The sex of most mammals, including humans, is genetically determined by the XY sex-determination system where males have X and Y (as opposed to X and X) sex chromosomes . During reproduction , the male contributes either an X sperm or a Y sperm, while the female always contributes an X egg. A Y sperm and an X egg produce a male, while an X sperm and an X egg produce a female. The ZW sex-determination system , where males have ZZ (as opposed to ZW) sex chromosomes, is found in birds, reptiles and some insects and other organisms. Members of Hymenoptera , such as ants and bees, are determined by haplodiploidy , where most males are haploid and females and some sterile males are diploid . [ citation needed ]
Many miles of hedgerows have been removed for various reasons over the last few decades. The remaining hedgerows on the Great Plains are habitat islands for those creatures that prefer the forest to the prairie. Along with the gallery forest found next to streams and rivers, hedgerows provide a place to live for many kinds of wildlife that would not otherwise be found on the prairie. In areas that have been converted to agriculture, hedgerows may be the only winter shelter available for wildlife. Osage Orange trees are the backbone of most of those hedgerows and are a distinctive member of the flora of the Great Plains.