Do birds have control over their feathers? For what purpose? How does this impact birders in the field (use the example of a seagull and loon to support your answer.

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.

it should be d) transitional fossils.

they show the gradualism of evolution throughout a period of time

la transducción de señal ocurre cuando una molécula de señalización de fluido extracelular activa un receptor de superficie de la célula.