IB Biology · Theme B

Form
and Function

The shape of life. Why every molecule, every cell and every organ is built the way it is — because structure determines what it can do.

10Topics
122Sub-topics
163Key terms
4Levels of organisation
B
Theme B · Four levels of organisation

From molecules to ecosystems.

IB Biology organises each theme across four scales — molecules, cells, organisms, ecosystems. Browse below.

B1Molecules

2 topics
B1.1

Carbohydrates and Lipids

13 sub-topics · 36 key terms

B1.1Theme B
B1.2

Proteins

12 sub-topics · 12 key terms

B1.2Theme B

B2Cells

3 topics
B2.1

Membranes and Membrane Transport

16 sub-topics · 29 key terms

B2.1Theme B
B2.2

Organelles and Compartmentalization

9 sub-topics · 14 key terms

B2.2Theme B
B2.3

Cell Specialization

10 sub-topics · 18 key terms

B2.3Theme B

B3Organisms

3 topics
B3.1

Gas Exchange

13 sub-topics · 40 key terms

B3.1Theme B
B3.2

Transport

18 sub-topics · 14 key terms

B3.2Theme B
HL only

Muscle and Motility

10 sub-topics · 0 key terms

B3.3Theme B

B4Ecosystems

2 topics
B4.1

Adaptation to Environment

8 sub-topics · 0 key terms

B4.1Theme B
B4.2

Ecological Niches

13 sub-topics · 0 key terms

B4.2Theme B