You probably can't distinguish them on Duolingo, but I believe that in real life, 'ist' would be very short and unstressed, said with a lower pitch than the subject ('er', in this case); while 'isst' would receive a slightly stronger stress than the subject. Of course, this is only true for simple factual statements, and, as in English, practically any word in the sentence could receive a stronger stress in order to emphasize something or show a contrast. Can any native speakers confirm this?
Edit: I just noticed that mizinamo's response to R.White's question below already explains this, but I'll keep what I wrote, since it's in response to a currently more highly-voted question, and therefore easier to see.
"ist" tends to be less stressed and "isst" tends to be a bit more stressed, but there are sentences where either of them could be stressed or unstressed depending on what you are emphasising.
And if you ignore sentence stress, the words themselves sound completely identical.
It's a bit like trying to distinguish between "She dyed" and "She died", or "They raised a house" and "They razed a house".
Only the ones with the big numbers :) Level 6 or less is more "tasted" - I wouldn't call it even beginner level.
Missing: Japanese, Greek, Slovak, Cornish, Klingon.
I'm not fluent in all of them, but those are the ones I can at least do simple tourist conversation in.
Nouns have an inherent gender; the gender does not depend on whether it is eating something or being eaten, whether it is being eaten by a man, a woman, an animal, or a group of intelligent towels. (If I, a man, love Mary, a woman, I don't say "I love him" with masculine "him" because the person loving is masculine!)
And the gender is there for historical reasons -- we say eine Banane, feminine gender, because our parents did so, and their parents, and so on.
There's usually no good "reason" one can point to for a given noun having a certain gender.
That's why you have to learn the gender of a noun along with the noun itself (and with the plural) -- as you can't usually guess those things from the shape or meaning of the noun.
So I thought it was "He is eating a banana."
Yes, that's also a perfectly fine translation.
It told me I was wrong
Do you have a screenshot of Duo rejecting that sentence? Then perhaps we can tell what might have happened.
Did you have a listening exercise, perhaps, instead of a translation exercise?
is there a seperate way of communicating a present tense chow down?
No. If the time is important, you can add an adverb such as gerade "right now", but there's no special verb form for "right now" versus "in general".