In a human karyotype, autosomes or “body chromosomes” (all of the non–sex chromosomes) are generally organized in approximate order of size from largest (chromosome 1) to smallest (chromosome 22). However, chromosome 21 is actually shorter than chromosome 22.
Trees need leaves for photosynthesis because leaves contain chlorophyll. As the article states, the food-making process stops after these trees lose their leaves. Some trees keep their leaves all year long.
