The document discusses the three domains of life - Archaea, Bacteria, and Eukarya. Archaea are prokaryotic cells with ether-linked membranes that often live in extreme environments. Bacteria are also prokaryotic but have ester-linked membranes and peptidoglycan cell walls. Eukarya have eukaryotic cells, ester-linked membranes, and no universal cell wall. The Eukarya domain includes four kingdoms: Protista, Fungi, Plantae, and Animalia. The document then explains taxonomic hierarchy from the highest level of kingdom down to the most specific level of species.

1. DIVERSITY OF LIVING WORLD
WORLD OF BIOLOGY
EDUCATOR- ASIT

2. THREE DOMAINS OF LIFE
 WHAT IS DOMAIN?
 Domains are our way of breaking down living things more
generally than before when we just went into kingdoms.
 There are three distinct domains in biology.
 There is the Archaea, the Bacteria, and the Eukarya.
 The three-domain system is a biological
classification introduced by Carl Woese et al. in 1990.

3. DOMAIN ARCHAEA
The Archaea possess the following characteristics:
1.Archaea are prokaryotic cells.
2.Unlike the Bacteria and the Eukarya, the Archaea have membranes composed of
branched hydrocarbon chains attached to glycerol by ether linkages.
3.The cell walls of Archaea contain no peptidoglycan.
4.Archaea are not sensitive to some antibiotics that affect the Bacteria, but are
sensitive to some antibiotics that affect the Eukarya.
5.Archaea often live in extreme environments and include methanogens, extreme
halophiles, and hyperthermophiles. One reason for this is that the ether-containing
linkages in the Archaea membranes is more stabile than the ester-containing
linkages in the Bacteria and Eukarya and are better able to withstand higher
temperatures and stronger acid concentrations.
6.Archaea contain rRNA that is unique to the Archaea as indicated by the presence
molecular regions distinctly different from the rRNA of Bacteria and Eukarya.

4. DOMAIN BACTERIA
Bacteria (also known as eubacteria or "true bacteria") are prokaryotic cells
that are common in human daily life, encounter many more times than the
archae bacteria. The Bacteria possess the following characteristics:
1.Bacteria are prokaryotic cells.
2.Like the Eukarya, they have membranes composed of unbranched fatty
acid chains attached to glycerol by ester linkages.
3.The cell walls of Bacteria, unlike the Archaea and the Eukarya, contain
peptidoglycan.
4.Bacteria are sensitive to traditional antibacterial antibiotics but are
resistant to most antibiotics that affect Eukarya.
5.Bacteria contain rRNA that is unique to the Bacteria as indicated by the
presence molecular regions distinctly different from the rRNA
of Archaea and Eukarya.
Bacteria include mycoplasmas, cyanobacteria, Gram-positive bacteria,
and Gram-negative bacteria.

5. DOMAIN EUKARYA
The Eukarya possess the following characteristics:
1.Eukarya have eukaryotic cells.
2.Like the Bacteria, they have membranes composed of unbranched fatty
acid chains attached to glycerol by ester linkages.
3.Not all Eukarya possess cells with a cell wall, but for
those Eukarya having a cell wall, that wall contains no peptidoglycan.
4.Eukarya are resistant to traditional antibacterial antibiotics but are
sensitive to most antibiotics that affect eukaryotic cells.
5.Eukarya contain rRNA that is unique to the Eukarya as indicated by the
presence molecular regions distinctly different from the rRNA
of Archaea and Bacteria.
The Eukarya are subdivided into the following four kingdoms:
1.Protista Kingdom
2.Fungi Kingdom
3.Plantae Kingdom
4.Animalia Kingdom

6. TAXONOMIC HIERARCHY
 “Taxonomic hierarchy is the process of arranging various
organisms into successive levels of the biological classification
either in a decreasing or an increasing order from kingdom to
species and vice versa.”
 Taxonomic Hierarchy Categories
 Kingdom
 The kingdom is the highest level of classification, which is divided into
subgroups at various levels. There are 5 kingdoms in which the living
organisms are classified, namely, Animalia, Plantae, Fungi, Protista,
and Monera.
 Phylum
 This is the next level of classification and is more specific than the
kingdom. There are 35 phyla in kingdom Animalia. For Example –
Porifera, Chordata, Arthropoda, etc.
 Class
 Class was the most general rank in the taxonomic hierarchy until phyla
were not introduced. Kingdom Animalia includes 108 classes including
class mammalia,reptilia,aves, etc. However, the classes used today
are different from those proposed by Linnaeus and are not used
frequently.

7.  Order
 Order is a more specific rank than class. The order constitutes one
or more than one similar families. There are around 26 orders in
class mammalia such as primates, carnivora, etc.
 Family
 This category of taxonomic hierarchy includes various genera that
share a few similarities. For eg., the families in the order
Carnivora include Canidae, Felidae, Ursidae, etc.
 Genus
 A group of similar species forms a genus. Some genera have only
one species and is known as monotypic, whereas, some have more
than one species and is known as polytypic. For eg., lion and tiger
are placed under the genus Panthera.
 Species
 It is the lowest level of taxonomic hierarchy. There are about 8.7
million different species on earth. It refers to a group of organisms
that are similar in shape, form, reproductive features. Species can
be further divided into sub-species.

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