define classification? for 11 th
Answers
Answer:
Biological classification is the scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing the group in a hierarchy of categories.
Importance of classification-
It is not possible to study every organism. Study of one or two organism of a group gives sufficient information about the essential features of the group.
It helps in identification of new organism.
Classification helps in knowing the relationship amongst different groups of organisms.
The organism of past cannot be studied without a proper system of classification.
Classification
Artificial system of classification
Natural system of classification
Phylogenetic system of classification
Artificial system of classification– Only one or two morphological characters for grouping of organism is used. Flowering and non-flowering plants, enaima and anaima. Aristotle classification.
Natural system of classification– Takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms. Bentham and Hooker classification, etc.
Phylogenetic System of Classification– Based on the evolutionary relationship of organisms. In this system organism are classified on the basis of their evolution on earth from primitive to highly evolved. Engler and Prantl classification and Hutchinson classification, etc.
Depending upon the type of system of classification organism are classified into following kingdom system.
Kingdom system of classification
Two kingdom : Plantae Animalia
Three kingdom : Plantae Protista Animalia
Five kingdom : Monera Protista Fungi Plantae Animaila
In two kingdom system of classification organisms are grouped on the basis of presence and absence of cell wall as proposed by Linnaeus( father of taxonomy).
Three kingdom systems- Haeckel separated unicellular animals, algae and fungi on the basis of lack of tissue differentiation and new kingdom Protista was introduced.
Five kingdom systems- R.H.Whittaker divided all the organism into five kingdom in order to develop phylogenetic classification.
Monera– The kingdom includes all prokaryotes- mycoplasma, bacteria, actinomycetes and cyanobacteria.
Unicellular, prokaryotes and contain the most primitive of living forms
The cells are microscopic and cell wall is generally present.
Genetic materials are not organized into nucleus and contain naked DNA.
Membrane bounded organelles are absent.
Reproduction is asexual except gene recombination.
Flagella may be present and are of single stranded.
Example- Blue-green algae, Bacteria, etc.
Bacteria are the most abundant micro-organism that can survive in all kinds of climate.
They are group of most primitive prokaryotes which live under most hostile conditions like extreme salty area (halophiles), hot springs (thermoacidophiles) and marshy area (methanogens). They differ from other bacteria in having different cell wall structure (absence of peptidoglycan). Methanogens are present in the gut of several ruminant animals like cows and buffalo, which is responsible for production of biogas (methane) from dung of these animals.
Eubacteria – They are called as true bacteria. They contain rigid cell wall, if motile contain flagellum. Cyanobacteria or blue-green algae are gram positive photosynthetic bacteria. They contain chlorophyll a and carotenoids. They may be unicellular, colonial or filamentous, fresh water, marine or terrestrial. Some of them have specialized heterocyst cells to perform nitrogen fixation (Nostoc and Anabaena).
Chemosynthetic bacteria oxidize inorganic substances like nitrate, nitrite, ammonia etc. to produce energy and help in recycling of nitrogen, phosphorous, sulphur etc.
Heterotrophic bacteria are most abundant and act as decomposer. They are helpful in production of curd, antibiotic and fixing nitrogen in leguminous plants. Some of them are pathogenic and cause disease like cholera, typhoid, tetanus and citrus canker.
Answer:
The definition of classifying is categorizing something or someone into a certain group or system based on certain characteristics. An example of classifying is assigning plants or animals into a kingdom and species. An example of classifying is designating some papers as "Secret" or "Confidential."