2 What is a plant? Multicelled Eukaryotic Autotrophic Cell wall made of celluloseAdditional CharacteristicsCuticleStomataSecondary products (poisons, lignin, sporopollenin)Starch storage
3 The Four PhylaBryophyta – mossesnonvascularPterophyta – fernsVascularSeedlessGymnosperm – conifers“Naked” seeds – not enclosed in an ovaryAngiosperm – flowering plantsSeeds contained in fruits – a mature ovaryGametophyte generation becomes reducedSperm goes from flagellated to pollenVascular plantsOrigin of the seedEmergence of flowering plantsPlant kingdom in monophyletic (derived from a common ancestor)
5 Why are Charophyceans thought to be ancestors of land plants? 1. Homologous Chloroplasts2. Biochemical similarity3. Similarity in the mechanisms of mitosis and meiosis4. Similarity in sperm structure5. Genetic relationship (rRNA)*** Modern Charophytes are not the ancestors of plants. Evidence shows that the modern Charophytes and plants both evolved from a common ancestor that would be classified as a Charophyte.
6 Adaptations of land plants (aka “embryophytes) Deal with drying out, UV light and reproduction without waterLigninSporopolleninReduced gametophyteGametangiaApical meristemSeedsPollen grainVascular tissue (xylem/phloem)
8 Antheridia Archegonia One generation is a Gametophyte (n) – multicelled individual made of haploid cells-- produces gametangia by mitosis…gametes within the gametangia are protected by a jacket of “sterile” cells (protects gametes and embryos).Antheridia – male gametangia…produces sperm Archegonia – female gametangia…produces eggOne generation is a Sporophyte (2n) – multicelled individual made of diploid cells-- produce haploid “spores” via meiosis-- spores divide via mitosis to produce gametophyteSterile cellsSterile cellsSpermEggAntheridiaArchegonia
9 Bryophytes Nonvascular Gametophyte is the dominant stage of life cycle Need water to reproduceLack lignin-fortified tissue
10 Gametophyte generation is dominant generation sporophyte is smaller and short lived. Depends on the gametophyte for water and nutrientsDiploid sporophyte produces haploid spores via meiosis in a structure called a sporangium
11 Adaptations of Pteridophytes (ferns) not seen in Bryophytes 1. Subterranean root system (Bryophytes had rhizoids)2. Stems3. Leaves4. Vascular Tissuea. Xylem – water, minerals up (dead cells)b. Phloem – sugars, amino acids throughout (living cells)5. Lignina. function in mechanical supportb. Xylem also has lignified cellsDominant phase of the fern life cycle is the sporophyte phase.
12 How is the reduced gametophyte an adaptation for seed plants? Spores are retained within the sporangia (not released)Gameotphyte develops within the wall of the sporeExposed to sun’s UV rays (mutations) – diploid can handle mutations more easily than haploids.Sporophyte embryo is dependent on tissues of the maternal gametophyteWhy not completely eliminate the gametophyte generation?Cooksonia – oldest fossilized vascular plant preserved down to the tissue – sporophyte was dominant stage and it was branched.
13 What is the significance of the seed What is the significance of the seed? The seed replaced the spore as the main means of dispersing offspringMulticelledSporophyte embryo packaged with food and protective coat (can withstand more harsh environments)Can disperse offspring more widelyAll seed plants are heterosporousMegasporangium is a solid fleshy structure called the nucellusInteguments envelop megasporangiumMegasporesFemale gametophyte develops within the wall of the megaspore nourished by nucellus. This contains the egg.Ovule
14 What is the advantage of pollen? Pollen grain = Male gametophyte (became vehicles for sperm cells in seed plants)Microspores develop into pollen grains which mature to be male gametophytes (protected by sporopolleninIf it lands close to the ovule, it elongates a tube that discharges one or more sperm into the female gametophyte within the ovule.Mode of travel different than water
15 Four Phyla of Gymnosperms Phylum Cycadophyta (thrived with the dinosaurs)Phylum Ginkgophyta (Ginko biloba is the only surviving species)Phylum GnetophytaPhylum Coniferophyta – most common
17 Adaptive value of the flower to plants: Pollination more specific (rely more on insects and other animals to transfer pollen, not just wind)Fruits (mature ovaries) protect dormant seeds and aid in their dispersal.Role of Ovaries and Ovules – the wall of the ovary thickens when an egg (ovule) is fertilized. This is the “fruit.” The seeds are fertilized ovules.Examples: pea pods, apples, orangesFeatures that aid in seed dispersalparachutes or propellers (wind)hollow inside (coconut) so it floatsBurrs to cling to fur (animal dispersal)Edible (animal disperal)