2. Systematics of Living Organisms - part 05 -Salient features of Five Kingdoms

 

2. Systematics of Living Organisms - part 05 -Salient features of Five Kingdoms

 Salient features of Five Kingdoms :
1. Kingdom Monera :

• It contains unicellular organisms with prokaryotic cellular organization. 
• Monera includes unicellular prokaryotic organisms.
• These are omnipresent. 
• They are found in all types of environment which are not generally inhabited by other living beings. 
• Few are photoautotrophs or chemoautotrophs; but majority are heterotrophic in nature.
•  These organisms do not have well defined nucleus.
• DNA exists as a simple double stranded circular single chromosome called as nucleoid.
• Smaller circular molecules of DNA as extrachromosomal genetic elements called plasmids are often present. 
• Cell wall is made up of peptidoglycan (also called murein) which is a polymer of sugars and amino acids.
• Membrane bound organelles e.g. mitochondria, chloroplast, endoplasmic reticulum are absent. 
• Ribosomes are smaller in size (70S) than in eukaryotic cells. 
• The mode of reproduction in monera is asexualor with the help of binary fission or budding.Very rarely,
• sexual reproduction is by conjugation method. 
• Morphologicaly, bacteria are categorised into four groups- 

1. the spherical- Coccus
2. the rod-shaped -  bacillus
3. the comma or kidney shaped- vibrio and 
4. the spiral- spirillum.

• On the basis of evolution, bacteria can be classified as - 

1. Archaebacteria and 
2. Eubacteria.

1. Archebacteria :

• These are differentiated from other bacteria on the basis of their different cellular features. 
• These bacteria are mostly found in the extreme environments; hence termed extremophiles. 
• They are found in a variety of places from volcanic craters to salty lakes and hot springs. 
• Their ability to withstand such hostile environment speaks of their capacity to survive in very severe conditions. 
• Bacteria that can withstand high salinities are called halophiles while those that withstand extreme temperature are known as thermophiles. 
• A very common example is of methanogenic bacteria found in gut of ruminants (cows and buffaloes). 
• These bacteria help in production of methane in biogas plants.

2. Eubacteria :

• These are commonly referred as true bacteria. 
• They have cell wall of peptidoglycan. 
  
• They are found as autotrophs and heterotrophs.
• The autotrophs can be photosynthetic like Chlorobium (Green sulphur bacteria) and Chromatium or chemosynthetic like sulphur bacteria.
• These are mostly multicellular filamentous forms living in fresh water. 
• The body is covered by mucilagenous sheath.
• The genetic material is typical prokaryotic. 
• Chl-a, Chl-b, carotenes and xanthothylls are the photosynthetic pigments.
•  Filaments show heterocyst which helps in nitrogen fixation.
• Heterotrophs are the most abundant.
• Most of them are decomposers and known for breaking down large molecules in simple molecules or minerals. 
• They can be anaerobes helping in -

1. curdling of milk (Lactobacilli)
2. fixation of nitrogen (Azotobacter)
3. antibiotic production (Streptomyces)
4. composting and degrading oil. 

• But the story doesn’t end here,some of them are pathogens i.e. causing disease (typhoid, cholera, tuberculosis, tetanus).

Mycoplasma :

• These are smallest of the living forms.
• They do not have cell wall. 
• Many forms are pathogenic. 
• They are found resistant to common antibiotics due to absence of cell wall.

2. Kingdom Protista :

• This group includes all the unicellular but eukaryotic organisms. 
• These organisms show link with all eukaryotic Kingdoms like Plantae, Fungi and Animalia.

a. Plant like protista :

• They are also termed Chrysophytes.
• They are commonly termed phyto-planktons.
• They are microscopic and mostly photosynthetic and are major producers in oceans. 
• Most of them are referred to as diatoms as the have body wall made up of two soap-box like fitting silica covers. 
• “Diatomaceous earth" is nothing but these shells left behind for so many years.
• Diatomaceous earth is granular hence finds use in polishing and filtration.

b. Animal like Protista :-

• They are also termed protozoans. 
• They lack cell wall. 
  
• They are heterotrophs. 
• They are believed to be primitive animal forms. 
• Amoeboid protozoans have pseudopodia as locomotory organs. 
• Amoeba is free living form but Entamoeba is endoparasite and causes amoebic dysentery. 
• Flagellated protozoans have flagella as locomotory organ. 
• Trypanosoma is a common flagellated pathogen which causes sleeping sickness.
• Paramoecium is a cilliate protozoan having cilia for locomotion. 
• In Paramoecium, gullet (a cavity) opens on the cell surface.
• Plasmodium is a sporozoan protozoa. It causes malaria. It forms spores in one of its life stage.

c. Dinoflagellates :- 

• These are aquatic (mostly marine) and photosynthetic.
  
   
• The cell wall is made up of cellulosic stiff plates. 
• They possess a pair of flagella. 
• They have a wide rangephotosynthetic pigments, which can be yellow, green, brown, blue and red. 
• Gonyaulax is dinoflagellate that is responsible for famous ‘red tide’. It makes even sea appear red.

d. Fungi like protista :- 

• They are commonly from the group Myxomycetes. 
• These are saprophytic organisms found on decaying leaves. 
• Their cells aggregate to form a large cell mass called plasmodium (not a malaria parasite). 
• The spores produced by plasmodium are very tough and survive even very harsh conditions.

e. Euglenoids :- 

• They lack cell wall but have a tough covering of proteinaceous pellicle.
• They possess two flagella, one short and other long. 
• They behave as heterotrophs in absence of light but possess pigments, similar to that of higher plants, for photosynthesis.

3. Kingdom Plantae:

• The kingdom is dominated by autotrophs. 
• It also includes some semiautotrophic members, the insectivorous plants like Venus fly trap, pitcher plant, bladderwort, as well as heterotrophic parasitic members like Cuscuta. 
• Members of this kingdom are multicellular, having eukaryotic cells containing chlorophyll. 
• Cells have cell wall mostly made up of cellulose. 
• Plants exhibit alternation of generation i.e., life cycle has two distinct phases. 
• Kingdom Plantae is divided into two major groups -  

1. Cryptogamae / Cryptogams and 
2. Phanerogamae / Phanerogams.

4. Kingdom Fungi : 

• These are eukaryotic heterotrophs showing extracellular digestion.
• They are found in warm and humid places. 
• They have simple body which may be unicellular or made up of long thread like structures called hyphae. 
• Large fungi such as mushrooms have a compact mass of cells. 
• Unicellular organisms have a protoplast with many nuclei. e.g. Rhizopus, Saccharomyces(Yeast-unicellular fungus).
• Filamentous fungi consist of a body called mycellium in which hyphae are present.
• The hyphae may be with septa or without septa. 
• They may be uni or multinucleate. 
• The non-septate multinucleate hyphae are called coenocytic hyphae. 
• The cell wall in fungi is composed of chitin, a polysaccharide or fungal cellulose. 
• The fungi exhibit hetrotrophic mode of nutrition. 
• Mostly they are saprophytic, some are parasitic or predators. 
• They reproduce sexually as well as asexually. 
• Asexual reproduction takes place by - 

1. fragmentation
2. fission and 
3. budding. 

• Some fungi are symbiotic; either live with algae as lichens or as mycorrhiza in association with roots of higher plants.
• They are useful as well as harmful. Mushroomsare consumed as food, yeast is used in bakery and breweries. 
• Penicillium, a fungus, is well known for antibiotic production.
• Harmful fungi cause diseases in plants and animals. e.g. Puccinia.
• The fungi are further classified on the basis of- Their structure, Mode of spore formation and Fruiting bodies as follows :

1. Phycomycetes 
2. Ascomycetes 
3. Basidiomycetes 
4. Deuteromycetes

1. Phycomycetes :

• These are commonly called algal fungi. 
• Mycelium is made up of aseptate coenocytic hyphae. 
• They commonly grow in moist and damp habitats, on decaying organic matter as well as in aquatic habitats or as parasites on plants.
• e.g. Mucor, Rhizopus (bread mould), Albugo(parasitic fungus on mustard).

2. Ascomycetes :

• These are called as sac-fungi. 
• These fungi are mostly multicellular. 
• Rarely unicellular varieties include yeast. 
• The hyphae are branched and septate. 
• Sac fungi can be decomposers, parasites or coprophilous (grow on dung). 
• Morels and truffles are varieties of sac fungi that are consumed as delicacies.
• Neurospora is useful in genetic and biochemical assays.
• Ex. Aspergillus, Penicillium, Claviceps, Neurospora, Saccharomyces.

3. Basidiomycetes :

• These are commonly called club fungi. 
• They have branched, septate hyphae.
•  e.g. Agaricus (mushrooms), Ganoderma (bracket fungi), U stilago (smuts), Puccinia (rusts), etc.

4. Deuteromycetes :

• These are called imperfect fungi, which are known to reproduce only asexually. 
• e.g. Alternaria, Colletotrichum.

5. Kingdom Animalia : 

• Members of this kingdom are heterotrophs; adapted to holozoic nutrition. 
• Most of them have capacity of locomotion. 
• They are multicellular eukaryotes where cellslack chlorophyll as well as cell wall. 
• Growth is determinate (follow definite pattern).

Do u know ?

• New variety of Banana seedlings produced by tissue culture technique like ‘Shrimanti’,Basarai, G-9 are virus free varieties.
• Viruses, Viroids are groups of acellular organisms that are not included in Whitaker’s Five Kingdom classification.