Ch 2Systematics of Living Organisms — Class 11 Biology, concept-first.

Living organisms display an enormous range of forms, sizes and ways of life. Since prehistoric times, human beings have depended on this diversity for food, medicine, shelter and safety, and that prac…

Living organisms display an enormous range of forms, sizes and ways of life. Since prehistoric times, human beings have depended on this diversity for food, medicine, shelter and safety, and that prac…

Classification is the arrangement of organisms, or groups of organisms, into distinct categories according to a particular, well-established scheme, based on the similarities and dissimilarities among…

It is believed that life on Earth began in a very simple form, and the constant struggle of early living beings to survive and adapt gave rise to progressively more complex forms — this ongoing proces…

Chemotaxonomy is a method of biological classification based on the similarities and differences in the structure of certain chemical compounds found in the organisms being classified — in short, clas…

Numerical taxonomy classifies organisms by quantifying their characters and applying an algorithm — such as cluster analysis — to group them, instead of relying on a subjective, qualitative evaluation…

A cladogram is a branching, tree-like diagram that represents a hypothetical relationship between organisms and their common ancestors — it is a visual comparison of how different groups are related t…

Phylogeny is the evolutionary relationship among organisms. It is an important tool in classification because it looks beyond mere morphological similarity to consider how one group of organisms is re…

DNA barcoding is a relatively recent method used to identify a species from its DNA sequence, obtained from a tiny tissue sample of the organism being studied.

Classification is not a single step — it proceeds through a hierarchy of steps, and each step in that hierarchy represents a particular rank or category.

A taxon is a taxonomic group of any rank within a classification system (as defined by H. J. Lam in 1948).

Working from the lowest rank upward, the taxonomic units of classification are:

Anything that becomes known to human intelligence needs a name, so that ideas about it can be communicated — this art of naming objects is the science of nomenclature.

Carl Linnaeus originally classified all living organisms into just two kingdoms — Plantae and Animalia — based on features such as mode of nutrition and whether the organism was migratory or sedentary…

Not every infectious biological entity fits inside a cell, and this section covers the acellular organisms — viruses, viroids and prions — none of which are part of Whittaker's Five Kingdom classifica…