Neurons are constantly carrying action potentials (meaning electrical signals) in order to result in a certain action carried out by the body. Therefore, Neurons need a high amount of ATP to carry an action potential throughout the nervous system to be processed by the brain and then initiate a motor (physical response)
For example if you touch a hot stove, sensory neurons will take the "hot" information from the hand to the spinal cord which has relay neurons which connect the action potential (which is the information) to the brain. The brain in response will interpret that information and initiate a motor response. Which will result in you taking your hand off the stove. This entire process of responding to stimuli takes a lot of energy to take place. Just the brain itself takes about 20% of all daily basal energy (which is the energy required to keep you alive).
B. They all have the same genes but some have hair and some don't
Explanation:
Type I genes tend to be involved in immune response or sensory receptors while type III genes are involved in cell to cell signalling and type II genes are a complex mix of all three types.
If the web happened to look like this one I attached then the anwser would be shrubs. If you take a look at the arrows the shrubs energy is moving to rats, insects and lizards which in turn feeds the coyotes. The starting point is shrubs and in general most food webs start with plants.
