How to Study Monera for NEET?
By: Dr. Pankaj Kumar
Tags: Mindmap, Medical Entrance, Biology, Neet, Monera

Monera is one of the key topics of Plant diversity and it is frequently figured in NEET. The questions are mostly conceptual and require very less factual details. Students, in general, suffer from the misconception that it requires lots of mugging. They often get confused after seeing the name of the species as an option which in more than one occasion symbolizes one or other groups. Answering such questions, therefore, require conceptual clarity.

Let’s try to understand the correct and pragmatic way to learn the concept of Monera from the NEET perspective.

Baterial Cell

Monera in NEET includes Eubacteria, Archaebacteria Cyanobacteria, Mycoplasma, Actinomycetes, Chlamydia, and Rickettsia. Eubacteria is the main where we need to learn the cellular structure and reproduction.

Conceptual Key Notes:

Concept of Eubacteria and Archaebacteria The cell wall of gram +ve and gram –ve bacteria The genetic makeup of Eubacteria and difference with a typical Eukaryotes and Bacterial reproduction. Archaebacteria and its forms Specialized cells of Cyanobacteria: Heterocyst, Harmogonia etc Commercial application of Actinomycetes & Nitrogen fixation by Frankia Nature of Rickettsia and Chlamydia

Eubacteria Vs Archaebacteria

Eubacteria are true bacteria. All bacteria having a cell wall is made up of peptidoglycan are true bacteria. On the contrary, Archaebacteria is a false bacteria as its cell wall is made up of polysaccharides.

Cell Wall of Gram ‘+’ve and Gram ‘-ve’

Cell walls of these two groups of bacteria are distinguished based on the amount of peptidoglycan and the presence of LPS. Gram ‘+’ve has 80% of a cell wall made up of peptidoglycan whereas in gram ‘-‘ve it constitutes just 10–15%. Secondly, LPS is not found in gram ‘+’ve bacteria. The reason for the retention of the crystal violet or gram stain by gram ‘+’ve is the structural distribution of peptidoglycan as shown in the diagram.

One interesting point is worth noting that almost all monerans which are included in the syllabus are gram ‘-‘ve except Actinomycetes.

Genetic Constitution of Eubacteria and Eukaryotes

Genome in Eubacteria is made up of circular chromosomes having circular DNA. They lack histone protein. A typical Eukaryotes has a linear DNA with histone protein. Secondly, prokaryotic genomes are further characterized by having a high amount of GC.

Bacteria are mostly reproduced by binary fission. Sexual reproduction in bacteria is absent as there is no meiosis. However, it undergoes genetic recombination to produce variants. Different types of genetic recombination (Transformation, Conjugation, Transduction, and Sexduction) have been recognized based on the mode of transfer of genetic material from the donor to recipient.

Typical genetic recombination of eukaryotes can be differentiated from moneran recombination based on the transfer of genome. In bacteria, it is always partial and forms merozygote. However, in eukaryote transfer of genome is complete and it forms a zygote.

Archaebacteria and its forms

Archaebacteria are ancient bacteria. They have gone for the least structural changes since their evolution, hence, known as living fossils. One of the reasons for resisting change is the presence of branched-chain lipid in their cell membrane which makes them environmentally tough. It exists in two forms: Obligate anaerobes and Facultative aerobe. Methanogens & Halophiles are obligate anaerobes. Thermoacidophyls are facultative aerobe.

Cyanobacteria

Cyanobacteria is a gram ‘-‘ve aerobic bacteria. Here photosynthesis is oxygenic. The ecological significance of cyanobacteria is owing to their ability to fix atmospheric N2. Heterocyst is the specialized cell having nitrogenase enzyme which carries the process of biological nitrogen fixation. Fragments of filaments of cyanobacteria form harmgonia.

Actinomycetes

Actinomycetes are soil bacteria where it acts as saprophytes. It forms a mycelial like structure and is often known as a connecting link between bacteria and fungi. It is commercially used for the production of wide-spectrum antibiotics. Frankia is a type of actinomycetes that are known for symbiotic nitrogen fixation.

Mycoplasma (PPLO)

It is the smallest living organism (0.1um) and even cannot be filtered by the bacterial filtrate. It lacks a cell wall, hence, can change its shape and therefore known as ‘Jokers among the plant kingdom’. It causes diseases like pleuropneumonia in human and witch broom’s disease in plants.

Rickettsia and Chlamydia

It is an obligate intracellular parasite and is often considered as a connecting link between Prokaryotes and viruses. It is known for causing diseases like hey fever, Rocky mountain fever, etc.

Chlamydia is also an intracellular parasite and causes human respiratory and genitourinary tract disease, and in birds, they cause respiratory disease.

Do’s:

1. Learn 2 to 4 representatives of each group.

2. Emphasize on those name having commercial/evolutionary significance

3. Ecological and evolutionary significance of the members of monerans

4. Build Mind Maps for Monerans.

5. Refer to Mind Maps — Biology — XI (Bestseller in amazon for NEET) https://www.amazon.in/BIOLOGY-MINDMAPS-Dr-Pankaj-Kumar/dp/B0863TWLKR

Don’ts:

1. Never try to over-emphasize in learning/mugging the name of species

2. Do not study the cellular details except those of bacteria.

(Next: How to Study Protista?)