Answer as soon as the respiratory system is responsible for the exchange of oxygen and what gas? a. nitrogen b. hydrogen c. water vapor d. carbon dioxide

Some birds look for food near cattle and other livestock. the movement of the cattle churns up the ground, making insects available to the birds. the cattle appear to be unaffected by the presence of the birds. what kind of relationship exists between the birds and the cattle? o a. parasitism o b. commensalism o c. predation o d. mutualism

Which could be a pathway of food through an ecosystem

Which of the following explains why a tree is often used as a model to represent the principle of common descent