Organism with heterozygous alleles received how many alleles from each parent?

What does the process of natural selection involve

Compare and contrast the bohr model and the electron cloud models of the atom.

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?