Biology · Kingdom Prokaryotae. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Bacteria grow in number, not in size. A cell divides into two by binary fission, which is asexual. The time taken for the population to double is the generation time. In a closed culture the numbers follow four phases: lag, log, stationary and death (decline).
Bacteria have no true sexual reproduction, but genes pass from one cell to another by conjugation, transformation and transduction. This is called genetic recombination.
Bacteria recycle nutrients, fix nitrogen and are used in industry, but some cause disease, so we control them by physical and chemical methods. Cyanobacteria such as Nostoc are prokaryotes that photosynthesise like plants and release oxygen.
In growth sums, students multiply by the number of generations when they should double each time. Six generations means × 26 = × 64, not × 6 or × 12.
Answer: 6 400 cells per mL.
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