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BackNext Home 1 21.2 What are the types of reproduction? AsexualSexual involves one parent involves no gametes offspring are genetically the same as the.

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Presentation on theme: "BackNext Home 1 21.2 What are the types of reproduction? AsexualSexual involves one parent involves no gametes offspring are genetically the same as the."— Presentation transcript:

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2 BackNext Home What are the types of reproduction? AsexualSexual involves one parent involves no gametes offspring are genetically the same as the parents usually involves 2 parents involves gametes involves fertilization offspring are genetically different from each of parents

3 BackNext Home How do organisms reproduce asexually? Binary fission in bacteria 1) Chromosome replicates single chromosome parent bacterial cell Extension

4 BackNext Home How do organisms reproduce asexually? Binary fission in bacteria 2) Cytoplasm divides into 2 parts single chromosome parent bacterial cell Extension

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

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

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

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

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

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

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

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

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

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

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

16 BackNext Home 15  flowering plants reproduce sexually by producing flowers 21.4How do flowering plants reproduce sexually? Extension

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

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

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

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

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

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

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

24 BackNext Home 23 ~ Word corner ~ ** Carp-  Fruit Carpel Brief Revision

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

26 BackNext Home 25  transfer of pollen grains from anthers to stigmas  male gametes fertilize the ovules insect-pollinationwind-pollination Pollination Pollination ( 傳粉作用 ) Extension

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

28 BackNext Home 27 scent nectaries Petal large brightly coloured Insect-pollinated flowers Extension

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

30 BackNext Home 29 scent nectaries Stigma sticky inside the flower firmly attached to style Insect-pollinated flowers Extension

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

32 BackNext Home 31 Petal small green or dull-coloured Wind-pollinated flowers scent nectaries Extension

33 BackNext Home 32 Pollen grain large in number smooth and dry small and light Wind-pollinated flowers scent nectaries Extension

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

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

36 BackNext Home 35 The growth of pollen tube and fertilization flower stalk sepal style Extension Fertilization 1Pollen grains land on the stigma of the same species.

37 BackNext Home 36 The growth of pollen tube and fertilization flower stalk sepal style Extension Fertilization 2Sugary solution at the tip of the stigma stimulates the pollen grain to develop a pollen tube.

38 BackNext Home 37 The growth of pollen tube and fertilization flower stalk sepal style Extension Fertilization 3Pollen tube grows down the style and eventually into the ovary by secreting enzymes to digest tissues of the style. The male gamete moves towards the ovule. male gamete

39 BackNext Home 38 The growth of pollen tube and fertilization flower stalk sepal style Extension Fertilization male gamete 4Pollen tube grows through the micropyle. The tip of the tube bursts to release the male gamete into the ovule. ovule micropyle ovary

40 BackNext Home 39 The growth of pollen tube and fertilization flower stalk sepal style Extension Fertilization male gamete ovule micropyle ovary 5Male gamete fuses with female gamete to form a zygote.

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

42 BackNext Home 41 consists of food store embryo seed coat dispersalseed Fruit fruit wall provides food protects made up of helpsprotects Fate of floral parts after fertilization Extension

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

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

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

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


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