BIOLOGY by Miller and Levine

Content Update
Chapter 20

Chapter 20, Figure 20-7

The original version of Figure 20-7 in the first few printings of the Dragonfly Book was perfectly accurate, but it neglected to point out where the sexual and non-sexual phases of the Plasmodium life cycle take place. A number of teachers inquired about this, so we decided to put this information in the figure.

As the new labels (below) point out, the sexual phases of the life cycle take place inside the body of the parasite's mosquito host. After a mosquito picks up gamete cells from the blood of an infected human, fertilization takes place in the gut of the mosquito. A diploid zygote is formed very briefly, and quickly undegoes meiosis, eventually producing haploid sporozoite cells that migrate to the salivary glands of the mosquito. The other stages of the parasite life cycle are haploid, including all stages inside the human host. A copy of the new figure is shown below (Posted 8/6/02):

Figure 20-7 Animallike protists can cause serious diseases, including malaria. The life cycle of Plasmodium, which causes malaria, is shown above.

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