Biology  5/e   Raven/Johnson
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Symbiotic origin of mitochondria and chloroplasts: It is evident that mitochondria were acquired by eukaryotes through symbiosis with aerobic prokaryotes. Chloroplasts are thought to have been acquired through symbiosis with anaerobic prokaryotes.

Flagella and cellular motility: Numerous eukaryotes possess flagella of a "9 + 2" structure, a structure unique to eukaryotes. Such flagella often provide the eukaryote with locomotion.

Evolution of mitosis: Prokaryotes divide by binary fission accompanied by equal distribution of genetic information. Eukaryotes move replicated genetic material in an orderly fashion, manipulated by microtubules.

Sexuality and multicellularity: Prokaryotes exchange genetic material, but is not an orderly, predictable manner as in eukaryotes. Prokaryotes are all haploid, thus lacking syngamy and meiosis characteristic of eukaryotes. Prokaryotes often adhere to each other following cell division and form three-dimensional structures, but do not have the kind of differentiation and interaction found in multicellular eukaryotes.

Life cycles of eukaryotes: Eukaryotes alternate syngamy and meiosis in their life cycles. The life cycles differ mostly in the placement of meiosis in the life cycle. Those with zygotic meiosis are predominantly haploid. For them, the diploid condition is terminated by meiosis soon after it is established by syngamy. Some eukaryotes are predominantly diploid with meiosis occurring in the formation of gametes (gametic meiosis) that will soon unite to re-establish the diploid condition. Other eukaryotes have sporic meiosis. Meiosis occurs in the formation of spores. The duration of diploid and haploid phases vary from one extreme to another.

Cyanobacteria, Heliobacterium, and Prochloron: Cyanobacteria are believed to be the source of chloroplasts of red algae. Heliobacterium is evidently the source of chloroplasts of brown algae, diatoms, and dinoflagellates. The chloroplasts of green algae evidently were derived from a bacterium like Prochloron.

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