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Characteristics and Classification of Living Organisms - Concept and use of a classification system

Grade 11A LevelBiology

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

🔑Concepts

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Living organisms are defined by seven characteristics (MRS GREN): Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition.

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Respiration is the chemical reaction in cells that breaks down nutrient molecules, such as glucose (C6H12O6C_6H_{12}O_6), to release energy for metabolism.

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The Binomial System is the scientific method of naming species using two parts: the genus (capitalized) and the species (lower case), both usually written in italics, e.g., PantheraPanthera leoleo.

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Classification aims to reflect evolutionary relationships. Modern classification uses sequences of bases in DNA and sequences of amino acids in proteins to determine how closely related organisms are.

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Groups of organisms which can reproduce to produce fertile offspring are defined as a species.

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Organisms are classified into a hierarchy: Kingdom→Phylum→Class→Order→Family→Genus→SpeciesKingdom \rightarrow Phylum \rightarrow Class \rightarrow Order \rightarrow Family \rightarrow Genus \rightarrow Species.

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Dichotomous keys are used to identify organisms based on a series of choices between alternative physical characteristics.

📐Formulae

C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

6CO2+6H2O→light + chlorophyllC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{light + chlorophyll}} C_6H_{12}O_6 + 6O_2

💡Examples

Problem 1:

Two organisms have very similar sequences of bases in their DNA. What does this indicate about their classification?

Solution:

It indicates they are closely related and share a recent common ancestor.

Explanation:

Modern classification relies on molecular phylogenetics. The more similar the DNA base sequences, the more closely related the organisms are in the PhylogeneticPhylogenetic tree.

Problem 2:

Identify the genus for the organism CanisCanis lupuslupus.

Solution:

CanisCanis

Explanation:

In the binomial system, the first name refers to the Genus and is always capitalized.

Problem 3:

Which characteristic of life is described by the removal of toxic materials and the waste products of metabolism?

Solution:

Excretion

Explanation:

Excretion specifically refers to the removal of metabolic waste (like CO2CO_2 or urea), whereas egestion is the removal of undigested food.