IB DP Biology- A2.2 Cell structure- IB Style Questions For HL Paper 2 -FA 2025

(a)

• Cell wall: Plant cells possess a cellulose cell wall surrounding the membrane, whereas animal cells do not.
• Chloroplasts: Chloroplasts occur in plant cells for photosynthesis but are absent in animal cells.
• Vacuoles: Plant cells usually contain one large permanent vacuole; animal cells may have small, temporary vacuoles.
(Additional point: Centrioles are present in animal cells but are generally absent in most plant cells.)

(b)

• Animal adaptations for herbivory: Many herbivores possess specialised grinding teeth or mouthparts that help break down fibrous plant tissues. Some species, such as ruminants, have complex digestive systems with microbes that break down cellulose.

• Plant defences against herbivores: Plants often develop physical barriers such as thorns, spines, or thick leaves. They may also produce chemical deterrents like toxins or bitter-tasting compounds that deter feeding.

(c)

Similarities in mitosis:

In both plant and animal cells, mitosis includes chromosome condensation, alignment at the metaphase plate, separation of sister chromatids, and formation of two genetically identical nuclei.

Differences in cytokinesis:

• Animal cells: Cytokinesis occurs by forming a cleavage furrow, where a contractile ring of actin and myosin tightens and pinches the cell into two.
• Plant cells: Due to the rigid cell wall, plant cells form a cell plate from Golgi-derived vesicles at the centre of the cell. This plate eventually develops into a new cell wall and membranes, separating the daughter cells.