Here is the question;
The evolution of the vast range of diversity and complexity of living organisms on earth is the result of selective pressures for solving the same basic "life problems".
The professor wants to know why this is true but I don’t get the question. If someone can help explain it way better than my text book does that would be great.
I suggest you watch Evolution-The Evolutionary Arms Race PBS on YouTube, parts 1-6 (each bout 10 minutes). You should have a good base understanding of what selective pressure (to survive) on basic life problems (competition for energy resourses to sustain life and propagation) as well as mutualistic symbiosis between Eukaryotic and Prokaryotic life.