Answer:
Explanation:
The human ear can easily detect frequencies between 20 Hz and 20 kHz. Hence, sound waves with frequency ranging from 20 Hz to 20 kHz is known are audible sound. The human ear is sensitive to every minute pressure difference in the air if they are in the audible frequency range.
Answer:
The correct answer will be option A.
Explanation:
The electrical impulses are generated in the sino-atrial node or SA node, a mass of cells which generates impulse in the upper atrium.
This electrical impulse transmits from the sino-atrial node to the atrio-ventricular node in the lower portion of the upper atrium through the internodal pathway- the pathway composed of atrial cells.
Once the impulse reaches the AV node, it is transferred to the ventricular portion of the heart through Bundle of His presence in the ventricular septum. This bundle of his divides into left and right ventricles through bundle branches and stimulates both the ventricles.
Thus, option-A is the correct answer.
Answer:
The eagles absorbed the DDT after eating large fish.
Explanation:
As from the diagram, we can see that DDT is introduced to zooplankton. Then zooplankton is eaten by small fish followed by large fish and lastly, the eagles feed on large fish.
DDT chemical -> Zooplankton -> Small fish -> Large fish -> Eagle