For a long time every living thing was either a plant or an animal. Then biologists looked at the cells, and the old order broke. In this course we see why two kingdoms were not enough, how Whittaker built five, and what makes a bacterium different from every other cell. We study the shapes of bacteria, the archaebacteria, the cyanobacteria and the bacteria that help us or harm us.
3 lessons, about 1 h 20 min3 simulations11 problems6 practice questionsPython in every lesson
Aristotle and Linnaeus used two kingdoms, plants and animals. This did not separate organisms with and without a nucleus, single-celled and many-celled ones, or those that make their food and those that do not. R. H. Whittaker proposed five kingdoms in 1969: Monera, Protista, Fungi, Plantae and Animalia. He used the cell structure, the body organisation, the mode of nutrition, the reproduction and the evolutionary relationships.
Kingdom Monera has the bacteria as its only members. They are prokaryotes, the most abundant organisms, and they live in every kind of place. By shape they are coccus, bacillus, vibrio or spirillum. They have a cell wall, but no nuclear membrane. They reproduce mainly by binary fission, and some by spores under bad conditions. The archaebacteria live in extreme places and have a different cell wall.
Cyanobacteria are photosynthetic autotrophs, some of which fix nitrogen. Chemosynthetic bacteria get energy from inorganic substances and recycle nutrients. Heterotrophic bacteria are the most abundant: they are decomposers, they make curd and antibiotics, they fix nitrogen in legume roots, and they cause diseases such as cholera, typhoid and tetanus. Mycoplasma are the smallest cells and have no cell wall.
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