What did the first americans have to depend on for their survival?

a) the environment
b) their enemies
c) dinosaurs
d) religious beliefs

The first Americans - this could be interpreted as the Native Americans who arrived, from Asia via Bering Strait, 12 000 years ago had to depend on their environment: the plants that grew in America, the animals they could find, and they had to devise ways to find those into food and shelter.

The main structural differences between plant and animal cells are the additional structures found in plant cells. These structures include: chloroplasts, the cell wall, and vacuoles.

Chloroplasts

In animal cells, the mitochondria produces the majority of the cells energy from food. Plant cells use sunlight as their energy source; the sunlight must be converted into energy in a process called photosynthesis. Chloroplasts are perform this function.  The energy conversion in plants is a complex set of reactions similar to those performed by mitochondria in animals.

The Cell Wall

Another structural difference between in plant cells is the presence of a rigid cell wall surrounding the cell membrane. The tough wall gives added stability and protection to the plant cell.  If you think about it, most animal cells are inside an organism that has either an exoskeleton or an endoskeleton,  built in structure.  Plants don't have a skeleton of any kind so the cells have to perform this.

Vacuoles

Vacuoles are large, liquid-filled organelles found only in plant cells. Vacuoles can occupy up to 90% of a cell's volume and have a single membrane. Their main function is as a space-filler in the cell, but they can also fill digestive functions and their interiors can be used as storage for nutrients.