Ascientsist is testing the effect of light on plants. he takes one plant and sets it on the window sill where it receives light for approximately 10 hours a day. the other plant he places in a dark refridgerator where it receives no light. the plants are the same species, the same size, receive the same water at the same time, the humidity is the same and they receive the same amount of plant food weekly. the plant on the window sill grows much bigger and appears much healthier. what has this scientist proven? explain.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.