Answer:
Troponin and calcium ions.
Explanation:
Troponin is a component of thin filament along with tropomyosin and actin. It is a protein complex to which calcium binds and start the production of muscular force.
Calcium also playing a very important role in muscle contractions, it binds with troponin and helping to move tropomyosin.
When calcium ion attached to troponin, then conformational changes occurs in troponin shape and moves which allow tropomyosin going away from its inhibitory position from the myosin-binding sites on actin. After this, the energized myosin head starts binding to the actin molecules and starts the cross bridge cycle, which helping in shortening the muscle's fiber.
D. They had larger beaks.
Due to the drought they would need to dig deeper for food. But their tiny beaks could not do that. So over time their beaks grew and adapted to the drought. Therefor the answer is D. They had larger beaks!
Hope this helped! <3
Heat from the sun makes it through near the Antarctic (where the hole is) is melting the ice and not allowing some key species to feed. seals don't have ice to come up for air through like normal so polar bears starve. loss of land means less food for a lot of species because the hunting grounds is closing and there is no room to expand.
Bile neutralises the stomach acid.
