Dr. calvin is giving a lecture on the properties of cardiac tissue. during the lecture, he states that the conduction tissue of the heart does not require any external stimulus to initiate its contractions. it has the ability to initiate its own electrical stimulation. to demonstrate this property, dr. calvin dissects a frog and places its heart in a petri dish with ringer's solution. he then asks his students to observe how the frog's heart continues to beat without any external stimulation. based on the information provided in this scenario, which property of the heart is dr. calvin trying to demonstrate?

they may bind directly to special “promoter” regions of dna, which lie upstream of the coding region in a gene, or directly to the rna polymerase molecule.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms

i took a test for bio that had this question and these were the correct answers, not sure if this is any now lol

the nervous system and the muscular system work together.  

sweat reaches the surface of the skin and evaporates into the air.

muscles underneath the skin relax, causing hair on the skin to lay flat.