Test: Biological Classification - 1

Five kingdom classification was proposed by R.H. Whittaker in 1969.
The kingdoms identified by him were:

• Monera
• Protista
• Fungi
• Plantae  
• Animalia

• Monera is a kingdom that contains unicellular organisms with a prokaryotic (is a unicellular organism that lacks a membrane- bound nucleus, mitochondria, or any other membrane- bound organelle.) cell organization, like bacteria.
• They are single- celled organisms with no true nuclear membrane. The taxon Monera was first proposed as a phylum by Ernst Haeckel in 1866. 

Species is the lowest or basic taxonomic category which consists of one or more natural populations of individuals that resemble one another more closely than individuals of other species, interbreed freely, have a distinct genetic setup and are reproductively isolated from others e.g., Panthera Leo (Lion), Mangifera indica (Mango), Solanum tuberosum (Potato).

• Symbiotic association between an alga and a fungus is called Lichens.
• Algae prepare food due to the presence of chlorophyll and fungus absorbs nutrients and provides protection to algae.

• Kingdom Protista, kingdom Fungi, kingdom Plantae possess nuclear membrane while kingdom Monera do not possess nuclear membrane.
• The kingdom Monera is considered the most primitive group. 
• These organisms are unicellular prokaryotes that do not have membrane-bound cell organelles such as the nucleus, mitochondria, chloroplasts, etc.

• Methanogens are group of obligate anaerobic ancient and primitive bacteria.
• Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane (biogas) from the dung of these animals.
• They are involved in methanogenesis and produce methane gas.

• Chitin is a modified polysaccharide that contains nitrogen.

• Chitin is synthesized from  long-chain of N-acetylglucosamine polymer and is a glucose derivative.

• This polysaccharide is a primary component of cell walls in the fungi, arthropod exoskeletons such as crustaceans and insects, mollusc's radula, cephalopod beaks, and fish.

• The cell wall of plants are made up of cellulose.

Fungi is important in nutrient cycle and acts as decomposer along with bacteria and minerlisers of the biosphere to regulate recycling of nutrients in the biosphere.

Viruses are acellular, which means they don't have a cellular structure. Bacteriophages are viruses that infect the simplest living species, and are one of the most complex virus particles.

• In Whittaker’s five kingdom of classification, kingdom protista, kingdom fungi, kingdom plantae and kingdom animalia are eukaryotic organisms.
• The kingdom monera includes prokaryotic organisms.

Prokaryotes differ from Eukaryotes in absence of nuclear membrane and membrane-bounded organelles like mitochondria, Golgi bodies etc.

Euglena is a special type of organism as it shows mixotrophic mode of nutrition i.e. in presence of sunlight it is phototrophic and in absence of sunlight it derives nutrition by saprophytic modes. In the presence of sunlight it is autotrophic.

• Reserve food materials can be fats or complex carbohydrates like Starch. In fungi, the reserve food material is a multibranched polysaccharide called Glycogen.
• In fungus, the food reserve is glycogen and fat.

• Viroids are smaller than viruses and cause potato spindle tuber disease.
• It was found to be a free RNA; it lacks the protein coat that is found in viruses, hence the name viroid.
• The RNA of the viroid was of low molecular weight.

Kingdom Protista has brought together Chlamydomonas, Chlorella which were earlier placed in Algae (within plants and both having cell walls) with Paramoecium and Amoeba which were earlier placed in the animal kingdom which lack cell wall.

Fig: Cyanobateria

A heterocyst is a differentiated cyanobacterial cell that carries out nitrogen fixation. The heterocysts function as the sites for nitrogen fixation under aerobic conditions. They are formed in response to lack of fixed nitrogen.

Hence, the correct option is 'B'

• Azotobacter is the gram-negative free-living soil microbes which are found in alkaline to the neutral soils.
• They are important in the nitrogen fixation process. They have a complete range of enzymes required for nitrogen fixation.
• They are non-photosynthetic and few of the Azotobacter species live in association with plants.

The Agaricomycetes belong to the Basidiomycota division of fungi. With the addition of Auriculariales and Sebacinales, the taxon is nearly identical to that established by Hibbett & Thorn for the Homobasidiomycetes.

• A virus is an infectious agent that typically consists of the nucleic acid molecule in a protein coat. Nucleic acid could be either DNA or RNA.
• In our environment, virus exists in two states - extracellular and intracellular.
• Extracellular before it invades the host cell and once the virus invades a host cell, it is in an intracellular state.
• Antibiotics can't kill viruses because viruses have a different structure and replicate in a different way.
• Antibiotics work by targeting the growth machinery in bacteria (Not viruses).

So, the correct option is  B: '(a) & (d)'.

• The natural classification system for organisms is based on a relationship of descent from a common ancestor.
• The organism is classified in this classification based on its vegetative characteristics, which are constant and do not change with the environment.
• This classification system eliminates the grouping of species that are diverse and unrelated.
• Bentham and Hooker proposed the first natural system of plant classification.

Plant cells have a cell wall made up of cellulose and chloroplast that contain chlorophyll for photosynthesis. Animal cell lacks both cell wall and chloroplast.

Asexual reproduction in fungi takes place by conidia, zoospore, sporangiospores, chlamydospore and oidia.
In some fungi, the spores are not formed inside a sporangium. They are born free on the tips of special branches called conidiophores. These spores thus formed are called conidiophores for example in Penicillium.

Fig: Formation of Conidiophores

• Bacterial cells are primitive cells hence, are called as prokaryotic cells. They do not possess membrane-bound organelles as mitochondria, Golgi complex etc.
• The processes which are carried out by such specialised organelles are carried over by plasma membrane of bacteria.
• The plasma membrane is a living membrane that forms the boundary between a cell and its environment. Some invaginations of the plasma membrane are called as mesosomes which are involved in the process of respiration and called as a respiratory centre.

• Viral infection occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells. 
• The viral disease includes common cold, flu and warts. They also cause severe illnesses such as HIV/AIDS, smallpox, Herps and Ebola. 
• Viruses are like hijackers. They invade living, normal cells and use those cells to multiply and produce other viruses like themselves. Hence, Tuberculosis is not a viral disease. It is a bacterial disease.

So, the correct answer is 'Tuberculosis'.

• They do not grow in polluted areas and are found growing well only in non-polluted areas.
• Lichens are called very good pollution indicators because these species are susceptible to certain pollutants.

Therefore, Lichens are the indicators of pollutants or pollution and do not grow in polluted areas.