G>S\text{Hierarchy Order: } D > K > P > C > O > F > G > S

💡Examples

Problem 1:

Identify the correct scientific name for a modern human based on the rules of binomial nomenclature.

Solution:

HomoHomo sapienssapiens

Explanation:

In binomial nomenclature, the first word represents the Genus (HomoHomo) and is capitalized. The second word represents the species (sapienssapiens) and is lowercase. Both should be italicized or underlined.

Problem 2:

If a wolf (CanisCanis lupuslupus) and a domestic dog (CanisCanis familiarisfamiliaris) are compared, which taxonomic levels do they share?

Solution:

They share all levels from Domain down to Genus.

Explanation:

Since both belong to the Genus CanisCanis, they must belong to the same higher levels: Family (CanidaeCanidae), Order (CarnivoraCarnivora), Class (MammaliaMammalia), Phylum (ChordataChordata), Kingdom (AnimaliaAnimalia), and Domain (EukaryaEukarya). They only differ at the species level.

Problem 3:

Calculate the number of possible outcomes in a 3-step dichotomous key where each step has exactly 2 choices.

Solution:

23=82^3 = 8

Explanation:

A dichotomous key branches by a factor of 22 at each level. For nn levels, the maximum number of organisms that can be identified is 2n2^n. Here, 2×2×2=82 \times 2 \times 2 = 8.

Linnaean Taxonomy - Revision Notes & Key Formulas | IB Grade 6 Science