Animals and plants were created by god for us to live with and to care for, but also to eat and to harvest from. Humans are above the animal level, and have souls, and have dominion over the entire earth. There can be different theories and answers based on different beliefs of evolution, but that's a whole other argument
Plants and animals were here before humans appeared on earth . . . .. . . .. . .. . .. . . . .. . . .. . . . . . . . . .. . . . . . . . . . . . . . . . .
Going by conventional theory of evolution, animals and plants have existed way before humans came into existence. Surely, with our apparently superior intelligence, it would make sense to subjugate any life form that is inferior in that respect since that they make avail opportunities for us to assert our dominance and be king of the hill. But, to say that animals and plants are reserved for us humans would be unfounded, egregious species elitism, as our advantages only allow us to trump over brute strength, environmental advantage, blistering speeds, sharp teeth, is that there are options where with our limited resources can achieve, and so, in a situation where such options are nonexistent, we become prey, be it for the animal/plant or nature (from the tsunami waves that smashes the head onto concrete ground, to the bacteria that decomposes our bodies in the absence of plants/animals) in general.
Another way to look at this question is the circle of life- while we force extinction unto some species, we allow the preservation of some, either for the reasons we lack the ability/resources to completely extinguish them (cockroaches and rats) or we find their existence essential to ours (cows and pigs), at the end of the day, we need them to survive as they, to some extent (again, depending on the situation), depend on us to survive, thanks to the development of the human race in ridding ourselves of our physical weaknesses to achieve our species' superiority. A barren world where no animal/plant exist, in all likelihood with today's advances in food production, we cannot exist; a world lush with flora and fauna can, potentially, exist without us.
Scientists do not invent anything, they merely discover the truth that already exists in nature, and the relationships between elements and components that are compatible by nature such as to form combinations like the iPhone; that is to say, the most intelligent of us, who pursue answers for the sake of those answers alone, not necessary for monetary profit or some other indirect impetus, are simply slaves, or in other words, participants to the nature around us- the Earth and beyond-, like the animals and the plants.
We are just put in the middle of the animals and plants, and since then, we have been interacting with them as they have been interacting with us. To question if our resources' role is completely servile, is like asking do Africans exist to serve the needs of the Caucasians, before slavery had been abolished? Just because the Caucasians were (arguably, are) more technologically advanced as a society in many ways, such as they benefit from a higher quality of living (perceived; being that the wolf does not envy us for our reality TV brothels and social media obsessions), the Africans do not exist for the sake of the Caucasians- it was just a matter of convenience during a time where hands were needed and were readily acquired at a very cheap price.