Characteristics and Classification of Living Organisms - Concept and use of a classification system
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Living organisms are defined by seven characteristics (MRS GREN): Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition.
Respiration is the chemical reaction in cells that breaks down nutrient molecules, such as glucose (), to release energy for metabolism.
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., .
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.
Groups of organisms which can reproduce to produce fertile offspring are defined as a species.
Organisms are classified into a hierarchy: .
Dichotomous keys are used to identify organisms based on a series of choices between alternative physical characteristics.
📐Formulae
💡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 tree.
Problem 2:
Identify the genus for the organism .
Solution:
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 or urea), whereas egestion is the removal of undigested food.