UniGeniusIB Biology

IB Biology

Biology syllabus: SL and HL

Four themes, 40 topics: 180 hours of content at HL against 110 at SL.

Your level
Weeks before your first biology paper
Hours a week for biology
Theme A: Unity and diversity 19 h
Theme B: Form and function 26 h
Theme C: Interaction and interdependence 31 h
Theme D: Continuity and change 34 h

26 weeks at SL, 104 hours in all

Start with Theme D

Continuity and change: 29.7 of your hours. It is 34 of the 110 hours of SL syllabus content, 31%.

Hours per theme
ThemeYour hoursShare of the syllabus
Theme D: Continuity and change29.731%
Theme C: Interaction and interdependence27.128%
Theme B: Form and function22.724%
Theme A: Unity and diversity16.617%

Week by week

  1. Week 1Theme D: Continuity and change
  2. Week 2Theme D: Continuity and change
  3. Week 3Theme D: Continuity and change
  4. Week 4Theme D: Continuity and change
  5. Week 5Theme D: Continuity and change
  6. Week 6Theme D: Continuity and change
  7. Week 7Theme D: Continuity and change
  8. Week 8Theme D: Continuity and change, Theme C: Interaction and interdependence
  9. Week 9Theme C: Interaction and interdependence
  10. Week 10Theme C: Interaction and interdependence
  11. Week 11Theme C: Interaction and interdependence
  12. Week 12Theme C: Interaction and interdependence
  13. Week 13Theme C: Interaction and interdependence
  14. Week 14Theme C: Interaction and interdependence
  15. Week 15Theme C: Interaction and interdependence, Theme B: Form and function
  16. Week 16Theme B: Form and function
  17. Week 17Theme B: Form and function
  18. Week 18Theme B: Form and function
  19. Week 19Theme B: Form and function
  20. Week 20Theme B: Form and function, Theme A: Unity and diversity
  21. Week 21Theme A: Unity and diversity
  22. Week 22Theme A: Unity and diversity
  23. Week 23Theme A: Unity and diversity
  24. Week 24Theme A: Unity and diversity
  25. Week 25Timed SL Paper 1 practice, then review every miss
  26. Week 26Timed SL Paper 1 practice, then review every miss

Check your themes with the free test

Paper 1Paper 1A multiple choice and Paper 1B data-based questions: 1.5 hours at SL, 2 hours at HL, 36%
Paper 2Data-based, short-answer and extended-response questions: 1.5 hours at SL, 2.5 hours at HL, 44%
Scientific investigationYour own investigation, a report of at most 3,000 words: 20%
Teaching hours150 at SL and 240 at HL, as for every Diploma subject

What HL adds

Six HL-only topics (origins of cells, viruses, classification and cladistics, muscle and motility, chemical signalling and gene expression) and more depth in many shared topics.

The practical side

40 hours at SL, 60 at HL, including the collaborative sciences project and the scientific investigation (10 hours).

Try 2 questions

Question 1
WXYZ
The diagram shows a bacterial cell. Which labelled structure is the site of protein synthesis?
Question 2
Line graph of initial rate (arbitrary units) against temperature: 10 °C: 6, 20 °C: 12, 30 °C: 22, 40 °C: 30, 50 °C: 14, 60 °C: 2.Initial rate / arbitrary units. 10: Initial rate 6; 20: Initial rate 12; 30: Initial rate 22; 40: Initial rate 30; 50: Initial rate 14; 60: Initial rate 2Initial rate / arbitrary units01020301020304050606122230142Initial rateTemperature / °C
Chart values
CategoryInitial rate
106
2012
3022
4030
5014
602
The initial rate of an enzyme-catalysed reaction was measured at six temperatures, using fresh enzyme and substrate each time. Which explains the change in rate between 40 °C and 60 °C?

Next step

Take the free testTake the course tour

Questions people ask

What is the difference between IB Biology SL and HL?

HL has 180 hours of content against 110, six extra topics and longer papers: Paper 1 is 2 hours against 1.5, Paper 2 is 2.5 hours against 1.5.

When was the current biology syllabus first examined?

In 2025, after first teaching in August or September 2023.

Are there options in IB Biology?

No. Every student takes the four themes, with HL topics added at HL.