Exam 2

Plantae is a monophyletic group with cellulose cell walls, photosynthetic (chlorophylls a and b), starch as energy storage product, alternation of generations life cycle, multiple adaptations for terrestrial lifestyle

Ecological roles: oxygen, carbon cycle, primary production, maintains soil structure

Economic roles: food, clothes, shelter/furniture, medicine, fuels, many products

Plant phylogeny: evolved from a green algal ancestor, especially the charophytes

Key traits that are in land plants but not charophytes: alternation of generations, sporopollenin in spore walls, multicellular dependent embryos, multicellular gametangia, apical meristems

Embryophytes: the embryos are protected and fed by the parent land plant

Four major groups of plants: non-vascular, seedless vascular, gymnosperms, angiosperms

Cuticle: covers leaves and other surfaces to prevent water loss

Stomata: pores that allow gas exchange (CO₂ in/O₂ out) guard cells control their opening/closure

Seeds: enclose, nourish and protect plant embryos and aid dispersal to new habitats

Pollen: a reduced male gametophyte that allows wind/animals to carry sperm to egg (allows fertilization to occur without water)

Vascular tissue: allows efficient fluid transport; its evolution allowed plants to grow larger

Lignin: provides rigid structural support (against gravity) in the vascular tissue

Flowers: attract pollinators for more efficient pollination and outcrossing

Fruit: protect and help disperse seeds

Nonvascular plants:

·       Small plants: no vascular tissue, need moist habitat, root-like structures called rhizoids

·       Dominant Gametophyte Generation

·       Short-lived sporophytes depend on gamete: sporophyte consists of foot, seta, and capsule

·       Gametangia on gametophyte: archegonia produce eggs; antheridia produce sperm

·       Flagellated sperm: need moisture for sperm to reach egg

·       Homosporous: single spore type

Phylum Marchantiophyta “liverworts”: lobed and leafy types, have gemmae cups for asexual reproduction, and lack cuticle and true stomata

Phylum Bryophyta “true mosses”: most abundant nonvascular group (over 10,000 species), stomata present in sporophyte, meristem present in sporophyte

Importance of sphagnum “peat moss”: carbon sink, fuel, horticulture

Vascular plants “tracheophytes”

·       Sporophyte dominant

·       True roots, stems and leaves

·       Vascular tissue allows plants to grow larger

o    Xylem- transports water and minerals

§   Tracheid and vessels, dead at maturity, secondary cell walls and have lignin

·       Phloem- transports sugars (~90% sucrose)

o    Sieve elements with companion

Seedless vascular plants: formed the first forests in the carboniferous period, gave rise to present-day coal deposits

·       Flagellated sperm

o    Water is still needed for fertilization

·       Most are homosporous

·       Club mosses, whisk ferns, horsetails, ferns

Phylum Monilophyta “ferns”: megaphylls “large leaves”, young fiddleheads uncoil to protect tips of developing leaves, underground stem, termed a rhizome for asexual reproduction

True ferns: sorus (clusters of sporangia) bisexual gametophyte independent of sporophyte, flagellated sperm, water required for reproduction

Unique ferns:

·       Horsetails

o    Whorled vegetative shoot with silica

o    Stalk with cone “strobilus” of sporangia

·       Whisk ferns

o    No leaves: photosynthesis conducted in stems

o    No roots: depend on symbiotic fungi for nutrients

o    Sporangia in nodes of stems

Phylum Lycophyta “club mosses”: microphylls (small leaves), strobili (cones) of sporangia in many species, flagellated sperm (water required for reproduction)

Heterosporous lifecycle: some lycophytes like Selaginella have a heterosporous life cycle, microspores and megaspores (all seed plants have a heterosporous life cycle)

Spores: produced in sporangia and protected by sporopollenin

Seed plants: gymnosperms and angiosperms, all have reduced gametophytes, heterosporous, seeds, ovules, and pollen

Seeds: have 2n embryo, stored food, coat, and protect the embryo and allow them to disperse to new habitats

Ovules: female megasporangium (megaspore) surrounded by integument, develop into seeds following fertilization

Pollen: male gametophytes surrounded by protective coat, transfer to megaspore, and is resistant to drying, eliminating dependance on water for fertilization

Angiosperms: ovules enclosed within ovaries, seeds enclosed within fruits, flowering plants.

Gymnosperms: ovules not enclosed within ovaries, exposed “naked” seeds, often have strobili or modified strobili, coniferous and taiga biomes, drought tolerant, can have fleshy ovules, and tracheids in xylem

Cycads: Phylum Cycadophyta, thrive in mild climates, have large compound leaves, bear strobili

Conifers: phylum Coniferophyta, dominant phylum of gymnosperms with the greatest and tallest variety of species, contain scale or needle like leaves and produce cones, have cuticle coating, adapt to cold and dry weather

Conifer life cycle: seeds develop in strobili, female (ovulate) cones contain ovules, males (staminate) cones are relatively small, and produce pollen

Phylum Anthophyta: Include basal angiosperms, monocots, and eudicots. Largest modern plant group, diverse habitats, sizes, structures, including all major food crops, medicines, clothing, aromatics

Sepals: collectively called the calyx, surround and protect the flower bud

Petals: also called the corolla, attract pollinators and protect reproductive parts

Perianth: formed from the corolla and calyx

Stamen: male structure, include the filament and anther, which produces pollen

Carpel/pistil: female structure, include the stigma, style, and ovary.

Stigma: where pollen lands

Pollination: transfer of pollen from stamen to carpel, facilitated by wind and animals. ~20% of angiosperms are wind pollinated, while more than 80% depend on pollinators

Monocots: embryos have one cotyledon, have ~90,000 species

Dicots: embryos have two cotyledons, have ~200,000 species

Cotyledon: embryonic (seed) leaves

Microsporangium: In anther produces via meiosis. Develops into multicellular male gametophytes that include a generative cell, which will produce sperm, and a pollen tube cell

Megasporangium: in ovule produces via meiosis. One becomes functional and develops into female gametophyte, which includes the egg and central cell with two polar nuclei

Following fertilization: in angiosperms, the ovules become seeds and the ovary becomes fruit

Roots: anchorage, absorption of water and nutrients, storage, interaction with soil fungi and bacteria

Root modifications: aerial and above ground roots, storage roots and pneumatophores

Stems: part of the shoot system, may be above or below ground, may be herbaceous or woody, supports the plant and holds leaves, flowers, and buds, can store food

Nodes: where leaves are attached to plant stem

Internode: the stem region between two nodes

Petiole: part of the leaf that connects to the stem

Leaves: conduct photosynthesis and contain the blade, lamina, tip, midrib, margin, vein, lamina, and petiole

Meristem: produce plant tissues, undifferentiated stems, retained throughout life, and have intermediate growth

Apical meristems: found at tips of roots and stems and in axillary buds of stems, produce growth in length

Primary growth: produces 3 major tissue types

Epidermal/dermal: primary growth tissue type that provides covering and protection

Ground: primary growth tissue type that provides photosynthesis, storage, support

Vascular: primary growth tissue type that provides water and nutrient transport and support

Epidermis: outer layer(s) of cells, all parts of plants are surrounded by this

Periderm: replaces epidermal tissue of the roots and stems and woody plants

Epidermal structures: stomata/guard cells, cuticle, root hairs, trichomes

Collenchyma: thick primary cell wall (cellulose), gives flexible support for growing stems

Sclerenchyma: thick, hardened secondary cell walls containing lignin

Sieve tube elements: contents disintegrate at maturity, leaving only thin layer of cytoplasm lining cell membrane, cells stack to form tubes for sugar transport

Companion cells: help with loading and unloading sugars

Secondary growth: increases width roots and shoots, formed from lateral meristems (cambiums), produces wood and bark

Vascular cambium: thin layer between xylem and phloem, adds secondary xylem and secondary phloem

Periderm: cork cambium and the cork it produces are called periderm, provide protection

Wood: secondary xylem, accumulates overtime, providing structural support and increasing width

Bark: cork and secondary phloem

Fibrous roots: thin, branching roots, absorb food

Taproots: thick, lateral roots that store food

Root Tip Zones: zone of cell division, elongation, and maturation

Root structure: includes root cap, epidermis, cortex, and vascular tissue

Rhizome: horizontal underground stem

Tuber: enlarged rhizome that stores food

Trichomes: deter herbivores, protect against UV light and water loss

Parenchyma: most abundant ground tissue, conducts photosynthesis, storage of sugars and starches, thin primary cell wall (cellulose)

Osmolarity: solute concentration

Fluid movement: fluids move from higher to lower pressure. Positive pressure pushes water, Negative pressure pulls water

Water transport: a passive process in plants. Absorbed at the roots, travels up through stems to the leaves, where it evaporates

Osmosis: water enters roots. Once in the xylem, water is pulled upwards by negative pressure created due to transpiration, indirectly powered by the sun

Cohesion: water molecules in the xylem are joined together, hydrogen bonds link water molecules together

Tension: as water evaporates from leaf surfaces, a pulling source is generated. Each water molecule leaving the leaf “pulls” the next one along

Transpiration: evaporation of water from the stomata

Adaptations to reduce water loss: guard cells in the stomata control evaporation by opening and closing through day and night.

Xerophytes: plants adapted to very dry climates

Epiphytes: plants that grow on other plants

Mesophytes: plants that live in moderately watered habitats

Hydrophytes: aquatic plants

Adaptations to reduce water loss: thick cuticle, multiple layers of epidermis, reduced leaf surface area, sunken stomata, trichomes

Leaf abscission/leaf drop: Occurs normally in some species to prevent water stress. Particularly valuable adaptation for desert plants and angiosperm of trees of seasonal cold habitats

Translocation: movement of sugars

Sources: photosynthetic tissue, storage tissue (in spring), sugars enter phloem

Sinks: non-photosynthetic tissue, actively growing tissues/organs, storage tissue (in fall)

Translocation at sources: sugars enter phloem by active transport creating high osmolarity. Water from xylem enters phloem due to osmotic gradient. The water influx creates high pressure.

Translocation at sinks: sugars leave phloem and enter sink tissue, osmolarity in phloem drops; water moves back to xylem, pressure declines

Sucrose: loading into phloem depends on ATP

Pressure-flow hypothesis: as water flows through phloem from sources to sinks, sugars are carried along by bulk flow

Kingdom Fungi: monophyletic group, heterotrophic via absorption, chitin cell walls, single celled or multicelled, most reproduce via spores, most nonmotile

Yeasts: single celled fungi structure

Hyphae: thin filaments in multicellular species

Septate hyphae: divided into individual cells by septa

Coenocytic hyphae: no septa; large cells with multiple nuclei

Mycelium: a mass or network of hyphae. The thin, abundant hyphae provide lots of surface area for absorptive nutrition

Exoenzymes: released into environment, digestion occurs externally, digested nutrients are absorbed

Haploid spores: produced on ends of hyphae, within sporangia, or within fruiting body. Dispersed by wind or animals

Budding: asexual reproduction, also use sporangium

Plasmogamy: only hyphae cytoplasm’s fuse in this stage of two different individuals fuse in a process

Heterokaryotic: contains genetically distinct haploid nuclei

 Karyogamy: AKA nuclear fission, produces a diploid zygote, undergoes meiosis to produce genetically distinct haploid spores

Saprophytes: fungi that breaks down dead organic matter, can digest touch organic polymers like cellulose and lignin

Mycorrhizae: fungi that form mutualistic relationships with plants

Lichens: symbiotic relationship between a fungus and a photosynthetic partner (either algae or cyanobacteria). Holds water, provides structure, captures minerals.

Haustorium: penetrates the cells of the living host and absorbs nutrients (parasitic)

Origin of fungi: diverged from a common unicellular flagellated ancestor, oldest are ~460 million years old

Phylum Chytridiomycota: most primitive fungi, appeared about 500 million years, chytrids are found everywhere, are saprophytes, produce zoospores

Zoospores: produce motile spores (flagella)

Chytrids: aseptate/coenocytic, mostly decomposers and parasites in aquatic habitats

Batrachochytrium dendrobatidis: parasitic chytrid that causes chytridiomycosis in amphibians

Phylum Zygomycota: asexual reproduction, aseptate, some form mycorrhizae, some parasitic (Rhizopus)

Zygosporangium: formed from in the sexual life cycle of Zygomycota that mating types conjugate via plasmogamy

Rhizopus stolonifer: zygospore fungi, black bread mold

Phylum Ascomycota: Sac fungi, can digest cellulose, composed of septate hyphae, edible morels and truffles, can cause diseases, can cause mycosis, include lichen fungi

Budding: form of asexual production, a small bulge forms on side of cell, receives a nucleus, pinches off parent, then grows to become full size

Conidia or Conidiospores: another form of asexual spores in Ascomycota

Ascus: fingerlike cell where karyogamy, meiosis and spore production occur

Ascomycete life cycle includes production of asci during sexual phase.

Ascus: four nuclei produced by meiosis, then divide once mitotically for a total of eight haploid ascospores

Phylum Basidiomycota: 22,000 species, septate hyphae, many decomposers, parasites (smuts, rusts)

Club fungi: usually reproduce sexually, haploid hyphae fuse, forming a dikaryotic mycelium

Dikaryotic: mycelium forming basidiocarps

Basidiocarps: fruiting bodies, mushrooms

basidia: club shaped structures on dikaryotic mycelium

Basidiospores: produces karyogamy followed by meiosis

Basidiomycete life cycle: characterized by the production basidia during sexual phase

Basidium: four basidiospores produced by meiosis

Phylum Glomeromycota: Arbuscular mycorrhizal, 160 species, arbuscules are branching invaginations that fungus makes when it invades plant roots, mutualism between fungus and plants