Lecture #7 Angiosperm Reproduction 1 Key Concepts: Life

Lecture #7  Angiosperm Reproduction 1 Key Concepts:  Life

Lecture #7 Angiosperm Reproduction 1 Key Concepts:

Life Cycles the alternation of generations The structure of a flower Development of the male gametophyte Pollination in all its glories Development of the female gametophyte Fertilization

Embryos, seeds and fruit Asexual reproduction 2 Diagram of the life cycle for plants 3 All eukaryotes cycle between a 1n and a 2n phase

Critical Thinking What is the haploid stage in animals??? 4 Critical Thinking What is the haploid stage in animals??? 5

X als m i n A Diagram of the life cycle for plants 6

Diagram of the life cycle for plants 7 All modern plants alternate between multicellular 1n and 2n generations Phlyogeny of plants

Our focus is on the most derived group of plants the angiosperms Evolution of reproductive strategies in the other divisions will be covered in 211

8 Angiosperms the flowering plants By far the most important phylum of plants in the modern flora ~90% of all extant plant species Dominate most ecosystems; significant components of nearly all others 1o ecological importance base of terrestrial food chain + many other ecosystem resources

1o economic importance food, building materials, pharmaceuticals, horticulture, floriculture, etc, etc, etc. 9 Angiosperms the flowering plants: diverse, important AND beautiful Images of some flowering plants

10 ALWAYS Diagram of the life cycle for plants 11 Key differences in spore fate:

microspore male gametophyte (pollen, released to the air) megaspore female gametophyte (retained in sporangia)

meiosis New sporophyte egg fertilization 1n 2n

seed (dispersed) sperm embryo zygote 12

Key differences in spore fate: microspore male gametophyte (pollen, released to the air) megaspore female gametophyte

(retained in sporangia) sperm egg What cell division process??? meiosis

seed (dispersed) New sporophyte fertilization 1n 2n embryo

zygote 13 Key differences in spore fate: microspore male gametophyte (pollen, released to the air)

megaspore female gametophyte (retained in sporangia) meiosis New sporophyte egg

fertilization 1n 2n seed (dispersed) sperm

embryo zygote 14 Critical Thinking What are the functional advantages to retaining the female gametophyte???

15 Critical Thinking What are the functional advantages to retaining the female gametophyte??? What is the functional advantage of a seed??? 16

Critical Thinking What are the functional advantages to retaining the female gametophyte??? What is the functional advantage of a seed??? 17 Key differences in spore fate: microspore

male gametophyte (pollen, released to the air) megaspore female gametophyte (retained in sporangia) meiosis

New sporophyte egg fertilization 1n 2n

seed (dispersed) sperm embryo zygote 18

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Diagram of the life cycle for plants 19 The life cycle of angiosperms takes place in the flower: Diagram of a flower

sepals petals stamens carpels Always in that order! 20 The life cycle

of angiosperms takes place in the flower: sepals petals stamens carpels Diagram of a flower

Always in that order! 21 Remember modern molecular evidence indicates four classes of angiosperms paleoherbs magnoliids

eudicots monocots ancestral 22 Paleoherbs and Magnoliids comprise about 3% of angiosperms Magnoliids

Paleoherbs Magnoliaceae, Aristolochiaceae, Lauraceae, Nymphaeaceae, nutmeg,etc black pepper, etc Images of these two classes of angiosperms

23 Modern evidence indicates 4 classes of angiosperms paleoherbs magnoliids eudicots

monocots ~ 97% of angiosperms ancestral 24 Monocots include grasses, sedges,

iris, orchids, lilies, palms, etc.. Images of examples of this class 25 Eudicots include 70+% of all angiosperms: Most broadleaf trees and shrubs Most fruit and vegetable crops

Most herbaceous flowering plants Images of examples of this class 26 Monocots vs. Eudicots we talked about differences in tissue arrangement; flowers vary too Monocots

Flower parts in multiples of 3 Parallel leaf venation Single cotyledon Vascular bundles in complex arrangement ~90,000 species Eudicots Flower parts in multiples

of 4 or 5 Netted leaf venation Two cotyledons Vascular bundles in a ring around the stem Modern classification indicates 2 small primitive groups + eudicots 200,000+ species 27

Stigma (style below) Petals Stamens Image of a monocot flower same on next 3 slides Sepals

A monocot flower 28 Critical Thinking How do you tell sepals from petals??? 29 Critical Thinking How do you tell sepals from petals???

30 Stigma (style below) Petals Stamens Sepals (note point of attachment)

A monocot flower 31 Stamens Petals Stigma (style below)

Image of a eudicot flower A eudicot flower Sepals 32 For all flowers, if all parts are present they

are always inserted in this order: Diagram of flower same on next slide sepals petals stamens carpels

33 The base of the carpel is the ovary The ovary contains at least one ovule Dont get these 2 terms

confused! 34 Ovaries develop into fruits ovules develop into seeds Diagram of flower and fruit 35

Image of eudicot flower, with developing and mature fruits 36 Hands On Go outside and find some flowers dont pick oleander!!! Its poisonous! While you are out, look for fruits Be back here in ~20 minutes

Images of oleander 37 Hands On Examine your flower whole Dissect your flower to find all the flower parts use the microscope as necessary Peduncle / pedicel Receptacle

Sepals Petals Stamens anther and filament Carpel stigma, style and ovary Ovules Sketch!!! 38

Angiosperm Life Cycle Diagram of angiosperm life cycle 39 Development of the male gametophyte

Diagram of angiosperm life cycle 40 Anther sacs are the microsporangia Images of anthers both monocot and eudicot 41

Micrograph of anther 42 Development of the male gametophyte Diagram of angiosperm life cycle

43 Micrograph of pollen Pollen is the male gametophyte 44

Pollination occurs when the pollen contacts the stigma pollen NEVER directly contacts the egg cell in the angiosperms Pollen tubes develop after pollination, elongating to eventually deliver sperm to the egg cell

Micrograph of elongating pollen tubes 45 Wind Pollination:

~ 25% of all angiosperms Lots of pollen Reduced sterile structures Exserted reproductive structures Feathery and/or sticky stigma surfaces Grasses, some asters, many trees Image of grass flowers

46 Close-up image of grass flowers 47 www.missouriplants.com Image of wind pollinated red maple flowers

Staminate Flowers Carpellate Flowers Acer rubrum red maple 48 Animal Vectors for Pollination: ~ 75% of all angiosperms Mostly insects, but also birds, bats and

other small mammals Incredible array of structural adaptations to attract pollinators: visual, scent, food, accessory structures. Many co-evolutionary relationships, Image of bee especially with insects pollinating redbud flower

49 From here through slide 75 images of adaptations for animal pollination 50 51 52

53 54 55 Alana Lea Night flying

bats and moths often pollinate white flowers 56 Critical Thinking Why would desert plants

often be pollinated by night flying animals??? 57 Critical Thinking Why would desert plants often be pollinated by night flying animals???

58 59 Critical Thinking Who on earth would pollinate a flower that smells like rotten meat??? 60

Critical Thinking Who on earth would pollinate a flower that smells like rotten meat??? 61 62 63

64 65 Co-evolution with the asters the Walmart strategy many small flowers open over time 66 Cluster of

flowers Flower, not petal 67 Critical Thinking What is the selective advantage of this pattern lots of flowers, opening over time, generalist pollinators???

Are there disadvantages??? 68 Critical Thinking What is the selective advantage of this pattern lots of flowers, opening over time, generalist pollinators??? Are there disadvantages???

69 Co-evolution with the orchids the Tiffany strategy fewer but highly specialized flowers 70

Orchid Bee Bee Orchid 71 Critical Thinking What is the selective advantage of this pattern highly specialized pollinators??? Are there disadvantages???

72 Critical Thinking What is the selective advantage of this pattern highly specialized pollinators??? Are there disadvantages??? 73

Critical Thinking In both asters and orchids many seeds are produced by each floral unit Which group of seeds would have the most genetic diversity??? 74 Critical Thinking In both asters and orchids many seeds are

produced by each floral unit Which group of seeds would have the most genetic diversity??? 75 Outcrossing Mechanisms Some species routinely self-fertilize (guarantees some seed production, can be less metabolically costly)

Most have some mechanism to promote outcrossing so that individuals do not self pollinate. 76 Critical Thinking Can you think of some mechanisms to promote outcrossing???

77 Critical Thinking Can you think of some mechanisms to promote outcrossing??? 78 Hands On Based on the structure, color, pattern, etc

of your flower, who do you think pollinates??? How about potential outcrossing mechanisms??? 79 Angiosperm Life Cycle Diagram of angiosperm life cycle

80 Carpel origin ovules are inside the ovary portion of the carpel Diagram showing proposed evolutionary mechanism for carpel development 81

Ovules are the megasporangia Diagram showing ovules inside ovary 82 Development of the female gametophyte

Diagram of angiosperm life cycle 83 Development of the embryo sac by 3 mitosis divisions, after meiosis produces the megaspore surviving megaspore 3 have degenerated

Diagram showing development of megaspore 84 Critical Thinking How many nuclei are produced by 3 mitosis divisions? 85

Critical Thinking How many nuclei are produced by 3 mitosis divisions? 86 Critical Thinking How many nuclei are produced by 3 mitosis divisions?

87 Critical Thinking How many nuclei are produced by 3 mitosis divisions? 88 The embryo sac is the female gametophyte

Note: embryo sac is 7 cells with 8 nuclei 89 Pollen tubes develop after pollination, elongating to deliver sperm to the embryo sac

Elongating pollen tubes 90 The pollen tube elongates and delivers two sperm Remember the ovule is inside the ovary. Pollen is delivered to stigma.

Diagram of double fertilization Pollen tube cell digests a tunnel toward micropyle, directed by chemical signals from the synergids 91 Remember the structure of the

embryo sac 92 Double fertilization produces 2n zygote and 3n endosperm 93 Double Fertilization: essentially

unique to angiosperms Found in one, small, possibly ancestral group of gymnosperms.where no endosperm is actually produced. Found in ALL angiosperms 94 Double fertilization produces 2n zygote and 3n endosperm

95 Endosperm function: Stores nutrients and carbohydrates Sometimes stored reserves are transferred to the developing embryo Sometimes the germinating seedling absorbs the stored reserves directly from the endosperm

96 Fertilization Zygote Embryo Diagram of fertilization and development of embryo 97 Embryonic Development

Diagram of embryonic development Many questions remain about factors that control development.. 98 Seed of shepherds purse showing embryo Direction of development is determined from first cell

division (terminal / basal) Terminal cell divides to produce embryo Basal cell divides to produce the suspensor (anchor, plunger, and nutrient conduit) Micrograph of developing embryo

99 Embryonic Development Diagram of developing embryo Other factors may include cell location, cytoplasm contents, regulatory genes, hormones

100 Embryo develops inside the seed, surrounded by endosperm and a seed coat Diagram of eudicot and

monocot seeds showing embryo and endosperm 101 Critical Thinking What is the chromosome number in the different parts of the seed??? Seed coat 1n, 2n, 3n??? Endosperm 1n, 2n, 3n???

Embryo 1n, 2n, 3n??? 102 Critical Thinking What is the chromosome number in the different parts of the seed??? 103

Critical Thinking What is the chromosome number in the different parts of the seed??? 104 Embryo develops inside the seed Radicle root Hypocotyl and

Epicotyl stem Diagram of eudicot and monocot seeds showing embryo and endosperm Cotyledon nutrients for seedling Plumule first true leaves

105 Critical Thinking Most seeds are shed in a dormant condition suspended metabolism What might make a seed germinate??? 106 Critical Thinking

Most seeds are shed in a dormant condition suspended metabolism What might make a seed germinate??? 107 Seed Germination Diagram of germinating seeds

108 Hands On Dissect the softened seeds Look for embryo, including cotyledons, and endosperm Use the microscope as necessary Sketch several species Discuss implications of varying amounts of cotyledon vs. endosperm

109 Fruits mature ovary + any accessory structures Diagram of flower and fruit 110 Fruits function mostly for seed

dispersal The ovary wall (pericarp) is typically the bulk of the fruit can be dry or fleshy Dry fruits typically disperse by gravity, wind currents, or explosions Some are carried by animals via sharp or barbed hairs Fleshy fruits are typically eaten my some animal, with the seeds planted in fecal droppings Most are indehiscent

111 From here through slide 118, images of fruits showing adaptations for dispersal 112 113 Fruits function mostly for seed

dispersal The ovary wall (pericarp) is typically the bulk of the fruit can be dry or fleshy Dry fruits typically disperse by gravity, wind currents, or explosions Some are carried by animals via sharp or barbed hairs Fleshy fruits are typically eaten by some animal, with the seeds planted in fecal droppings Most are indehiscent

114 115 116 Fruits function mostly for seed dispersal The ovary wall (pericarp) is typically the bulk of the fruit can be dry or fleshy

Dry fruits typically disperse by gravity, wind currents, or explosions Some are carried by animals via sharp or barbed hairs Fleshy fruits are typically eaten my some animal, with the seeds planted in fecal droppings Most are indehiscent 117 Coconut palms and the founder effect.

118 Hands On Did you find any fruits, or partially developed fruits? Examine them for structure-function relationships Class discussion on grocery store fruits vs. vegetables

119 Angiosperm Life Cycle REVIEW Diagram of angiosperm life cycle 120

???s Diagram of plant life cycle 121 Asexual Reproduction Images of asexual reproduction

122 Critical Thinking Pros and cons of asexual reproduction??? 123 Critical Thinking Pros and cons of asexual reproduction???

124 Key Concepts: QUESTIONS???

Life Cycles the alternation of generations The structure of a flower Development of the male gametophyte Pollination in all its glories Development of the female gametophyte Fertilization Embryos, seeds and fruit Asexual reproduction

125

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