Present images on a whiteboard of Dolly the sheep, a strawberry plant with runners, potato, daffodil, bacteria splitting in two, clone troopers from Star Wars and a Dr Who cloned character. What do all these images have in common?
Explain that although cloning is an imaginary recurring theme in science fiction, it really does occur naturally in plants. Plants can reproduce asexually (producing clones) or sexually (producing seeds). Cloning is less common in animals, although identical twins are human clones. Some animals can now be artificially cloned. In the lesson pupils will compare sexual and asexual reproduction in plants and make a clone.
Dissect a flower: Give each pupil a magnifying glass and flower. The biological function of a flower is to effect reproduction. Now take apart (dissect) the flower, sticking each part to a sticky strip. Explain the purpose of each bit of the flower (sepal, petal, stamen, carpel) and label them. When the strip is complete it can be preserved with a cover of 'sticky back plastic'. A seed is formed after pollination and when it germinates it will produce a plant similar, but not identical to the parents.
Make a clone: Many plants also produce asexually. Give examples of these such as a spider plant or strawberry - which occur naturally. Emphasise these plants are genetically identical to the parent. Plant breeders can take advantage of this by taking 'cuttings' (taking a piece of a plant to make more). Plants are also selected for desirable characteristics in this way. Different types of cuttings can be taken at different times of the year such as hardwood in winter. Learn how to take soft wood, semi ripe and hardwood cuttings.
Top Banana: So why persist in reproducing sexually? Asexual reproduction seems a faster and more efficient way to reproduce. As a case study, the banana can be explained as an asexual clone produced from a propagation of a plant with no seeds. Give pupils a slice of banana to eat while you compare it to the image of a wild, seed packed banana on the whiteboard. The variety of bananas we eat however have little natural resistance to pests and diseases. Discuss the advantages and disadvantages of sexual and asexual reproduction. What can be done to save the banana (as we know it) from extinction?
In groups, draw and label a simple picture of a plant to show all the ways in which a plant can reproduce. Include propagation techniques used by plant breeders.
Label which plants use sexual and asexual reproduction.
Present back as a group including the advantages and disadvantages of each method.