I often get asked about what a student should concentrate on if they want to become a zoologist. I find this a very tricky question, because zoology is a very wide discipline, with subfields of it often not having much to do with each other. The lists here reflect my own bias as someone interested only in systematics and evolution, and ecology (the latter unrelated to the previous two).
Note that I’m not including typical obligatory courses – evolution, ecology, biochem, genetics, etc. Just courses that are usually (in my experience) offered as optional or specialisation modules, or that you might not consider as essential. It’s aimed at first-year bio students, but I see no reason why high-school students can’t begin their studies early (as I did, but mostly because I hated school, not out of ambition).
The list is not comprehensive; if you have any other ideas, comment/e-mail and I’ll consider.
Physics: I cannot stress this enough. A knowledge of classical physics goes a long way towards making the various contrivances that animals have more understandable. Optics for the more complex visual systems; mechanics for locomotion types and biomechanics; waves for audio systems. You don’t have to go the mathematical route (I don’t), just an intuitive understanding of such things.
Organismic Biology: Take as many as you can. Even if it’s not your taxon of interest, you should endeavour to have as wide a grasp of the animal kingdom as possible. Usually, an invertebrate zoology course is more than enough for this (vertebrate zoology is limited by the fact that they have no diversity, but it also doesn’t harm to take one); but if you find specialised ones (biology of mammals, of insects, of Crustacea, etc.), all the better. Also take as many courses on individual systems (there will often be one on nervous systems, for example).
Cladistics: You must learn about cladistics. You will definitely learn about molecular phylogenetics since it’s in vogue, but a knowledge of classical methods will be much more useful to you. I guarantee it. *bias alert*
Palaeozoology: Don’t even think you can study modern animals without knowing their evolutionary history. For general zoology, a simple evolution of animals series of lectures is enough, or evolution of mammals, insects, whatever your taxon of interest is.
Neuroethology: A specialised course in this is critical; while it may be touched on in a general ethology or ecology course, neuroethology is, in my opinion, a field that anyone interested in animal ecology should have a grasp of – how animals perceive their environment and react to it.
Zoogeography: These are specialised courses in animal biogeography and dispersal. Take them.
Ecology of xyz: Where xyz is a geographical area. Take as many as you can; similar to the organismic biology, you should strive to know as many different ecosystems as possible, to get different insights into a system you will study in the future (I know that my experiences from Germany are pretty useful to me here in Cyprus, even though the ecosystems are very different).
Statistics: Goes without saying. Don’t just take the typical “stats for biologists” courses. Dig deeper, the effort is worth it.
Conservation: Even if conservation isn’t your interest, conservation biologists often have some good ideas and are the most well-versed people in the specific ecology of their animal groups/ecosystems. So I recommend conservation biology courses, because the amount of knowledge you get is really quite valuable.
Programming: Learn some programming languages. R, Python, Perl, and/or C are my choices. They will make your life easier. Even if you can’t learn a new language, at least know how to work a command line.
Maths: Many systematists fall into the trap of making a checklist and copying the methods from papers, without thinking of what they’re doing. This is the primary reason for a paper being full of shit. You have to understand the algorithms, why you’re doing this analysis instead of that, what a bootstrap really is, etc. Or else you can never ever hope to properly interpret your trees.
History: While the history of biology is interesting, thats not what I’m talking about. It’s more the methods historians of biology use. This is so you avoid synonymies and can identify when a hypothesis you propose was actually proposed by Herpaderp in 1947 and you just brought it back from the dead. Related with this is a good knowledge of libraries and archives, and the ability to conduct searches in ancient documents written on paper (how quaint!). The ability to understand written Western European languages is also useful. Many ancient texts were written in Latin, French, Italian, even Spanish. You don’t have to be fluent in the language, just be able to parse the sentences.
Taxonomy: Some will scold me for mixing these two together, but I must recommend a course in taxonomic principles and rules. At the very least, it will teach you how to get a proper taxon sampling and how to properly describe any new species your systematic analyses might bring up.
Morphology: Just to counteract the molecular phylogenetics you will most likely have shovelled down your throat. Morphological phylogenetics is regaining ground nowadays, and we need to push for it to become commonplace again. Morphometrics is also recommended.
Palaeontology: Confucius say, “Systematist who ignore fossil record is a moron.” True story. As a systematist, your job is to figure out the evolutionary history of your taxon, and the only tangible evidence of it is the fossil record. Take a palaeontology course to find out all the pitfalls and dangers of palaeontological data (biases, etc.) and you will be much better equipped to do your job; make sure basic geology is included (often the first 2 lectures are basic geology and sedimentology). Historical Geology would be a natural companion, to know in what kind of environment the animals were living in.
Palaeobiology: This is a subdiscipline of palaeontology, the one that investigates evolutionary patterns in the fossil record (e.g. those species curves through time). I recommend it so that you can integrate palaeobiological methods with your analysis; the potential is then there to not only uncover the history and relationships of your taxa, but also to say something about evolution in general.