Structural Organisation in Plants and Animals
Domain 2 tests plant morphology and anatomy and the four animal tissue types. Expect questions on root, stem and leaf modifications, tissue systems, vascular bundle arrangement and tissue identification.
Core rules
- Meristematic tissues are apical, lateral or intercalary; permanent tissues are simple (parenchyma, collenchyma, sclerenchyma) or complex (xylem, phloem).
- Dicot stems usually have vascular bundles in a ring, conjoint, collateral and open; monocot stems have scattered bundles and no cambium. Dicot roots have two to four xylem poles; monocot roots usually have more.
- Leaf anatomy: monocot leaves are isobilateral with parallel venation; dicot leaves are dorsiventral with reticulate venation.
- Animal tissues: epithelial (covering/lining), connective (blood, bone, cartilage, adipose), muscular (skeletal, smooth, cardiac) and nervous. Blood is connective tissue because cells sit in a matrix.
- Organs combine tissues; anatomy links structure to function, such as xylem for water transport and alveoli for gas exchange.
Worked example
A transverse section shows scattered vascular bundles, no cambium and a large pith. Identify the organ. Scattered bundles indicate a monocot stem, not a dicot stem (ring) or root (xylem in a central cylinder). No cambium means no secondary growth. The pith confirms stem, because a monocot root would show a vascular cylinder with many xylem poles.
Traps
- Calling blood epithelial tissue; it is connective.
- Saying monocot stems have open bundles; they are closed.
- Confusing collenchyma (living, thickened corners) with sclerenchyma (dead, lignified).
- Treating intercalary meristem as lateral; it occurs at leaf bases and internodes.