What do the tropopause, stratopause,mesopause all in common?

There are four layers to the Earth's atmosphere: the troposphere, stratosphere, mesosphere, and thermosphere (in order of ascending altitude from the Earth's surface). The troposphere, stratosphere, and mesosphere together are known as the homosphere, while the thermosphere is also known as the heterosphere. The homosphere is characterized by relatively constant components of gases, which decrease in density with altitude. Pressure, similarly, decreases with altitude. In the troposphere, dry air is composed of roughly 78% nitrogen (N2), 21% oxygen (O2), and < 1% Argon (Ar). Water vapor is a variable gas that may comprise roughly 1% - 4% of the troposphere, and there are other variable gases of minute proportions given in parts per million (ppm) or parts per billion (ppb) [N.B. variable gases can have significant impact on the atmosphere in spite of small proportions; consider greenhouse gases such as carbon dioxide, methane, and ozone.] The stratosphere and mesosphere have similar compositions to the troposphere although at lower densities. The stratosphere contains a higher proportion of ozone which protects the Earth's biosphere from UV rays. The composition of the thermosphere is extremely sparse and includes nitrogen (N2) and oxygen (O2) as well as atoms of oxygen (O), nitrogen (N) and lighter gases helium (He) and hydrogen (H). The tropopause, stratopause, and mesopause are phenomena that occur at the top of the troposphere, stratosphere, and mesosphere, respectively, and are characterized by temperature inversion. The stratopause is a region of maximum temperature for the stratsophere, while the tropopause and mesopause are regions of minimum temperature for the troposphere and mesosphere, respectively. While density and pressure decrease with altitude, temperature decreases through the troposphere, increases through the stratosphere, decreases through the mesosphere, and again increases through the thermosphere. While temperatures in the thermosphere become very "hot" with altitude, temperature as measured by the speed of molecules, the sparseness of molecules in the thermosphere would cause a person to freeze even at the high temperatures; the molecules become so far apart so as to rarely collide.