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Reproduction.

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Presentation on theme: "Reproduction."— Presentation transcript:

1 Reproduction

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

3 Two types of reproduction
Asexual Sexual

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

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

6 division of unicellular organisms into equal halves e.g. Amoeba
Binary fission Binary fission division of unicellular organisms into equal halves e.g. Amoeba

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

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

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

10 Budding the new cell breaks off from the parent cell

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

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

13 Fragmentation e.g. spirogyra

14 Amazing power of regeneration in starfish
Fragmentation Amazing power of regeneration in starfish

15 Fragmentation

16 regeneration in flatworm
Fragmentation regeneration in flatworm

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

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

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

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

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

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

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

24 Vegetative propagation
Examples of storage organs Tuber Bulb Rhizome Corm 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

25 Vegetative propagation
Tuber Vegetative propagation of a potato plant

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

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

28 Vegetative propagation
Tuber Vegetative propagation of a potato plant

29 Vegetative propagation
Bulb onion bulb

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

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

32 Vegetative propagation
Rhizome Growth of a ginger rhizome

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

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

35 Vegetative propagation
Corm Gladiolus

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

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

38 Vegetative propagation
Corm

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

40 Artificial propagation by cutting

41 Artificial Vegetative reproduction

42 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.

43 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. 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.

44 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.

45 Grafting peach into plum
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 These peach grafts were been successful and have already produced blossoms This wild plum tree has now become half peach and half plum

46 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!)

47 ADVANTAGES and DISADVANTAGES
What are the ADVANTAGES and DISADVANTAGES of Artificial Propagation ?

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

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

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

51 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.

52 Micro propagation by tissue culture

53 Tissue culture

54 Application of tissue culture

55 Application of tissue culture
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 )

56 20.3 Sexual reproduction in flowering plants
flowering plants reproduce sexually by producing flowers anther stamen stigma filament style carpel petal ovary ovule nectary receptacle sepal sepals, petals, stamens and carpels are attached to this flower stalk Structure of a flower

57 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

58 make up the second ring (corolla) of a flower
petal Petals make up the second ring (corolla) of a flower may be brightly-coloured to attract insects 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

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

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

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

62 Pollination the transfer of pollen grains from anthers to stigmas
fertilization of male & female gametes in ovules cross-pollination self-pollination 1 Pollination 2 wind-pollination insect-pollination

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

64 Cross-pollination and self-pollination
pollen grains are transferred within the same plant

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

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

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

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

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

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

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

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

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

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

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

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

77 Outbreeder or Inbreeder?
Often one can tell just by looking at a flower whether it cross-pollinates or self-pollinates. OUTBREEDER INBREEDER self-incompatible self-compatible large flowers small flowers bright colors mono-colored nectaries present nectaries absent scented flowers unscented flowers nectar guides present nectar guides absent anthers far from stigma anthers close to stigma many pollen grains fewer pollen grains style not included in flower style included in flower

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

79 The growth of pollen tube and 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

80 The growth of pollen tube and fertilization
Pollen 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. style male gamete flower stalk sepal The growth of pollen tube and fertilization

81 The growth of pollen tube and fertilization
After 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. style ovule male gamete ovary flower stalk sepal micropyle The growth of pollen tube and fertilization

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

83 20.4 What happens to the floral parts after fertilization?
wither and drop off remains of stigma and style scar stamen sepal integument seed coat petal ovary wall fruit wall ovule seed ovum embryo A Bauhinia flower after fertilization Fruit(pod) splits open to two halves

84 undeveloped plant embryo
Fruits and seeds Fruit consists of protects helps fruit wall seed plant dispersal made up of seed coat protects undeveloped plant embryo provides food food store

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

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

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

88 adaptive features of fruits and seeds are
Dispersal wind dispersal animal 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

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

90 vegetative propagation
Concept diagram asexual reproduction can be by binary fission budding vegetative propagation spore formation by the formation of artificially achieved by stem tuber bulb rhizome corm cutting

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

92 contraceptive methods
Concept diagram for fertilization fertilization copulation or IVF produces forms if no fertilization occurs if fertilization occurs fruit zygote contains develops into menstruation pregnancy seeds repeats in prevented by protect embryo menstrual cycle contraceptive methods finally into new organism


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