W
warm-blooded
Animals that have developed fat and fur, hair, or feathers in order to retain heat produced by metabolic activities. Also known as endothermic. Warm-blooded animals are able to thrive in various climates, because they are minimally affected by environmental fluctuations in temperature.
X
xylem
Vascular tissue composed of cells that are dead at maturity; transports water and dissolved minerals upward from the roots to the shoot.
Z
zygote
In sexual reproduction, the diploid product of the fusion of the father’s haploid sperm cell and the mother’s haploid ovum (egg) cell. The single-celled zygote divides billions of times to form a whole individual.
