Direct observation is the simplest and most effective method to determine population size

I think that this is a true statement: it's better than determining the population size by indirect means, for example by judging how much food they ate or by judging by just a sample of the population. I would maybe add that  this method can be supported by technology, for example taking a picture of the population and analyzing the picture later.

Only algae, oak trees, and bermuda grass produce atp by photosynthesis i am almost positive

Neurotransmitters are messengers responsible for communication between neurons. they are released from synaptic vesicles and are received by receptors.  the communication is referred to as neurotransmission. the following statement is true about neurotransmitters: a. they're stored in synaptic vesicles in the axon.