Nervous systems are required by animals to respond to stimuli and have complex senses such as taste, touch, sight, smell, or sound. these are carried by nerves to and from the brain and spinal cord. of all major animal phyla, which does not have nerves?

Porifera

Explanation: Is the correct answer for Pennfoster.

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 

the answer is a) cell division.

hope this !