chapter 2

• Atom


  Smallest and most fundamental unit of matter, consisting of a nucleus surrounded by electrons
• Molecule


  Chemical structure consisting of at least two atoms held together by one or more chemical bonds
• Macromolecule


  Large molecule typically formed by polymerization, e.g. DNA
• Organelle


  Small structure that exists within cells, e.g. mitochondria and chloroplasts
• Cell


  Smallest fundamental unit of structure and function in living organisms
• Cells


  • Classified as prokaryotic or eukaryotic
  • Prokaryotes are single-celled or colonial organisms without membrane-bound nuclei or organelles
  • Eukaryotes have membrane-bound organelles and a membrane-bound nucleus
• Tissue


  Groups of similar cells carrying out similar or related functions
• Organ

  Collections of tissues grouped together performing a common function
• Organ system


  Higher level of organization consisting of functionally related organs, e.g. circulatory system
• Organism


  Individual living entity, including single-celled prokaryotes and eukaryotes
• Population


  All the individuals of a species living within a specific area
• Community


  Sum of populations inhabiting a particular area
• Ecosystem

  All the living things in a particular area together with the abiotic, non-living parts of that environment
• Biosphere


  Collection of all ecosystems, representing the zones of life on Earth
• Hierarchical classification is a system of grouping things according to a hierarchy or levels and orders
• Levels of hierarchical classification

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• For humans, the classification is: Animalia (kingdom), chordata (phylum), mammalia (class), primates (order), hominidae (family), homo (genus), sapien (species)
• Robert Whittaker proposed the Five Kingdom Classification, dividing organisms into five main kingdoms based on characteristics like cell structure, mode of nutrition, and reproduction
• Five Kingdoms

  • Monera
  • Protista
  • Fungi
  • Animalia
  • Plantae
• Monera (Prokaryotes)


  • Typically unicellular
  • Genetic material is naked circular DNA without a nuclear envelope
  • Only ribosomes and simple chromatophores as subcellular organelles
  • No sap vacuoles, may have gas vacuoles
  • Predominant mode of nutrition is absorptive, some are photosynthetic or chemosynthetic
  • Non-motile or move by beating of simple flagella or gliding
• Bacterial Shapes


  • Cocci (oval or spherical)
  • Bacilli (rod-shaped)
  • Vibrios (small, comma or kidney-shaped)
  • Spirillum (spiral or coiled)
  • Filamentous
  • Stalked
  • Budded
• Bacterial Structure


  • Capsule (slimy layer)
  • Cell wall (made of polysaccharides, proteins, lipids)
  • Plasma membrane (thin, elastic, selectively permeable)
  • Cytoplasm (complex aqueous fluid with various biomolecules)
  • Nucleoid (naked circular DNA)
  • Plasmids (small circular extrachromosomal DNA)
  • Flagella (for motility)
  • Pili or Fimbriae (hair-like appendages)
• Types of Bacteria by Nutrition

  • Autotrophic (synthesize own food from inorganic substances)
  • Heterotrophic (depend on external organic materials)
• Heterotrophic bacteria include parasites, saprotrophs, and symbionts
• Autotrophic bacteria


  Bacteria able to synthesize their own food from inorganic substances, as green plants do
• Heterotrophic bacteria


  Bacteria that cannot synthesize their own organic food and depend on external organic materials
• Types of heterotrophic bacteria

  • Parasites
  • Saprotrophs
  • Symbionts
• Kingdom Protista

  • Contains all single-celled eukaryotes
  • Primarily aquatic
  • Forms a link with the kingdoms of plants, animals and fungi
  • Cells have a well-defined nucleus and membrane-bound organelles
• Characteristics of Protists

  • Some have flagella or cilia
  • Reproduce asexually and sexually
  • May be photosynthetic or holotrophic
  • May be saprotrophic, parasitic or symbiotic
  • May have mixotrophic nutrition
• Grouping of unicellular protists

  • Photosynthetic protists (e.g. dinoflagellates, diatoms, euglenoids)
  • Consumer protists (e.g. slime moulds or myxomycetes)
  • Protozoan protists (e.g. zooflagellates, sarcodines, sporozoans, ciliates)
• Life cycle in some protists

  1. Zygote (2n) divides by meiosis to produce vegetative cells (1n)

  2. Vegetative cells divide by mitosis

  3. Some vegetative cells produce gametes

  4. Gametes combine in fertilization to form a zygote
• Chrysophytes


  • Comprise diatoms and golden algae
  • Microscopic, float passively in water currents (plankton)
• Dinoflagellates


  • Usually marine and photosynthetic
  • Cell wall has stiff cellulose plates
  • Have two flagella, one longitudinal and one transverse
• Euglenoids


  • Mostly freshwater
  • No cell wall, have a flexible protein-rich layer called a pellicle
  • Have two flagella, one short and one long
• Nutrition in Euglena

  Mixotrophic - photosynthetic when light is available, saprophytic in darkness
• Slime moulds


  • Saprophytic protists
  • Body can move through decaying matter, engulfing organic material
  • Form an aggregation called a plasmodium under suitable conditions
  • Produce resistant spores that can survive for years
• Major groups of protozoan protists


  • Flagellated protozoans
  • Amoebid protozoans
  • Sporozoans
  • Ciliated protozoans
• Flagellated protozoans

  • Use flagella for locomotion
  • May be free-living, parasitic, commensal or symbiotic
  • Generally uninucleate, occasionally multinucleate
• Amoebid protozoans


  • Develop pseudopodia for locomotion and feeding
  • Mostly free-living, found in freshwater, seawater and damp soil
• Sporozoans

  • All are endoparasites
  • Some cause severe diseases like coccidiosis in birds
  • Nutrition is parasitic, phagotrophy is rare