BIO121PPT - Reproduction in Flowering Reproduction Plants...

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Unformatted text preview: Reproduction in Flowering Reproduction Plants Plants Chapter 36 Sexual Reproduction Costly, and often complicated, but often Costly, worth it in the long run. worth Genetic diversity gained through sexual Genetic recombination lets individuals survive in changing environment as well as to exploit new environments. 1 Lily Flower Flower Parts 1 Sepals Sepals – cover and protect flower parts in bud cover Petals – attract animal pollinators to flower attract Stamens Stamens – produce pollen grains produce 2 Flower Parts 2 Each stamen consists of Each stamen – a thin stalk (filament) – attached to a saclike structure (anther) Carpel – female reproductive unit Flower Parts 3 Pistil – a single carpel or group of fused carpels single Each pistil has 3 sections: pistil has – stigma, where pollen grains land – style, through which pollen tube grows – ovary, containing one or more ovules containing ovules 3 Female floral parts Male floral parts Pollen grain (each will produce two sperm cells) Stigma Style PISTIL (consisting of one or more carpels) Anther STAMEN Filament Ovary Ovules (each producing one egg cell) Petal Sepal Receptacle Peduncle Fig. 36-1b, p. 768 Pollen Pollen – forms within pollen sacs in anther forms Each pollen grain contains 2 cells pollen contains – 1 generates two sperm cells – 1 produces a pollen tube through which produces pollen through sperm cells reach the ovule sperm 4 Eggs Structures formed in the ovule: – 1 egg egg – 2 polar nuclei polar – several other nuclei Egg and polar nuclei participate in and polar participate fertilization fertilization Egg and Egg Pollen Pollen 5 Pollinating Agents Pollinating Insects Insects Ultraviolet Markings on Ultraviolet Insect-Pollinated Flowers Insect 6 Pollinating Agents 2 Birds Pollinating Agents 3 Mammals 7 Learning Objective 4 Define coevolution Define coevolution Give examples of ways that plants and Give their animal pollinators have affected one another’s evolution another Coevolution Reciprocal adaptation – 2 species (flowering plant, animal pollinator) species form interdependent relationship affecting one another’s evolution another evolution Example: Example: – flowers with large, showy petals and scent – bees with hairy bodies that catch pollen grains bees 8 Woodcock Orchid Mimics bees Comet Orchid and Comet “The Moth that was Predicted” 9 All flowering plants are dependent All upon animal pollenators. pollenators 1. True 2. False 0% Fa ls e Tr ue 0% 0 of 406 Pollinating Agents Wind Wind – flowers make large amounts of pollen flowers – have smaller petals or no petals – no scent or nectar 10 Wind Pollination Sexual Reproduction Costly, but often worth it. Genetic diversity gained through sexual Genetic recombination lets individuals survive in changing environment as well as to exploit new environments. 11 Pollination and Fertilization Pollination – transfer of pollen grains from anther to stigma Fertilization – after pollination – fusion of gametes Flowering Plants Undergo double fertilization in ovule Undergo in Egg fuses with 1 sperm cell – forming zygote (fertilized egg) forming zygote – zygote develops into embryo in seed zygote seed 2 polar nuclei fuse with 1 sperm cell – forming triploid nutritive tissue (endosperm) forming (endosperm) 12 Anther Pollen grains Fig. 36-9a, p. 775 1 Pollination occurs. Generative cell Tube cell Style Pollen grain Ovary Ovule (containing female gametophyte) Integuments Meiosis and mitosis Megasporocyte Fig. 36-9b, p. 775 13 Stigma Pollen tube 2 Pollen tube grows through style to ovule in ovary. 2 polar nuclei Zygote Sperm cells Female gametophyte Egg 3 Two sperm cells move down pollen tube and enter ovule. Tube nucleus Fig. 36-9c, p. 775 3 nuclei fuse to form endosperm Zygote 4 Double fertilization occurs. Fig. 36-9d, p. 775 14 Mature Seed Contains Contains – a young plant embryo – nutritive tissue for use during germination: nutritive endosperm or cotyledons (seed leaves) cotyledons Tough, protective seed coat surrounds seed Tough, seed Seed Structure 15 Relationships Ovules: potential to develop into seeds potential seeds Ovaries: potential to develop into fruits Ovaries: fruits Fruits: mature, ripened ovaries Fruits: ovaries Seeds: enclosed within fruits Seeds: fruits Germination (Seed Sprouting) Internal factors – maturity of the embryo – presence or absence of chemical inhibitors – presence or absence of hard, thick seed coats 16 Germination (Seed Sprouting) External environmental factors – requirements for oxygen, water, temperature, requirements and light Example: Example: – before germinating, dry seeds absorb water before by imbibition imbibition Imbibition 17 Germination and Growth Plants only reproduce sexually. 1. True 2. False 3. Well, false, but Well, 0% W el l, fa ls e, bu t w he n. .. 0% Fa ls e 0% Tr ue when they don’t, when t, it’s more by it more “accident” than by than adaptation. adaptation. 0 of 406 18 Asexual Reproduction Parental genotype is preserved Genetic similarity may be advantageous if Genetic environment is stable environment Don’t need to “hook up”. need Can usually still reproduce sexually later. New shoot Scale leaf (at node) Adventitious roots Stolon (runner) Stolon Fig. 36-21e, p. 784 19 Suckers Develop from roots with adventitious buds – produce additional roots, new plants 20 Agricultural Propagation of Agricultural Bananas Bananas Plantlets Develop on leaves with meristematic Develop tissue along their margins tissue 21 Plant Growth and Plant Development Development Chapter 37 To what kind of external stimuli To may plants respond? may Light Gravity Touch Pheromones and Pheromones other chemicals other 5. All of these and All more more 6. Plants cannot Plants respond to external stimuli stimuli 1. 2. 3. 4. 91% 1% 0% 1% 1% Li g ht G ra Ph vi ty er om To on uc es Al h lo an ft d he ot Pl h. se an . an ts d ca m nn or ot e re sp o. . 5% 22 Learning Objective 1 Describe phototropism, gravitropism, and Describe phototropism gravitropism and thigmotropism thigmotropism Phototropism Growth in response to the direction of light 23 Gravitropism Growth in response to gravity Fig. 37-2b, p. 790 24 Thigmotropism Growth in response to contact with a solid Growth object object Who wrote a classic book on insectivorous Who plants published in 1875? plants 1. Gregor Mendel 2. Abraham Lincoln 44% 41% 3. Charles Darwin 4. Dr. Wiles Science Guy Science 4% 6% 6% G re go rM A en br de ah l am Li nc C ol ha n rle s Da rw in Bi ll D Ny r. W e, il e th s e Sc ie nc .. . 5. Bill Nye, the Bill 25 KEY CONCEPTS A plant may respond to an external stimulus, plant such as light, gravity, or touch, by a directional growth response, or tropism, and other environmental stimuli such as pheromones from other plants pheromones Study of tropisms has helped biologists Study elucidate links between the external environment and internal signals such as hormones hormones Learning Objective 2 Describe a general mechanism of action Describe for plant hormones, using auxin as your plant using auxin as example example 26 Plant Hormones Organic compounds produced by plants Act as highly specific chemical signals Elicit responses that regulate growth and Elicit development development Who performed a classic experiment on the Who mechanisms of phototropism in the 1870’s? mechanisms 1. Gregor Mendel 56% 2. Abraham Lincoln 3. Charles Darwin 33% 4. Dr. Wiles 5. Robert Pattinson Robert Pattinson 9% 1% Dr .W R il e ob s er tP at tin so n G re go rM en Ab de ra l ha m Li nc ol Ch n ar le s D ar w in 1% 27 Darwins’ Experiments (1870s) Phototropism experiments on grass seedlings Phototropism – Covered coleoptile tip, plant didn’t bend bend – Removed coleoptile tip, plant didn’t bend bend – Bottom of coleoptile shielded from light, coleoptile Bottom bent Darwins’ Experiments (1870s) Darwins 28 Darwins’ Experiments (1870s) Conclusion: Some substance is Some transmitted from upper part to lower part that causes the plant to bend that Frits Went’s Experiments Frits Went Experiments (1920s) (1920s) Isolated phototropic hormone from oat Isolated coleoptiles coleoptiles – removed coleoptile tips, placed on agar blocks removed Placed agar blocks squarely on decapitated coleoptile; normal growth resumed – substance (auxin) diffused from coleoptile tip, substance to agar, to decapitated coleoptile 29 Went’s Experiments (1920s) KEY CONCEPTS Hormones are chemical signals Hormones responsible for coordinating and regulating many aspects of plant development many 30 KEY CONCEPTS Growth and development are influenced Growth by a plant’s iinternal conditions and signals nternal by from its external environment from Learning Objective 4 List several ways each of these hormones List affects plant growth and development: auxins, gibberellins, cytokinins, & auxins gibberellins cytokinins ethylene. ethylene 31 Auxin Cell elongation Cell Tropisms Apical dominance Apical Inhibition of axillary buds by apical meristem Fruit development Fruit Stimulates root development on stem cuttings cuttings Effects of Auxin Phototropism Root Development 32 Shaded side of coleoptile Light rays Illuminated side of coleoptile Fig. 37-6, p. 794 Gibberellins Flowering Germination Stem elongation 33 Cytokinins Promote cell division Promote and differentiation and Delay senescence Delay senescence – the natural aging the process process Ethylene A plant pheromone Ripening fruits Apical dominance Leaf abscission Wound response Thigmomorphogenesis – developmental response to mechanical developmental stressors such as wind Senescence Senescence 34 Ethylene and Fruit Ripening Learning Objective 6 How do varying amounts of light and How darkness induce flowering? darkness 35 Photoperiodism Any response of plants to the duration and Any timing of light and dark Flowering is a photoperiodic response in many plants Circadian Rhythm Circadian A regular period in growth or activities that regular approximates the 24-hour day approximates hour – reset by rising and setting of the sun reset Examples: Examples: – opening and closing of stomata – sleep movements 36 KEY CONCEPTS Growth and development are influenced Growth by a plant’s iinternal conditions and signals nternal by from its external environment from Who was born on February 12th, exactly 202 years ago this Saturday? exactly 68% 1. George George 4. 5. 21% 6% 3% 2% W as hi ng A br to ah n am Li nc Ch ol n ar le s D ar w in Dr .W Al il e lo s ft he ab ov e 3. G eo rg e 2. Washington Washington Abraham Lincoln Charles Darwin Dr. Wiles All of the above 37 To which of the following fields of To study did Darwin contribute? study Evolution Botany Zoology Geology Oceanography Psychology Anthropology Philosophy All of these and All more! more! 91% 4% 3% 0% 0% 1% 0% 0% 0% Ev ol ut io n Bo ta ny Zo ol og y G eo O ce lo an gy og ra ph Ps y yc An hol og th y ro po Al lo Ph log y ft ilo he so se ph an y d m or e! 1. 2. 3. 4. 5. 6. 7. 8. 9. Q & A Session Monday: Regular lecture time. Bring your questions. Bring 38 ...
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