After reading the above information, one reason different members of crow populations have a different rate of survival is there is always a chance that that some other variation will also effect some of the crows ability to survive. Another reason is that the vision, muscle strength and size can influence survival.
The right ventricle pumps the oxygen-poor blood to the lungs through the pulmonary valve. The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle through the mitral valve. The left ventricle pumps the oxygen-rich blood through the aortic valve out to the rest of the body.
It is released through nitrogen - fixing bacteria
There is no such thing ? It can't be an organism if it does not do any of the above
