The shape of the lesson
By the end of the lesson, learners can
- One parent, no gametes: In the lab, choose asexual (runners) and grow the offspring.
- Spotting examples: Exam questions often show a diagram or describe an organism and ask whether it reproduces asexually.
- Good for crops, risky in the wild: Extended.
- Definition: genetically identical offspring from one parent.
- Spot it: one parent, new individual grows from part of it, no gametes, no fertilisation.
- Advantages (Extended): fast, one parent, good features kept, uniform crop.
- Disadvantages (Extended): no variation, so disease or change can kill all; competition with parent.
One picture every idea returns to
Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent. There are no gametes and no fertilisation, so the offspring (clones) have the same genes as the parent and as each other. Extended: it is fast and needs only one parent, but the lack of variation means a whole population can be wiped out by one change, such as a new disease.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, One parent, identical offspring.. A strawberry plant sends out runners and new plants root along them. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: One parent, no gametes | In the lab, choose asexual (runners) and grow the offspring. Project tab 1 of the lab (Asexual and sexual reproduction) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Spotting examples | Exam questions often show a diagram or describe an organism and ask whether it reproduces asexually. | Pairs |
| 21 to 30 min | Teach and check: Good for crops, risky in the wild | Extended. Project tab 1 of the lab (A disease strikes the clones) and let a student drive it while the class predicts. | Think-Pair-Share |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 17 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Good for crops, risky in the wild, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Think-Pair-Share
Pose the question, give thirty seconds of silent thinking, then a minute to compare with a partner before a few pairs share with the class. The silent minute is the part that cannot be cut.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Asexual offspring are not just similar to the parent: they are genetically identical. | If you see variation between asexual offspring, it must be caused by the environment, not by their genes. |
| Do not just write "it is quicker" or "there is no variation". | Say why it matters: for example, no variation means no individual is likely to be resistant, so the whole population or crop could be lost. |
Asexual reproduction: worksheet
6 questions, 17 marks. Written in the style of the papers; no past paper question is reproduced.
Describe what is meant by asexual reproduction.
Read the descriptions and state whether each is asexual or sexual reproduction. (a) A yeast cell grows a bud that separates to form a new cell. (b) Pollen from one rose plant lands on the stigma of another rose plant. (c) A gardener plants a cut piece of geranium stem, which grows roots.
Two potato plants grown from tubers of the same parent plant reach different heights. Explain how this can happen if they are genetically identical.
Extended. Discuss two advantages and two disadvantages of asexual reproduction for a crop such as bananas.
Extended. In a model, nine plants produced by asexual reproduction and ten plants produced by sexual reproduction were exposed to a disease. None of the asexual plants survived; four of the sexual plants survived.
(a) Calculate the percentage of the sexual plants that survived. (b) Explain the difference between the two groups.
Extended. A single spider plant is carried to a new island. Suggest why asexual reproduction helps it to colonise the island, and one risk to the population later.
Answer key and marking notes
- A process that produces offspring from one parent (no gametes, no fertilisation).
- The offspring are genetically identical to the parent and to each other.
- (a) Asexual: one parent, no gametes (budding).
- (b) Sexual: pollination leads to fusion of gamete nuclei from two plants.
- (c) Asexual: a cutting from one parent grows into a genetically identical plant.
- Their genes are the same, so the difference is not inherited.
- It is caused by the environment, for example different amounts of light, water or mineral ions.
- Advantage: all plants keep the desirable features of the parent, such as high yield or good flavour.
- Advantage: it is quicker than growing from seed and the crop is uniform, so it can be harvested at the same time.
- Disadvantage: there is no genetic variation, so a disease or pest that kills one plant can kill the whole crop.
- Disadvantage: no new varieties are produced, so the crop cannot be improved or adapt to changing conditions.
- (a) 4 ÷ 10 × 100 = 40%.
- (b) The asexual plants are genetically identical, so none had resistance to the disease and all died.
- The sexual offspring show genetic variation, so some happened to be resistant and survived.
- Only one parent is needed, so it can reproduce without a mate.
- Runners produce many new plants quickly while conditions are suitable.
- Risk: the whole population is genetically identical, so a change in the environment or a new disease could kill them all.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which statement is true of all offspring produced by asexual reproduction?
- AThey are genetically identical to their single parent
- BThey are formed when two gamete nuclei fuse
- CThey show more variation than their parents
- DThey need pollen from a different plant
A single bacterium divides into two cells every 20 minutes. How many genetically identical bacteria are there after 2 hours, starting from one?
- A64
- B12
- C32
- D128
Which of these is an example of asexual reproduction?
- AA daffodil bulb dividing to form new bulbs
- BA bee carrying pollen between two daffodils
- CA daffodil seed forming inside the ovary
- DA sperm and egg fusing in a frog
A gardener takes ten cuttings from one geranium. All have red flowers, but some grow taller than others. What is the best explanation for the height difference?
- ADifferences in their environment, such as light or water
- BDifferences in the genes they received from two parents
- CMutations caused by cutting the stems
- DSome cuttings were produced by fertilisation
Which feature is NOT found in asexual reproduction?
- AFertilisation
- BOne parent
- CMitosis to form new cells
- DGenetically identical offspring
Field P was planted with cuttings from one apple tree; field Q was grown from seeds. A new fungal disease reached both fields. The chart shows the survivors. Which explanation fits the data?
- AField P plants are genetically identical, so none had resistance
- BField P plants were younger, so their immune systems were weaker
- CField Q plants were genetically identical, so all resisted equally
- DThe fungus can only reproduce on plants grown from cuttings
Why do commercial growers often propagate a high-yielding variety of potato from tubers rather than from seeds?
- AAll new plants keep the parent's high-yield features
- BTubers give more genetic variation in the crop
- CTubers protect the crop against all new diseases
- DSeeds cannot grow into potato plants at all
An aphid population reproduces asexually all summer, then sexually in autumn before winter. What is the most likely advantage of this pattern?
- ARapid growth in summer, then variation to survive changing conditions
- BVariation in summer, then identical offspring for the winter
- CAsexual reproduction in summer avoids the need for food
- DSexual reproduction in autumn makes the population grow faster
Quiz key
Asexual reproduction uses one parent and no gametes, so the offspring are clones of the parent. Fusion of gamete nuclei is fertilisation (sexual reproduction); extra variation comes from sexual reproduction; pollen from another plant is cross-pollination.
2 hours = 120 minutes = 6 divisions, and 26 = 64. 12 adds 2 each time instead of doubling; 32 is only 5 divisions; 128 is 7 divisions.
A bulb splitting produces clones from one parent. The bee transfers pollen (sexual reproduction in plants), a seed forms after fertilisation, and sperm and egg fusing is fertilisation.
Cuttings are clones, so their genes are the same; height differences must be environmental. There are not two parents; cutting does not cause mutations; and no fertilisation is involved in taking cuttings.
Asexual reproduction has no gametes, so there is no fertilisation. It does involve one parent, new cells made by mitosis and genetically identical offspring.
Clones share the same genes, so if one is not resistant none are (field P: only 1 survivor). Seed-grown plants vary, so some (24) happened to be resistant. Plants do not have immune systems like animals; field Q is the varied one, not the identical one; fungi do not choose plants by how they were grown.
Asexual reproduction copies the parent's genes exactly, so the desired yield is kept and the crop is uniform. Tubers give no variation, a uniform crop is more (not less) at risk from new diseases, and potatoes can grow from seed, but the offspring vary.
Asexual reproduction is fast while food is plentiful; sexual reproduction produces varied offspring, so some are likely to survive the harsh, changing winter. The summer offspring are identical, not varied; reproduction always needs food; and sexual reproduction is slower, not faster.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.