The action potential is caused by permeability changes in the plasma membrane.

True

Explanation:

During resting potential, the inside of the membrane is more negative compared to the outside. The activation gates of Na+ channels are closed and the membrane is impermeable for sodium ions. When a stimulus is strong enough to fire an action potential, change in the shape of the channel proteins opens the activation gates.  

Now, the gated Na+ channels are opened making the membrane more permeable for sodium ions.  The membrane is permeable for sodium ions for a brief period only when both activation and inactivation gates are open. This allows the entry of sodium ions inside the axon and makes is more positive.

ecological efficiency: % of usable energy transferred as

biomass from one trophic level to the next typical is 10% efficient (90% of

energy is lost),is diagramed as the pyramid of energy flow. then osprey eagle

are tertiary consumer and the shrimp are primary consumer, so to balance

mass of shrimp (1/0.1) / 0.1 = 100 kg