The major organ of the circulatory system, the heart

Yes the heart is the major organ of the circulatory system it's main function is to propel blood throughout the body.

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.

some of your causes might be acidic rain or natural wildfires that cause the parks to be degraded

hope this any more questions i am here plz mark brainliest