Z


zona pellucida ZO-nah pel-LU-seh-dah A thin, clear layer of proteins and sugars that surrounds a secondary oocyte. 217

zone of cell differentiation The hindmost region of the subapical region of a root, where tiny root hairs protrude from epidermal cells. 547

zone of cell division The meristematic part of the subapical region in a plant's root. 547

zone of cell elongation The middle part of the subapical region of a root, where rapid cellular elongation lengthens the root. 547

zooplankton ZO-O-PLANK-tun Abundant protozoa and microscopic animals in bodies of water. 458

zygomycetes zi-go-mi-SEETS Fungi that have thick, black zygospores. 478

zygospore zi-go-SPOOR Sexual structure of zygomycetes that consists of zygotes within thick black coats. 481

zygote ZI-goat In prenatal humans, the organism during the first 2 weeks of development. Also called a preembryo. In plants, the fused egg and sperm that grows into a sporophyte. 192

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