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Today’s Plan: 3/30/10 Bellwork: Mass plants and record data (15 mins) Plant Phylogeny Begin Mosses (45 mins) Plant Notes (25 mins) Today’s Plan: 3/31/2010 Bellwork: Mass Plants and record data (15 mins) Moss/Fern Lab (45 mins) Notes continued (25 mins) Today’s Plan: 4/6/10 Bellwork: Discuss last week/due dates(5 mins) Leaf, Stem, and Root lab (50 mins) Finish plant phylogeny notes, begin Plant structure and function notes (25 mins) Plant evolution and phylogeny Plants are belived to have evolved from green algae about 500 million years ago There are 4 main things that plants and algae have in common: Rosette-shaped cellulose-synthesizing complexes Peroxisome enzymes (that minimize loss of organic products of photorespiration) Flagellated sperm (in some plant species) Phragmoplast (microtubule structure that forms between the daughter nuclei, which allows the cell plate to form between the two new cells Moving to land Why move to land? No water to filter out sunlight Abundance of space with minimal competition More abundant CO2 in air than in water In order to colonize land, plants required the following adaptations: A root system for absorbing water and anchoring Structural adaptations to allow the organism to be upright Structural adaptations to prevent the organism from drying out How’d they do it? Before the evolution of roots, plants used mycorrhizal relationships for absorption of water and nutrients from the soil Plants evolved a waxy cuticle Plants produced secondary compounds (not primary products of plant metabolism) that produce strong tastes and odors to deter attack by pathogens and predators, and to block harmful UV rays Plant Derived Characters Alternation of Generations (doesn’t occur in green algae, so it appears to have convergently evolved) Haploid gametophyte, Diploid sporophyte Walled spores produced in sporangia Multicellular gametangia Structures that produce gametes Apical Meristems Regions of growth where the plant elongates at the ends of the stem Figure 30-15 Egg (n) Gametes are produced in gametangia Haploid (n) Diploid (2n) Sperm (n) Zygote (2n) (retained on parent) Multicellular adult (n) Spores (n) Figure 30-16 Haploid (n) Diploid (2n) Gametes (n) Gametophyte (n; multicellular, haploid) Zygote (2n) Sporophyte (2n; multicellular, diploid) Spores (n) Figure 30-13 Antheridium Sperm form in antheridia. Eggs form in archegonia. Egg Plant Phylogeny Of course, there’s much debate about the degree to which plants are related to one another, but based on certain characteristics, we group plants into 3 main categories: Nonvascular plants (Bryophytes) Seedless Vascular Plants (Ferns and Fern allies) Seed Plants (two sub-groups): Naked-seed plants (Gymnosperms) Flowering plants (Angiosperms) Figure 30-9 Eukarya Green plants Land plants Vascular plants Seed plants Gymnosperms Flowers Seeds Vascular tissue Green algae Nonvascular plants Seedless vascular plants Ability to live on land Chloroplasts containing chlorophyll a + b and -carotene Angiosperms Figure 30-7l Nonvascular plants do not have vascular tissue to conduct water and provide support. Hepaticophyta (liverworts) Anthocerophyta (hornworts) Bryophyta (mosses) Seedless vascular plants have vascular tissue but do not make seeds. Lycophyta (lycophytes or club mosses) Psilotophyta (whisk ferns) Sphenophyta (horsetails) Pteridophyta (ferns) Figure 30-7c Seed plants have vascular tissue and make seeds. Cycadophyta (cycads) Ginkgophyta (ginkgo) Other conifers (redwoods, junipers, yews) Gnetophyta (gnetophytes) Pinophyta (pines, spruces, firs) Anthophyta (angiosperms or flowering plants) Some distinctions Vascular Tissue This is a series of tubes for carrying water and nutrients up and down the plant. There are 2 types: Phloem-carries sugars from photosynthesizing parts to the rest of the plant (mostly downward moving) Xylem-carries water and nutrients (mostly upward moving) Includes tube shaped cells called tracheids and contain lignin Spores vs. Seeds Spores are haploid cells that will grow into multicellular gametophytes Seeds are analogous to eggs of birds. They contain the plant embryo, endosperm (nutirent tissue), and a protective seed coat Figure 30-11 First vascular tissue Simple waterconducting cells Tracheids Vessel elements Ends have gaps in secondary cell wall (inside) Primary wall (with cellulose) Primary wall (with cellulose) Lignin Little structural support. Found in fossils and presentday mosses Ends have gaps through primary and secondary cell walls Primary wall (with cellulose) Primary wall (with cellulose) Secondary wall (with lignin) Secondary wall (with lignin) Some structural support. Found in fossils Increased structural support. Found in all vascular plants Found in gnetophytes and angiosperms Figure 30-20a Seeds package an embryo with a food supply. Embryo Nutritive tissue Protective coat Non-vascular plants (Bryophytes) Consist of 3 phyla: Hepatophyta (liverworts), Anthocerophyta (hornworts) and the Bryophyta (Bryophyta) Gametophyte is the dominant portion of the life cycle Spores need moist soil or tree bark to produce the protonema (filaments that absorb water and minerals via osmosis), which produce “buds” with an apical meristem that produces the gametophore Gametophyte is anchored by rhizoids, which are long, tubular cells or filaments of cells When mature, the gametophyte forms the gametangia, which forms the gametes. The antheridia produces a flagelated sperm which swims to the archegonium which contains the egg Sporophyte Remains attached to the gametophyte, as it cannot survive on its own when young. The foot of the sporophyte stays embedded in the archegonium to absorb nutrients The seta(e) conducts the absorbed nutrients to the sporangium (which is also called a capsule) The sporangium produces the spores via meiosis. Peristomes appear as teeth on the upper part of the capsule which can open under moist conditions to release spores, and close under dry conditions In the hornworts and mosses, the sporphytes have stomata which are the same in function to those on the leaves of more complex plants Figure 30-17a Mosses: Gametophyte is large and long lived; sporophyte depends on gametophyte for nutrition. Archegonium Haploid (n) Diploid (2n) FERTILIZATION Egg (n) Eggs form in archegonia Zygote (2n) Sperm swim to egg Sperm form in antheridia Developing sporophyte (2n) Mature sporophyte (2n) Developing sporophyte (2n) Spores (n) are produced in sporangia by meiosis, dispersed by wind Mature gametophyte (n) Developing gametophyte Mature gametophyte (n) Spore (n) Figure 30-35 Moss in dry weather Moss in wet weather Figure 30-36 Marchantia bryophyta Figure 30-37 Phaeocerus leavis Figure 30-18 Hornwort gametophytes and sporophytes Horsetail gametophytes and sporophytes Figure 30-41 Equisetum arvense The Ecological Importance of Bryophytes Like lichens, can live in extreme environments b/c they can survive losing most of their water, then rehydrating, so they’re a good source of food for organisms all over the planet One wetland moss, peat moss, forms extensive deposits of decayed organic matter (peat), this is a source of fuel in Europe and Asia, and is a good soil conditioner for plants that are transported, as it absorbs lots of water Peat acts as a carbon reservoir to help stabilize atmospheric carbon concentration as well Peat also inhibits decay, so things that die in peatlands are preserved for thousands of years Seedless vascular plants Ferns and Fern allies Sporophyte is the dominant part of the life cycle-this is the leafy plant that you’re used to seeing (the gametophyte is extremely small) Vascular Tissue-Allows the plant to get much taller than the Bryophytes Evolution of roots and leaves Roots also contain lignified vascular tissue and serve to anchor as well as absorb. Scientists think that they may have evolved from underground portions of stems. It is believed that the evolution of roots is the result of convergent evolution and not from a common ancestor of all plants Leaves are believed to be evolved from Microphylls, small spine-shaped with 1 bundle of vascular tissue, into megaphylls, complex with branched vascular tissue Spore Variation-sporophylls first evolved in these plants (leaves that have sporangia). These are sometimes called fertile fronds Sporangia are called sori and are usually on the sporophyll Most are homosporous (producing one type of sporangium and spore with a bisexual gamete) Seed plants are heterosporous, producing megaspores (develop into female gametes), or microspores (develop into male gametes) Figure 30-17b Ferns: Sporophyte is large and long lived but, when young, depends on gametophyte for nutrition. Spore (n, dispersed by wind) Spores are produced in sporangia Mature gametophyte (n, underside) Developing gametophyte (n) 1 mm Sporophyte (2n; develops on gametophyte) Archegonium Mature sporophyte (2n) Gametophyte (n; side view) Sperm swim to egg Zygote (2n) Sperm develop in antheridia Eggs develop in archegonia Figure 30-42 Ferns range in size. Gonocormus minutus Dicksonia antarctica Fern sporangia Polypodium vulgare Collection of sporangia Figure 30-19 Figure 30-10 Cuticle is a waxy layer that prevents water loss from stems and leaves. Cuticle Leaf cross section Moist photosynthetic cells Stomata have pores that allow gas exchange in photosynthetic tissues. Pore Guard cells Stoma Classification of Seedless Vascular Plants 2 Phyla: Lycophyta-club mosses, spike mosses, and Quill worts This is the most ancient group of vascular plants Despite the common names, they are not true mosses Pterophyta-ferns, horsetails, Whisk ferns These are most closely related to the seed plants and are the most widespread group of seedless vasculars Many whisk ferns are “living fossils” b/c they closely resemble fosslized plants Figure 30-39 Lycopodium species Figure 30-40 Tmesipteris species The Importance of Seedless Vascular Plants The evolution of these plants meant the acceleration of photosynthesis, which prompted a rapid drop in carbon dioxide levels in the atmosphere (by as much as a factor of 5) These plants formed the first forests, which became peat and eventually coal Figure 30-4 Plant-based fuels COAL FORMATION 1. Dead plant material Wood Coal accumulates in marshy or boggy habitats. Petroleum and natural gas What energy sources do you think will be important in the future? 2. If oxygen in water is scarce, the organic matter decays only partially, forming peat. Peat Pressure Pressure Sediments Coal 3. If the peat deposits are later covered by sediments and compressed, the resulting pressure and heat change them into coal. Seed Plants Like the seedless vasculars, Sporophyte is dominant , and gametophyte is microscopic This has the advantage of protecting the delicate eggs produced by the gametophyte from environmental stresses as it’s retained within the parent sporophyte Integument protects the megasporangium within the parent plant. Ovule is formed by the megasporangium, megaspore, and integument Pollen is the microspore of the plant which consists of the male gametophyte enclosed in the pollen wall Seeds are considered an evolutionary advantage because it contains endosperm and protects the embryo from dessicating (the seed coat is thicker than the wall of a spore), and seeds can be dispersed in a number of ways Animals Wind, water Gymnosperms These are the first of the seed plants, but produce what’s called a “naked” seed, since the seed is not encased in a fruit Seeds are typically produced within cones Include the following Phyla Cycadophyta (cycads)-2nd largest group of gymnosperms, with about 130 surviving species today, but were the dominant plant during the age of dinosaurs Ginkophyta (ginkos)fan-like leaves, and originally thought to be extinct. Only male trees are planted b/c the seeds produced by the female smell rancid Gnetophyta-tropical plants in 3 genera Coniferophyta (pines, sequoia, juniper, firs)-largest and most diverse group of gymnosperms Figure 30-21 Pollen grains disperse via wind Cones with microsporangia Microspore (n) forms pollen grain Pollen grain (male gametophyte Megasporangium Four meiotic products; one is large and forms the megaspore (n) Three meiotic products die Ovulate cone Pollen grain Ovules (contain megasporangia) Female gametophyte (n) Mother cell (2n) Archegonia Embryo (2n) Eggs (n) Mature sporophyte (2n) Developing sporophyte Seed (disperses via wind or animals) Pollen produces sperm Megaspore divides to form female gametophyte (n), which produces archegonia and eggs by mitosis. (Only one egg is fertilized and develops.) Note that the red dots here and elsewhere represent nuclei Figure 30-44 Cycas revoluta Figure 30-45 Fossil ginkgo Ginkgo huttoni Living ginkgo Ginkgo biloba Figure 30-47 Cones that produce macrosporangia and pollen Picea abies Pollen Cones that produce macrosporangia and eggs Picea abies Figure 30-48 Thuja plicata Angiosperms These are the flowering plants and produce fruits that house the seeds These are advantageous b/c of the greater variety of ways that animals can help with pollination and dispersal The fruit contains more endosperm and is the mature ovary of the plant Flowers have adaptations that ensure pollination, like nectar, scent, color, and shape 2 main types: Monocotyledons Dicotyledons MONOCOTS Figure 30-27 Cotyledon Parallel veins in leaves (bundles of vascular tissue) Flower petals in multiples of 3 Branching veins in leaves Flower petals in multiples of 4 or 5 DICOTS One cotyledon (inside seed) Vascular tissue scattered throughout stem Two cotyledons Vascular tissue in circular arrangement in stem Figure 30-22 Pollen grains disperse via wind or animals (the red dots here Pollen lands and elsewhere are nuclei) near female MITOSIS gametophyte; produces pollen tube Microspore (n) Pollen grain and sperm forms pollen grain (male gametophyte) Anther Sperm travel down growing pollen tube to reach egg Stamen Carpel Flower Ovule MITOSIS Ovary Megasporangium Mature sporophyte flower (2n) Megaspore (n: retained in ovary) Nutritive tissue Female gametophyte (n: retained in ovary) Endosperm (3n) forms nutritive tissue in seed Embryo (2n) Zygote (2n) Developing sporophyte Seed (disperses via wind or animals) Egg Figure 30-49 Animal-pollinated flower (this species produces both pollen and eggs in the same flower) Ornithogalum dubium Wind-pollinated flower (this species has separate male and female flowers) Acer negundo Male flower Acer negundo Female flower Figure 30-23 Carrion flowers smell like rotting flesh and attract carrion flies. Hummingbird-pollinated flowers are red and have long tubes with nectar at the base. Bumble-bee-pollinated flowers are often bright purple. Figure 30-25 Fruits are derived from ovaries and contain seeds. Seed Wall of ovary Many fruits are dispersed by animals. The Importance of plants Carbon-fixation (photosynthesis) Plants are the basis of food chains Many plants are used medicinally Many plants were selectively bred by humans for food 80% of all calories consumed by humans comes from 6 crops: wheat, rice, maize, potatoes, casava, and sweet potatoes Figure 30-2 Tertiary Consumers: Secondary carnivores eat carnivores. Secondary Consumers: Carnivores eat animals. Primary Consumers: Herbivores eat plants. Producers: Plants form the base of the terrestrial food chain. Figure 30-4-Table 30-1 Figure 30-3 Plants were domesticated at an array of locations. Maize Wild ARTIFICIAL SELECTION CHANGES THE TRAITS OF DOMESTICATED SPECIES. Less oil rich Domestic Oil rich 1. Observe variation in kernel oil content. 2. Plant oil-rich seeds and grow to maturity. North America Sunflower 3. Harvest kernels South America from mature plants. Repeat steps 1–3. Potato 4. After many generations, kernel oil content increases.