Bio rev notes

• Biodiversity refers to the number and types of organisms present on earth
• Nomenclature:

  • Common name or vernacular name is the name of an organism in the local language of a region
  • Biologists assign standard names to organisms which are used worldwide
  • The process of assigning a standard name or scientific name to an organism is called nomenclature
  • Scientific names have two components: generic name and specific name or specific epithet
  • The system of providing a name with two components is called Binomial nomenclature, given by Carolus Linnaeus
• Rules for Writing Scientific Names:

  • Biological names are generally in Latin or Latinised
  • The first word in a scientific name denotes the generic name and starts with a capital letter
  • The second word represents the specific epithet and is written with a small letter
  • Both words in a scientific name are separately underlined or printed in italics
  • At the end of the biological name, the name of the author is written in an abbreviated form
• Classification:

  • Scientists categorised all organisms into various groups and classes based on similar characteristics, called classification
  • Classification helps in identification of an organism, study of fossils, finding evolutionary pathways, and understanding group features
• Three domains of life:

  • Bacteria, Archaea, and Eukarya
  • Carl Woese's classification in 1990 divided cellular life forms into archaea, bacteria, and eukarya
• Archaebacteria:

  • Live in extreme habitats like salty areas, hot springs, and marshy areas
  • Have a different cell wall structure and can survive in extreme conditions
  • Methanogens are responsible for producing methane from the dung of ruminant animals
• Bacteria:

  • Sole members of the Kingdom Monera
  • Most abundant microorganisms found almost everywhere
  • Grouped based on shape: Coccus, Bacillus, Vibrium, and Spirillum
  • Show extensive metabolic diversity, with some being autotrophic and others heterotrophic
• Eukaryotes:

  • Organisms with a true nucleus and membrane-bound organelles
  • Can be unicellular or multicellular
  • Reproduce asexually and sexually
  • Examples include animals, plants, fungi, and protists
• Taxonomy:

  • The process of classifying living organisms into different taxa
  • Basis of modern taxonomic studies includes external and internal structure, cell structure, development process, and ecological information
• Systematics:

  • Study of species features, diversities, and relationships with other species
  • Includes identification, nomenclature, classification, and evolutionary relationships
• Taxonomic Categories:

  • Species, Genus, Family, Order, Class, Phylum/Division, Kingdom
  • Each category represents a rank or taxonomic unit
• Kingdom Monera:

  • Unicellular prokaryotes
  • Most abundant microorganisms found everywhere
  • Grouped based on shape: Coccus, Bacillus, Vibrium, and Spirillum
  • Utilise different strategies for obtaining food
• Bacteria can derive their nutrients from nitrates, nitrites, and ammonia and use the released energy for their ATP production
• Bacteria that feed on dead remains of plants and animals are called saprophytes
• Bacteria that draw nutrients from living organisms are called parasites
• Bacteria that live in association with other living organisms and derive nutrients without causing harm are called symbionts
• The most common method of reproduction in bacteria is fission
• Bacteria can also reproduce through a primitive type of sexual reproduction called conjugation
• Bacteria produce spores under unfavorable conditions
• Bacteria are grouped into Archaebacteria and Eubacteria
• Archaebacteria:

  • Primitive prokaryotes
  • Found in harsh habitats like extreme salty areas, hot springs, and marshy areas
  • Cell wall consists of non-cellulosic polysaccharides or proteins and lacks peptidoglycan
• Eubacteria:

  • True bacteria
  • Have a rigid cell wall and flagellum if motile
• Cyanobacteria:

  • Also known as blue-green algae
  • Found in habitats with sufficient moisture and suitable temperature
  • Bloom in polluted water bodies
  • Show different morphological forms like unicellular, colonial, and filamentous
  • Some cyanobacteria have special cells called heterocysts to fix atmospheric nitrogen
  • Photosynthetic autotrophs due to the presence of chlorophyll-a
• Mycoplasmas:

  • Smallest living cells known
  • Lack a cell wall and can survive without oxygen
  • Most are pathogenic and cause diseases in animals and plants
• Kingdom Protista includes unicellular eukaryotes with a well-defined nucleus and membrane-bound organelles

  • Acts as a link between the kingdom Monera and other kingdoms (Fungi, Plantae, and Animalia)
  • Primarily aquatic
  • Some have flagella or cilia for movement
  • Reproduce asexually and sexually through cell fusion and zygote formation
• Chrysophytes:

  • Include diatoms and desmids (golden algae)
  • Microscopic and aquatic organisms found in freshwater and marine habitats
  • Most are photosynthetic and diatoms are chief producers in oceans
  • Cell walls form two thin overlapping shells rich in silica
• Dinoflagellates:

  • Mostly marine and photosynthetic
  • Cell wall made of cellulose plates
  • Some have two flagella
  • Red dinoflagellates undergo rapid multiplication and release toxins causing red tides
• Euglenoids:

  • Freshwater organisms found in stagnant water
  • Body covered by a protein-rich layer called pellicle
  • Have two flagella, one long and one short
  • Can prepare food through photosynthesis in the presence of sunlight
• Slime Moulds:

  • Saprophytic protists found in cool, moist, shady places with decaying twigs and leaves
  • Form an aggregation called plasmodium under favorable conditions
  • Plasmodium can move by forming pseudopodia
  • Transform into fruiting bodies with spores under unfavorable conditions
• Protozoans:

  • Heterotrophs living as predators or parasites
  • Four major groups: Amoeboid, Flagellated, Ciliated, Sporozoans
• Kingdom Fungi:

  • Fungi prefer warm and humid places
  • Except yeast, fungi are filamentous with bodies consisting of hyphae forming mycelium
  • Hyphae can be aseptate or septate
  • Cell wall made of chitin and polysaccharides
  • Heterotrophic feeding methods: saprophytes, parasites, symbionts
  • Reproduce vegetatively, asexually through spores, and sexually through fruiting bodies
• Fungi reproduce through vegetative means, asexual reproduction, and sexual reproduction involving plasmogamy, karyogamy, and meiosis

  • Sexual cycle involves three steps: plasmogamy, karyogamy, and meiosis
  • Dikaryophase is a condition with two nuclei per cell between plasmogamy and karyogamy
  • Kingdom Fungi divided into Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes based on morphology and reproduction
• Phycomycetes:

  • Found in aquatic habitats, decaying wood, moist places, or as obligate parasites
  • Aseptate mycelium with coenocytic condition
  • Reproduce asexually through zoospores or aplanospores and sexually through fusion of gametes
• Ascomycetes:

  • Known as sac-fungi
  • Unicellular (yeast) or multicellular (Penicillium)
  • Saprophytic, decomposers, coprophilous, or parasitic
  • Branched and septate mycelium
  • Reproduce asexually through conidia and sexually through ascospores in ascocarps
• Basidiomycetes:

  • Grow in soil, on logs, and as parasites
  • Branched and septate mycelium
  • Reproduce sexually through basidium producing basidiospores
• Deuteromycetes:

  • Imperfect fungi with unknown sexual stages
  • Reproduce only by asexual spores (conidia)
  • Septate and branched mycelium
  • Decomposers aiding in mineral cycling
• Kingdom Plantae:

  • Photosynthetic autotrophs with eukaryotic cells containing chloroplasts and cellulose cell walls
  • Alternation of generation with diploid sporophytic and haploid gametophytic phases
  • Includes algae, bryophytes, pteridophytes, gymnosperms, and angiosperms
• Viruses and Lichens are also topics covered in the Biology exam
• Viruses:

  • Non-cellular organisms that remain in inert crystalline form outside the living cell
  • Obligate parasites that take over the machinery of the host cell to replicate themselves, killing the host
  • W.M. Beijerinck called fluids as 'contagium vivum fluidum' as extracts of infected plants of tobacco that could cause infection in healthy plants
  • Virus means venom or poisonous fluid, term given by Pasteur
  • D.J. Ivanowsky found that certain microbes caused Tobacco Mosaic Disease in tobacco plant
• • W.M Stanley showed viruses could be crystallised to form crystals of protein, which are inert outside their specific host
  • Consists of a protein coat called capsid and a genetic material which may be either RNA or DNA
  • Genetic material of virus is infectious
  • Viruses infecting plants have single-stranded RNA, while those infecting animals have single or double-stranded RNA or double-stranded DNA
  • Viruses infecting bacteria are known as bacteriophages and have double-stranded DNA as genetic material
  • Capsid made of small sub-units called capsomeres which protect the nucleic acid