Los pulmones y el sistema respiratorio permiten la entrada del oxígeno del aire en el organismo, así como la expulsión de dióxido de carbono al espirar. La respiración es el término que se utiliza para denominar el intercambio de oxígeno procedente del entorno por el dióxido de carbono que se produce en las células.
Answer:
A
Explanation:
Today, the atmosphere holds about 21 per cent oxygen. ... When the first simple organisms appeared in the oceans more than 3.5 billion years ago, the atmosphere was mostly nitrogen, hydrogen, water vapor, and carbon dioxide
Answer:
negative response
Explanation:
There exists three types of responses to a certain stimuli, a positive, negative, or ignoring. A positive response is when the subject is attracted to the stimuli, while a negative response is when the subject wants to avoid the stimuli. Therefore in this situation we can say that this is a negative response when the mouse hides. In this case the hawk flying over is the stimuli and the rat is trying to avoid the hawk by hiding.
