Question 9 A mitochondrion is an example of a(n)
(a) Organelle.
(b) Nucleolus.
(c) Cytoplasm.
(d) Golgi apparatus.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.

i'd have to say the answer is probable the second option "the geosphere interacting with the atmosphere"