According to the reading passage, the early birds can be (are) more productive. But the lecture disagrees with the arguement(s) of th(e) pass(a)ge.
First of all, the passage implied that if we wake up ealrier(,) (then) we can use time for constructive purpose. In contrary, the lecture argued that if we wake up early we cannot use the time in productive way. According to the lecture, if we try to wake up early, we have to go to the bed ealry. Hence, there will be no time to use although we wake up ealrier. Also, even if we wake up earlier our body cannot withstand the tireness. Thus, we cannot do any productive thing (Therefore, we can never be productive).
Secondly, the author indicated that morning hours can be (are) productive, becasue there are few distractions. On the other hand, the professor asserted that the morning hours are not always productive. He mentioned body natural rhythm. It means that some people can be very tire(d) in the morning, instead of night time. Therefore, those people cannot use the morning time efficiently.
>>can not -> cannot