Are you aware that plants and animals diverged very early in earth's evolutionary history?
For the1st 2 billion years, there were species from the Bacteria domain and Archaea domain. Both domains are unicellular organisms, with prokaryotic cells, hence these organisms are called collectively as prokaryotes.
Eukaryotic cells didn’t exist until around 1.6 billion years ago, with earlier eukaryotic organisms or eukaryotes being unicellular organisms
Multicellular organisms such as animals and plants didn’t evolve from earlier eukaryotes until later.
Before them were the earliest multicellular eukaryotes, that start appearing in fossil records in the Ediacaran period. Around mid to late Ediacaran, the earliest invertebrates (animals) appeared as primitive sponges and other extinct invertebrates.
Then a glaciation period cause climate change between the end of Ediacaran and start of Cambrian period, which resulted radiations and diversity of more multicellular invertebrates, which you know as the Cambrian Explosion. Marine Arthropoda, like trilobites began appearing in fossils in this period, are also invertebrates.
This Cambrian Explosion started around 542 million years ago, and lasted for 20 million years. Eventually the earliest vertebrates were earliest jawed fishes.
Land plants didn’t exist until after the Cambrian (Ordovician period, becoming more diverse in the Silurian period), but they evolve green algae. When the earliest green algae exist, I don’t know, you would need to ask someone more knowledgeable about the green algae and land vegetation.
What I do know about green algae, is that their cell have photosynthesis capability, like the land plants.
I also know that earlier vegetation did reproduce from seeds until Devonian period, and there were no evidence of flowering plants until 160 million years ago in the Mesozoic era.
Before plants had seed, primitive plants reproduce and propagate through spores. Some plants still exist today, reproduce through spores, like mosses, liverworts and hornworts being the most commonly seen today.
Anyway, you keep mentioning humans and oak trees. Although animals and plants have eukaryotic cells, their evolution are separately in their evolution as animals and plants, and I don’t have the knowledge to pinpoint WHEN and HOW the eukaryotes diversified into what form form the paths of animals and plants, but it definitely predated the Ediacaran period.
You remember I mentioned green algae, and that land plants evolved from them, I don’t know enough about WHEN green algae first exist, and WHAT they evolved from.
Perhaps algae that capable of photosynthesis, evolved from the prokaryotic Cyanobacteria species, because the Cyanobacteria were the first organisms capable of photosynthesis, and introduced free oxygen in the atmosphere, around 2.7-2.6 billion years ago.
