1. 1
   A gardener pulls up a young bean seedling and examines its root system. Close to the root tip, the root surface appears covered in thousands of tiny, hair-like projections, each a single elongated cell.

   (a)

   Which feature of these cells most increases the surface area available for absorbing water and mineral ions from the soil?

   [1 mark]

   • AA thick waxy cuticle covering the outer cell wall
   • BA long, thin extension of the cell that projects out into the soil
   • CA large number of chloroplasts packed into the cytoplasm
   • DA reduced number of mitochondria compared with other root cells

   (b)

   The gardener notices that the concentration of mineral ions, such as nitrate, is often much lower in the soil water than inside the root hair cells. Despite this, the cells continue to take up nitrate ions from the soil. Which process allows the cells to do this?

   [1 mark]

   • ADiffusion
   • BOsmosis
   • CActive transport
   • DTranspiration

   (c)

   Explain how the structure of a root hair cell is adapted to absorb water and mineral ions from the soil.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A scientist cuts across the trunk of a young tree and examines the ring of transport tissue just beneath the bark under a microscope. She finds two distinct types of tissue: one made of long, hollow, dead cells with thickened walls, and another made of living, elongated cells arranged in tubes.

   (a)

   The dead cells forming this tissue are joined end to end, with thickened, strengthened walls. Which tissue has she identified?

   [1 mark]

   • AMeristem
   • BPhloem
   • CEpidermis
   • DXylem

   (b)

   Next to the tissue described above, the scientist finds a second tissue made of living, elongated cells joined into tubes, which uses energy from respiration to move dissolved sucrose around the tree. Which tissue has she identified?

   [1 mark]

   • AXylem
   • BCambium
   • CPhloem
   • DCortex

   (c)

   Explain how the structure of xylem tissue is adapted to transport water and minerals through the plant.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A horticulturist takes a thin section from the middle of a healthy leaf and examines the layers of cells inside using a microscope. She describes an upper layer of tightly packed, column-shaped cells containing many chloroplasts, sitting above a looser layer of irregularly shaped cells with air spaces between them, all enclosed by a transparent outer layer.

   (a)

   Explain how this internal leaf structure is adapted for efficient photosynthesis.

   [3 marks]

   (b)

   The horticulturist also notes that the lower, loosely packed layer of the leaf has large air spaces between its cells, and that the outer layer on the underside of the leaf contains many small pores, each surrounded by a pair of specialised cells that can change shape to open and close the pore. Explain how these features adapt the leaf for efficient gas exchange.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A plant biologist compares two species growing in a hot, dry desert region. Both species have small, thick, needle-like leaves covered in a very thick waxy outer layer, and both have far fewer pores on their leaf surfaces than a typical woodland plant, with most of these pores located on the shaded underside of the leaf.

   (a)

   Explain how the leaf size and shape, the waxy outer layer, help these desert plants to survive in an extreme, arid environment.

   [6 marks]

   (b)

   Explain how having fewer pores, located mainly on the shaded underside of the leaf, helps these desert plants survive, and evaluate the trade-off this creates between gas exchange and water loss.

   [6 marks]

   Total for question 4: 12 marks

End of questions