Unlike fishes with bony skeletons, a shark's skeleton is made out of cartilage. ... Sharks, rays, skates, and chimaeras (also know as rat fishes) all have cartilaginous skeletons.
        
             
        
        
        
Answer:
 A Sunlight enables this plant to make its own food. Soil Soil is a mixture of rock fragments, nutrients, air, water, and the decaying remains of living things.
Explanation:
 
        
             
        
        
        
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. 
 
        
             
        
        
        
A human needs approximately 2-5 percent of protein for the typical energy needed daily. Protein is one of the most important building blocks in the body. It helps the bones, muscles, skin, blood, and cartilage. A humans nails and hair are made of protein. The protein your body uses also repairs tissues and build new ones. 
        
             
        
        
        
the layer on the top. the layer with the most minerals.