Chapter 30 Notes
Chapter 30 Notes Life103
Popular in Biology of Organisms-Animals and Plants
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This 4 page Class Notes was uploaded by Courtney Potter on Thursday October 29, 2015. The Class Notes belongs to Life103 at Colorado State University taught by Shane Kanatous; Graham Peers in Summer 2015. Since its upload, it has received 17 views. For similar materials see Biology of Organisms-Animals and Plants in Entomology at Colorado State University.
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Date Created: 10/29/15
Chapter 30 The Evolution of Seed Plants Seeds and Pollen Grains Are Key Adaptations for Life on Land Advantages of Reduced Gametophytes Microscopic gametophytes which rely on the sporophyte of the plant for nutrition 0 Develop from spores within sporangia o The sporophytes which they reside shields them from drying out Heterospory Megasporangium produces one type of megaspore that produces female gametophytes Microsporangium produces two types of microspores which become male gametophytes Ovues and Production of Eggs Gymnosperms have one layer of integument surrounding their megasporangia o Angiosperms have two layers of integument surrounding their Megasporangia o This is called and ovule Megasporangia megaspore and integument 0 Female gametophyte inside ovulum produces more eggs Polen and Production of Sperm Microspore develops into pollen grain which coats male gametophyte and is surrounded by protective substance from drying out called sporopollenin o Pollination transfer of pollen to seed plant with ovules o Carried by the wind or animals 0 Flagella lost in most gymnosperms and all angiosperms Evolutionary Advantage of Seeds 0 Once sperm fertilizes egg the ovule turns into a seed Multicellular verses unicellular spores Seeds can live for days to years verses the short lifespan of a spore because they have an embryo protected by the seed coat 0 Unlike spores they have a supply of food within the seed 0 In favorable landing conditions the food provides growth for the sporophyte embryo as it becomes a seedling Gymnosperms Bear quotNaked Seedsquot Typically on Cones 0 Most are Conifers such as pines firs and redwoods 0 Naked seeds exposed on Sporophylls modi ed leaves that form strobili cones Life Cycle of a Pine Heterosporous The conifer is a sporophyte the cones are the sporangia ovulate and pollen cones o Ovulate cone has two ovules each has megasporocytes which undergo meiosis and produce haploid megasporesgtmegaspore develops into female gametophytes which are in sporangia o Pollen cone has cells called microsporocytes which undergo meiosis producing haploid microsporesgt the microspore develops into pollen grain Eary Seed Plants and the Rise of G ymnosperms First seed plants found 360 mya and the rst gymnosperms found 305 mya o lived in moist Carboniferous period dominated by lycophytes horsetails and seedless vascular plants 0 Permian climate drier allowed gymnosperms to take over Thick cuticles and needle shaped leaves G ymnosperm Diversity Phylum Cycadophyta 0 Most endangered of all plant groups 0 Have large cones and palmlike leaves 0 Sperm is agellated o Phylum Ginkgophyta o Ginkgo Biloba only surviving species 0 Flagellated sperm 0 Phylum Gnetophyta o Gnetum o Ephedra o Welwitschia o Grouped together by molecular systematics live in deserts and tropical areas 0 Phylum Coniferophyta o Largest phylum with 600 species 0 Variation of trees pine needles leaves northern and southern hemispheres woody cones and eshy cones deciduous and evergreens The Reproductive Adaptations of Angiosperms Include Flowers and Fruits Characteristics of Angiosperms Classi ed as Phylum Anthophyta 0 Flowers 0 Structure specialized for reproduction pollen grain transported by insects and wind Has four modi ed leaves called Sporophylls Sepals green and enclose the ower before it opens sterile Petalattracted pollinators brightly colored sterile Stamen reproductive organ that produces microspores that make male gametophytes that turn into pollen grain Filament stalk Anther sac o Carpels make megaspores which become female gametophytes Stigma sticky part that receives pollen Style leads from stigma to ovary Ovary contains one or more ovules 0 Flowers with all four organs are complete those without all four are incomplete 0 Fruits o Ovary walls thickens after seeds develop from ovules 0 Protect seeds and aid in dispersal OOOO Angiosperm Life Cycle 0 On anther microsporangium has microsporocytes that undergo meiosis producing microspores Each male gametophyte has two haploid cells one makes two sperm the other forms a tube cell that produces a pollen tube 0 Each ovule has female gametophyte known as embryo sac few cells one is an egg Pollen grain adheres to stigma pollen tube penetrates micropyle discharging two sperm into ovule Diploid zygote formed 0 Develops into sporophyte embryo with rudimentary root and the cotyledons seed leaves 0 Other sperm fertilizes the central cell of female gametophyte making it a triploid endosperm 0 Double fertilization ensures that plants don t waste resources on infertile eggs Angiosperm Diversity Began in the Cretaceous period 0 Basal Angiosperms o 100 species three lineages o Magnoliids o Magnolias laurels and pepper plants 0 8000 species 0 Woody and herbaceous species Eudicots 0 170000 species 0 Flowering plants and trees legumes 0 Two true cotyledon Human Welfare Depends on Seed Plants 0 Most of our food comes from angiosperms and we use them to feed livestock Arti cial selection has made the fruit from some angiosperms bigger Flowering plants also provide coffee beans cocoa tea leaves spices Used for medicines and to harvest wood Threats to Plant Diversity 0 Tropical forests have twothirds of people living around them and cutting them down faster than they can grow 0 Loss of forests keeps more atmospheric carbon dioxide into the atmosphere causing global warming 0 loss of insects and other animals because of it