SPI Biology · Free notes
Plant Biology: SPI Biology
Plant Biology has 8 questions in the SPI bank, all from the LWS mocks, and six of them are EASY. Three of them are about photosynthesis: its three events, the black paper experiment and the tiny share of sunlight plants use. The other five ask about guard cells, root nodules, respiring seeds, a plant hormone and a tropism. The two MODERATE questions both turn on getting a detail of photosynthesis exactly right, so read that page slowly.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Nutrition and Respiration in Plants
6 questionsA green plant makes its own food from carbon dioxide and water using sunlight, takes in gases through its stomata, and like every living thing respires to release energy from that food.
Plant Hormones and Movements
2 questionsPlants have no nerves, so they control growth with chemicals called plant hormones, and they respond to light, gravity, water and chemicals by growing towards or away from them.
Formula & revision sheet
0 formulas · 5 reference tables · 8 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 5 reference tables · 8 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (3)
Photosynthesis: raw materials, events and experiments3 rows
| Experiment | What is taken away | Result | It shows |
|---|---|---|---|
| Part of a leaf covered with black paper | Light, from that part | No starch where covered | Light is necessary Air still reaches the covered part, so the black paper tests light only. |
| Variegated leaf (green and white patches) | Chlorophyll, from the white part | Starch only in green parts | Chlorophyll is necessary |
| Plant in a jar with potassium hydroxide | Carbon dioxide (KOH absorbs it) | No starch | Carbon dioxide is necessary |
Stomata and root nodules5 rows
| Plant | Group | Root nodules with Rhizobium |
|---|---|---|
| Pea | Legume | Yes |
| Gram | Legume | Yes |
| Groundnut | Legume | Yes |
| Wheat | Cereal (grass) | No |
| Rice | Cereal (grass) | No |
Respiration in plants and seeds3 rows
| Seeds | Alive | Respiration |
|---|---|---|
| Germinating | Yes | Fast, gives out much carbon dioxide |
| Dry | Yes, but resting | Very slow |
| Boiled | No | None Boiled seeds are used only as the control: they show nothing happens without life. |
Watch out for (5)
- Putting ATP and NADPH in the dark phase→ Photosynthesis: raw materials, events and experiments
- 10% for the sunlight plants use→ Photosynthesis: raw materials, events and experiments
- Reading the black paper test as a carbon dioxide test→ Photosynthesis: raw materials, events and experiments
- Picking a cereal for Rhizobium→ Stomata and root nodules
- Plants respire only at night→ Respiration in plants and seeds
Reference tables (2)
The five plant hormones5 rows
| Hormone | Main job | Promotes or stops growth |
|---|---|---|
| Auxin | Cell lengthening, bending towards light | Promotes |
| Gibberellin | Stem lengthening | Promotes |
| Cytokinin | Cell division | Promotes |
| Abscisic acid | Fall of leaves and fruits, wilting | Stops Abscisic acid is the one growth stopper among them. |
| Ethylene | Ripening of fruit | Ripens |
Tropisms: growing towards or away4 rows
| Tropism | Stimulus | Example |
|---|---|---|
| Phototropism | Light | A shoot bending to a window; a sunflower following the sun A question may call the stimulus 'day or night': it means light. |
| Geotropism | Gravity | Roots growing downwards |
| Hydrotropism | Water | Roots growing towards wet soil |
| Chemotropism | Chemicals | Pollen tube growing to the ovule |
Watch out for (3)
- Thinking every plant hormone promotes growth→ The five plant hormones
- Touch-me-not as a tropism→ Tropisms: growing towards or away
- Shoots and roots answer gravity the same way→ Tropisms: growing towards or away
Question weightage by concept
5 concepts · 8 questions — where the marks actually sit, so you know what to drill first
Question weightage by concept
5 concepts · 8 questions — where the marks actually sit, so you know what to drill first
| Concept | Qs | Share |
|---|---|---|
| Photosynthesis: raw materials, events and experiments | 3 | 38% |
| Stomata and root nodules | 2 | 25% |
| Respiration in plants and seeds | 1 | 13% |
| Concept | Qs | Share |
|---|---|---|
| The five plant hormones | 1 | 13% |
| Tropisms: growing towards or away | 1 | 13% |
Test yourself on a real paper
Sit a past SPI paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.