Horses, cows, pigs, chickens, rabbits, turtles, birds, and many others.
However, horses, cows, pigs and rabbits only eat grain when they are fed to them by humans... usually to fatten them up. Normally they would eat leaves from pastures and other vegetables. There are no mammals who eat a significant amount of grain as part of their natural diet. That includes humans up until the last 10k years (advent of agriculture) and that quantity was still much, much lower than it was after the industrial revolution. It then grew progressively worse as low fat diets that suggested more grain were promoted by US and other governments... right in line with "the obesity crisis" and type II diabetes.
In other words... "it's for the birds"
No. A shark's skeleton is made from cartilage, a material softer and more flexible than bone. Sharks are cartilaginous fishes which means they have a skeleton of cartilage. This skeleton is usually calcified but it is not true bone. The fins of a shark contain cartilaginous rodlike supports called ceratotrichia. Cartilaginous fishes are composed of two groups: sharks and rays (Subclass Elasmobranchi) and chimaeras (Subclass Holocephali).
The ecological niche of a animal is both its "address" and its "profession". It explains where in the ecosystem you will find the animal and what it will do there.
The basical niche is described by the abiotic factors, that surround the animal. The real niche, the animal is living in is most likely much smaller as biotic factors like competition, predation and so on also play a role in defining the niche!
The early mole digs the deepest hole.
There are a few different ways to classify foods. The food groups are fruits, vegetables, grains, protein, and dairy. The 7 classes are carbohydrates, proteins, minerals, fats, fiber, vitamins, and water. These can be broken down into categories such as macro-nutrients (carbohydrates, proteins, and fats), micro-nutrients are needed in smaller amounts (vitamins, fruits, and vegetables), inorganic micro-nutrients (minerals), and some classify water as a class too.