The hard structure is to protect the offspring from harm. If you seen a mother bird before they often sit on their eggs to keep the baby birds warm and safe, that is why the eggs have a hard structure, so the mother bird doesn't accidentally crush the baby birds.
Plus I believe that when the baby birds are about to hatch they will peck at the egg cracking it slightly signally the mother bird to get off of the eggs and watch their babies being born.
Hope this helped :)
Have a great day
Answer:
ligand; ions; ligand; ions; nervous system
Explanation:
Ligand-gated ion channels are transmembrane protein complexes that open when they bind to their corresponding ligands (e.g., neurotransmitters). This type of receptor is known to modulate the synaptic transmission between neuron cells or neuron and muscle cells. In the nervous system, ligand-gated ion channels located at sites of synaptic contact determine the ion flow in response to neurotransmitter binding. Some examples of ligand-gated ion channels include gamma-aminobutyric acid A (GABA-A) and nicotinic cholinergic receptors.
Answer:
Oxygen to us, climate/weather patterns, and provides us with seafood
Explanation:
