Which of the following best summarizes the function of the respiratory system?
a. to transport oxygen to cells and wastes away from cells.
b. to protect the organs in the chest cavity c. to move oxygen from the air into the body and carbon dioxide from the body into the air
d. to provide a barrier between the body and the environment
c** which of the following is not true about the structure of an alveolus?
a. it has thick walls to trap gases that enter during breathing.
b. it has high surface area to allow lots of gas exchange.
c. it has a high concentration of oxygen and a low concentration of carbon dioxide.
a**

After reading the paragraph below, answer the questions that follow. researchers have created a robot that has a very thin leg that is moved by cardiac (heart) cells contracting in unison. the robot, made of a polymer similar to that used in making contact lenses, is bathed in heart cells with supporting cells, which then attach to the robot and provide movement as they contract. all of the cardiac cells working together can cause the robot leg to move in a way that individual cells could not. this is an example of a. emergent properties of cells. b. energy flow through an ecosystem. c. adaptation. d. internal environment regulation.

Which element forms the basis of all organic organisms a carbon b oxygen c hydrogen d nitrogen

The illustration shown is an ovum, a female sex cell. a mutation in this cell may be passed to the woman’s offspring during a) birth. b) mitosis. c) dna replication. d) sexual reproduction