Structural Organisation in Animals and Plants: Tissues, Anatomy and Organ Systems
This domain tests tissue identification from descriptions, the anatomy of dicot and monocot organs, secondary growth, and the functional anatomy of the earthworm, cockroach and frog. Answers should name the tissue and justify the identification.
Plant tissues and anatomy
- Meristems: apical (height), lateral cambium (girth), intercalary (grass bases).
- Simple permanent tissues: parenchyma, collenchyma, sclerenchyma. Complex tissues: xylem (tracheids, vessels, fibres, parenchyma) and phloem (sieve tubes, companion cells, phloem fibres, parenchyma).
- Dicot stem: conjoint, collateral, open bundles in a ring, endarch xylem, collenchymatous hypodermis.
- Monocot stem: scattered, conjoint, closed bundles with no cambium and a sclerenchymatous hypodermis.
- Dicot root: radial bundles with two to four xylem arches (tetrarch), exarch xylem; monocot roots are polyarch.
- Secondary growth comes from the vascular cambium and cork cambium.
Animal tissues and organ systems
- Epithelia (squamous, cuboidal, columnar, ciliated), connective tissues (areolar, adipose, cartilage, bone, blood), muscle (skeletal, smooth, cardiac) and neural tissue.
- Cockroach: 10 pairs of spiracles, Malpighian tubules for excretion, crop and gizzard, hepatic caeca.
- Earthworm: closed circulation, nephridia for excretion, clitellum in segments 14 to 16.
- Frog: three-chambered heart, ureotelic, external fertilisation.
Worked example
A transverse section shows scattered vascular bundles, a sclerenchymatous hypodermis and no cambium. Scattered closed bundles exclude dicot stem and root, and the sclerenchymatous hypodermis confirms a monocot stem, which cannot undergo secondary growth.
Traps that cost marks
- Xylem is endarch in stems and exarch in roots.
- Sieve tubes lack a nucleus, but their companion cells are nucleated.
- Do not describe a monocot stem as having secondary growth.
- Dicot leaves are dorsiventral; monocot leaves are isobilateral.