I've made a few corrections for capitalization, comma splices, and awkward or ambiguous phrasing. But I think it might be better to sit down with your teacher before you submit this and ask him or her for some more in-depth guidance.
A phobia is a significant fear of a certain living thing, object, or situation that causes someone to feel danger. This is a part of our DNA, as something that stays with human beings for our survival. Most phobias trigger our flight or fight instincts that used to keep us alive; however, in modern society, these phobias frequently overwhelm us when there is no real danger.
Why do we have fears? Humans are animals with urges, and we are wired to respond to stimuli and threats as our genetic ancestors did. Some phobias are part of a larger disorder, such as anxiety. We are adapted for survival in ways that no longer are relevant. We may have commonly feared fire until we learned how to control. Therefore, our common fear of fires went away to some extent. I say “common,” because when we are born, we fear most things, but when we grow up around certain things, we become used to them. That’s why we are not scared of cars, but we are scared of monsters because they are shown to us in a fearful manner.
In conclusion phobias are something we evolve and grow up with. We create some phobias. And we get rid of some phobias by using self-confidence, exposure therapy, and relaxation. Phobias affect all of us in different ways, but they still affect all seven billion of us.