Mammals are homoeothermic, which means they can adjust their body temperature as per change in temperature of the surroundings. This is called homeostasis.
Homeostasis is a self-regulatory process by which some organisms such as mammals, birds maintains their internal environment constant.
For examples, the body of a human body functions optimum at normal temperature which is 37°C. If the body temperature increases well above 37°C, then by self-regulatory process body bring down temperature to the normal.
These pairs are found in double strand of DNA and RNA where the bonds between them connect the two strands making the double stranded structures possible.