Gametes that are the same in size and shape. Having gametes of different size and shape. Usually oogamous organisms have eggs and sperm. The female gonad in animals.
I think simple diffusion is a former of active transport
A comet. It’s a smaller celestial body that’s composed of mainly ice and dust.
I'm no expert but probably not because eventually they'll get eaten as nature's way of stopping a population get too big (the food chain)