HELP PLEASE The fluid mosaic model of membrane structure suggests that membranes

are composed of a single fluid layer of phospholipids and proteins
are composed of a fluid bilayer of fatty acids with proteins associated on the outer and inner surfaces
are composed of protein molecules embedded in a fluid bilayer of phospholipids
are composed of a fluid phospholipid bilayer sandwiched between two layers of hydrophilic proteins

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation

most community's take hundreds of years to become stable

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).