Some <u>birds</u> are both primary consumers and secondary consumers.
<u>Explanation:</u>
Primary consumers are the class of animals that are feeding upon the producers as their primary food. Secondary consumers are the class of animals that are feeding upon a primary consumer to feed themselves.
Some of the birds like sparrow, humming birds etc feed on fruits and seeds of plants to maintain their lives. They are thus the primary consumers. Others like eagle, crow eats on flesh of primary consumers. So they are secondary consumers. Thus birds can be both primary consumers and secondary consumers.
C. a rise in blood carbon dioxide concentration
Explanation:
Negative feed back mechanism refers to the control mechanism in which a product of a particular pathway controls the switch on and switch off of that particular pathway.
Since breathing increases the blood oxygen concentration and lowers carbon dioxide concentration and pH. The sensors that regulate the breathing should respond to oxygen concentration as the carbon dioxide is the by-product of respiration and is responsible for increasing blood pH. Thus increased Carbon dioxide levels in blood is the only factor which will trigger breathing.
More oxygen becomes available in the water helping the marine or freshwater creatures live. <span />
Most soil originated from weathered rock.
