A chromosome is a DNA (deoxyribonucleic acid) molecule with part or all of the genetic material (genome) of an organism. Essentially, chromosomes are the basic building block of who we, as humans, are. They make up or DNA structure and are responsible for if we have blue eyes or black hair, without chromosomes, us as humans wouldn't exist. We, as humans, are the organisms that chromosomes make.
Photosynthesis Is generally the opposite of cellular respiration. To drive the organisms metabolism photosynthesis has an exothermic reaction.
The neuron, or the impulse-conducting cell of nervous tissue.
From reasoning and analyzing evidence. Hope this helped :D