Unique Features of all Living organism:-
✅Life span

The living organisms shows two types of features characteristic features and defining features

  • In plants, this growth by cell division occurs continuously throughout their life span.
  • In animals, this growth is seen only up to a certain age. However, cell division occurs in certain tissues to
    replace lost cells.
  • Unicellular organisms grow by cell division
  • In majority of higher animals and plants, growth and
    reproduction are mutually exclusive events.
  • In living organisms, growth is from inside
  • Increase in body mass is considered as growth.

Growth,cannot be taken as a defining property of living organisms. Conditions under which it can be observed in all living organisms have to be explained and then we understand that it is a characteristic of living systems. A dead organism does not grow.

  • Reproduction is a characteristic of living organisms.In multicellular organisms, reproduction refers to the production of progeny possessing features more or less similar to those of parents.
  • Two type of reproduction,sexual and asexual
  • Fungi multiply and spread easily due
    to the millions of asexual spores they produce.
  • In Planaria (flat worms): True regeneration
  • The fungi, the filamentous algae, the protonema of mosses, all easily multiply by fragmentation.
  • Bacteria, unicellular algae or Amoeba, reproduction is synonymous with growth, i.c., increase in number of cells.
  • There are many organisms which do not reproduce (mules, sterile worker bees, infertile human couples, etc

Reproduction cannot be an all-inclusive defining characteristic of living organisms.

  • No non-living object is capable of reproducing or replicating by itself.
  • The sum total of all the chemical reactions occurring in our body is metabolism.It is two types,anabolism and catabolism
  • No non-living object exhibits metabolism.
  • An isolated metabolic reaction(s) outside the body of an organism, performed in a test tube is neither living nor non-living.

Hence, while metabolism is a defining feature of all living organisms without exception, isolated metabolic reactions in vitro are not living things but surely living reactions.Hence, cellular organisation of the body is the defining feature of life forms.

  • The most obvious and technically complicated feature of all living organisms is this ability to sense their surroundings or environment and respond to these environmental stimuli
  • which could be physical, chemical or biological. Photoperiod affects reproduction in seasonal breeders.
  • Human being is the only organism that is aware of himself, i.e., has self-consciousness.
  • Consciousness is the defining property of living organisms.

The number of species that are known and described
range between 1.7-1.8 million. This refers to biodiversity

  • Largest group is insecta.
  • Maximum Biodiversity is found in tropical rain forest:
  • Around 1500 new species discovered every.
    There is a need to standardise the naming of living organisms
    such that a particular organism is known by the same name all over the
    world. This process is called nomenclature. Obviously, nomenclature or naming is only possible when the organism is described correctly and we
    know to what organism the name is attached to. This is identification.

Binomial nomenclature system given by Carolus
. Each name has two components — the generic
name and the specific epithet.

Tautonyms: If both generic and specific names are same,
these are called tautonyms. Homonym-one name for two different species

Taxonomy is derived from two words taxis means arrangement,nomos means rules.The branch of taxonomy includes classical taxonomy and modern taxonomy

  • Father H. Santapau – Father of Indian Taxonomy.
  • William Roxburgh – Father of Indian Botany and Indian Herbaria.
  • The term taxonomy was coined and used by French botanist A.P. de Candolle (1813) in his book Theorie Elementaire de La Botanique.
  • Aristotle-The founder of taxonomy

Nomenclature: Standardize the naming of living organisms

  • International Code for Botanical Nomenclature (ICBN).
  • International Code of Zoological Nomenclature (ICZN).
  • Biological names are generally in Latin and written in italics. They are latinized or derived from Latin irrespective of their origin,
  • The first word in a biological name represents the genus while the second component denotes the specific epithet.
  • Both the words in a biological name, when handwritten,are separately underlined, or printed in italics to indicate their Latin origin.
  • The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter.
  • Name of the author appears after the specific epithet, i.e., at the end of the biological name and is written in an abbreviated form.

Characterization, identification, classification and
nomenclature are the processes that are basic to taxonomy.

The word systematics is derived from the Latin word ‘systema’
which means systematic arrangement of organisms.

Linnaeus used Systema Naturae as the title of his

based on characteristics, all living organisms can be classified
into different taxa. This process of classification is taxonomy.

The scope of systematics was later enlarged to include identification, nomenclature and classification. Systematics takes into account evolutionary relationships between organisms

Classification is not a single step process but involves hierarchy of steps
in which each step represents a rank or category. Since the category is a
part of overall taxonomic arrangement, it is called the taxonomic category
and all categories together constitute the taxonomic hierarchy.

Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as taxon

Kingdom ➡️Division ➡️Class➡️ Order➡️ Family➡️ Genus ➡️Species

species:Taxonomic studies consider a group of individual organisms with
fundamental similarities as a species. One should be able to distinguish
one species from the other closely related species based on the distinct
morphological differences.

Genus comprises a group of related species which has more characters
in common in comparison to species of other genera. We can say that
genera are aggregates of closely related species.

Family;has a group of related genera with still less
number of similarities as compared to genus and species. Families are
characterised on the basis of both vegetative and reproductive features of
plant species.

order :and other higher taxonomic categories are identified based
on the aggregates of characters. Order being a higher category,
is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as
compared to different genera included in a family.

Class:This category includes related orders.

Common classes included in phylum In plants, classes with a few similar
characters are assigned to a higher category called Division.

as we go higher from species order to kingdom, the number of common characteristics goes on decreasing.Lower the taxa, more are the characteristics that the members within the taxon share. Higher the category, greater is the difficulty of determining the relationship to other taxa at the same level. Hence, the problem of classification becomes more complex.

Herbarium is a store house of collected plant specimens that are dried,
pressed and preserved on sheets. These specimens, along with their descriptions on herbarium sheets, become a
store house or repository for future use . The herbarium sheets
also carry a label providing information about date and place of collection, English, local and botanical names, family, collector’s name, etc. Herbaria
also serve as quick referral systems in taxonomical studies.

Biological museums are generally set up in educational institutes such
as schools and colleges. Museums have collections of preserved plant
and animal specimens for study and reference. Specimens are preserved
in the containers or jars in preservative solutions.
Zoological Parks
These are the places where wild animals are kept in protected environments under human care and which enable us to learn about their food habits and behaviour.

Key is another taxonomical aid used for identification of plants and animals based on the similarities and dissimilarities. The keys are based on the contrasting characters generally in a pair called couplet. It represents
the choice made between two opposite options. This results in acceptance
of only one and rejection of the other. Each statement in the key is called
a lead.


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