11bio2

Biological Classification

Explore the fascinating world of biological classification systems and understand how living organisms are categorized into different kingdoms.

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Chapter Overview

Brief Introduction

Biological classification is the scientific arrangement of organisms in a hierarchical series of groups based on their similarities and relationships. This chapter explores the evolution of classification systems from Aristotle to Whittaker's five-kingdom system, focusing on the characteristics of Monera, Protista, and Fungi kingdoms.

Learning Objectives

• Understand the evolution of classification systems
• Learn about Whittaker's five-kingdom classification
• Study the characteristics of Kingdom Monera
• Explore the diversity of Kingdom Protista
• Comprehend the features of Kingdom Fungi
• Understand viruses, viroids, prions, and lichens

Key Topics Covered

• History of classification systems
• Five-kingdom classification
• Kingdom Monera - Bacteria and Archaea
• Kingdom Protista - Diverse eukaryotic organisms
• Kingdom Fungi - Structure and classification
• Viruses, viroids, and prions
• Lichens as symbiotic associations

Interactive Chapter Index

Classification Systems

Explore how classification systems have evolved from Aristotle to Whittaker's five-kingdom system.

Kingdom Monera

Learn about bacteria and archaea - the prokaryotic members of the living world.

Kingdom Protista

Discover the diverse world of single-celled eukaryotic organisms.

Kingdom Fungi

Understand the unique characteristics and classification of fungi.

Viruses & Viroids

Explore the acellular infectious agents that challenge our definition of life.

Chapter Summary

Review the key concepts and takeaways from this chapter.

Full Chapter Notes

2.1 Evolution of Classification Systems

Since the dawn of civilization, humans have attempted to classify living organisms. Early classifications were based on practical needs like food, shelter, and clothing rather than scientific criteria.

Historical Development:

• Aristotle: Earliest scientific classification using simple morphological characters (plants: trees, shrubs, herbs; animals: red blood/no red blood)
• Linnaeus: Developed the two-kingdom system (Plantae and Animalia) that included all plants and animals respectively
• Limitations of Two-Kingdom System: Didn't distinguish eukaryotes/prokaryotes, unicellular/multicellular, photosynthetic/non-photosynthetic organisms
• Whittaker (1969): Proposed the five-kingdom classification (Monera, Protista, Fungi, Plantae, Animalia) based on cell structure, body organization, mode of nutrition, reproduction, and phylogenetic relationships

Characters	Monera	Protista	Fungi	Plantae	Animalia
Cell type	Prokaryotic	Eukaryotic	Eukaryotic	Eukaryotic	Eukaryotic
Cell wall	Noncellulosic (Polysaccharide + amino acid)	Present in some	Present with chitin	Present (cellulose)	Absent
Nuclear membrane	Absent	Present	Present	Present	Present
Body organisation	Cellular	Cellular	Multicellular/loose tissue	Tissue/organ	Tissue/organ/organ system
Mode of nutrition	Autotrophic (chemosynthetic and photosynthetic) and Heterotrophic (saprophytic/parasitic)	Autotrophic (Photosynthetic) and Heterotrophic	Heterotrophic (Saprophytic/Parasitic)	Autotrophic (Photosynthetic)	Heterotrophic (Holozoic/Saprophytic etc.)

Q: Why was the two-kingdom classification system found to be inadequate?

A: The two-kingdom system was inadequate because:

1. It didn't distinguish between eukaryotes and prokaryotes
2. It didn't separate unicellular and multicellular organisms
3. It grouped photosynthetic (green algae) and non-photosynthetic (fungi) organisms together
4. Many organisms didn't fit neatly into either plant or animal categories
5. It didn't account for differences in cell structure, nature of wall, mode of nutrition, habitat, and evolutionary relationships

2.2 Kingdom Monera

Bacteria are the sole members of the Kingdom Monera. They are the most abundant microorganisms, found almost everywhere - from soil to extreme habitats like hot springs, deserts, snow, and deep oceans.

Bacterial Characteristics:

• Shapes: Spherical (Cocci), rod-shaped (Bacilli), comma-shaped (Vibrio), spiral (Spirilla)
• Structure: Simple but complex in behavior with extensive metabolic diversity
• Nutrition: Some are autotrophic (photosynthetic or chemosynthetic), most are heterotrophic
• Reproduction: Mainly by fission, sometimes spores, and primitive DNA transfer

Figure: Different shapes of bacteria - Cocci, Bacilli, Vibrio, Spirilla

2.2.1 Archaebacteria

Special bacteria that live in extreme habitats:

• Halophiles: Extreme salty areas
• Thermoacidophiles: Hot springs
• Methanogens: Marshy areas, gut of ruminants (produce methane/biogas)

They differ from other bacteria in cell wall structure, which helps them survive extreme conditions.

2.2.2 Eubacteria

Also called 'true bacteria', characterized by:

• Rigid cell wall
• Flagellum if motile
• Cyanobacteria: Photosynthetic (chlorophyll a), some can fix atmospheric nitrogen in heterocysts (e.g., Nostoc, Anabaena)
• Chemosynthetic bacteria: Oxidize inorganic substances for energy, play role in nutrient recycling
• Heterotrophic bacteria: Most abundant, decomposers, used in making curd, antibiotics, nitrogen fixation; some are pathogens

Mycoplasma: Organisms that completely lack a cell wall, smallest living cells, can survive without oxygen. Many are pathogenic in animals and plants.

Q: What are the main differences between archaebacteria and eubacteria?

A: The main differences are:

• Habitat: Archaebacteria live in extreme environments (hot springs, salty areas, marshy areas) while eubacteria are found in more common environments
• Cell wall: Archaebacteria have different cell wall structure (without peptidoglycan) compared to eubacteria
• Membrane lipids: Archaebacteria have unique membrane lipids with ether linkages, while eubacteria have ester-linked lipids
• RNA polymerase: Archaebacteria have more complex RNA polymerase similar to eukaryotes
• Methanogenesis: Only archaebacteria can produce methane

2.3 Kingdom Protista

All single-celled eukaryotes are placed under Protista, though the boundaries of this kingdom are not well defined. Protists are primarily aquatic and form a link between plants, animals, and fungi.

General Characteristics:

• Eukaryotic (well-defined nucleus and membrane-bound organelles)
• Some have flagella or cilia
• Reproduce both asexually and sexually
• Primarily aquatic

2.3.1 Chrysophytes

Includes diatoms and golden algae (desmids):

• Found in freshwater and marine environments
• Microscopic, float passively (plankton)
• Most are photosynthetic
• Diatoms have silica-embedded cell walls forming two overlapping shells
• Diatomaceous earth (accumulated cell walls) used in polishing, filtration
• Major producers in oceans

2.3.2 Dinoflagellates

Mostly marine and photosynthetic:

• Appear in various colors (yellow, green, brown, blue, red) based on pigments
• Cell wall has stiff cellulose plates
• Most have two flagella (longitudinal and transverse)
• Red tides caused by rapid multiplication (e.g., Gonyaulax) can release toxins

2.3.3 Euglenoids

Mostly freshwater organisms found in stagnant water:

• No cell wall, have protein-rich pellicle making body flexible
• Have two flagella (short and long)
• Photosynthetic in sunlight, heterotrophic when deprived of sunlight
• Pigments identical to higher plants
• Example: Euglena

2.3.4 Slime Moulds

Saprophytic protists:

• Move along decaying matter engulfing organic material
• Form plasmodium (aggregation) under suitable conditions
• Form fruiting bodies with spores during unfavorable conditions
• Spores are resistant and dispersed by air

2.3.5 Protozoans

All are heterotrophs, live as predators or parasites, primitive relatives of animals:

• Amoeboid protozoans: Freshwater/marine/moist soil, move with pseudopodia (e.g., Amoeba), some parasitic (e.g., Entamoeba)
• Flagellated protozoans: Free-living or parasitic, have flagella (e.g., Trypanosoma causes sleeping sickness)
• Ciliated protozoans: Aquatic, move with cilia (e.g., Paramoecium)
• Sporozoans: Have infectious spore-like stage (e.g., Plasmodium causes malaria)

Figure: Examples from Kingdom Protista - Dinoflagellates, Euglena, Slime mould, Paramecium

Q: Why are protists considered a "catch-all" kingdom in biological classification?

A: Protists are considered a "catch-all" kingdom because:

1. They include all single-celled eukaryotes that don't fit into the other eukaryotic kingdoms
2. They show tremendous diversity in form, structure, and mode of life
3. Some protists are plant-like (algae), some are animal-like (protozoa), and others are fungus-like (slime molds)
4. The boundaries of the kingdom are not well defined - what one biologist considers a protist, another might classify as plant or fungus
5. They represent a transitional group showing characteristics that would later evolve into plants, animals, and fungi

2.4 Kingdom Fungi

A unique kingdom of heterotrophic organisms showing great diversity in morphology and habitat. Examples include mushrooms, yeast, molds, and pathogens like wheat rust.

General Characteristics:

• Structure: Mostly filamentous (except unicellular yeasts), body consists of hyphae forming mycelium
• Cell wall: Composed of chitin and polysaccharides
• Nutrition: Mostly saprophytic (absorb organic matter from dead substrates), some parasitic or symbiotic (lichens, mycorrhiza)
• Reproduction: Vegetative (fragmentation, fission, budding), asexual (spores), and sexual (oospores, ascospores, basidiospores)
• Sexual cycle: Plasmogamy (fusion of protoplasm), karyogamy (fusion of nuclei), meiosis (haploid spores)

Figure: Structure of fungi showing hyphae and mycelium

2.4.1 Phycomycetes

Found in aquatic habitats, decaying wood, or as plant parasites:

• Aseptate and coenocytic hyphae
• Asexual reproduction by zoospores (motile) or aplanospores (non-motile)
• Sexual reproduction by zygospore formation (isogamous or anisogamous)
• Examples: Mucor, Rhizopus (bread mold), Albugo (parasite on mustard)

2.4.2 Ascomycetes (Sac Fungi)

Mostly multicellular (e.g., Penicillium), some unicellular (e.g., yeast):

• Saprophytic, decomposers, parasitic or coprophilous (grow on dung)
• Branched and septate mycelium
• Asexual spores called conidia produced on conidiophores
• Sexual spores called ascospores produced in sac-like asci (arranged in ascocarps)
• Examples: Aspergillus, Claviceps, Neurospora (used in genetic studies), morels and truffles (edible delicacies)

2.4.3 Basidiomycetes

Include mushrooms, bracket fungi, puffballs, rusts and smuts:

• Grow in soil, on logs, tree stumps, or as plant parasites
• Branched and septate mycelium
• Asexual spores generally not found, vegetative reproduction by fragmentation
• Sex organs absent, plasmogamy by fusion of vegetative cells
• Dikaryotic stage (n+n) gives rise to basidium where karyogamy and meiosis occur
• Basidiospores produced exogenously on basidia (arranged in basidiocarps)
• Examples: Agaricus (mushroom), Ustilago (smut), Puccinia (rust fungus)

2.4.4 Deuteromycetes (Imperfect Fungi)

Called "imperfect" because only asexual stages are known:

• When sexual forms discovered, moved to appropriate classes (Ascomycetes/Basidiomycetes)
• Reproduce only by asexual spores (conidia)
• Septate and branched mycelium
• Saprophytes, parasites, or decomposers
• Examples: Alternaria, Colletotrichum, Trichoderma

Figure: Classification of fungi - Phycomycetes, Ascomycetes, Basidiomycetes, Deuteromycetes

Q: What are the key differences between the four classes of fungi?

A: The key differences are:

Feature	Phycomycetes	Ascomycetes	Basidiomycetes	Deuteromycetes
Hyphae	Aseptate, coenocytic	Septate	Septate	Septate
Asexual spores	Zoospores/aplanospores	Conidia	Generally absent	Conidia
Sexual spores	Zygospores	Ascospores in asci	Basidiospores on basidia	Unknown (imperfect)
Fruiting body	Absent	Ascocarp	Basidiocarp	Absent
Examples	Mucor, Rhizopus	Penicillium, yeast	Mushrooms, rusts	Alternaria

2.5 Viruses, Viroids, Prions and Lichens

These acellular entities were not included in Whittaker's five-kingdom classification but are important biological entities.

Viruses

Non-cellular organisms with inert crystalline structure outside living cells:

• Obligate parasites - take over host cell machinery to replicate
• Discovered as causal organism of tobacco mosaic disease (Dmitri Ivanowsky, 1892)
• Consist of genetic material (DNA or RNA, never both) surrounded by protein coat (capsid made of capsomeres)
• Plant viruses: usually single-stranded RNA
• Animal viruses: single or double-stranded RNA or double-stranded DNA
• Bacteriophages: viruses infecting bacteria, usually double-stranded DNA
• Cause diseases like mumps, smallpox, herpes, influenza, AIDS in humans; mosaic formation, leaf curling in plants

Figure: Structure of viruses - (a) Tobacco Mosaic Virus (TMV) (b) Bacteriophage

Viroids

Discovered by T.O. Diener (1971) causing potato spindle tuber disease:

• Smaller than viruses
• Free RNA without protein coat
• Low molecular weight RNA

Prions

Infectious agents consisting of abnormally folded protein:

• Similar in size to viruses
• Cause neurological diseases like BSE (mad cow disease) in cattle and CJD in humans

Lichens

Symbiotic associations between algae (phycobiont) and fungi (mycobiont):

• Algae provides food (autotrophic), fungi provides shelter and absorbs nutrients/water
• So closely associated they appear as single organisms
• Good pollution indicators - don't grow in polluted areas

Q: Why are viruses considered to be on the borderline between living and non-living?

A: Viruses are on the borderline because they show characteristics of both living and non-living entities:

Living characteristics:

• They contain genetic material (DNA or RNA)
• They can reproduce (inside host cells)
• They can evolve through mutations
• They show adaptation to specific hosts

Non-living characteristics:

• They lack cellular structure
• They don't grow or divide
• They don't metabolize energy
• They can be crystallized like chemicals
• They are inert outside host cells

This dual nature places them in a unique position between living and non-living world.

Chapter Summary

Key Takeaways:

• Classification systems have evolved from Aristotle's simple system to Whittaker's five-kingdom classification
• Kingdom Monera includes all prokaryotic organisms (bacteria and archaea) showing extensive metabolic diversity
• Kingdom Protista includes all single-celled eukaryotes (Chrysophytes, Dinoflagellates, Euglenoids, Slime-moulds, Protozoans)
• Kingdom Fungi includes heterotrophic organisms with chitinous cell walls, classified into four groups based on reproduction
• Viruses, viroids and prions are acellular infectious agents not included in the five-kingdom system
• Lichens are symbiotic associations between algae and fungi, serving as pollution indicators

NCERT Solutions

Question 1: Discuss how classification systems have undergone several changes over a period of time?

Classification systems have changed over time due to:

1. Early classifications: Based on practical needs (food, shelter) not scientific criteria
2. Aristotle's system: Simple morphological characters (plants: trees/shrubs/herbs; animals: red blood/no red blood)
3. Linnaeus's two-kingdom system: Plantae and Animalia, but had limitations:
   • Didn't distinguish eukaryotes/prokaryotes
   • Grouped unicellular/multicellular together
   • Mixed photosynthetic/non-photosynthetic organisms
4. Five-kingdom system (Whittaker, 1969): Based on cell structure, body organization, nutrition, reproduction, phylogeny:
   • Monera (prokaryotes)
   • Protista (unicellular eukaryotes)
   • Fungi (separated from plants due to chitinous walls, heterotrophic nature)
   • Plantae
   • Animalia
5. Current changes: Three-domain system divides Monera into Archaea and Bacteria, with Eukarya as third domain

Question 2: State two economically important uses of: (a) heterotrophic bacteria (b) archaebacteria

(a) Heterotrophic bacteria:

1. Making curd from milk (Lactobacillus)
2. Production of antibiotics (Streptomyces)

(b) Archaebacteria:

1. Methanogens produce biogas (methane) from dung
2. Some are used in bioremediation of polluted environments

Question 3: What is the nature of cell-walls in diatoms?

Diatoms have cell walls with the following characteristics:

• Composed of two thin overlapping shells that fit together like a soap box
• Embedded with silica which makes them indestructible
• The silica walls are porous and have intricate patterns
• Accumulation of these walls over billions of years forms diatomaceous earth

Question 4: Find out what do the terms 'algal bloom' and 'red-tides' signify.

Algal bloom:

• Rapid increase in algae population in aquatic systems
• Often caused by nutrient pollution (eutrophication)
• Can deplete oxygen in water, harming other organisms

Red tides:

• Specific type of algal bloom caused by dinoflagellates (e.g., Gonyaulax)
• Water appears red due to pigments in the algae
• Can release toxins that kill marine animals
• May cause shellfish poisoning in humans

Question 5: How are viroids different from viruses?

Feature	Viroids	Viruses
Size	Smaller than viruses	Larger than viroids
Genetic material	Only RNA	DNA or RNA
Protein coat	Absent	Present (capsid)
Host	Only plants	Plants, animals, bacteria
Discovery	T.O. Diener (1971)	Dmitri Ivanowsky (1892)
Example	Potato spindle tuber viroid	TMV, HIV, influenza virus

Question 6: Describe briefly the four major groups of Protozoa.

The four major groups of protozoa are:

1. Amoeboid protozoans:
   • Move using pseudopodia (false feet)
   • Live in freshwater, seawater or moist soil
   • Marine forms have silica shells
   • Example: Amoeba, Entamoeba (parasitic)
2. Flagellated protozoans:
   • Move using flagella
   • Can be free-living or parasitic
   • Example: Trypanosoma (causes sleeping sickness)
3. Ciliated protozoans:
   • Move using cilia
   • Aquatic, actively moving
   • Have gullet for food intake
   • Example: Paramecium
4. Sporozoans:
   • Have infectious spore-like stage in life cycle
   • All are parasitic
   • Example: Plasmodium (causes malaria)

Question 7: Plants are autotrophic. Can you think of some plants that are partially heterotrophic?

Yes, some plants are partially heterotrophic:

1. Insectivorous plants: Supplement nutrition by trapping and digesting insects
   • Example: Bladderwort, Venus fly trap
   • Grow in nitrogen-deficient soils
2. Parasitic plants: Derive some or all nutrients from other plants
   • Example: Cuscuta (dodder)
   • Have haustoria to penetrate host plants
3. Saprophytic plants: Obtain nutrients from dead organic matter
   • Example: Some orchids, Monotropa (Indian pipe)

Question 8: What do the terms phycobiont and mycobiont signify?

These terms refer to the components of lichens:

• Phycobiont: The algal component of lichen
  • Autotrophic (can photosynthesize)
  • Provides food for the fungal partner
  • Usually a green alga or cyanobacterium
• Mycobiont: The fungal component of lichen
  • Heterotrophic
  • Provides shelter and absorbs mineral nutrients and water
  • Usually an ascomycete fungus

Question 9: Give a comparative account of the classes of Kingdom Fungi under the following: (i) mode of nutrition (ii) mode of reproduction

Class	Mode of Nutrition	Mode of Reproduction
Phycomycetes	Saprophytic or parasitic	Asexual: zoospores or aplanospores Sexual: zygospores by gamete fusion
Ascomycetes	Saprophytic, decomposers, parasitic or coprophilous	Asexual: conidia on conidiophores Sexual: ascospores in asci (ascocarps)
Basidiomycetes	Saprophytic or parasitic	Asexual: rare Sexual: basidiospores on basidia (basidiocarps) after dikaryotic stage
Deuteromycetes	Saprophytic or parasitic	Only asexual: conidia Sexual reproduction unknown (imperfect fungi)

Question 10: What are the characteristic features of Euglenoids?

Characteristic features of Euglenoids:

1. Mostly freshwater organisms found in stagnant water
2. No cell wall, instead have protein-rich pellicle making body flexible
3. Have two flagella - one short and one long
4. Photosynthetic in presence of sunlight (contain chlorophyll)
5. Behave like heterotrophs (predators) when deprived of sunlight
6. Pigments identical to higher plants
7. Example: Euglena

Question 11: Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.

Structure of viruses:

• Non-cellular, inert crystalline structure outside living cells
• Consist of genetic material (DNA or RNA) surrounded by protein coat (capsid)
• Capsid made of protein subunits called capsomeres
• Some have additional envelope (e.g., HIV)
• Shape varies - helical (TMV), polyhedral (Adenovirus), complex (Bacteriophage)

Nature of genetic material:

• Either DNA or RNA, never both
• Plant viruses: usually single-stranded RNA
• Animal viruses: single or double-stranded RNA or double-stranded DNA
• Bacteriophages: usually double-stranded DNA
• Genetic material is infectious

Four common viral diseases:

1. Influenza (Flu)
2. Common cold (Rhinovirus)
3. AIDS (HIV)
4. Chickenpox (Varicella-zoster virus)

Practice Questions

1. Which of the following is NOT a characteristic of Kingdom Monera?

a) Prokaryotic cells b) Absence of nuclear membrane c) Presence of chitin in cell wall d) Most extensive metabolic diversity

Correct Answer: c) Presence of chitin in cell wall

Explanation: Kingdom Monera has cell walls made of polysaccharides and amino acids, not chitin. Chitin is found in fungal cell walls.

2. Which group of organisms is responsible for red tides?

a) Diatoms b) Dinoflagellates c) Euglenoids d) Slime moulds

Correct Answer: b) Dinoflagellates

Explanation: Red tides are caused by rapid multiplication of red dinoflagellates like Gonyaulax, which make the sea appear red and can release toxins.

3. The dikaryotic phase is characteristic of which fungal group?

a) Phycomycetes b) Ascomycetes c) Basidiomycetes d) Both b and c

Correct Answer: d) Both b and c

Explanation: Both Ascomycetes and Basidiomycetes have a dikaryotic stage (n+n) in their life cycle before karyogamy occurs.

1. What are the main differences between archaebacteria and eubacteria?

Answer:

Key differences between archaebacteria and eubacteria:

1. Habitat: Archaebacteria live in extreme environments (hot springs, salty areas) while eubacteria are found in common environments
2. Cell wall: Archaebacteria lack peptidoglycan and have different cell wall composition
3. Membrane lipids: Archaebacteria have ether-linked lipids while eubacteria have ester-linked lipids
4. RNA polymerase: Archaebacteria have complex RNA polymerase similar to eukaryotes
5. Methanogenesis: Only archaebacteria can produce methane

2. Why are fungi placed in a separate kingdom from plants?

Answer:

Fungi are placed in a separate kingdom because:

1. Nutrition: Fungi are heterotrophic (absorb nutrients) while plants are autotrophic (photosynthetic)
2. Cell wall: Fungi have chitin in their cell walls while plants have cellulose
3. Storage: Fungi store food as glycogen (like animals) while plants store starch
4. Body organization: Fungi have filamentous structure (hyphae) while plants have tissue/organ structure
5. Reproduction: Fungi reproduce via spores, with unique sexual reproduction phases

1. Compare the five-kingdom classification system with the earlier two-kingdom system. What advantages does the five-kingdom system offer?

Answer:

Two-kingdom system (Plantae and Animalia):

• Based mainly on mobility and nutrition
• Plants: immobile, autotrophic
• Animals: mobile, heterotrophic
• Limitations:
  • Didn't distinguish prokaryotes and eukaryotes
  • Grouped unicellular and multicellular organisms together
  • Mixed photosynthetic and non-photosynthetic organisms
  • Many organisms didn't fit clearly into either kingdom

Five-kingdom system (Monera, Protista, Fungi, Plantae, Animalia):

• Based on cell structure, body organization, mode of nutrition, reproduction, and phylogenetic relationships
• Advantages:
  • Separates prokaryotes (Monera) from eukaryotes
  • Creates Protista for unicellular eukaryotes
  • Recognizes Fungi as distinct kingdom based on chitinous walls and heterotrophic nutrition
  • Better reflects evolutionary relationships
  • Accommodates diverse forms of life more accurately

2. Describe the economic importance of bacteria with examples.

Answer:

Beneficial aspects:

1. Food production:
   • Making curd (Lactobacillus)
   • Cheese and yogurt production
   • Fermentation of foods (vinegar, pickles)
2. Industrial uses:
   • Production of antibiotics (Streptomyces)
   • Vitamin production (E. coli produces vitamin K)
   • Biogas production (methanogens)
3. Agriculture:
   • Nitrogen fixation (Rhizobium in legume roots)
   • Decomposition of organic matter
   • Nutrient cycling (nitrogen, phosphorus, sulfur cycles)
4. Bioremediation:
   • Cleaning oil spills (oil-eating bacteria)
   • Sewage treatment

Harmful aspects:

1. Diseases in humans: Cholera (Vibrio cholerae), typhoid (Salmonella typhi), tuberculosis (Mycobacterium tuberculosis)
2. Plant diseases: Citrus canker (Xanthomonas), fire blight in apples
3. Food spoilage: Causing decomposition of stored food

Interactive Flashcards

What are the main characteristics of Kingdom Monera?

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• Prokaryotic cells (no nucleus or membrane-bound organelles)
• Cell wall present (non-cellulosic, made of polysaccharides and amino acids)
• Most abundant microorganisms
• Found in diverse habitats including extremes
• Show most extensive metabolic diversity
• Reproduce mainly by fission

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