This is because the animals which live in them have different shapes and sizes.
they come in all different shapes and sizes
Crystals of the same substance form a similar structure in nature, but there are many basic crystaline structures in different substances
there skin grows and then they change their shells so make sure you have plenty of shells in different shapes and sizes
Cells are different shapes and sizes because they have different functions. The functions dictate the shapes and sizes.
Because animals are all different shapes and sizes
Why are humans different shapes and sizes? Every living thing is different (More or less)
If they were the same shapes and sizes then life would be exceedingly boring.
Pot racks come in several different sizes and shapes. Different retailers offer a wide variety of different sizes and shapes, but most are similar, and alike in color.
If they are the same shapes but differ only in size, then they are SIMILAR shapes. Otherwise, they are simply different shapes.
Yes Aliens come in all shapes and sizes from all over the Galaxy. if they were real.
Yes, there are different shapes and sizes of satellite dishes. You can find the best one for your home at www.montanasatellite.com/satellite_dish_covers.htm
Hohokam artifacts made from seashells occur in various sizes and shapes.