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BIOA02H3 (153)
Chapter 25

BIOA02 TEXTBOOK NOTES CHAPTER 25.docx

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Department
Biological Sciences
Course Code
BIOA02H3
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Monica Sauer

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Plants—Pg. 547 - 576 25.1 DEFINING CHARACTERISTICS OF LAND PLANTS  Mycorrhizas: symbiotic associations with certain soil fungi  Alternation of generations: The regular alternation of mode of reproduction in the life cycle of  Role of fungus: Fungus colonizes the plant roots and grows beyond the plant roots an organism, such as the alternation between diploid (sporophyte) and haploid (gametophyte) phases in plants 25.2C VASCULAR TISSUE WAS AN INNOVATION FOR TRANSPORTING SUBSTANCES  Meiosis in animals & plants: meioses in animals gives rise to gametes, sperm or eggs, (haploid)WITHIN A LARGE PLANT BODY but in plants meiosis gives rise to spores (haploid)  Reason for plants having intense competition for light: since early plants needed water, they  Spores: haploid reproductive structure (usually a single cell) that can develop into a new would grow close to the ground near waternot effective for capturing light (hard to individual without fusing into another cell photosynthesize)  Sporophyte: ‘phyte’ means plant hence ‘spore producing plant’.  Solutions to overcome the problem: xylem & phloem, lignin for strength  Individual of the diploid generation produced through fertilization in organisms that  Xylem: specialized tissue that transports water through the plant body and is made up of cells undergo alternations of generationsproduces haploid spores whose walls are reinforces with lignin  Gametophyte: means ‘gamete producing plant’.  Lignin: tough complex polymer that strengthens the cell wall and allows for upright growth  Individual of the diploid generation when a spore germinates and grows directly by mitotic  Advantages: Increase surface area to absorb sunlight  grew larger divisions in organisms that undergo alternation of generations  Vascular tissue: (vas = duct or vessel) One of the 3 tissue systems in plants that provide the  Haploid phase of cell cycle: begins in specialized cells of the sporophytehaploid cells are foundation for plant organs produced by meiosis  Composition: transport tubes for water and nutrients  When a spore germinates (grows): divides by mitosisproduce a multicellular haploid  Vascular plants: (tracheophyte) plants with xylem, phloem and usually well developed roots, gametophyte stems & leaves  Function of gametophyte: nourish & protect the upcoming sporophyte generation  Phloem: food conducting tissue of a vascular plant  Final feature of land plants: embryo (new sporophytic generation) is retained inside  Conducts sugars throughout a plant that is made from leaves to the rest of the plant gametophyte generation  Examples of vascular plants: ferns, conifers and flowering plants  Difference growth—Vascular & nonvascular plants: vascular plants grow very large due to the 25.3 THE TRANSITION TO LIFE ON LAND support of lignin and open vascular system; non vascular systems are small  Ancestor of modern plants: green algae living near water edge or moist places  Apical meristems: only found in vascular plants  Type of these algae: charophytes  Region of constantly dividing cells near the tips of shoots and roots that produce all tissues  Kingdom plantae: taxonomic kingdom encompassing all living or extinct plants of the plant body  # of phyla: 10  Foundation for extensive branching & root systems in vascular plants: meristem tissue 5.2A EARLY BIOCHEMICAL & STRUCTURAL ADAPTATIONS ENHANCED PLANT 25.2D ROOT AND SHOOT SYSTEMS WERE ADAPTATIONS FOR NUTRITION & SURVIVAL SUPPORT  Greatest challenge for plants: survive in dry terrestrial conditions  Body of non vascular plants: not differentiated into true roots & stems  Early plants limited: cuticle & specialized tissues that transports water from the soil  Cause of evolution of sturdy stem: capacity to synthesize lignin throughout the whole body  Roots: anchoring structures that also absorb water & nutrients in association with mycorrhizal  Result: restricted them to moist habitats fungi  Type of plants: Poikilohyric  Rhizome: a horizontal, modified stem that can penetrate a substrate and anchor the plant  Poikilohyric Plants: little control over their internal water content  Early vascular plants: did not have true rootseventually developed specialized root systems  Cuticle: a outer waxy layer that prevents water loss from plant tissues  Simple stems of early plants become more specialized by: developing shoot system  Ability to regulate water in later evolving plants: could restrict water loss due to cuticles  Shoot systems: stems and leaves of a plant covering their outer surface & stomata  Formation: from apical meristems  Stomata: (singular = stoma, stoma means mouth) ;pores in the cuticle covered surfaces that  Function: absorption of light energy from the sun and carbon dioxide from the air open & close to regulate water loss  Representations of Leaves: modification of stems  Function: carbon dioxide to enter leaves & oxygen and water to exit the leaves  Formation of leaves: when small neighbouring stem branches became joined by thin, web-like tissue containing cells that had chloroplast 25.2B SYMBIOTIC ASSOCIATIONS WITH FUNGI WERE LIKELY REQUIRES FOR EVOLUTION LAND PLANTS 25.2E IN THE PLANT LIFE CYCLE, THE DIPLOID PHASE BECAME DOMINANT 1 | P a g e  As plants evolved on land Haploid gametophyte phase become physically smaller, less 25.3A LIVERWORTS MAY HAVE BEEN THE FIRST LAND PLANTS complex & shorter lifespan  Hepatophyta: phylum that includes liverworts & their bryophyte relationships  Formation of sporophyte generation: begins after fertilization, when the zygote divides by  # of species of liverworts: 6000 mitosesproduces a multicellular diploid organisms  Description: flat branching ribbon like plate of tissue closely against damp soil simple  Body: eventually develop capsules called sporangia which produces spores by meiosis body is called thalus  Sporangia: (angium = vessel or chamber) produces spores via meiosis  Thalus: a plant body not differentiated into stems, roots or leaves  Cause of diploid dominance over time: in haploid plants, there is only one strand of DNAif it  Function of rhizoids: anchor gametophytes to their substrate gets harmed, the plant can be fatal… but in diploid there are “back up” DNA and better survival  Lacking features: none have true stomata guarantee  Production of sexual organs: separate male and female gametophytes  Evolutionary trend of dominance of gametophyte to dominance of sporophyte: Green algae,  Motile sperm released from antheridia swim through surface water to reach eggs in bryophytes, ferns, gymnosperms, angiosperms archegonia  After fertilization small diploid sporophyte develops into the archegonium matures 25.2F SOME VASCULAR PLANTS EVOLVED SEPARATE MALE AND FEMALE and produces haploid via meiosis GAMETOPHYTES  During meiosissex chromosomes segregate, thus some have male genotype & other have  Homosporous: (same spore) when a plant makes 1 type of spore female genotype  Usually a gametophyte that produces such spores is bisexualcan produce both egg and  In Liverworts: spores develops inside sporangia that splits open to release the spores sperm  spore is carried by air currentsto a suitable location that germinatesrise to haploid  Heterosporous: produce 2 types of spores in 2 types of sporangia gametophyte—either male or female  Description of spores: one type is smaller than the other  Gemmae: (gem = bud) small cell masses that form in cuplike growths on thallus  Microspores: smaller sporesdevelops into male gametophyte  Megaspores: larger sporesdevelops in female gametophyte 25.3B HORNWORTS HAVE BOTH PLANTLIKE AND ALGALIKE FEATURES  Found in: vascular plants—gymnosperms & angiosperms  # of species: 100  Anthocerphyta: phylum comprising hornworts 25.3 BRYOPHYTES: NONVASCULAR LAND PLANTS  Description of thallus: short  Bryophytes: (bryon = moss) lack internal transport vessels & are poikilohydric  Description of sporangium: long and pointed (like a horn) & splits into 2 or 3 ribbon like section  Examples: liverworts, hornworts & mosses when it releases pores  Function: small bodies trap particles of organic & inorganic matter  Sexual reproduction: same way in liverworts & reproduces asexually by fragmentation as pieces of thallus breaks off and develop new individuals  Effect: help build soil on bare rock & stabilizing soil surfaces (esp in harsh environments)  Location: grow on wet sites along creek banks  Retain many features of algal ancestors 25.3C MOSSES MOST CLOSELY RESEMBLE VASCULAR PLANTS  Produce flagellated sperm that must swim through water to reach eggs  # of moss species: 1000  Lack complex vascular system  Bryophyta: phylum of nonvascular plants including mosses & their relatives  Composition: have parts that are rootlike, stemlike and leaflive  Moss cycle:  Rhizoids: are like “roots”  Begins: when a haploid spore lands on a wet soil surface  Anchor plant to its substrate & do not take up any water or nutrients from substrate  After the spore germinates: elongates and branches into protonema  Stems and leaves: are not true since it does not have vascular tissues  After several weeks of growth: bud like masses on protonema develop into leafy green  Sporophyte phase: tiny and lives for a short time gametophytes  Bryophyte gametophyte: produce gametes sheltered within a layer of protective cells  Protonema: (“first thread”) structure that arises when a liverwort or moss spore germinates and called gametangium eventually gives rise to a mature gametophyte  Gametangium: flask shaped structures called archegonia that are formed from bryophyte  Sexual reproduction eggs  Production of antheridia and archegonia: tips of male and female gametophytes  Archegonia: (archi = first & gonos = seed)  Movement/Role of sperm: released from antheridia swims through a film of water to the  Antheridia: (antheros = flowerlike; singular is antheridium) Flagellated sperm form in archegonia attracted by a chemical gradient secreted by each eggfertilize eggs rounded gametangia sperm are produced  Fertilization: produces the new sporophyte generation inside the archegoniumin the  Movement/Role of sperm: swims through a film of water to the archegoniafertilize eggs form of diploid zygotes that develop into small, mature sporophyteseach consisting of a  Each fertilize eggs: gives rise to diploid embryo sporophyte which stays attached to sporangium on a stalk gametophyte and produces sporescycle repeats  Relation between sporophyte and gametophyte: sporophyte relies on gametophyte for  Relation between sporophyte and gametophyte: gametophyte is larger, long lived and nutrition and food photosynthetic and sporophyte is attached to gametophyte and depends on it for nutrition  Monophyletic group: did not evolve from a co
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