What’s the difference between internal stimuli and external stimuli

What are the genotypic and phenotypic ratios

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 ?

Who determined the nature of chemical bonds?