IGCSE Biology | Practice Test | 25 Questions
State two physical features of most leaves that make them well adapted for photosynthesis.
Name the waxy, transparent layer found on the outer surface of a leaf.
State two functions of the cuticle.
Name the two types of mesophyll found in a dicotyledonous leaf.
Which layer of the leaf is the main site of photosynthesis? Give one reason why.
What are stomata? State where they are mainly found on a leaf.
State the function of guard cells.
Name the two types of tissue found in a vascular bundle.
State the function of xylem in a leaf.
State the function of phloem in a leaf.
Explain why palisade mesophyll cells are found near the top of the leaf, just below the upper epidermis, rather than near the bottom.
A student examines a leaf cross-section under a microscope. She sees loosely arranged, irregularly shaped cells with large gaps between them.
(a) Name this tissue.
(b) Explain how the gaps between these cells help the leaf carry out photosynthesis.
Epidermal cells contain no chloroplasts. Explain how this feature helps the plant photosynthesise.
Describe how guard cells control the opening and closing of a stoma.
A plant is kept in the dark overnight.
(a) Predict what will happen to its stomata during the night.
(b) Explain what happens to gas exchange when the plant is returned to light the next morning.
Explain why palisade mesophyll cells contain more chloroplasts than spongy mesophyll cells.
A leaf is large and flat, and is also very thin. Explain how each of these two features is an adaptation for photosynthesis.
Explain how the cuticle reduces water loss while still allowing photosynthesis to occur in the cells below.
A student says: “Sealing all the stomata permanently would help the plant by stopping water loss.”
Give two reasons why this would actually harm the plant.
Phloem carries sugars away from the leaf. Explain why this transport is important for photosynthesis to continue.
A cross-section through a dicotyledonous leaf shows the following layers, from top to bottom:
- Layer 1: A thin, waxy, transparent coating
- Layer 2: A single layer of transparent, flat cells with no chloroplasts
- Layer 3: Tall, tightly packed cells containing many chloroplasts
- Layer 4: Loosely arranged, irregular cells with large air spaces between them
- Layer 5: A single layer of flat cells containing small pores, each controlled by two curved cells
(a) Name each of the five layers described above.
(b) Explain how Layer 3 is adapted for photosynthesis. Give two points.
(c) Explain how Layer 4 and its air spaces are adapted for gas exchange. Give two points.
Vascular bundles run through the leaf as veins, containing xylem and phloem.
(a) State the substance carried by xylem to the leaf and explain why it is essential for photosynthesis.
(b) State the substance carried away from the leaf by phloem and explain why it is important that this substance is removed.
(c) Explain why having xylem and phloem close together in the same vascular bundle is an advantage for the leaf.
Palisade mesophyll cells and spongy mesophyll cells both play important roles in the leaf.
(a) Describe two structural differences between palisade cells and spongy cells.
(b) Palisade cells carry out more photosynthesis than spongy cells. Explain why, referring to two structural features of palisade cells.
(c) Explain why the spongy mesophyll is still important, even though it carries out less photosynthesis than the palisade layer.
Stomata and guard cells control gas exchange and water loss in a leaf.
(a) Describe what happens to guard cells when a plant is in bright light, and explain how this opens the stoma.
(b) Explain why it is an advantage for stomata to be on the lower epidermis rather than the upper surface of the leaf.
(c) Due to a mutation, a plant’s stomata remain permanently open. State one benefit and one disadvantage of this for the plant.
A student says: “Every layer and structure in a leaf works together to make photosynthesis as efficient as possible.”
Using your knowledge of leaf structure, explain how four different structures in a dicotyledonous leaf are adapted to maximise the rate of photosynthesis.
For each structure: name it, describe the relevant feature, and explain how that feature helps photosynthesis.
