Which is an example of an external stimulus?
a sudden change of air temperature
an artificial light thst attracts insects
an increase in the amount of water available to a plant
a decrease in oxygen levels in the blood during exersise

Cell specialization occurs by the process ofa. reproductionb. differentiationc. maturationd. growth

When analyzing tree rings, what do scientists assume a thin ring indicates?

Which best explains how a heat pump can heat a room? cold air from the house is moved through pipes, where it absorbs thermal energy. warm air from outside is pushed into the house to replace the cold air. combustion warms the air when chemical energy is transferred to thermal energy. fuel is used to move a piston, which pushes warm air into the house.