Because people back then did not have enough access to technology like we do today
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.
Bacteriophage means “eater of bacteria,” and these spidery-looking viruses may be the most abundant life-form on the planet. HIV, Hepatitis C, and Ebola have given viruses a bad name, but microscopic phages are the good guys of the virology world.
Temperature. Also, you should put more detail into your question, as it's not entirely clear what your asking.
1. Temperate deciduous forests
2.?
3.savannas
4.temperate grassland
