Which sequence of organisms best represents the flow of energy in an ecosystem?
a
secondary consumers ==> producers ==> heterotrophs
b
carnivores ==> decomposers ==> producers
c
consumers ==> heterotrophs ==> saprophytes
d
autotrophs ==> herbivores ==> carnivores

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.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.