Biological Classification

Biological Classification

• Classification involves identifying, naming, and grouping living organisms, and are considered scientific practices.
• Taxonomy or Systemics is the branch of biology focused on classification.

Two Kingdom Classification

• Involves Autotrophs like plants; Cellwall, donot locomotate.
• Involves Heterotrophs like animals; Holozoic, donot locomotate.

Why Two Kingdom Classification Was Not Sufficient

• Prokaryotes and eukaryotes were grouped together.
• Bacteria and cyanobacteria ended up in the plant kingdom.
• Heterotrophs and autotrophs were placed together; fungi (heterotroph) ended up with plants.
• There was no differentiation between unicellular and multicellular organisms.
• Protozoans (unicellular) ended up with multicellular animals.
• Simple organisms were placed with highly complex organisms.
• Protozoans ended up with humans in the animal kingdom and bacteria ended up in the plant kingdom.

Three Domain Classification

• Carl Woese proposed the Three Domain Classification in 1990.
• Carl Woese won the national medal of science in November 2000.
• A new category for classification of life was created: the domain.
• The domain is a classification category above the kingdom.

Five Kingdom Classicication

• Proposed by R.H. Whittaker in 1969.
• Main criteria for classification include the following:
• Complexity of cell structure; prokaryotic or eukaryotic.
• Body organization; unicellular or multicellular.
• Mode of nutrition; autotroph, heterotroph, or holozoic.
• Lifestyle; producer, consumer, or decomposer.
• Phylogenetic relationship; evolutionary history.

Five Kingdom Classification: Monera (Prokaryote)

• The cell structure is unicellular prokaryotic.
• Nutrition is absorptive or photosynthetic.
• Movement is by flagella using tubulin.
• Reproduction is asexual.
• Includes bacteria and cyanobacteria (blue green algae).

Five Kingdom Classification: Protista (Protozoa)

• The cell structure is unicellular eukaryotic.
• Nutrition is absorptive or photosynthetic.
• Movement is by flagella, cilia, streaming.
• Reproduction is both asexual and sexual.
• Includes Phytoplankton and Zooplankton.

Five Kingdom Classification: Fungi

• Multicellular eukaryotes.
• The cell structure contains a chitinous cell wall.
• Nutrition is heterotrophic; absorptive, saprobic.
• Reproduction is both asexual and sexual.
• Yeasts (Unicellular) moulds and mushrooms, belong here.

Five Kingdom Classification: Plantae

• Cell structure: cellulosic cell wall, presence of plastids
• Nutrition: Autotrophic
• Movement: Non-motile
• Reproduction: Both asexual and sexual
• Includes algae, Bryophytes, ferns, gymnosperms and Multicelled eukaryotes.

Five Kingdom Classification: Animalia

• Cell structure: without cell wall, and plastids
• Nutrition: Heterotrophic
• Movement: Highly motile
• Reproduction: Both asexual and sexual
• Includes Sponges, Invertebrates, vertebrates and Multicelled eukaryotes

Kingdom Monera

• Includes prokaryotic unicellular organisms.
• Are cosmopolitan (i.e., found everywhere)
• Live in extreme habitats like hot springs and snow, and can exist as endoparasites.
• The cell wall is non-cellular (peptidoglycan) = polysaccharide + amino acids.
• Motility is achieved by flagella, gliding, or the organism may be non-motile.
• Nutrition is autotrophic.
• Sexual reproduction involves conjugation, transduction, and transformation.
• Asexual reproduction occurs via binary fission.
• A nervous system is absent..

Archaebacteria

• Archaebacteria means ancient or primitive.
• Prokaryotic and microscopic oldest anaerobic bacteria
• Live in very harsh habitats
• Possess a rigid cell wall of peptidoglycan (muramic acid).
• Three types of archae bacteria include the following:
• Methanogens
• Halophiles
• Thermoacidophiles.

Methanogens

• Live in marshy places, swamps, and the guts of cattle and termites.
• Methane makers.

Halophiles

• Thrive in salt.
• Live in the Dead Sea, the Great Salt Lake, and salt evaporation ponds.
• They are anaerobic bacteria which develop a purple-colored pigment under high light intensity and produce ATP.

Thermoacidophiles

• "Thermo" means heat.
• Live in hot sulfur springs.
• Prefer temperatures above 60°C.
• Can live below freezing, like the ocean waters around Antarctica.

Eubacteria

• "Eu" means True.
• Unicellular, prokaryotic organisms.
• Possess cell walls made of peptidoglycan.
• Lack a well-organized nucleus, Golgi apparatus, and mitochondria (absent).
• Smallest of all living organisms

Classification of Bacteria (on Shape)

• Bacteria exist in spheres (cocci):

• Diplococci (e.g., Streptococcus pneumoniae).

• Streptococci (e.g., Streptococcus pyogenes).

• Tetrad.

• Staphylococci (e.g., Staphylococcus aureus).

• Sarcina (e.g., Sarcina ventriculi).

• Bacteria exists in rods (bacilli):

• Chain of bacilli (e.g., Bacillus anthracis).

• Flagellate rods (e.g., Salmonella typhi).

• Spore-former (e.g., Clostridium botulinum).

• Bacteria exist in Spirals:

• Vibrios (e.g., Vibrio cholerae).

• Spirilla (e.g., Helicobacter pylori).

• Spirochaetes (e.g., Treponema pallidum).

Division of Bacteria on the Basis of Presence of Flagella

• Monotrichous: single flagellum
• Cephalotrichous: multiple flagella located at one pole of the cell
• Amphitrichous: flagella at both poles of the cell
• Peritrichous: flagella surrounding the cell
• Lophotrichous
• Atrichous: no flagella.

Distinguishing Gram-Positive and Gram-Negative Bacteria

• Gram-positive:
  • Retain stain; Yes, purple
  • Cell wall; Smooth (20-80nm)
  • Teichoic acid; Present
  • Murein; 70-80 %
  • Susceptible to antibiotics; Yes, few are pathogenic
• Gram-negative:
  • Retain stain; Donot
  • Cell wall; Wavy (8-12nm)
  • Teichoic acid; Absent
  • Murein; 10-20%
  • Susceptible to antibiotics; Resistant to antibiotic, mostly pathogenic

Bacterial Nutrition

• Heterotrophic (take in food):
• Saprophytic is bacteria of decay.
• Parasitic is eg. Streptococci
• Autotrophic (make food):
• Photosynthetic is eg. Purple sulphur bacteria
• Chemosynthetic is eg. Nitrifying Bacteria

Reproduction in Bacteria

• Cell replicates its DNA.
• Cytoplasmic membrane elongates, separating DNA molecules.
• Cross wall forms as the membrane invaginates.
• Cross wall forms completely.
• Formation and seperation into Daughter cells

Cyanobacteria

• Also known as blue-green algae.
• Can be unicellular, colonial, or form trichomes surrounded by a gelatinous sheath.
• Prokaryotic organisms with cell walls made of peptidoglycan.
• Photosynthetic autotrophs.
• Contain characteristic pigments of c-phycocyanin (blue), c-phycoerythrin, carotene, and chlorophyll a.
• Reproduce via binary fission and fragmentation; sexual reproduction is not reported.
• Some bacteria contain heterocysts for N2 (nitrogen) fixation; this can be seen in nostoc, anabaena, and oscillatoria.

Mycoplasm

• Discovered by Nocard and Roux in 1998.
• Smallest known prokaryotes, lacking a cell wall.
• PPLO (pleuropneumonia-like organism).
• Highly pleomorphic (vary in shape).
• Can cause pneumonia and urethritis in animals.
• Cause diseases like bunchy top of banana, little leaf of bringal, and witches' broom of legumes in plants.

Kingdom Characteristics

• Eubacteria:
• Cell type; Prokaryotic
• Cell structure; Cell wall, peptidoglycan
• Body type; Unicellular
• Nutrition; Autotrophic and heterotrophic
• Example; Enterobacteria and Spirochetes
• Archaebacteria:
• Cell type; Prokaryotic
• Cell structure; Cell wall, no peptidoglycan
• Body type; Unicellular
• Nutrition; Autotrophic and heterotrophic
• Example; Methanogens
• Protista:
• Cell type; Eukaryotic
• Cell structure; Mixed
• Body type; Unicellular and multicellular
• Nutrition; Autotrophic and heterotrophic
• Example; Amoebas, Euglenas and Kelps
• Fungi:
• Cell type; Eukaryotic
• Cell structure; Cell wall, chitin
• Body type; Unicellular and multicellular
• Nutrition; Heterotrophic
• Example; Yeasts and Mushrooms
• Plantae:
• Cell type; Eukaryotic
• Cell structure; Cell wall, cellulose
• Body type; Multicellular
• Nutrition; Autotrophic
• Example; Ferns and Pine trees
• Animalia:
• Cell type; Eukaryotic
• Cell structure; No cell wall
• Body type; Multicellular
• Nutrition; Heterotrophic
• Example; Birds and Earthworms

Kingdom- Protista: Chryosophytes (Diatoms/Desmids (Golden Algae))

• Habit: aquatic
• Nutrition: autotrophic
• Reproduction: Asexual- binary fission and Sexual - fusion of gametes
• Economic important: producers of oceans i.e., phytoplanktons, metal polishing, tooth paste, making sound proof rooms plus insulators, between the walls of refrigerators

Diatoms

• Characterized by being unicellular with a silica-based cell wall.

Dinoflagellates (Golden Brown Photosynthetic Organism)

• Habit: mostly marine, but few are freshwater forms.
• Nutrition: holophytic, with photosynthesis.
• Reproduction:
  • Asexual via zoospores.
  • Sexual via isogametes or anisogamous.
• Responsible for red tide (red sea) and exhibit bioluminescence.
• An Example is Gonylaux (red tide).

Euglenophyta

• Habit: fresh water form
• Nutrition: mixotrophic
• Reproduction: Sexual reproduction not observed and asexual reproduction is Longitudinal binary fission
• Mixotrophic: create own food via light and are heterotrophic with no light.

Slime Mould

• Habitat: Terrestrial.
• Nutrition: Saprophytic, they engulf organic material from dead decaying twigs and leaves.
• Asexual reproduction: fragmentation, sporangia bearing spores
• Reproduction: Sexual- fusion of gametes

Fungi Kingdom: General Characteristic

• Fungi are found in cool, dark, damp, and moist places and on wet logs and skin.
• Nutrition: saprophytic, parasitic, and symbiotic.
• Thallus: aseptate and septate.
• Cell wall: chitin or fungal cellulose.
• Reproduction: Asexual reproduction via conidia, fragmentation, and spores and sexual reproduction spores formation.

Sexual Cycle in Fungi

• Involves three steps:
• Plasmogamy (when the plasmo equals protoplasm).
• Karyogamy (when the karyon equals the nucleus).
• Meiosis in zygote forms haploid spores.

Dikaryon

• A special type of heterokaryon.
• Long-lasting.
• As cells divide, the n + n state is retained.

Phycomycetes

• Habitat: Moist and damp places, decaying wood
• Nutrition: Saprotroph
• Cell wall: Fungal cellulose
• Thallus: Aseptate (coenocytic, i.e. multinucleated)
• Reproduction:
  • Asexual: Zoospore or aplanospore
  • Sexual: Zygospore
• Example: Rhizopus (bread mould)

Ascomycetes (Sac Fungi)

• Found in moist and damp places, decaying wood
• Nutrition: Saprotroph, parasitic, decomposers or coprophilus
• Cell wall: Chitin
• Thallus: Septate and branched
• Reproduction:
  • Asexual: Conidia, budding
  • Sexual: Ascospores
• Example: Yeast, penicillium, aspergillus, neurospora

Basidiomycetes

• Decomposers of wood, wet logs, on the branch of tree, in moist soil
• Nutrition: Saprotroph
• Cell wall: Chitin/fungal cellulose
• Thallus: Septate and branched
• Reproduction:
  • Asexual: not seen, but fragmentation occurs through vegetative reproduction.
  • Sexual: basidiospores
• Example: Mushroom, puff ball, bracket fungi

Deuteromycetes (Imperfect Fungi)

• Habitat: Litter and involved in mineral recycling
• Nutrition: Saprotroph
• Cell wall: Chitin / fungal cellulose
• Thallus: Septate and branched
• Reproduction: Asexual via conidia, and no sexual reproduction has been reported.
• Trichoderma belongs here.

Protozoa

• Protozoa are aquatic and are fresh water forms.
• Holozoic in nutrition.
• Asexual via Binary fission, Multiple fission and sexual reproduction in amoeba has not yet been reported.
• Also includes Paramecium and Sporozoan via conjugation, or genetic fusion.
• Amoeba, Plasmodium, Paramoecium, Trypanosoma belong here.

Classification of Protozoa Based on Mode of Locomotion

• Amoeboids, which use pseudopodia.
• Ciliates, which use cilia.
• Flagellates, which use flagella.
• Sporozoa, which are non-motile.

Viruses

• These are simple living entities/particles comprised of macromolecules; DNA and RNA and Proteins.
• They are obligate parasites, as they are totally dependent on their host.
• Infect and parasitize all forms of life, including bacteria.

Viruses as Living or Non Living

• They lie on the border line of both:
  • Living Characters:
  • posses DNA or RNA
  • ability to reproduce
  • cause infection.
  • undergo mutation/genetic recombination.
  • Non-Living Characters:
  • sub cellular (non cellular).
  • do not respire/excrete.
  • can be crystallized

Contagium Vivium Fluidum (Infectious Living Fluid)

• Beijerinck coined the Latin name "virus" in 1897 to mean poison.
• Filtered plant juices and found that they caused healthy plants to become sick.
• Stanley crystallized sap from sick tobacco plants in 1935.
• Discovered that viruses were made of nucleic acid and protein.

Discovery of Viruses

• Mayer discovered in 1883 that disease is contagious; small, and may be bacteria.
• Ivanowsky discovered a pathogen and filtration in 1893, that found very small bacteria/toxin.
• Beirjerinck found that it could reproduce only in a host and couldn't be cultivated, or inactivated by alcohol in 1897.

Viroids

• In 1971, T.O. Diener discovered a new infectious agent that was smaller than viruses and cause potato spindle disease.
• Lacks a protein coat.
• Contains RNA of low molecular weight.

Lichens

• Lichens represent a symbiotic association of algae and fungi and are pollution indicators.
• Algal component is called phycobiont (phyco = algal)
• Fungal component is called mycobiont (myco = fungi)