Seeds and spores are both reproductive organs in the plant kingdom. While they both serve the same purpose, they are very different in terms of how they accomplish this purpose. One of the main ways that seeds and spores differ is that spores are how bacteria, plants, fungi and algae reproduce. Seeds are the primary method that flowering plants reproduce.
One of the easiest ways to distinguish a seed from a spore is the size. If you are able to see it with your naked eye, it is a seed. Spores are microscopic. There are two types of spores. Homosporous plants produce spores that are identical in size, while heterosporous plants produce a larger female spore and smaller male spore.
Seeds are large organisms with multiple layers. Inside the seed is a small ecosystem with everything the young plant needs in order to sustain itself. It is fertilized and contains food and protection, giving it the ability to survive and thrive even in harsh circumstances. A spore is a singular organism and can survive for a long period of time, no matter the circumstance.
In flowering plants, you can find seeds in the fruits or in the flowers. Spores are usually found under the leaves of the fern, fungi or moss.
Seeds and spores both need water to grow. However, a seed can sprout without the presence of an excessive amount of water. Spores needs marshy, dark, wet conditions to be able to sprout.