Plus One Botany Notes Chapter 1 Biological Classification is part of Plus One Botany Notes. Here we have given Kerala Plus One Botany Notes Chapter 1 Biological Classification.
|Text Book||NCERT Based|
|Chapter Name||Biological Classification|
|Category||Kerala Plus One|
Kerala Plus One Botany Notes Chapter 1 Biological Classification
Biological classification is the scientific procedure of arranging organisms in a hierarchial series of groups and sub-groups on the basis of their similarities and dissimilarities.The earliest attempt for scientific classification was done by Aristotle. Aristotle classified plants into trees, shrubs and herbs and classified animals into red blooded animals and animals without red blood.
Need of classification
- The study of one or two organism is not sufficient to know the essential features of the group
- All kinds of organisms do not occur in one locality
- Helps in knowing the relationship amongst different groups of organisms.
- Helps in knowing the evolutionary relation-ship between organisms.
Types of classification system
Depending upon the types of system of classification, organisms are classified into following kingdoms.
Two Kingdom Classification
Carolus Linnaeus introduced Two Kingdom classification. The two kingdoms are Plantae and Animalia.
Disadvantages of Two Kingdom Classification
- It grouped bacteria, blue green algae, fungi, mosses, ferns, gymnosperms and the
angiosperms under plantae.
- Fungi are included under plantae but they are heterotrophs.
- Euglena is included in plantae but it has both plant and animal behaviour.
- Lichens are included in plants but they are symbiotic organisms.
Five Kingdom Classification
It was introduced by R.H. Whittaker in 1969.
The five kingdoms are :
The criteria for 5 kingdom classification are the following:
- Cell structure
- Thallus organization
- Mode of nutrition
- Phylogenetic relationships
Advantages of five kingdom classification
- It exhibits phylogenetic relationship between diverse groups of organisms.
- Separation of prokaryotes in a separate kingdom of Monera is justified because they differ from all other organisms in their structural organisation.
- Inclusion of Euglena and Chlamydomonas in Protista is also justified.
- Fungi is grouped under a separate kingdom.
- Protozoa is excluded from kingdom anima-lia
Disadvantages of five kingdom classification
- Monera and protista are heterogenous groups because both include photosynthetic and heterotrophic forms and also with and without cell wall.
- Both unicellular and multicellular algae are placed under Kingdom Plantae.
- Viruses and viroids have not given any place in classification.
Six Kingdom classification
Proposed by Carl Woese. He suggested a separate kingdom for,Archaebacteria. According to this classification three also been proposed.
Three domains of life:
These are Archaea, Bacteria and Eukarya. Archaea has kingdom Archaebacteria, Bacteria has kingdom Eubacteria and Eulcaryata has kingdoms Protista, Fungi, Plantae and Animalia.
Five kingdom classification
Monera includes all prokaryotes such as
- Cyanobacteria (Blue – green algae)
Bacteria are classified into 4 types based on their shape.
- Coccus : Spherical shaped bacteria
- Bacillus : Rod shaped bacteria
- Spirillum : Spiral shaped bacteria
- Vibrio : Comma shaped bacteria
Bacteria are autotrophic and heterotrophic in nature. Autotrophs are classified into photo-synthetic autotrophs and chemosynthetic au-totrophs. Majority of bacteria are heterotrophs.
Archaebacteria are living in harsh environmental conditions. They are three types.
- Halophiles: Living in salty areas.
- Thermoaddophiles: Living in hot springs.
- Methanogens: Living in marshy areas and in the guts of ruminant mammals such as cows and buffaloes. Methanogens are producing methane (biogas) from dung.
Eubacteria are otherwise called ‘true bacteria’. They are characterized by the rigid cell wall. If they are motile flagella are seen. They are classified into autotrophs and heterotrophs. The autotrophs are photosynthetic autotrophs and chemosynthetic autotrophs.
They are also known as cyanobacteria or blue green algae They have chlorophylla pigment. They may be unicellular, colonial or filamentous. They may be fresh water or marine. The colonies are generally surrounded by a gelatinous sheath. They often form algal bloom in polluted water. The specialized ceils called heterocysts
They release energy and produce ATP by oxidising various inorganic substances like nitrites, nitrates and ammonia. They play a great role in the recycling of nitrogen, phosphorus, iron and sulphur.
Majority of them are decomposers. They helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots etc. Some of them are pathogens, they cause many diseases like cholera, typhoid, tetanus etc. in humans and citrus canker disease in citrus plants. Bacteria reproduces through binary fission. They also produce endospores.
They have no cell wall. They can live without oxygen. Many of them causes diseases in animals and plants.
Protista are unicellular eukaryotic organisms. Protista are primarlily aquatic. They are autotrophs (photosynthetic) or heterotrophs. Protista reproduces both sexually and asexually. Some of them have flagella or cilia. The groups of protista are:
It includes diatoms and golden algae (desmids). They are fresh water and marine. They are planktons and most of them are photosynthetic. The cell wall of diatoms have two thin overlapping shells which fit together as in the soap box. The cell wall is embedded with silica.
The cell walls of the diatoms are left behind after their death and the cell wall deposits of diatoms are called ‘diatomaceous earth’. Diatomaceous earth is used polishing, filtration of oils and syrups.
These organisms are mostly marine and photosynthetic. They appear yellow, green, blue or red in colour. The cell wall has stiff cellulose plates on the outer surface. They have two : flagella; one lies longitudinally and the other lies transversely. The rapid multiplication of Gonyaulax causes red tide in sea. Toxins are released by dinoflagellates and which kills aquatic animals.
Majority of them are fresh water organisms. They have no cell wall the cell is covered by a protein sheath called ‘pellicle’. They have two flagella one is long and the other is short. They are photosynthetic in the presence of light and behave as predators in the absence of light.
4. Slime Moulds
Slime moulds are saprophytic organisms. They : live on decaying plant materials and engulf food materials from them. Under suitable conditions the cells will aggregate and a complex structure is formed called plasmodium. During unfavourable conditions a number of spores are produced inside the sporangia.
All protozoans are heterotrophs. They live as parasites or predators. Four groups of protozoans are the following.
- Amoeboid protozoans:
They live in fresh water, sea water and in moist soil. They move and capture prey by using pseudopodia, amoeba marine forms have silica shells on their surface,
eg., Amoeba, Entamoeba.
- Flagellated protozoans:
The members of this group are either free-living or parasitic. They have flagella. The parasitic forms causes diseases. Sleeping sickness is caused by trypanosoma.
- Ciliated protozoans
The cell is covered by many cilia. They have a cavity called gullet that opens to the outside of the cell surface,
- Sporozoans: An infectious spore-like stage is present in their life cycle. Plasmodium causes malaria.
Fungi are heterotrophic organisms. They are usually saprophytes. Parasitic and symbiotic fungi are also seen. Fungi are cosmopolitan and occur in air, water, soil, and on animals and plants. Fungi are commonly multicellular filamentous but yeast is unicellular. Their body consists of long slender thread like structure called hyphae. The network of hyphae is known as mycelium.
Some hyphae are continuous without any septa called coenocyte. Others have septae or cross walls in their hyphae. The cell walls of fungi are composed of chitin and polysaccharides.
It reproduces vegetatively by fragmentation, asexually by producing spores, (conidia, zoospores, etc.) and sexually by producing spores like oospore, ascospores, and basidiospores.
The sexual cycle involves the following steps:
- Fusion of protoplasm between two motile or non-motile gametes called plasmogamy.
- Fusion of two nuclei called karyogamy.
- Meiosis in zygote resulting in haploid spores.
During sexual reproduction two haploid hyphae come together and fuse. In some fungi the fusion of two haploid cells results in the formation of diploid cells (2n). In some others like ascomycetes and basidiomycetes an inter-mediate dikaryotic stage (n + n) i.e,. two nuclei per cell occur. Such a condition is called dikaryon and the phase is called dikaryo phase. Later the parental nuclei fuse and the cells become diploid. Then the fungi form fruiting bodies from this mycelium and reduction division occurs. So haploid spores are formed.
The fungi are divided into four classes, they are:
They are found on decaying wood and damp places. Some of them are parasitic. The mycelium is aseptate and coenocytic.
A sexual reproduction takes place by zoospores or aplanospores. Sexual reproduction is taking place by the fusion two gametes from different strains. A zygospore is developed by the fusion of gametes. The fusion may be isogamy, anisogamy or oogamy,
eg., Albugo. Rhizopus, Mucor, etc.
Ascomycetes are called ‘sac fungi’. They are saprophytic, decomposers, parasitic or coprophilous (growing on dung). They are mostly multicellular. But yeast is a unicellular ascomycetes. The mycelium is septate and branched. Asexual reproduction is through spores called conidia( exogenous spores). Sexual spores are called ascospores, produced inside the ascus of ascocarp.
Basidiomycetes are called ‘club fungi’. They are growing on soil, logs, tree stumps, and in plants as parasites. Vegetative reproduction is through fragmentation. Asexual spores are not produced. Sexual reproduction is through basidiospores. They produce basidiospores on basidia of basidiocarp.
Deuteromycetes are also called fungi imperfect. The sexual reproductive phase of this fungi is not known. When the sexual phase is discovered it will move into other fungal groups. The mycelium is septate and branched. They are saprophytes, decomposers or parasites. Vegetative reproduction is taking place through fragmentation. Asexual reproduction is through conidia.
They are multicellular eukaryotic organisms. They are photosynthetic autotrophs. The cell consists of cellulose cell wall and chloroplasts. The life cycle of plants have a diploid sporophytic stage and a haploid gametophytic stage. The sporophytic and gametophytic sta-ge al-ternate with each other. It is called alternation of generation. Some plants are heterotrophs or partial heterotrophs.
eg., parasitic plants like Cuscuta Loranthus etc., insectivorous plants like Dionea, Nepenthus, Utricularia etc. The plant groups are Al- pe, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms.
They are multicellular eukaryotes. The cells have no cell wall. They exhibit heterotrophic mode of nutrition, which are called holozoic nutrition. They are directly or indirectly depend on plants for their food. The members have well developed control and co-ordination mechanisms. Mostly they are free living. Some are parasitic and some others are symbiotic.
In five kingdom classification viruses, viroids ; and lichen are not included. The viruses are non cellular organisms.
Outside the living cells they are inert but when they enter into a living cell they shows the features of life. They are obligate parasites The name of the virus is given by Louis Pasteur. M.W. Beijerinek (1898) demonstrated the extract of the infected tobacco plant cause infection to healthy plants. W.M. Stanley crystalised the viruses in 1935.
Virus consists of a nucleic acid (DNA or RNA) covered by protein sheath. The protein sheath is called capsid. The capsid is made up of a number of sub units called capsomeres. The capsomeres are arranged in helical or polyhedral geometric forms. Generally the viruses that attacks plants have a single stranded RNA.
Viruses cause common flu, influenza, mumps, small pox, herpes, AIDS, etc. in humans. In plants it causes mosaic disease, leaf rolling, leaf curling, yellowing, vein clearing, dwarfing and stunted growth etc.
In 1971, T.O. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. It was found to be a free RNA; it lacked the protein ; coat that is found in viruses, hence the name viroid. The RNA of the viroid was of low molecular weight.
Lichens are symbiotic association of fungi and algae. The algal component is called phycobiont and the fungi component is called mycobiont. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients for algae. Lichens are good pollution indicators. They do not grow in polluted areas.
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