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Reproduction the process of producing offspring necessary for the continuation of a species Reproduction.

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Presentation on theme: "Reproduction the process of producing offspring necessary for the continuation of a species Reproduction."— Presentation transcript:

1

2 Reproduction

3 the process of producing offspring necessary for the continuation of a species Reproduction

4 AsexualSexual Two types of reproduction

5 AsexualSexual involves one parent involves no gamete (sex cell) offspring are genetically identical to the parents – mitotic cell division usually involves 2 parentsusually involves 2 parents involves gametesinvolves gametes involves fertilizationinvolves fertilization –fusion of the nuclei of male & female gametes  zygote offspring are genetically different from each of their parentsoffspring are genetically different from each of their parents Two types of reproduction

6 Types of asexual reproduction Examples of asexual reproduction Vegetative propagation Spore formation Budding Binary fission Fragmentation

7 division of unicellular organisms into equal halves e.g. Amoeba

8 Binary fission nucleus nucleus divides equally into two by mitosis cytoplasm constricts two daughter Amoebae are formed

9 Budding production of buds, which grow to new individuals e.g. yeast

10 Budding vacuole nucleus a yeast cell a bud is formed nucleus divides into two a nucleus remains in the parent cell a nucleus moves into the bud

11 the new cell breaks off from the parent cell Budding

12 Spore formation produced in large numbers. occurs in fungi e.g. Mucor, Rhizopus

13 Fungi are saprophytes- causing rotting of dead organic matters Produce spores for reproduction and dispersal Spore formation

14 Fragmentation e.g. spirogyra

15 Fragmentation Amazing power of regeneration in starfish

16 Fragmentation

17 regeneration in flatworm

18 Vegetative propagation development of new plants from vegetative / food storage organs occurs in flowering plants e.g. potato, onion, ginger, Gladiolus Vegetative propagation

19 development of new plants from vegetative / food storage organs 1. Bulb 2. tuber 3. rhizome 4. corm

20 Vegetative propagation 1When conditions become unfavourable such as winter, storage organ bud the aerial parts of the plant die and the storage organ stops growing underground. It survives through bad conditions for growth. aerial parts

21 Vegetative propagation 2When conditions are suitable for growth, a new plant develops from a bud. The storage organ provides food for the development of the new plant.

22 Vegetative propagation They absorb water and minerals. The shoot grows up and develops leaves. adventitious roots aerial shoot 3Adventitious roots are formed.

23 Vegetative propagation 4The storage organ dries up as food is used up for growth. leaf

24 Vegetative propagation 5The plant can now survive on its own by food made from photosynthesis. Some food made from photosynthesis is passed to a new storage organ. new storage organ previous storage organ

25 Vegetative propagation 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

26 Vegetative propagation Tuber Vegetative propagation of a potato plant

27 Vegetative propagation Tuber Vegetative propagation of a potato plant In winter 1The aerial shoots die but the new tubers remain dormant. 2Each bud can produce a new independent plant. In spring

28 3The buds use the food stored in the tuber to produce adventitious roots and shoots. shoot tuber formed by last year’s plant adventitious roots 4Excess food made in the leaves is sent to the underground shoots and stored. old tuber new tubers eye (a bud) In summer

29 Vegetative propagation Tuber Vegetative propagation of a potato plant

30 Bulb Vegetative propagation onion bulb

31 Bulb Vegetative propagation Growth of an onion bulb 1The bud remains dormant. fleshy leaf scale leaf bud stem root

32 2After dormancy, the bud develops. The fleshy leaves provide food for the development of the shoot. They become dry scale leaves after their food storage has been used up. 3The leaves make and provide food for the growth of a new bud. new bulb leaf fleshy leaf new flower stalk

33 Rhizome Vegetative propagation Growth of a ginger rhizome

34 Rhizome Vegetative propagation Growth of a ginger rhizome The food produced from photosynthesis passes downwards to the underground parts.

35 Rhizome Vegetative propagation Growth of a ginger rhizome The food produced from photosynthesis passes downwards to the underground parts. Food passes upwards from the older parts to the growing regions. lateral bud grows into daughter rhizome

36 Corm Vegetative propagation Gladiolus

37 Corm Vegetative propagation Growth of a Gladiolus corm 1Food stored in the swollen stem is passed upwards to the bud for its growth. remains of last year’s corm scale leaf bud In spring

38 2When the leaves are well developed, the food they made is passed down to the new corm. 3A new corm is developed over the old one each year. new corm leaf aerial shoot old corm new corm

39 Corm Vegetative propagation

40 Artificial vegetative propagation vegetative propagation done artificially can produce desired varieties quickly method: taking of ‘cuttings’ e.g. Coleus (stem), African violet (leaves)

41 Artificial propagation by cutting

42 Artificial Vegetative reproduction

43 Importance of Vegetative Propagation  It is the only means of reproduction for seedless plants such as pineapples, seedless grapes, oranges, roses, sugarcane, potato, banana, etc.  Plants raised through vegetative propagation are genetically similar. It preserves the type of characters that a plant breeder desires to retain.  It is very economical and easy method for the multiplication of plants.

44 Artificial propagation by grafting Eg. Fruit trees Ornamental plants Bauhinia of HK Grafting is a method of asexual plant propagation where the tissues of one plant are encouraged to fuse with those of another.asexualplant propagationtissuesplant In most cases, one plant is selected for its roots, and this is called the stock or rootstock. The other plant is selected for its stems, leaves, flowers, or fruits and is called the scion.rootsrootstockstemsleaves flowersfruits

45 Artificial Vegetative reproduction  To ensure a quick growth union, all cut surfaces are covered with a soft wax to prevent drying. The tissues of both the stock and the scion will fuse together and will make organic connection, getting nourishment from the stock, but producing fruits of scion retaining parental characters. Grafting is not possible is monocot plants since cambial activity is essential for the union of stocks and scion.  Grafting blends the properties of two plants. It is also used in the production of dwarf fruit trees for the home gardens. High quality roses are usually grafted on wild rose root stocks. Other plants where grafting has been performed successfully are rubber, apple, pear, mango and guava.

46 Grafting peach into plum This wild plum tree has now become half peach and half plum These peach grafts were been successful and have already produced blossoms Main grafting steps: Trimming bark after cutting a branch to be grafted Next: Budwood inserted into branch Completed bark graft which has been tied with tape and waxed with grafting wax

47 The ‘grafted’ Bauhinia appear in two segments: the upper half is Bauhinia blakeana 洋紫荊 and the lower half is Bauhinia purpurea 紅花羊蹄甲. When you look at the joint carefully, then you will notice that the bark textures on both halves are significantly different. Also, the leaves on the branches and those near the foot vary a little bit. When we see the ‘grafted’ Bauhinia, Bauhinia blakeana is just one of the tree names. Bauhinia purpurea is another one. (Well, if the foot of this tree does have leaves and flowers, then it should be labeled with two names!)

48 What are the ADVANTAGES and DISADVANTAGES of Artificial Propagation ?

49 External agents? Good characters? Vegetative propagation Advantages Disadvantages Speed?

50 Undesirable characters…. Offspring are identical….. Diseases in parents….. Vegetative propagation Advantages Disadvantages Overcrowding….. No external agents or other plants are needed Good characters are passed to the offspring A relatively quick way to produce new plants

51 No external factors or other plants are needed for reproduction Undesirable characters are passed on to the offspring Offspring have no new features No new features in offspring to adapt to any changes in environmental conditions Disease of the parent plants can easily be transmitted to the offspring Good characters of the parent are passed to the offspring Vegetative propagation Advantages Disadvantages A relatively quick way to produce new plants Overcrowding can occur which causes competition for resources

52 Importance of Vegetative Propagation  It is the only means of reproduction for seedless plants such as pineapples, seedless grapes, oranges, roses, sugarcane, potato, banana, etc.  Plants raised through vegetative propagation are genetically similar. It preserves the type of characters that a plant breeder desires to retain.  It is very economical and easy method for the multiplication of plants.

53 Micro propagation by tissue culture

54 Tissue culture

55 Application of tissue culture

56  Micro propagation of plants Plant tissue in very small amounts can produce hundreds or thousands of plants continuously. By using tissue culture methods, millions of plants with the same genetic characteristics can be obtained.  Improved crop In crop improvement efforts, pure strains can take six to seven generations of self-pollination or crosses. Through tissue culture techniques, homozygous plants can be obtained in a short time by producing haploid plants through pollen culture, anther or ovaries followed by chromosome doubling.  Production of disease-free plants (virus) Tissue culture technology has contributed in a plant that is free from viruses. In plants that have been infected with the virus, the cells in the bud tip (meristem) is an area that is not infected with the virus. In this way virus-free plants can be obtained from the meristem.  Genetic transformation For example, bacterial gene transfer (such as cry genes from Bacillus thuringiensis) into the plant cells )

57 20.3 Sexual reproduction in flowering plants flowering plants reproduce sexually by producing flowers Structure of a flower carpel stigma style ovary ovule sepal anther filament stamen petal nectary receptacle flower stalk sepals, petals, stamens and carpels are attached to this

58 Structure of a flower Sepals make up the outermost ring (calyx) of a flower protect the inner parts of the flower when it is a bud sepal

59 Petals may be brightly-coloured to attract insects make up the second ring (corolla) of a flower petal nectaries may be present at the base to produce nectar which attracts insects may have insect guides to lead insects towards the nectaries insect guide

60 Stamens male reproductive organs filamentanther supports anther consists of 2-4 pollen sacs inside which pollen grains are formed anther pollen sacs filament when anthers ripen pollen sacs split open to release pollens which contain male gametes

61 Carpels the centre of a flower each consists of –stigma (receives pollen grains) –style (carries the stigma) –ovary (with ovules inside) stigmastyle female reproductive parts

62 Carpels ovules are protected by integument which has a small hole (micropyle) ovules contain the female gametes stigma style ovary each ovule is attached to the ovary wall by a stalk ovary wall ovule integuments female gamete micropyle Structure of a carpel

63 Pollination Pollination –the transfer of pollen grains from anthers to stigmas  fertilization of male & female gametes in ovules cross-pollinationself-pollination wind-pollinationinsect-pollination 1 2

64 Cross-pollination and self-pollination –pollen grains are transferred to a different plant Cross-pollination

65 Cross-pollination and self-pollination –pollen grains are transferred within the same plant Self-pollination

66 Inbreeding (Self-pollination) Advantages: 1.Preserves well-adapted genotypes 2.Insures seed set in the absence of pollinators Disadvantages: Decreases genetic variability

67 Outbreeding (Cross-pollination) Advantages: 1.Increases genetic variability 2.Strong evolutionary potential 3.Adaptation to changing conditions 4.Successful in long-term Disadvantages: 1.Can destroy well-adapted genotypes (offspring are not guaranteed to be viable) 2.Relies on effective cross-pollination

68 Wind-pollination and insect-pollination Wind pollination Insect pollination —pollinated by wind —pollinated by insects Wind-pollinated flowers Insect-pollinated flowers The flowers are structurally adapted to pollination.

69 Structural adaptation of wind-pollinated flowers scent nectaries pollen grain large number smooth and dry light in weight

70 scent nectaries stigma large feathery projects outside the flower for picking up pollen grains from air Structural adaptation of wind-pollinated flowers

71 scent nectaries petal small green or dull- coloured stigma pollen grain Structural adaptation of wind-pollinated flowers

72 scent nectaries anther hangs outside the flower, exposed to wind loosely attached to filament so that light wind can shake it petal stigma pollen grain Structural adaptation of wind-pollinated flowers

73 scent nectaries pollen grain smaller number rough and sticky/ with hooks heavier pollen grains of this flower stick onto the leg of the bee Structural adaptation of insect-pollinated flowers

74 scent nectaries stigma smaller sticky remains inside the flower Structural adaptation of insect-pollinated flowers pollen grain

75 scent nectaries petal larger brightly- coloured stigma Structural adaptation of insect-pollinated flowers pollen grain

76 scent nectaries anther inside the flower where insects will brush against it firmly attached to prevent from being torn away by insects petal stigma Structural adaptation of insect-pollinated flowers pollen grain

77 Outbreeder or Inbreeder?  Often one can tell just by looking at a flower whether it cross- pollinates or self-pollinates. OUTBREEDERINBREEDER self-incompatibility Size of flowers colors nectaries scent nectar guides anthers position Number of pollen grains style position

78 Outbreeder or Inbreeder?  Often one can tell just by looking at a flower whether it cross- pollinates or self-pollinates. OUTBREEDERINBREEDER self-incompatibleself-compatible large flowerssmall flowers bright colorsmono-colored nectaries presentnectaries absent scented flowersunscented flowers nectar guides presentnectar guides absent anthers far from stigmaanthers close to stigma many pollen grainsfewer pollen grains style not included in flowerstyle included in flower

79 Fertilization The growth of pollen tube and fertilization 1Pollen grains land on the stigma of the same species. flower stalk sepal style

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

81 Fertilization The growth of pollen tube and 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 style flower stalk sepal

82 Fertilization The growth of pollen tube and fertilization 4After growing into the ovary, the tube grows through the micropyle of the ovule and the tip of the tube bursts to release the male gamete into the ovule. ovule male gamete micropyle ovary style flower stalk sepal

83 Fertilization The growth of pollen tube and fertilization 5The male gamete enters the ovule and fuses with the female gamete to form a zygote. ovule male gamete micropyle ovary style flower stalk sepal

84 20.4What happens to the floral parts after fertilization? 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

85 consists of Fruits and seeds food store undeveloped plant embryo seed coat plant dispersalseed Fruit fruit wall provides food protects made up of helpsprotects

86 Fruits and seeds Structure of a mung bean seed External appearance seed coat –surrounds the embryo and protects it from damage and against attack of micro- organisms such as bacteria and fungi micropyle –a hole through which embryo absorbs water before it germinates hilum –a scar on the surface of the coat; formed when the ovule detaches from the ovary wall

87 Structure of a mung bean seed Embryo cut opened plumule –develops into the shoot radicle –develops into the root cotyledons –act as food stores –contain starch and proteins to supply food for the plumule and radicle to develop embryo

88 Dispersal of seeds and fruits Why seeds and fruits have to be dispersed to distances far away from parents ? To reduce overcrowding and competition for materials. To colonize new areas which are suitable for seed germination and survival of species.

89 Dispersal wind dispersalanimal dispersal adaptive features of fruits and seeds are small light may have wings/feathery hair brightly-coloured sweet, juicy and good to eat may have hooks

90 Concept Concept diagram Reproduction can be can be asexual reproduction sexual reproduction

91 Concept Concept diagram asexual reproduction can be by can be by binary fission budding vegetative propagation spore formation stem tuber bulbrhizomecormcutting by the formation of by the formation of artificially achieved by artificially achieved by

92 Concept Concept diagram in flowering plants in flowering plants male gamete flower copulation or IVF fertilization sexual reproduction forms forms female gamete in mammals in mammals pollination fertilization involves involves by by fusion is called and and after after for for

93 Concept Concept diagram copulation or IVF fertilization produces produces fertilization for for forms forms zygotefruit contains contains menstruationpregnancy if if fertilization fertilization occurs occurs if no if no fertilization fertilization occurs occurs menstrual cycle contraceptive methods seeds embryo new organism protect protect develops into develops into finally into finally into repeats in prevented by


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