What happens if photosynthesis didn't produce oxygen?

There would be no oxygen for us to breathe in, thus making no Carbon Dioxide for the plants. We would all be dead in a short time, and all the plants would die along with us.

1 / The plants would die

2 / The food we get from them would no longer exist

3 / There will be higher concentrations of carbon dioxide in the air

4 / Herbivorous animals would have to eat something else or face extinction.

5 / If there were no plants, then medical reseach would be affected.

6 / The balance of the ecosystem will not exist

7 / Eventually we would either evolve (to survive) or die.