Describe one niche in the ecosystem.

Niche can be described as the role or position that a particular organism has in its ecosystem.

For example, honeybees which will gather nectar from flowers to make honey is an example of a niche. The particular role of honeybees in an ecosystem is to collect nectar in that ecosystem from different flowers and to produce honey. Other organisms living in the same environment will not perform the same function in the ecosystem.

the answer is a or when it says crossing over

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.