I remember back in 10th grade I learned that birds that had beaks that were easier to break the seeds carried those traits to their babies and the whole area had that type of beak since it was necessary to break some seeds. So the beaks that were a disadvantage no longer existed and the beaks that became an advantage passed along to all the other birds.
Side note: if they all had the same beak they could all fight for the same type of seeds and probably have some sort of intense competition but idk if that’s necessary
A) One species always outcompetes the other until only one species remains.
You could have made sure the books were the same weight and your friends could have done it at the same time as you
Water is capable of dissolving a variety of different substances, which is why it is such a good solvent. And, water is called the "universal solvent" because it dissolves more substances than any other liquid. This is important to every living thing on earth.
I hope that’s help:)
If i remember correctly it sends signals to your brain. hope that helps if not im sorry