21.2 What are the types of reproduction?

1. 21.2 What are the types of reproduction? Reproduction Asexual Sexual • usually involves 2 parents • involves gametes • involves fertilization • offspring are genetically different from each of parents • involves one parent • involves no gametes • offspring are genetically the same as the parents

2. Extension 21.3 How do organisms reproduce asexually? Binary fission in bacteria single chromosome parent bacterial cell 1) Chromosome replicates

3. Extension 21.3 How do organisms reproduce asexually? Binary fission in bacteria single chromosome parent bacterial cell 2) Cytoplasm divides into 2 parts

4. Extension 21.3 How do organisms reproduce asexually? Binary fission in bacteria single chromosome parent bacterial cell 3) Two identical daughter cells are formed

5. Extension Vegetative propagation in flowering plants vegetative parts (e.g. stems, roots & leaves)  new plants allows the plants to survive in poor conditions

6. Extension Vegetative propagation in flowering plants Examples of storage organs : Tuber Bulb Rhizome Corm • short swollen underground stem • e.g. Gladiolus • corm • horizontally growing underground stem • e.g. ginger • rhizome • swollen underground stem • e.g. potato • tuber • short underground stem with layers of fleshy ‘scale leaves’ • e.g. onion bulb

7. Extension Tuber e.g. potato tuber In winter In spring  each bud grows into a new plant  aerial shoots die  new tubers remain dormant

8. Extension In summer Tuber e.g. potato tuber shoot old tuber dries out new tuber formed adventitious roots  new leaves carry out photosynthesis  excess food sent to underground shoots  buds use the stored food  adventitious roots and shoots develop

9. Extension Bulb e.g. onion bulb fleshy scale leaf dry scale leaf bud  bulb remains dormant under unfavourable conditions

10. Extension Bulb e.g. onion bulb new flower stalk fleshy leaf leaf new bulb  green leaves make food  bud develops into a shoot using stored food

11. Extension Rhizome e.g. ginger rhizome aerial shoot In spring In summer leaf older parts  food made from photosynthesis is passed down to the underground parts  food is passed from the older parts to the growing regions

12. Extension Corm e.g. Gladiolus corm In spring bud scale leaf remains of last year’s corm  stored food is passed to bud for growth

13. Extension Corm e.g. Gladiolus corm aerial shoot leaf new corm new corm old corm  excess food made is passed down to new corm  a new corm is developed

14. Extension Artificial vegetative propagation  vegetative propagation carried out artificially  produce desired varieties  e.g. cuttings (插條法) in African violet

15. Extension 21.4 How do flowering plants reproduce sexually?  flowering plants reproduce sexually by producing flowers

16. Extension Structure of a flower stigma anther stamen filament style carpel petal ovary ovule nectary sepal receptacle flower stalk • sepals, petals, stamens and carpels are attached to this • attaches flower to the main stem

17. Extension Structure of a flower sepal Sepals (萼片)  the outermost ring (calyx 花萼) of a flower  protect the inner parts of the flower when it is a bud

18. Extension Structure of a flower Petals (花瓣) petal  the second ring (corolla花冠) of a flower  may be brightly coloured to attract insects

19. Extension Structure of a flower Petals (花瓣) petal insect guide  may have nectaries to produce nectar which attracts insects  may have insect guides to lead insects towards the nectaries

20. Extension Structure of a flower Stamens (柱頭)  male reproductive organs filament anther consists of pollen sacs supports anther when anthers ripen pollen sacs split open to release pollen grains anther pollen sacs filament

21. Extension Structure of a flower stigma (柱頭) style (花柱) Carpels (心皮)  female reproductive parts  the centre of a flower  each consists of • style (carries the stigma) • stigma (receives pollen grains) • ovary (with ovules inside)

22. Extension Structure of a flower Carpels (心皮) stigma style ovary wall integuments female gamete ovary ovule micropyle

23. Brief Revision ~ Word corner ~ Carpel ** Carp-  Fruit

24. Extension Structure of a flower Flowers Bisexual (兩性) Unisexual (單性) have both stamens and carpels in one flower have either stamens or carpels in one flower

25. Extension Pollination •  transfer of pollen grains from anthers to stigmas • male gametes fertilize the ovules Pollination (傳粉作用) insect-pollination wind-pollination

26. Extension Wind-pollinated flowers - pollinated by wind The flowers are structurally adapted to pollination. Insect-pollinated flowers - pollinated by insects

27. Extension Insect-pollinated flowers scent Petal nectaries • large • brightly coloured

28. Extension Insect-pollinated flowers scent Pollen grain nectaries • small in number • rough and sticky/ • with hooks • large and heavy pollen grains stick onto the leg of the bee

29. Extension Insect-pollinated flowers scent Stigma nectaries • sticky • inside the flower • firmly attached to style

30. Extension Insect-pollinated flowers scent Anther nectaries • inside the flower where insects will brush against it • firmly attached to filament

31. Extension Wind-pollinated flowers scent Petal nectaries • small • green or dull-coloured

32. Extension Wind-pollinated flowers scent Pollen grain nectaries • large in number • smooth and dry • small and light

33. Extension Wind-pollinated flowers scent Stigma nectaries • large and feathery • hand outside the flower for picking up pollen grains from air • loosely attached to the style

34. Extension Wind-pollinated flowers scent Anther nectaries • hangs outside the flower, exposed to wind • loosely attached to filament so that light wind can shake it

35. Extension Fertilization • Pollen grains land on the stigma of the same species. style flower stalk sepal The growth of pollen tube and fertilization

36. Extension Fertilization • Sugary solution at the tip of the stigma stimulates the pollen grain to develop a pollen tube. style flower stalk sepal The growth of pollen tube and fertilization

37. Extension Fertilization • Pollen tube grows down the style and eventually into the ovary by secreting enzymes to digest tissues of the style. style The male gamete moves towards the ovule. male gamete flower stalk sepal The growth of pollen tube and fertilization

38. Extension Fertilization • Pollen tube grows through the micropyle. The tip of the tube bursts to release the male gamete into the ovule. style ovule male gamete ovary flower stalk sepal micropyle The growth of pollen tube and fertilization

39. Extension Fertilization • Male gamete fuses with female gamete to form a zygote. style ovule male gamete ovary flower stalk sepal micropyle The growth of pollen tube and fertilization

40. Extension Fate of floral parts after fertilization wither and drop off remains of stigma and style scar stamen sepal seed coat integument petal ovary wall fruit wall seed ovule ovum embryo A Bauhinia flower after fertilization Fruit (pod) splits open to two halves

41. Extension Fate of floral parts after fertilization Fruit consists of protects helps fruit wall seed dispersal made up of seed coat protects embryo food store provides food

42. Extension Structure of a mung bean Micropyle (珠孔) • a hole through which embryo absorbs water Hilum (種臍) • a scar; formed when the ovule breaks from the ovary wall Seed coat (種皮) • protects the embryo from damage and against attack of micro-organisms External appearance

43. Extension Structure of a mung bean Plumule (胚芽) Cotyledons (子葉) • develops into shoot • as food stores • provide food for plumule and radicle to develop Radicle (胚根) • develops into root Embryo (胚胎) Seed cut opened

44. Extension Advantages and disadvantages of sexual reproduction in flowering plants Advantages 1offspring are genetically different from the parents  variations (變異) to adapt the environment 2avoid overcrowding and competition 3avoid transmission of diseases

45. Extension Advantages and disadvantages of sexual reproduction in flowering plants Disadvantages 1slow way to produce new plants 2external agents are needed for pollination