Organism (Microorganism, plant and animals) who posses life is living.
Life is a complex organisation expressing itself through chemical reactions and exhibit characteristics of living organisms.
Characteristics of Living Organisms: Growth, reproduction, metabolism. cellular organisation, consciousness (ability to sense environment), self replicating and self regulation.
Characteristics of Living Organisms:
The characteristic of living organisms is given below -
Non Definning property
1) Growth: All living organisms can undergo the process of growth and development that results in an increase in the mass and number of cells. Multicellular organisms grow by cell division. The growth of plants and animals takes place with the help of cell division. In the case of plants, the cell division occurs throughout their life while in the case of animals the cell division occurs up to a certain age, and then the cells lose their capability to divide.
It results in an increase in body mass and increases in the number of cells.
Examples: Mountains, boulders, sand mounds, etc grow by the accumulation of the materials although they are non-living. So, growth cannot be taken as the factor which categorizes the organism as living.
2) Reproduction: The ability to produce young ones is the process of reproduction which is observed only in the case of living organisms. In the case of fungi, reproduction occurs through asexual spores, while in the case of hydra budding occurs and in planaria regeneration occurs which are all the asexual methods of reproduction.
Reproduction is the increase in the number of cells while in the case of mules, infertile human couples, etc reproduction is absent. So, reproduction is simply synonymous with growth which is not appropriate to distinguish the living organisms.
Definning property
3) Consciousness The living organisms whether prokaryotes or eukaryotes respond according to their surroundings and the stimuli present around them, it may be physical, chemical, or biological. The living organisms are sensitive about their surroundings and are responsible in accordance with their stimuli. The stimuli can either be biological, physical, or chemical.
4) Metabolism: As the body and organs are the constituents of different chemicals, they perform various metabolic functions that result in the conversion of chemicals into other biomolecules. All plants, animals, and microbes exhibit metabolism. It is absent in the case of non-living organisms but may be introduced through the in-vitro method.
Reproduction is the increase in the number of cells while in the case of mules, infertile human couples, etc reproduction is absent. So, reproduction is simply synonymous with growth which is not appropriate to distinguish the living organisms.
5) Cellular Organization: It is the defining characteristic of living organisms since all living organisms are made up of cells that help in performing various cellular functions resulting in the growth and development, reproduction, metabolism, etc in the body. Since non-living organisms are not made up of cells so they do not have cellular organization.
6) Movement: The lining organisms show movement and locomotion and more specifically plants move according to the movement of the sun.
Example: The flame of a candle and a crystal do not show movement while if we take mango trees then we can see they undergo movement, growth, and development along with reproduction and results in the production of more trees through their seeds. Thus mango trees are said to be alive as they show movement while candles flame and crystal are not alive.
Also, the organisms that are aware and are conscious of their surroundings will be living organisms.
Taxonomy: Taxonomy is the study of the classification, characterization, nomenclature, and identification of organisms and it is a branch of science. Systematics is another branch of science that includes the study of the classification, nomenclature, identification, and evolutionary history of an organism..
The term Systematics is derived from the Latin word ‘systema’ which means the systematic arrangement of organisms. Linnaeus published his book Systema Naturae where the classification of plants, animals were based on taxonomy.
Neo-systematics is the branch of systematics that deals with the species to be the product of evolution. In 1940, Julia Huxley was the one who developed this concept. It involves the known characteristics of an organism and also the known evidence from different fields of biology.
Identification: It is the method of pacing the organisms in their exact place based on their classification. The identification of organisms can be done with the help of taxonomic keys.
Classification: The classification is the process of grouping various living organisms based on the common features that they share. A single group consists of those organisms that have similar common features. To make classification easier various groups are forms in which different organisms are placed depending upon their characteristics.
Characterization: The studying and understanding of characters of organisms and categorizing them like external and internal structure (morphology and anatomy), the structure of the cell (cytology), developmental process (embryology), and ecological information (ecology) of the organism.
Nomenclature (naming): The naming of living organisms is called nomenclature. There are two types of names, one is vernacular (common names) and the other is the scientific name. Local names are used in local languages or common language and are easy for the local peoples but these names are not used by biologists because:
1. For many species a single local name is often used.
2. The local names sometimes lead to incorrect meanings about the organism.
3. In different regions of the country or world, the different local names are used for one organism. Scientific names: The names are given according to certain rules and are followed by the biologist all over the world. To make it common around the world various international codes have been established.
These codes are:
• ICBN-International Code of Botanical Nomenclature
• ICZN-International Code of Zoological Nomenclature
Binomial Nomenclature:
Carl Linnaeus is credited with introducing binomial nomenclature in 1753 with the book Species Plantarum. In biological nomenclature, the name of an organism is composed of two terms, the first of which indicates the genus, and the second of which indicates the species. E.g., Mangifera indica Linn. Mangifera is the genus name and indica is the species name. The name of this species was first given by Linnaeus, who was able to give scientific names: Identification, nomenclature, and classification of organisms are all part of this branch of biology.
Rule for Nomenclature:
Latinised names are used.
the First word is the genus, second word is species name.
Printed in italics; if handwritten then underlined separately.
First word starts with a capital letter while the species name is written in small letters.,
Eg: Mangifera indica- Mangifera is the genus name and indica is the species name.
Taxonomic Categories:
In 1956 the term Taxon was introduced and in 1964, Mayr defined taxon to be the various categories based on different characters of the organisms that consist of a taxonomic group of any rank.
Taxonomic Hierarchy:
Various organisms in different categories depending upon their common characters to make classification easier. These groups together are called taxonomic hierarchies. The taxonomic hierarchy includes. Kingdom, division of the kingdom, phylum, class, order, family, genus, and species. Species are the lowest while the kingdom is the highest rank within the hierarchy. It is also called the Linnaean hierarchy as it was first proposed by Carolus Linnaeus, the Father of Systematic Botany. The hierarchy includes seven obligate categories.
They are as follows-
Kingdom - Animalia
↑
Phylum - Chordata
(Division in case of plants)
↑
Class - Mammalia
↑
Order - Primata
↑
Family - Hominidae
↑
Genus - Homo
↑
Species – sapiens
Species: It is the lowest category of the taxonomic hierarchy. There are around 8.7 million species observed on earth till now while their rest are left undiscovered. It refers to a group of organisms that are similar in shape, form, generative options. Species may be more divided into subspecies. It was first defined by Ernst Mayr in 1964 that the species are the interbreeding populations that are reproductively isolated from other such groups. The term species was first introduced by the biologist John Ray.
E.g.: sapiens.
Genus: A category that is placed above species as they consist of a group of related species. Genus are of various types based on the number of species present like monotypic (one genus present), and polytypic (several species present). For e.g., the genus Panthera constitutes both lion and tiger.
Family: This taxonomic category consists of related genera having similar characteristics. For e.g., the families Canidae, Felidae, Ursidae, etc come under one order Carnivora.
Order or Cohort: This taxonomic category is more specific than the class as it consists of one or more similar families. The class Mammalia consists of around twenty-six orders that include primates, Carnivora, etc.
Class: It was the most general taxonomic category before the introduction of phyla. In the animal kingdom, there are around 108 classes that include Pisces, reptilia, aves, etc. The categories used in classification now are different from those of the Linnaeus taxonomy.
Phylum: This category is more specific than the kingdom. In the animal kingdom, there are around thirty-five phyla that include phylum Arthropoda, Chordata, etc.
Kingdom: The highest level of classification is the kingdom which is further divided into various subgroups. The total kingdoms of the living organisms are five in number that includes Monera, Protista, Fungi, Plantae, and Animalia.
Taxonomical Aids:
Taxonomic guide or taxonomic aids refers to the techniques, stored information and procedures useful in identification and classification of entities. They are:
Herbarium
A herbarium is the storeroom of assembled plant samples. These samples are dried, squeezed and protected on sheets after which they are systematically ordered in accordance with the classification system universally accepted. The Herbarium sheet consists of marks concerning the scientific name, date, the spot of gathering, name of the collector, family and much more concerning the sample.
Museums
It is a repository, having an assembly of different plant and animal samples preserved for study and further information source. Here the entities are preserved either as dry samples or in additive arrangements. It usually has an accumulation of skeletons of animals too.
Zoological park
Here, wild animals are ensured with secured conditions of nature. Renders a good chance to focus on the behavioural aspects and sustenance inclinations for these animals.
Botanical Garden
It consists of an accumulation of living plant species developed to identify and also as an information source. Every plant has a label exhibiting its scientific name and family name.
Key
Keys(Used for identification of plants and animals on the has of similarities and dissimilarities)
Couplets are the two alternate characteristic statements used in keys to identifying organisation.
Each Statement of the key is called a lead
Other Taxonomic Aids: Various other taxonomic aids including flora, manuals, monographs, and catalogues also serve as taxonomic aids for correct identification.
Flora: (Index to plant species found in a particular area.
Manuals: (Provide information for identification of name of species-area.)
Monograph: (Contain information on any one taxon.)
Catalogue: It consists of the list of publications that include the books, periodicals, and dictionaries containing new information for taxonomic studies.