I don't know why but I feel so lonelyWhat is frequency

How do you transfer mrna into codons ? i'm so confused : (

Which direction does the energy flow in this energy pyramid ?

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled