I dont think it does, it does. Even with completely normal lighting. why do YOU think its doing that?
Edit: I just tried to take a picture, normal room lighting, shutter speed 1/4000 ISO at 200 and the photo is so dark I can barely make out an outline.
you need to go back to Digital-Photography-School.com and read those lessons because you should be able to answer that question if you read them.
Each element of the EXPOSURE triangle (that word should be a BIG hint) controls light. How much light comes in or doesn't come into the lens.
Here's my basics for beginners on the exposure triangle: Your camera is like an eyeball. The shutter is the eye lids that open and close. The iris is the aperture and the retina is the sensor.
Shutter speed is like blinking your eye. If it is open for a long time a lot of light reaches the sensor. If it opens and closes very fast less light gets through it. Very slow shutter=lots of light. Shutter speed is a written as a fraction so if you are shooting at 1/40 of a second you are shooting for a WHOLE lot longer than 1/4000 of a second. Very fast shutter=little light. Shutter controls blur in that if it is open for a long time your subject or even your hand holding the camera can move. That movement is recorded on the sensor as blur.
Rule of thumb for shutter:
To hand hold your camera for STILL LIFE without seeing the shake of your hand the shutter needs to be equal to or greater than the focal length of your lens, but not less than 1/80.
To shoot a live but VERY still subject your shutter must be no slower than 1/125
To shoot a moving subject such as a child your shutter must be about 1/250 or higher.
To shoot a fast moving subject (running) you are looking at a shutter of 1/500 or more.
To shoot a race car you are looking at that shutter of 1/4000
Aperture is the blades of the lens. It is easier to think about what % of CLOSED they are when you read the numbers. F/1.8 would only be a little bit closed whereas f/5.6 would be more closed. A wide aperture is a low number and a small aperture is a high number.
If your iris is wide open it lets in a lot of light. if it is closed or stopped down it lets only a little light come through
Aperture also controls Depth of Field (DOF) or depth of focus. DOF is how much of an image is in focus front to back. Think about when you can't see something. You squint to make that opening smaller so more is in focus. So a smaller aperture (higher number) is going to make more things sharp. A wide aperture (low number) will have less things in focus.
A good rule to start by is that your aperture has to be equal to or greater than the subjects in your image. It has no scientific bearing, just happens to work pretty well.
ISO is how sensitive your sensor (retina) is to light. If it is a low number it's only a little sensitive. You need a lot of light to get exposure. If it is a high number it needs less light to get proper exposure.
ISO also controls noise. The higher the ISO the more prone you are to getting noise in your image. We've already had a discussion about ISO and hopefully you have gotten the jist of it from that. You want to use the lowest possible ISO that will allow you to get proper exposure. Do not underexpose for the sake of using a lower ISO, it's just going to cause you more problems.
Now you have to balance all 3 of those things. It sounds complicated, but really it's not.
First you have to decide what your priorities are. You were shooting a toddler. He was trapped so he's not running, but he probably is squirmy. You have to stop that motion. You NEED a shutter of 1/250. He's the only subject in your image so your lowest Aperture is fine and will allow you to get the most light in the lens you possibly can. You are probably limited with your lens to a max of f/3.5 if you do not zoom at all, so that's the best you can do. Your last resort to get exposure is to raise the ISO until you can get proper exposure.
What proper exposure is and how your camera lies (not really) to you is a whole other post.