It can be kind of hard to tell from photos.
Your house plans (blueprints) would tell you for sure, presuming the house was built faithfully to the plans. You really should have a good look at the plans, or get somebody knowledgeable to look at this in person. Or both.
Do you know which direction the joists are running? Floor and ceiling joists will be perpendicular to the load bearing walls (or beams!), not parallel to them. If the joists pass across the top of the wall (or beam) unbroken, then the wall is possibly not load-bearing, depending on your joists, the length of the span after you remove the wall, and the load on the floor above.
If the ends of the joists are resting on the wall or beam, then it is definitely load-bearing.
if there isn't another floor above this one, and you have engineered, prefabricated trusses holding up your roof, this won't be load-bearing. The trusses are engineered to handle the load of the roof by themselves. If they aren't engineered trusses, that doesn't apply.
Is the long common wall of the living room/dining room/kitchen directly on top of (parallel with) the long wall downstairs, and is the opening between the dining and living rooms perpendicular to that long wall downstairs? It looks like the photos might be from different directions? If so, then the common wall with the kitchen is probably the load-bearing wall, and the opening between the living and dining rooms may or may not be, depending on how the joists are laid out.
But you really should look at the plans or get somebody knowledgeable to take a look in person.
I wouldn't trust a random individual on the internet to correctly identify bearing walls. There are general guidelines for identifying bearing walls, but many exceptions to the rules.
Get a competent person in your kitchen to look at the structure. From there, you can figure out the engineering.
Best Answer
It took me a while to figure our the drawing of the first floor are first floor and ceiling, not first floor and floor joists. (Is the first floor is a concrete slab?)
There's a 6x12 beam (triple 2x12) in the first floor ceiling supported at one end by the alcove wall.
Superimposing the top floor over the lower floor shows that above the wall with the alcove is a wall of the upstairs closet and above that a beam that's supporting the air conditioner.
So yeah, it's extremely structural.
It may be possible to fit a new beam (green) to carry the end of the 6x12 and connect them with a suitable hanger bracket, but you'll probably need an engineer to figure out what type of beam, and there will be a big hole in the ceiling to repair. The walls at either end of the beam will probably need to be strengthened too. Additionally the 6x12 is now spanning a greater distance and may also need to be upgraded.