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Published byCharity Powell Modified over 9 years ago
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Plant Life Cycles
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Plant Evolution Descendants from green algae (~450mya) –C–Contain cellulose in cell walls –C–Contain chlorophyll –S–Starch stored Land Plants Must Overcome –D–Drying out –G–Gas exchange –N–Nutrient transport system –S–Support
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Land adaptations Cuticle: Waxy coating prevents water loss Stomata: pores that open/close to permit gas exchange Roots & Stems: support Vascular system: tissue that transports nutrients –N–Nutrients & water go up plant –S–Sugars go down the plant
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General Plant Life Cycle Alternation of generations Gametophyte (haploid) –H–Haploid spores created by meiosis –G–Gametophyte grows from spore –G–Gametophyte has sperm & egg cells
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Sporophyte (diploid) –D–Diploid zygote created from sperm & egg –Z–Zygote grows into a mature sporophyte –S–Sporophyte creates haploid spores by meiosis Gametophyte grows from spore (cycle restarts)
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Mosses Nonvascular, seedless Grow low to ground to retain moisture Lack true leaves –L–Leaf-like structures only 1 cell thick Rhizoids anchor into soil Early inhabitant of new ecosystems (succession)
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Moss Life Cycle Gametophyte phase –D–Dominant stage –C–Carpet of moss growing near ground Female gametophyte: produces egg Male gametophyte : produces sperm –S–Sperm swims through water to fertilize egg (zygote created) Sporophyte phase –S–Sporophyte stalk grows up from the zygote –S–Sporangia contain haploid spores –H–Haploid spores land Gametophyte stage restarts
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Ferns Seedless, vascular plants –V–Vascular: allows taller growth Rhizoids: underground stems draw nutrients Fronds: leaves uncurl –s–sporangia on underside
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Fern Life Cycle Sporophyte phase –D–Dominant stage –S–Sporangia produces haploid spores –S–Spores released into air Gametophyte phase –S–Spores land & grows into prothallus Female gametophyte: produces egg Male gametophyte : produces sperm –S–Sperm swims to egg –Z–Zygote begins sporophyte stage
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Conifers Seed advantages –D–Don’t depend on water –P–Protects & nourishes embryo –A–Allow plants to grow in new locations Conifers: woody cone houses seeds –M–Male cones: produce pollen –F–Female cones: produce egg Pines, redwoods, spruce, cedar
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Conifer Life Cycle Sporophyte phase –C–Cones grow on mature tree –F–Female cones: contains female gametophyte (megaspore) –M–Male cones: contains gametophyte (microspores) Microspores released & stick to female cones Pollen tube grows from pollen towards the egg Sperm travels down pollen tube (zygote created) Sporophyte stage restarts Seeds released to grow into new sporophyte
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male female
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Flowers Reproductive structure of flowering plants Sepals –o–outer ring of leaves –p–protection Petals –I–Inner ring of leaves –B–Brightly colored to attract pollinators Open petals & sepals reveal male and female structures
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Female Carpal –I–Inner most part –O–Ovary: within the base (female gametophyte) –S–Style: long stalk –S–Stigma: sticky tip, collects pollen Male Stamen –S–Surrounds carpal –F–Filaments: long stalks –A–Anther: produces pollen (male gametophyte)
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A) Microspores (male gametophyte) produced within anthers
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B) Two events: 1. Microspores (male gametophyte) released into the air, wind, or transferred via animals 2. Microspores stick to stigma
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C) Pollen tube grows from the pollen…towards the ovary
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C) Continued: Two sperm cells from the microspore travel down the pollen tube
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D) Double fertilization: 1 sperm fuses w/ egg (zygote created) 1 sperm fuses w/ the embryo sac (endosperm created)
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E) Ovule wall hardens into a seed; Embryo develops
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F) Ovary grows a fleshy tissue (fruit) over the seed
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G) Seed germinates (starts to grow)
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Fruit Production In the seed –E–Embryo –E–Endosperm (nourishes seed) Surrounding ovary grows into a fruit Fruit attracts animals to eat and spread the seeds Fruit seeds in fox droppings
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End of the Semester!
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