I believe the answer you are looking for is median.
example:
2 4 6 |8| 10 12 14
median: 8
three on each side of "8"
Answer:
directional selection, is a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.
1) d. mitochondria
These are found in both plant and animal cells.
2) b. fluid
http://1kai.dokkyomed.ac.jp/mammal/en/genus_list.html
