How would having larger seeds give a plant a better chance for survival?

Answer 1

I can think of a good example. I started two water plants from seed last summer. One was a lotus plant from a seed about the size of a very small grape. The sprout that emerged from it was pretty strong and survived being planted in clay soil and then submerged in water and subjected to heat fluctuations, wind, etc. On the other hand, the seed that I bought for water lilies were so small that I had to start several in order to get a couple to actually sprout, and then the sprouts were soooo delicate that I gave up on them. The larger seed/sprout, in other words, had a much better chance of survival in nature. The larger lotus seed was not only protected in a hard nut-like shell but it had a bigger storage of nutrients to give the seedling a "jump start".

Answer 2

Larger seeds should have more food stored inside to give the embryo a good start until the seedling is big enough to make its own food.