No.
No they do not. They all have the same size of cells.
No. they vary according to function.
no there are regular sizes and minis and keychains
IT IS THOUGHT THAT ALBERT EIENSTEIN HAD THE BIGGEST BRAIN not quite sure who has the biggest brain now
No, all multicellular organisms have the same size cells.
It might not always seem like it, but I'm sure that EVERY HUMAN has a brain. I'm pretty sure they are all the same size too, but smarter people have more wrinkles in their brain.
Some examples of big animals with relatively small brains are elephants, blue whales, and sperm whales. These animals have massive bodies, but their brain size in proportion to their body size is smaller compared to other animals.
All of the animals cell are almost same. They have the same structures, and organelle. But they have different gene. That's what makes them different from us.
No. They are all similar in size. However, larger animals do have more cells. For example, there is a big brick house and a small brick house. The bricks are all the same size but, the big brick house has more bricks.
As a fellow mammal, the cat's brain doesn't have anything the human brain doesn't have. The human brain has about 1,000 neurons compared to the cat's 100, but all the basic brain structures are the same, differing only in size and ratio.
Nothing at all
No, not every animal needs a brain. A jellyfish does not have a brain, it barely has any organs.