The largest common entry code in the country. One CAO code, twenty six different degrees at the end of it, and two separate decisions along the way that most applicants do not know are coming.
When you put DN200 on the CAO form you also pick a stream from a drop down: Explore Multiple Streams, Biological/Biomedical/Biomolecular, Earth and Environmental, Chemistry, Mathematics, Physics, or Science, Mathematics and Education. UCD is explicit that everybody is applying to the same course regardless of the stream they picked, and that you can change your mind when you arrive. DN200 can only appear once on your form.
The stream is not your degree. It decides which core modules you are registered to in first year, and those modules decide which subjects are open to you in second year. So the stream is a starting position with consequences, rather than either a commitment or a formality.
Twelve modules across the year, six each trimester, and a maximum of eight in any one trimester. Eleven of the twelve have to come from within Science. That leaves one free elective, in the spring only, which can be anything in UCD: a language, philosophy, psychology, a Discovery module.
Twenty to thirty hours a week of scheduled class time depending on your modules, including labs and tutorials. Lab and tutorial slots are allocated automatically after you register online. Labs run at around twenty four to thirty two students.
SCI10010 is core for every stream, whichever
one you pick.
| Stream | Stage 1 core |
|---|---|
| Biological, Biomedical, Biomolecular | SCI10010 BIOL10110 CHEM10050 MATH10290 MATH10310 |
| Earth and Environmental, Environmental Biology | SCI10010 BIOL10110 CHEM10050 MATH10290 MATH10310 |
| Earth and Environmental, Geology | SCI10010, GEOL10020 or GEOL10060, MATH10290 MATH10310 |
| Chemistry, including Medicinal, Sustainable and Biophysical | SCI10010 CHEM10050 MATH10290 MATH10310 |
| Mathematics, including Applied, Financial and Statistics | SCI10010 ACM10060 MATH10340 MATH10350 STAT10060 |
| Physics, including Theoretical and Astronomy and Space | SCI10010 PHYC10080 MATH10340 MATH10350 or MATH10400 |
| Science, Mathematics and Education | Varies by specialism. All five include SCI10010 MATH10350 MATH10410, plus MATH10340 or MATH10290, and STAT10060 |
| Explore Multiple Streams | No separate list. You must meet the core requirements for at least two degree subjects. |
A code and a title tell a student nothing. This is what you would actually be doing in each one, and where the same subject comes in two versions, which is which.
SCI10010A group project. You pick a scientific problem, read the actual literature on it and write a review. The point is not the topic, it is learning to work in a team, find sources, and write like a scientist rather than like somebody answering an exam question. Core for every stream.
This is the most consequential choice in first year and it looks like paperwork. There are two calculus modules and two linear algebra modules. The pairs are not equivalent, and taking the lighter pair quietly closes Maths, Physics and Education at the end of the year.
MATH10290Vectors, matrices and systems of equations, pitched at biology, chemistry and earth science students. The lighter of the two.
MATH10340The same territory at the level a maths or physics degree needs, with applications worked through properly. Take this one instead of MATH10290 if there is any chance you want Maths, Physics or an Education combination.
MATH10310Differentiation and integration for biological, chemical and earth science students. The lighter of the two.
MATH10350The demanding counterpart. The other half of the substitution. MATH10340 and MATH10350 together are what keep the quantitative doors open.
MATH00010A bridging module for students who did not get O1 or H5 in Leaving Certificate Maths. You take it in the first trimester, and you need an A minus in it. If that applies to you, read the note below carefully.
MATH10400An online module in the summer trimester, taken instead of MATH10350 by students who had to sit MATH00010. In other words, weaker Leaving Certificate Maths does not close off the mathematical sciences, but it does cost you a summer.
MATH10410Educational theory on how maths and science are learned and taught, plus public engagement and science communication. There is an optional primary school observation placement. Core for all five Education combinations, and the module that tells you early whether teaching is genuinely for you.
STAT10060Statistical modelling and data analysis for scientists. Worth taking seriously even if statistics is not your plan: it is the module whose skills turn up in every research job on this list.
ACM10060Differential equations and what they are used for. Required in Stage 1 for Theoretical Physics, and if you miss it you have to take ACM10100 in Stage 2 instead.
ACM10080Mechanics and mathematical methods. This is the conditional core for anybody who did not get H5 in Leaving Certificate Applied Maths, and you need it or the Leaving Certificate grade to study any Physics subject.
ACM10100The same mathematics pointed at economic and financial problems. The Stage 2 substitute for ACM10060.
PHYC10070Newton's laws, work and energy, sound, light, heat, electricity and magnetism. For students who did not do Leaving Certificate Physics at H5 or above. Also the module that keeps Neuroscience and Physiology open, which is not obvious from the title and catches people out.
PHYC10080Special relativity and the beginnings of quantum mechanics, applied to atoms, nuclei and particles. Required in Stage 1 to study any Physics subject in Stage 2. It is the interesting one and it is also the gate.
PHYC10050The solar system, planets around other stars, the sun, how stars live and die, black holes and the Big Bang. Needed in Stage 1 or Stage 2 for Physics with Astronomy and Space Science.
BIOL10110How cells are built and how they work, and the fundamentals of genetics. The foundation module for the ten biological subjects.
CHEM10050Organic chemistry, meaning the chemistry of carbon compounds, and how it applies in living things. Core for biology and chemistry streams alike.
BMOL10030The molecular basis of disease, across the nervous system, the heart and circulation, infection, hormones and immunity, including risk factors and current treatments. One of the three programme cores you need two of to keep the biological subjects open, and the most directly medical module available in first year.
BIOL10130UCD does not publish a description we could read for this one. It is one of the three programme cores, so what matters for planning is that it counts.
BIOL10140Description not published anywhere we could read. Also one of the three programme cores.
GEOL10060A broad introduction to the Earth as a system and to earth science as a subject.
GEOL10020How minerals and igneous, sedimentary and metamorphic rocks form, and why those materials matter economically and environmentally. Either this or GEOL10060 keeps Geology open.
GEOL10030Intensive, mostly outdoors, and largely residential. Strongly recommended in Stage 1 for a practical reason rather than an academic one: it clashes with Stage 2 Geology, so if you do not take it now you may not get to take it at all.
Descriptions above are shortened and rewritten in plain English from UCD's official module descriptors. The official wording, learning outcomes and assessment breakdown for any UCD module are worth reading before you register, and a student can look up any code directly.
This is the part that catches people. A module you skip in first year can quietly close a degree subject two years later, and nothing announces it at the time. UCD puts it drily: if you defer too many programme cores in Stage 1, this may limit some of your options in Stage 2.
Below is what has to be taken in Stage 1 to keep each family of subjects available. A student who is genuinely undecided should read the Maths row first, because the Maths modules are the main lever for keeping several doors open at once.
| To keep this open | You need in Stage 1 |
|---|---|
| Genetics, and the nine other biological subjects | SCI10010 BIOL10110 CHEM10050 MATH10290 MATH10310, plus at least two of BIOL10130 BIOL10140 BMOL10030 |
| Any Physics subject | PHYC10080, which itself needs PHYC10070 or H5 Leaving Cert Physics. You also need ACM10080 or H5 Applied Maths. |
| Theoretical Physics | ACM10060 in Stage 1. Miss it and ACM10100 has to replace it in Stage 2. |
| Physics with Astronomy and Space Science | PHYC10050, in Stage 1 or Stage 2 |
| Geology | GEOL10060 or GEOL10020. GEOL10030 is strongly recommended in Stage 1 because it clashes with Stage 2 Geology. |
| Neuroscience or Physiology | Leaving Cert Physics, or PHYC10070 in Stage 1 |
| Any Mathematical Sciences degree | Without O1/H5 Leaving Cert Maths you must take MATH00010 and get an A minus, then MATH10400 in the summer trimester in place of MATH10350. |
| Keeping Maths, Physics and Education open together | Take MATH10340 rather than MATH10290, and MATH10350 rather than MATH10310. This is the single most useful substitution for an undecided student. |
Check these against the current UCD Science Stage 1 Guide before acting on them. Module codes change, and the copy of the guide available to us self identified as 2023 to 2024 even where it was indexed as current. The principle holds year to year. The specific codes may not.
Most students expect one. There are two, two years apart, and only the second one is competitive.
The selection window for 2026 to 2027 is 20 to 24 July. UCD states plainly that this is not competitive for anybody who has progressed to Stage 2. You get any subject whose Stage 1 core modules you took, which is why the table above matters.
This is your degree. Stages 3 and 4 are spent on it. For most subjects you simply choose. For three of them, you apply and wait.
Three majors are competitive: Neuroscience, Pharmacology and Physiology.
Places are awarded on Stage 2 GPA, decided after both Stage 2 trimesters. Some majors cap Stage 3 at forty places. If one of those three is the reason a student is choosing DN200, they need to know that before they apply, because it is not a decision they get to make. It is one made about them after two years of work.
There is a further trap in the combinations. Taking Pharmacology with Neuroscience forces you to carry a third subject, and adding Physiology forces a fourth. The three subjects that are hardest to get are also the three that cost you the most room to manoeuvre.
Two pairs cannot be combined at all: Physiology with Plant Biology, and
Statistics with Theoretical Physics. And you must keep at least two degree subjects
alive through Stage 2, with Geology the only single subject exception. Medicinal
Chemistry additionally requires CHEM20080 and CHEM20140 by
the end of Stage 2.
These are not twenty six versions of the same thing. The interest profile behind Statistics is not the interest profile behind Zoology, and a student who enjoys one may well not enjoy the other. The letters beside each subject are its Holland interest code: I investigative, R realistic, A artistic, S social, E enterprising, C conventional.
Research and biotech, clinical genetics in the health service, plant and animal breeding, and the standard route into a genetics or genomics PhD. Strong demand from the pharmaceutical sector here.
Laboratory research, biotech and pharma process roles, and a common feeder into graduate medicine and research masters.
Drug discovery, quality control and analytical roles across the Irish pharma cluster, and research. One of the broadest of the biological subjects.
Pharmaceutical and food manufacturing, public health laboratories, environmental testing, and infection research. Consistently one of the most employable science degrees in Ireland.
Agri-food research, crop science, conservation and Teagasc-type roles. Smaller field, and the climate and food security work in it is growing.
Ecology and conservation, wildlife and fisheries bodies, zoos and aquaria, environmental consultancy. Field-heavy, and much of the work is short contract early on.
Environmental consultancy, EPA and local authority work, ecological impact assessment. Steady demand from planning and infrastructure.
Research, neuroimaging and clinical research roles, and a common route into graduate medicine or a research PhD. Awarded on Stage 2 GPA.
Drug development, clinical trials, regulatory affairs and medical science liaison work. Very well aligned to the Irish pharmaceutical industry. Awarded on Stage 2 GPA.
Clinical measurement and physiology roles in hospitals, sports and exercise science, and graduate entry to medicine and allied health. Awarded on Stage 2 GPA.
Analytical and process chemistry across pharma, food and materials, plus research. The broadest of the four and the easiest to move around within.
Drug discovery and design, the most directly pharma-facing of the chemistry subjects. Note the two extra Stage 2 modules it requires.
Structural biology, instrumentation and analytical technique work. Sits between chemistry and physics and suits somebody who likes both.
Green chemistry and process improvement, environmental monitoring, and the sustainability and compliance roles that manufacturers are hiring into now.
Semiconductors and medical device manufacturing, instrumentation, data and modelling roles, teaching, and research. A physics degree is read by employers as evidence of quantitative ability rather than as training for one job.
Research, and heavily into quantitative finance, data science and modelling. Mathematically the most demanding subject in DN200.
Space sector work, which now genuinely exists in Ireland through ESA contracts, plus instrumentation, data and research.
Finance, actuarial work, data science, teaching and research. One of the most portable degrees on this list.
Modelling and simulation across engineering, climate, epidemiology and finance. The subject for somebody who wants the maths pointed at something.
Data analysis and data science, clinical trials, actuarial and insurance work, and the Central Statistics Office. Very strong employment record, and often overlooked by students who have not met it as a subject.
Geotechnical and site investigation work for construction and infrastructure, groundwater and environmental consultancy, minerals, and increasingly geothermal energy. Field-based, and the only DN200 subject that can be taken singly.
Five combinations, all leading to registration as a post-primary teacher of Maths and one other subject. Different work from the rest of the list, and the interest profile says so: these are the only Social-led subjects in DN200.
Post-primary teaching of Biology and Maths, with the teaching qualification built in rather than added afterwards.
Post-primary teaching of Chemistry and Maths. Both are subjects schools struggle to staff.
Post-primary teaching of Physics and Maths, and the single hardest combination for schools to recruit.
Post-primary teaching of Applied Maths and Maths.
Post-primary teaching of Computer Science and Maths, and a route into a subject that is still establishing itself in schools.
Ask at the open day: what Stage 1 modules do I need for the subject I have in mind, how many students applied for each competitive major last year and how many got it, and what happens to a student who does not.
Checked against UCD on 24 August 2026. Points are 2025 entry, the most recent published. Sources: the UCD Science prospective and current student pages, the UCD Science Stage 1 and Stage 2 guides, the UCD Science Pre Stage 2 Advisory of February 2026, which is where the three competitive majors are named, and myUCD.
Two cautions. The copy of the Stage 1 Guide available to us self identified as 2023 to 2024 even where it was indexed as current, so treat the module codes as indicative and check the current guide before relying on them. The principle, that Stage 1 choices gate Stage 2 subjects, does not change year to year.
A figure circulates that 98 per cent of DN200 students get their first choice of Stage 3 major. It is deliberately not on this page: it does not appear on any UCD page we could read, and a reassuring number nobody can stand over is worse than no number at all. If UCD publishes it, we will add it and cite it.