It's quite simple. We are a question and answers site on Biology. We are one of the sites within the larger SE network. We dwarf against sites like StackOverflow in terms of mass. But also within the scientific subclass, we are small compared to Physics and Chemistry.
We mainly thrive because of questions on Genetics, and related disciplines within the Molecular Biology. Questions on Evolution are relatively many too, although stuff like Neuroscience does get some attention too.
The downvoting - the voting system is a core component of the SE network (see here). In a nut shell, and imo, it's all about getting the good posts a good score, and the lesser quality ones low scores. It's mainly a system devoted to rank answers from better to worse. However, question voting is great too, as it brings (bad) questions in the spot light. This is important for moderators and other high-rep users who do not have the time to sift through all the questions, but rather look at the dash board for the odd posts out.
It seems you are one of many that takes downvotes personally. Don't. It's part of the system. To be blunt, like it, or leave it.
Now, in fact, in my opinion downvoting is used way too sparsely. It's a strong motivator to improve posts and further, posts with downvotes tend to be removed by the bot, which comes in handy especially for sites still in beta that have to deal with fields of dead and decaying questions that wreck havoc on site stats (Death Valley). As mods can't close-vote without using the mod-hammer, mods tend to downvote a lot. It's not to be mean, it's part of the system.