COMPARING ASEXUAL AND SEXUAL REPRODUCTION

1. COMPARING ASEXUAL AND SEXUAL REPRODUCTION ABBOTTS

2. TOPICS • Advantages and disadvantages of asexual reproduction • Advantages and disadvantages of sexual reproduction

3. PLANT REPRODUCTION • Is the ability of living organisms to produce a new generation of themselves • Important for survival and evolution of a species

4. TYPES OF REPRODUCTION

6. ASEXUAL REPRODUCTION • Also called vegetative propagation • Production of a new generation of the same species by one parent • Takes place by mitosis • All new organisms are genetically identical to their parents and to each other • Such organisms are called clones

7. VEGETATIVE REPRODUCTION STEMS • RUNNERS Grow from the the stems of some plants eg strawberry and give rise to a new plant

8. STOLON Long thin stems that go across the ground Chlorophytum

9. VEGETATIVE REPRODUCTION STEMS • RHIZOMES • Underground stems with nodes that produce shoots and roots • Shoots develop into new plants • Eg kikuyu grass

10. VEGETATIVE REPRODUCTION • BULBS short underground stems surrounded by fleshy leaves that store nutrients New swollen stems grow and develop from axillary buds Eg onion STEMS

11. VEGETATIVE REPRODUCTION • STEM TUBERS • swollen underground stems with stored nutrients • Buds are present that can sprout and to stems that develop into new plants • E.g. Potato

12. ROOTS VEGETATIVE REPRODUCTION Suckers develop from Roots and grow into new plants

13. ROOTS VEGETATIVE REPRODUCTION • Root tubers are swollen roots • E.g. dahlia

14. LEAVES VEGETATIVE REPRODUCTION • New plants can develop directly from leaves • EgStreptocarpus spp. Streptocarpus leaf cuttings

15. ARTIFICIAL VEGETATIVE REPRODUCTION • CUTTINGS • A piece of the plants stem is cut off below a bud • Placed in damp soil • Roots develop at the bottom • New plant develops • Eg carnation

16. ADVANTAGES OF ASEXUAL REPRODUCTION • Only one parent needed and all individuals can produce offspring • No special organs of reproduction are required (eg flowers) • The process is simple and fast – only mitosis involved • No outside agents such as pollinators are needed • Little energy is used (do not have to produce reproductive organs)

17. ADVANTAGES OF ASEXUAL REPRODUCTION • New plants are genetically identical • No variation • Successful varieties are maintained • Will be the same year after year good for commercial crops • Eg potatoes and strawberries

18. ADVANTAGES OF ASEXUAL REPRODUCTION • Asexual reproduction is useful in stable conditions • If the parent is well adapted to a particular environment the offspring also will be • A favourable mutation can spread rapidly, enabling a population to adapt quickly to any new environmental conditions Mutation = change in a chromosome resulting in a new characteristic

19. ADVANTAGES OF ASEXUAL REPRODUCTION • By avoiding seed dormancy, plants can be propogated throughout the year independent of seasonal changes Germination after seed dormancy Germination dormancy

20. DISADVANTAGES OF ASEXUAL REPRODUCTION • No variation – no chance of improving the quality of the species • Overcrowding may occur and resources such as food might be in short supply • Genetic weaknesses cannot be bred out • Infectious diseases (caused by viruses) are likely to be passed on to the new crop No variation Overcrowded basil

21. SEXUAL REPRODUCTION IN PLANTS • Is the production of a new generation by bringing together the genetic material of two parents • The offspring will therefore be genetically different from the parents

22. PROCESS OF SEXUAL REPRODUCTION IN PLANTS • Diagram • Parents produce gametes in sex organs • Male and femae gametes are brought close together by pollination • Male and female gametes fuse (fertilisation) • Zygote grows into a new plant

23. ADVANTAGES OF SEXUAL REPRODUCTION • Results in variation which: • Is the basis of evolution • Gives organisms a better chance of survival in an unstable environment as the offspring may be able to adapt to the new conditions • May prevent the spread of disease as the offspring might be genetically resistant to a particular disease • Can result in the quick elimination of harmful mutations Mutation = change in a chromosome resulting in a new characteristic

24. ADVANTAGES OF SEXUAL REPRODUCTION • Seeds are usually dispersed widely which gives them more space and nutrients

27. Droseracistiflorais a plant with a wide range of floral colour variations and many of these can be observed in fynbos and renosterveld habitats during spring. Flowers vary in size and colour.

28. DISVANTAGES OF SEXUAL REPRODUCTION • There is a high expenditure of energy • In plants special organs of reproduction need to be produced e.g. flowers • The reproduction process is slow • Unfavourable mutations and recessive genes might be passed on to the offspring • Outside agents might be needed in plants to carry pollen or seeds

29. HOW DO ASEXUAL AND SEXUAL REPRODUCTION COMPARE

30. THE END