<span>This is due to much of the energy that is consumed by lower trophic levels of the food chain/food web being used at that lower level. This energy is stored or used and, therefore, unavailable to the organisms higher up in the chain. As the chain lengthens, less energy is available, usually as a factor of 10 (1/10 of the energy taken in by the level below the consumer is available to the consumer's level, for example).</span>
I am pretty sure that a point mutation that creates a premature stop codon is called a synonymous mutation. It also can be called silent mutation, if you have it in you option list, feel free to use it, it is the same. That will definitely help you.
For each of the examples, simple diffusion, carrier, and channel mediated, each type involves the flow down a concentration gradient. This means that the molecules flow from an area of high concentration to an area of low concentration. In turn, this allows for a passive process, meaning no ATP is needed! I hope this explains your question.
