In your own words define the following terms : Heat, thermal energy, conduction, convection, radiation

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

only about ten percent of the energy at one trophic level is passed on to organisms at the next trophic level. the remainder of the energy is used in life processes or lost as heat.