Leaves have evolved at least twice 🤔

The correct answer is, "We don't know son. You could become a paleo-biologist and be the one to figure it out!"

Hm, I was intrigued and looked at the evolution of plants. This made me realize how paraphyletic gymnosperms and angiosperms really are! We just don't know how angiosperms exactly started out and if they might be monophyletic. And in case of gymnosperms, they are consisting of many very different plant groups that evolved independently.

So gymnosperms were probably the first plants to evolve seeds and they "include conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae". That doesn't really give an answer but that's the best we can do?

It was previously widely accepted that the gymnosperms originated in the Late Carboniferous period, replacing the lycopsid rainforests of the tropical region, but more recent phylogenetic evidence indicates that they diverged from the ancestors of angiosperms during the Early Carboniferous.[12][13] The radiation of gymnosperms during the late Carboniferous appears to have resulted from a whole genome duplication event around 319 million years ago.[14] Early characteristics of seed plants are evident in fossil progymnosperms of the late Devonian period around 383 million years ago. It has been suggested that during the mid-Mesozoic era, pollination of some extinct groups of gymnosperms was by extinct species of scorpionflies that had specialized proboscis for feeding on pollination drops. The scorpionflies likely engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms.[15][16] Evidence has also been found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatid lacewings, a now-extinct family with members which (in an example of convergent evolution) resembled the modern butterflies that arose far later.

Wow, so there was already pollination going on before flowering plants even existed??? By scorpionflies who's ancestors I frequently see? And there were butterfly-like insects long before real butterflies existed? Look how butterfly-like they were! This is wild!!

Integumented indehiscent mega sporangium with one functional megaspore?

Once.

But once is all you need.

Leaves evolved more times if you include blades of algae

At least once

The original comic was drawn by Chris Halberk, if I'm not mistaken.

Depends on what you mean by leaf, some plants has phylloclades, which is the widened stem to look like leaves. You can see this in acacia trees, you see those tiny leaflets those are the actual leaves on the stem

Ask your school teacher tomorrow.

Which came first, the plant or the seed?