List the structure(s) that form the boundary between the inside and the outside of each cell in Model 2.

you are the source of the heat energy. you can minimize the heat energy by selecting the appropriate clothes to wear.

the sun d the answer is sun

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

clumped distribution, because you'de have all of the population gathered in a relatively small are.

it's the most common because it provides protection and a mate for reproduction

example: humans, seeweed, cattles, etc.