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Classification and Diversity - Linnaean Classification

Grade 7IB

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

🔑Concepts

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Linnaean Classification is a hierarchical system used to organize and categorize all living organisms based on shared physical characteristics and evolutionary relationships.

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There are eight main taxonomic levels (taxa). From the most inclusive to the most specific, they are: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species (Domain→SpeciesDomain \rightarrow Species).

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Binomial Nomenclature is the formal system of naming species. Each name consists of two parts: the GenusGenus (capitalized) and the speciesspecies epithet (lowercase). Both must be italicized or underlined.

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A species is the most specific level of classification, defined as a group of organisms that can interbreed to produce fertile offspring.

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Dichotomous Keys are identification tools that use a sequence of 22 choices (couplets) to lead the user to the correct name of an organism.

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Organisms are more closely related if they share more taxonomic levels. For example, two organisms in the same FamilyFamily are more related than two that only share the same OrderOrder.

📐Formulae

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

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

Diversity Index (Simpson’s):D=1−(∑n(n−1)N(N−1))\text{Diversity Index (Simpson's)}: D = 1 - \left( \frac{\sum n(n-1)}{N(N-1)} \right)

💡Examples

Problem 1:

Determine the scientific name of the African Lion if its genus is PantheraPanthera and its species is leoleo.

Solution:

Panthera leoPanthera\ leo

Explanation:

According to binomial nomenclature, the first letter of the Genus is capitalized, the species name is lowercase, and the entire name is italicized or underlined.

Problem 2:

Based on the Linnaean hierarchy, which two of the following three organisms are most closely related? 1. Ursus americanusUrsus\ americanus (American Black Bear), 2. Ursus maritimusUrsus\ maritimus (Polar Bear), 3. Melursus ursinusMelursus\ ursinus (Sloth Bear).

Solution:

Ursus americanusUrsus\ americanus and Ursus maritimusUrsus\ maritimus

Explanation:

Both the American Black Bear and the Polar Bear share the same genus, UrsusUrsus. The Sloth Bear belongs to a different genus, MelursusMelursus. Organisms in the same genus share more recent common ancestors.

Problem 3:

Identify the level of classification that comes immediately after 'Class' when moving from most general to most specific.

Solution:

Order

Explanation:

The hierarchy follows the sequence: Kingdom →\rightarrow Phylum →\rightarrow Class →\rightarrow Order →\rightarrow Family →\rightarrow Genus →\rightarrow Species. Therefore, 'Order' follows 'Class'.

Linnaean Classification - Revision Notes & Key Formulas | IB Grade 7 Science