I recently heard a non-native speaker have difficulty with words beginning <bio>. One thing one can safely say about such words is that the beginning is never pronounced biːəʊ. The <i> always represents the diphthong aɪ.
In a few words the second part of the prefix bears the main stress of the word and the pronunciation is baɪˈɒ. Here are some examples:
biography biology bionic
Notice the pronunciation of biographical = ˌbaɪəˈɡræfɪkl and biological = ˌbaɪəˈlɒdʒɪkl.
In some other words it is the first syllable of the prefix which bears the main stress. Here are some examples of this:
biome = ˈbaɪəʊm
biopic = ˈbaɪəʊpɪk
biopsy = ˈbaɪɒpsi
biorhythm = ˈbaɪəʊrɪðm
bioscope = ˈbaɪəʊskəʊp or ˈbaɪəskəʊp
biosphere = ˈbaɪəʊsfɪə or ˈbaɪəsfɪə
In longer words the first syllable of the prefix tends to bear a secondary stress. Examples:
ˌbioˈchemistry ˌbiodiˈversity ˌbioengiˈneering ˌbiotechˈnology
In some words of this sort the prefix can be pronounced ˌbaɪə, but you won’t go wrong if you stick to ˌbaɪəʊ for all of them.
2013_11_23