Bacteria, Fungi and Plants: Structure, Life Activity, Classification
Bacteria are prokaryotic, mostly single-celled, with a cell wall, capsule, flagella and a nucleoid. They reproduce by simple binary fission, can form spores, and are classified by shape (cocci, bacilli, spirilla) and by nutrition (autotrophic, heterotrophic, saprotrophic, parasitic). Bacteria are decomposers, nitrogen fixers, and agents of disease and fermentation.
Fungi are eukaryotic heterotrophs with chitinous walls, absorbing nutrients. Unicellular yeasts and multicellular moulds and cap fungi exist. They reproduce by spores and by budding (yeasts); the body is a mycelium of hyphae. They are decomposers and symbionts (lichens = fungus + alga/cyanobacterium), and cause disease and food spoilage.
Plants are autotrophic, with cellulose walls, chloroplasts and a life cycle alternating haploid gametophyte and diploid sporophyte. Classification runs: kingdom → division → class → order → family → genus → species. Algae, mosses, ferns, gymnosperms and angiosperms differ in tissue complexity and reproduction: mosses need water for fertilisation, ferns have spores and vascular tissue, gymnosperms have seeds in cones, angiosperms have flowers and fruits enclosing seeds. The double name (genus + species) is the binomial system.
Traps
Do not call fungi plants (no chlorophyll, chitin walls) or bacteria fungi. Remember that lichens are a symbiosis, not a single organism. In classification, kingdom is the broadest listed unit and species the narrowest.
Worked example
"An organism has chitin walls, no chlorophyll and absorbs nutrients." It is a fungus, not a plant (chlorophyll absent) and not a bacterium (eukaryotic, chitin wall).