The growth rate is determined by how fast the population of a country or a zone increases. This factor is higher in developing countries than in developed countries. One factor that contributes to this is the low birth rate in developed countries as people have fewer children in these countries, and therefore there are fewer births per year than in developing countries. This is influenced by the accessibility to contraceptive methods, higher education levels, and cultural values. Also, fewer births mean the population will grow slowly, and therefore the growth rate is lower.
The fatty acids in the tail of a phospholipid molecule are non-polar and hydrophobic.
Fats that you take in from your food is used to build membranes. Membranes can be represented by models such as The Fluid Mosaic Model, which displays the phospholipid bilayr, and other tissues on the membrane.