Which would best be used as an index fossil? O A. alligator bones, because they have lived a long time with relatively few changes in body structure
O B. petrified wood, because it clearly shows the parts of the wood replaced by minerals
O C. sedimentary rock, because it is found in horizontal layers created in succession
O D. trilobites, because they lived for a short period of time and then became extinct

q: compare the parts of a cell and the cell as a whole to another common nonliving system (i.e., a car, a city,

a:

comparing this to the inside of a food building/company.

all cells are surrounded by a plasma membrane, which protects the cell from its environment, keeping toxic substances out of the cell. it regulates which molecules are allowed to enter and exit the cell.

regulates all cell activity such as cellular metabolism, and growth in addition to storing and maintaining the cell's dna for transcription and replication. determines what proteins to make.

contains the organelles; site of most cell activity

the place where ribosomes do their working activity.

builds the proteins.

prepares proteins for use or export.

responsible for breaking down and absorbing materials taken in by the cell.

maintains cell shape.

transforms one form of energy into another.

≅200-130 milions years ago pangea splited in 2 continents