Exam 1 Study Guide
Exam 1 Study Guide BSC2011
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This 22 page Study Guide was uploaded by Anisha Jagnarine on Tuesday February 9, 2016. The Study Guide belongs to BSC2011 at University of Florida taught by Dr.Norman Douglas,Dr.Jennie DeMarco,Dr.Keith Choe in Winter 2016. Since its upload, it has received 114 views. For similar materials see Biology 2 in Biology at University of Florida.
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Exam 1 Smokin Notes Introduction to Plants Plants are involved in biodiversity food, shelter, clothing ultimate source of primary production medical uses political issues climate change A Brief Overview of Phylogenetics Tree of Life all living things can be trace back to a common ancestor Prokaryotic domains Bacteria Archaea Eukaryotic domain Eukaryota Phylogenies vs. Phylogenetic Trees Phylogeny: true evolutionary relationship between organisms Phylogenetic tree: comes as close to the true phylogeny as possible Dichotomous: gives rise to two lineages Causes of speciation geographic separation biological events that lead to reproductive isolation Clades and Monophyletic Groupings Taxon: any group of species designated with a name Monophyletic clades: groups of taxa that include an ancestor and all of its descendants, but no other organisms a group is only monophyletic if you can get that group (and only that group) by cutting the tree in exactly one place How Phylogenetic Trees are Created Gather data morphological characteristics molecular sequences Analyze the data maximum parsimony method The Importance of Homologous Characters Homologous traits (homologies): any heritable trait shared by more than one species and inherited from a common ancestor Derived trait: a trait that has evolved from an ancestral trait synapomorphies: shared, derived traits Homoplasies: traits that are shared not due to a common evolutionary history but rather because of convergent evolution or evolutionary reversals convergent evolution: occurs when similar traits evolve in diﬀerent lineages due to similar evolutionary pressures, such as similar environments bat wings and bird wings are homoplasies evolutionary reversals: occurs when a character reverts from a derived state back to an ancestral state common in molecular data Creating Phylogenies Outgroup: serves as our reference point because it has the ancestral traits; closely related to the in-group, but not closely related enough to be inside the group of interest Ingroup: the group of organisms that we are interested in Ancestral traits: traits of the ingroup that are the same as those of the outgroup Derived traits: traits of the in-group that are diﬀerent from those of the outgroup maximum parsimony principle: distributing the branches of the tree in order to group the synapomorphies in the simplest way - the way that requires the fewest steps to explain the evolutionary relationship between organisms The Importance of Monophyletic Groupings Monophyletic group: includes a common ancestor and all of its descendants nested sets: a monophyletic group may be nested in a larger monophyletic group for example, mammals are a nested set in the monophyletic grouping of all vertebrates Photosynthesis and Endosymbiosis The Three Domains of Life Eukarya are more closely related to Archaea than to Bacteria therefore Eukaryotes are in a clade with Archaea but not Bacteria Photoautotrophs Photoautotrophs: organisms that use sunlight to create ATP, which they then use in the process of carbon ﬁxation (turning carbon dioxide into glucose and other complex organic molecules) generate oxygen as a byproduct of photosynthesis Cyanobacteria: the most important photosynthetic prokaryote in our class use chlorophyll a in photosynthesis Increasing atmospheric oxygen levels allowed for the diversiﬁcation of plant and animal life Endosymbiosis and the Rise of the Eukaryotic Cell Primary endosymbiosis: a process in which a heterotrophic, early eukaryotic cell engulfed a specialized prokaryotic cell. The eukaryotic cell then integrated it into its body as an organelle (formed a symbiotic relationship) created the eukaryotic cells that would eventually become land plants, red algae, and green algae chloroplasts derived from primary endosymbiosis are are a synapomorphy of all plants photosynthesis is not a synapomorphy of all plants Secondary endosymbiosis: a process in which a large eukaryotic host cell engulfed a smaller algal cell (either red or green algae) and formed a symbiotic relationship with it secondary endosymbiosis with green algae gave rise to euglenoids secondary endosymbiosis with red algae gave rise to dinoﬂagellates and stramenopiles (diatoms, golden brown algae, and brown algae) chloroplasts have 3 membranes Tertiary endosymbiosis: a process in which a cell engulfed another cell that was itself a product of secondary endosymbiosis gave rise to dinoﬂagellates (including the one that causes red tide) chloroplasts have 4 membranes Characteristics of mitochondria and chloroplasts that prove the endosymbiotic theory they have their own DNA their DNA consists of a single, circular chromosome they have two membranes Lateral gene transfer: occurs when genes move from one species to another endosymbiosis is an example The Evolution of Plants green plants are a monophyletic subset of all plants, and streptophytes are a monophyletic subset of all green plants all plants have chloroplasts derived from primary endosymbiosis involving cyanobacteria All plants have chlorophyll a Glaucophytes microscopic, freshwater alga forma a sister group with the rest of Plantae have chloroplasts that have retained their peptidoglycan cell walls Red Algae almost all multicellular, although there are some unicellular red algae phycoerythrin: causes red color chloroplasts contain carotenoids and chlorophyll a plants retained their cellulose cell walls Green Plants monophyletic group that consists of green algae and land plants includes chlorophytes, coleochaetophytes, charophytes, and other green algae and land plants two synapomorphies chlorophyll b starch characteristics their chloroplasts developed from primary endosymbiosis their chloroplasts consists of both chlorophyll a and chlorophyll b they store carbohydrates as actual starch Green Algae consist of chlorohphytes, coleochaetophytes, charophytes, and other green algae not a monophyletic group (excludes land plants) chlorophytes range from unicellular organisms to large, branched seaweeds that exist in salt water, fresh water, or even moist soil ﬂagellated cells with two anterior whiplash ﬂagella unicellular, multicellular, and some are colonial phycoplast: an array of microtubules that organizes cell division the phycoplast is an arrangement of transverse ﬁbers arranged parallel to the plane where the new cell wall will be formed daughter nuclei generally close to the phycoplast isogamy: form of sexual reproduction in which an organism produces gametes of similar morphology (both male and female) other green algae catch all group for green algae that don’t ﬁt well into the other groups Streptophytes monophyletic subset of green plants that consists of two groups of green algae (coleochaetophytes and charophytes) and land plants Chlorophyta: true green algae Streptophyta: green algae more closely related to land plants Streptophytes: phragmoplast: an array of microtubules oriented parallel to the mitotic spindle separated the daughter nuclei and eventually grows into a cell wall that separates the cell into two daughter cells synapomorphies oogamy: a form of cellular reproduction that involves the production of distinct male and female gametes - sperm and egg retain their eggs in the parental organism grow at an apical meristem plasmodesmata: channels that join the cytoplasmm of adjacent cells allows cells to communicate with one another facilitated the evolution of multicelluarity parenchyma: primary tissue type in streptophytes Land Plants embryophytes enclose their eggs in a protective embryo evidence for land plants varying gene sequences: molecular clock fossils: carbon dating 11 clades (textbook omits one clade for a total of 10) Adaptations to Life on Land cuticle: coating of waxy lipids that traps the water and protects it against evaporation on on the top and bottom of the plant’s leaves stomata: openings through which plants can exchange gases with the outside environment UV absorptive pigments: protect against UV radiation accessory pigments thick spore walls sporopollenin: a polymer that resists decay and keeps spores from drying out mutualists associations with fungi mycorrhizae: mutualistic associations between fungi and underground plant structures (suavely roots) rctomycorrhizal fungi essentially expand the surface area of roots, making them more eﬃcient at acquiring water and nutrients multicellular gametangia gametangia: multicellular organs in which gametes are produced archegonia: female gametangia, which produce eggs via mitosis and serve as the site of fertilization antheridia: male gametangia, which produce sperm with two sub apical whiplash ﬂagella via mitosis protect the Jegg and sperm from drying out embryos tiny diploid plants initially surrounded and nourished by the cells of the gametophyte zygote: diplod, forms when the sperm make their way down the archegonium the embryo will initially be housed and nourished in the gemetangium of the gametophyte, but will grow into a multicellular sporophyte alternation of generations synapomorphy of all land plants sporophyte: multicellular diploid form gametophye: multicellular haploid form diploid sporophyte -> meiosis -> haploid spores -> mitosis -> haploid gametophytes -> mitosis -> gametes (gametangia) -> fertilization -> diploid zygote -> mitosis -> embryo -> female gametangia: archegonium male gametangia: antheridium multicellular haploid forms (gametophyte) and multicellular diploid forms (sporophyte) What were the First Land Plants? liverworts: tiny plants don’t have true stomata Further Diversiﬁcations of Land Plants bryophytes: liverworts, hornworts, mossses signaling proteins and genetic info that helped them avoid desiccation drawbacks: osmosis swimming sperm no strong supportive tissue adaptations vascular tissue that assists in the movement of water and sugars xylem: pipe that brings water and nutrients from the roots to the top of the plant phloem: takes sugars from sources (photosynthetic parts) to sinks (parts that need them) reproductive mechanisms that don’t depend on water pollen partnerships with land animals that promote growth and reproduction ﬂowers fruit Overview of the Evolution of Land Plants bryophytes: paraphyletic group of land plants consisting of nonvasulcar, herbaceous plants liverworts mosses hornworts characteristics lack vascular tissue: they use osmosis and diﬀusion small swimming sperm with two ﬂagella lack true plant organs (root, stem, leaves) gametophyte is the dominant stage of the life cycle (photosynthetic, charismatic generation) sporophyte is nutritionally dependent on the gametophyte mutualistic associations with fungi epiphytic: live on top of other plants Key Adaptations in Bryophytes liverworts: most ancient of the bryophytes gametophyte can be ﬂattened (thalloid) or leafy rhizoids: extensions of the plant body that anchor the plant in the soil live in moist habitats sporophyte stalk and capsule where the haploid spores are produced elater: grows alongside the spores in the sporophyte; assist in the dispersal of spores gemma cups: where asexual gemmae (tiny pieces of liverwort) are made perianth: leafy liverworts; where archegonia are produced thalloid liverworts have palm tree structures were archegonia and antheridia are produced mosses consist of small plants with erect, leafy gametophytes hydroid: poorly developed conducting tissues have stomata sporophyte contains a capsule that is connected to the gametophyte via a seta operculum: cap like structure on the distal end peristome teeth: increase the eﬃciency of spore dispersal hygroscopic: change shape as the humidity changes perigonium: groups of antheridia perichaetium: groups of archegonia two kinds of mosses sphagnum: ancient moss lineage important role carbon storage dung mosses hornworts: sporophytes look like horns largest and most independent sporophytes one chloroplast indeﬁnite cell division symbiotic relationship with nitrogen ﬁxing cyanobacteria Alternation of Generations multicellular diploid sporophyte makes haploid spores through meiosis in sporangium multicellular haploid gametophyte makes gametes through mitosis mitosis occurs in gametangia male: antheridium female: archegonium fertilization: diploid zygote is formed forms an embryo through mitosis Comparing Alternation of Generations with the Life Cycle of Green Algae land plants evolved to have a multicellular haploid forms (gametophyte) and multicellular diploid forms (sporophyte) Sporophyte multicellular diploid sporophyte is a synapomorphy of all land plants spores are protect from desiccation and decay by an outer layer of sporopollenin spores are diﬀerent because of crossing over and independent assortment The Gametophyte genetically identical to the spores that they germinate from gametes all have the same DNA content Life Cycle of Bryophytes begins with the release of spores from the sporangium the capsule that releases spores is connected to the gametophyte via the seta (a stalky part of the sporophyte) rhizoids: specialized root like tissue that anchors the gametophyte requires lots of water unbranched sporophytes with single sporangia Dominant Lineage Shifts: From a Dominant Gametophyte to a Dominant Sporophyte in bryophytes: sporophyte is nutritionally dependent on the gametophyte in vascular plants: sporophytes that are independent of the gametophyte dominant sporophyte provides structural support and assists in spore dispersal Vascular Plants (Tracheophytes) have vascular tissue (xylem and phloem) Synapomorphies of Tracheophytes tracheids elongated, ornamented, thick walled cells in the xylem tissue that conduct water not alive at maturity vessel elements: stack end to end to form xylem vessels that are more eﬃcient than tracheids phloem living tissue that distributes sugars, amino acids, and other important organic products throughout the plant ﬂows in the opposite direction of the xylem (leaves downward instead of from the root upwards) branched sporophyte independent of the gametophyte xylem provides internal support that allows for more surface area for the production of spores true organs roots root hair: tiny extensions that increase surface area for absorption root tip: primary area of growth leaves phloem begins here and takes sugars doesn to the stem and roots veins: bundles of xylem and phloem (vascular tissue) that extend from the leaf to the rest of the plant stomata: small openings where gas is exchanged stems Internal Conduction of Water and Sucrose major synapomorphy that distinguishes tracheophytes from bryophytes tracheophytes evolved because of the branched sporophyte xylem: water transport phloem: sugar transport A Detailed Look at the Xylem and Water Transport vascular cylinder: consists of the xylem and phloem xylem: lies in the center of the stem of plants and is composed of tracheids (long elongated, thick, dead, water conducting cells) tracheids provide strength through lignin (touch, complex polymer deposits) have pits in their walls that allow for cross ﬂow of water between xylem vessels vessel elements: larger diameters and more eﬃcient than tracheids in ﬂowering plants How Water Enters the Root plasmodesmata: junction between abutting plant cells that allow for the constant ﬂow of cytosol between cells symplast: cytoplasmic continuum apoplast: cells walls plus extracellular spaces cell walls of roots hairs are hydrophilic and provide water access to the apoplast two ways for water transport symplastic route: route through the cytosol, which is connected by plasmodesmata apoplastic route: route through the cell wall and extracellular spaces endodermis: innermost layer of cells in the root cortex controls access to the vascular cylinder Casparian strip: blocks water water must cross a member to get into the xylem xylem sap: water and minerals Stomata and Xylem Function stomata primary structured used in the exchange of water and gases guard cells: specialized type of parenchyma cell that regulates gas enhance and water loss by opening and closing open during day and close at night (avoid transpiration) mechanism: plant needs stomata to open: guard cells pump K and HCl in increases concentration of K and HCl water diﬀuses into the cell -> turgid -> open stomata when stomata is open plant loses oxygen and water and gains carbon dioxide Transpiration, Cohesion, and Tension Mechanism transpiration occurs when water vapor is lost through the stomata negative pressure pulls the water up cohesion: sticking to itself caused by hydrogen bonding adhesion: sticking to to other substances caused by hydrogen bonding capillary action: occurs when liquid ﬂows in tight spaces even against gravity surface tension: water sticks to itself strongly capillary action and surface tension combine to pull the water up the column (like a meniscus) Detailed Look at Phloem and Sugar Transport sieve tube elements: long chains of sieve tubes (cells without ribosomes, vacuoles, and nuclei) companion cell: adjacent to each sieve tube with a nucleus and ribosome that serve the companion cell and sieve tube brain of the phloem characteristic of angiosperms sieve plates: have pores where phloem sap ﬂows through phloem cells are alive at maturity no pores pressure ﬂow model translocation: the ﬂow of nutrients from the leaves due to positive pressure phloem sap: sucrose, ﬂows from source to sink sugar source: leaves sugar sink: tubers of bulbs Classifying Vascular Plants lycophytes: club mosses small leaf (microphylls) euphyllophytes: everything else true leaves (megaphylls) have vascular tissue (unlike bryophytes) The Importance of Ferns, Horsetails, and Lycophytes Devonian Period: earlest fossil of lycophytes allowed plants to grow tall due to lignin live in drier habitats Lycophytes (Club Mosses) lycophytes: sister group to the remaining vascular plants synapomorphies microphylls: small ﬂat leaves with a single midvein in Selaginella, the sporangia lie along the stem independent sporophyte and gametophyte sporophyte is dominant stobili: sporangia that exist outside of the microphylls have vascular tissue Euphyllophytes all of the other vascular plants that are not lycophytes horsetails ferns gymnosperms angiosperms true leaf plants characteristics overtopping growth: one branch diﬀerentiates and grows on top megaphylls: provide plants with an evolutionary advantage because they spread out the photosynthetic surface; modiﬁed branches monilophytes (ferns and horsetails) sori:clusters of sporangia on the undersides of its leaves spores released -> mature gametophyte -> antheridium & archegonium -> sperm & egg -> fertilization -> zygote -> embryo -> sporophyte -> homosporous: produces a single type of spore horsetails sister plants to ferns equisetum non photosynthetic, reduced leaves of the horsetails form distinct circles around the stem, and they have irregularly branching roots ferns contain sporangia on both their leaves and their modiﬁed leaves leptosporangia: sporangia that have arisen from a single epidermal cell stalked, thin wall annulus: single row of specialized cells sporophyte dominant frond: leaf stipe: leaf stalk ﬁddleheads: coiled leaves sori: small clusters of bumps indusium: ﬂap of green tissue that covers sori seed plants (gymnosperms and angiosperms) gymnosperms (cycads, ginkgo, gnetophytes, conifers) angiosperms (ﬂowering plants) Seed Plants (Spermatophytes) have seeds: provide secure dormant stage for embryo dominant group of land plant gymnosperms angiosperms characteristics seeds: embryo and its nutritive tissue, surrounded by sporophyte and gametophyte tissue woody secondary growth: allowed plants to grow outwards heterospory: a plant that produced two types of spores: the microspore (male) and the megaspore (female) megaspore: made in the megasporangium and produce the megagametophyte microscpore: made in the microsporangium and produces microgametophyte fertilization: sperm from pollen fuse with the egg reduction in the number of megaspores in the sporangium mother cell: only cell to go through meiosis and produce four daughter cells sporophyte dominance sporophyte generation is dominant and the gametophyte is nutritionally dependent increasing trend in plant evolution no water required for fertilization male gametophyte is moved to female via wind, water, etc no swimming required What is Wood? primary growth: vertical growth from apical meristems secondary growth: old xylem cells get ﬁlled with resin; structural support allows for girth and protection better competitor woodiness evolved independently vascular cambium: cylinder of meristemic cells that develops from parenchyma adds the secondary xylem (wood) toward the inside add the secondary phloem (inner bark, conducts sugar) toward the outside cork cambium: second lateral meristem generates the periderm: consists of cork cambium and the cork cells that it produces outer bark: made up of all the tissues external to the vascular cambium trees increase in thickness each year due to the accumulation of secondary xylem toward the inside of the vascular cambium Gymnosperms look like trees produce structures that protect naked trees haploid gametophyte generation is small in both time and stature no ﬂowers or fruits categories cycads: group of primitive seed plants i.e. palm trees ﬂagella: motile sperm symbiotic relationships with Nostoc, nitrogen ﬁxing cyanobacterium dioecious: separate male and female plants produce male and female cone like structures seeds are on their leaves beetles ginkgo female: oﬀensive odor Chinese horticulturists dioecious motile sperm deciduous: they lose their leaves herbal medicines gnetophytes another clade conifers most specie-rish scented resins: protect against insects and fungal infections cold resistant megastobilius: female cone; megasporangia that make megagametophytes; pine cone microstrobilus: male cone; microsporangia that make microgametophytes; herbaceous pines everything else cyprus junipers catch all Flowering Plants (Angiosperms) angiosperms: plants with seeds that are surrounded by an ovary synapomorphies ﬂowers fruits: ovules (embryonic seeds) reduced gametophytes: only about 7 cells and 8 nuclei double fertilization a process in which two fertilization events take place one sperm fertilizes the egg to form a diploid zygote the other sperm fuses with the two polar nuclei to form a triploid nucleus that develops in the endosperm production of triploid endosperm: nourishes the sporophyte ovules and seeds enclosed in a carpel: embryonic seeds called ovules are enclosed in the female part of the plant (carpel) germination of pollen on the stigma: pollination occurs when pollen is transferred to an anther or a stigma abiotic agents: wind and water biotic agents: birds and bats leaves with net venations: megaphyll leaves with network of veins vessels in xylem: angiosperm xylem contains tracheids but it also contains vessel elements (water transport) and ﬁbers (structure) A Closer Look at the Structure stamen: male reproductive unit ﬁlament: stalk anther: produces pollen carpel: female unit (plural: pistil) stigma: sticky surface that attracts pollen style: slender neck-like portion that leads to the ovary ovules: embryonic seeds inside the ovary perianth: nonreproductive organs sepals: green, outside petal; protective function petals: diﬀerent color; attraction calyx: collection of sepals corolla: collection of petals evolutionary trends bilateral symmetrical reduced number of ﬂower parts diﬀerentiations of sepals and petals fusion of ﬂower parts A Closer Look at Fruits fruit: swollen ovary that contains seeds accessory fruits: strawberries Flower, Fruits, Reproductive Success pollination syndrome: set of ﬂower characteristics that are suited to certain animal pollinators angiosperms have coevolved with the animals that pollinate them in order to increase the chances of reproductive success Development of Seeds in Gymnosperms key innovation: novel trait that allowed the seed plants to successfully evolve and diversify Development of Male and Female Gametophytes development of the microgametophyte occurs within the walls of the spore itself the resulting gametophyte exists within the spore pollen grain: mature male gametophyte that consists of generative cell: sperm tube cell nucleus: pollen tube development of the megagametophyte the naked ovules are typically found on the upper surface of a seed scale complex in female cones integument: surround ovules divides by mitosis to form the archegonia and the pollen chamber (will be the pollen tube) Development of Seeds seed: formed when the egg inside the ovule is fertilized by the sperm from a pollen gain components seed coat: protective coat formed from the integument embryo: embryonic sporophyte is the diploid result nutritive tissue: contains stored food reserves tissue of the female gametophyte, which is haploid single seed contains the parent sporophyte (seed coat), the haploid gametophyte (nutritive tissue), and next generation diploid sporophyte (embryo) Advantages of Seeds dispersal nourishment no need for moisture dormancy Development of Seeds in Angiosperms Development of Female Gametophyte ovary comes from parental tissue (diploid) ovules: diﬀerentiated tissues remaining megaspore is what ultimately forms the megagametophyte, which produces the archegonia and eggs 3 rounds of mitosis = 8 nuclei no new cells made synergids: near the micropyle (small opening in the ovule) polar nuclei: middle antipodal: farthest from micropyle 7 cells 3 antipodal (1 nucleus each) two synergids (one nucleus each) egg cell/central cell: two polar nuclei antipodal cells and synergies will eventually degenerate, leaving only the egg cell and the two polar nuclei 8 nuclei are identical gametophyte is nutritionally independent on the sporophyte Development of the Male Gametophyte anther: location where the microgametophyte (pollen) begins to develop diploid mother cells undergo meiosis to produce four haploid microspores wall of the nucleus becomes hard and sculptured with a sporopollenin wall resulting in the pollen grain generative cell: forms the sperm tube cell: forms the pollen tube A Closer Look at Pollination and Fertilization in Flowering Plants the reduced female gametophyte has either nuclei (the synergies, antipodal, and polar nuclei) male gametophyte has two cells (tube and generative) both sperms cells enter the female gametophyte to reproduce (double fertilization) one sperm forms the diploid zygote one sperm forms the two polar nuclei to form a triploid nucleus 3n primary endosperm nucleus and the 2n zygote the integuments completely grow over to form the seed coat. The ovule will therefore develop into a seed, and the ovary will develop into the fruit that encloses the seeds embryo may develop either one or two cotyledons (seed leaves) absorb the endosperm and enlarge; they will become photosynthetic upon germination Diﬀerences between Gymnosperm Seeds and Angiosperm Seeds the nutritive tissue in the gymnosperm seed is the haploid megagametophte tissue in the angiosperm, the nutritive tissue is primarily the triploid endosperm the seed coats in gymnosperms are typically derived from a single integument in the angiosperm, seed coats are derived from two integuments Reproductive Strategies in Flowering Plants perfect ﬂower: functional stamens and carpels bisexual imperfect ﬂower: either stamen or carpel unisexual monoecious: both staminate and carpellate ﬂowers one house self-fertilization mechanisms that make it impossible or diﬃcult to self fertilize mechanistic block: the way the anthers are situated temporal block: pollen is only released at certain times genetic block: self incompatibility (ability to reject its own pollen) dioecious: has only staminate or carpellate ﬂowers two houses exist on separate ﬂowers Plant Adaptations to Climate xerophytes: special adaptation that help them avoid drought and grow in arid evironments life cycle through rainy periods succulent leaves or stems (leaves or stems are ﬂeshy and store water) tissues with high solute concentrations, which promotes the uptake of water from the environment shallow roots modiﬁed leaves (Spines) that reduce water loss thick cuticles and a leaf epidermis covered in trichomes stomata located in sunken cavities light colors to reﬂect light and maintain a lower internal temp cactus (xerophyte): have spines, shallow roots, and specialized structures for water shortage convergent evolution: similar adaptation because of similar habitats/environment pressures RuBisCo: an enzyme that catalyzes an important step in the Calvin cycle in which CO2 binds to RuBP converts gaseous CO2 to nongaseous form photorespiration: ineﬃcient process by which an increase in oxygen level inhibit the calvin cycle shuts down glucose production C3 plants: ﬁx carbon in their mesophyll; evapotranspiration C4 plants: separate carbon ﬁxation from the calvin cycle in space, using mesophyll and bundle sheath cells mesophyll cells (enzyme PEPC adds CO2 to a 3C compound called PEP) and bundle sheath cells Kranz anatomy CAM plants: separate carbon ﬁxation from the calvin cycle in time by opening their stomata to take in CO2 at night and only using it during the day pineapples Plant Adaptations to Low Nutrient Levels carnivory: venus ﬂy trap symbiotic relationships with nitrogen ﬁxing bacteria: legumes fungal associations: assist the plants in acquiring nutrients Other Adaptations adaptations to deal with low levels of light rapid vertical growth lianas: woody vines epiphytes: plant that grows on top of another plant too much water drop tips: act like a gutter Defenses against Herbivory mechanical defenses: external structures i.e. bark, hairs, latex channels, thorns chemical defenses: reduces digestibility of plant Constitutive Defenses against Herbivory constitutive defenses: always on thick cell walls, cuticle, bark, etc trichomes: ﬁne, hair like outgrowths that protect against insects laticifers: latex, poisonous sharp structures: spines, thorns secondary metabolites: non protein amino acids, alkaloids, glucosinolates, tannins, sterols, various terpenes chemical warfare such as nicotine Induced Defenses produced when a pathogen is present elicitors: pathogens Avr: genes that code for elicitors Resistance (R) genes: speciﬁc for certain elicitors; confer resistance local response: hypersensitive: limited to the area surrounding the infection; apoptosis PR proteins: enzymes that hydrolyze the pathogens cell wall phytoalexins: antibiotics systematic response: entire plant; salicylic acid creates siRNA that prevents viral replication Plant Growth meristems apical: primary growth at the roots and shoots lateral meristems: secondary growth; width photoreceptors pigments that are associated with light-absorbing proteins hormones: chemical signals that present in low concentrations Photoreceptors and Plant Growth photoperiodism: physiological response to a photoperiod short day: ﬂower only when the period of darkness is long and the day is short long day: ﬂower only when the period of darkness is short and the day is long night length: length of period of darkness phytochrome: pigment that perceives the interruption of dark periods Pr Pfr: responsible for cell responses circadian rhythms: endogenous (continuous) entrainable (reset) The Genetic Control of Flowering vegetative growth: produces leaves, axillary buds, and stems inﬂorescence meristem: produces leafy bracts and new meristems between the bracts and the stem ﬂoral meristems: give rise to single ﬂowers determinate growth The Genetic Basis of Flower Development meristem identity genes: LEAFY/APETALA1 causes ﬂowering ﬂoral organ identity genes: homeotic genes that determine the fate of the various ﬂoral organs The Role of Plant Hormones many hormones do similar things Ethylene response to stress (ﬂooding, drought, etc) causes ripening in nearby fruits opposes growth Gibberellins stem elongation and cell elongation fruit growth and maturation seed germination Auxin chemical substance that promotes elongation of target tissues phototropism: plants response to light gravitropism: response to gravity apical dominance: growing up more than out tip of the plant is the only part to sense light the tip produces a substances that travels down the plant light promotes cell elongation on the shaded side dark side has more auxin polar transport: auxin is produced at the coleoptile tip and diﬀuses down the coleoptile body in one direction promotes stem elongation and phototropism positive phototropism: auxin concentration causes rapid growth on the shaded side negative phototropism: bending away from light acid growth hypothesis: auxin stimulated the expression of genes that codes for proton pumps that move protons into the cell wall from the cells interior; results in elongation due to water uptake gravitropism: positive: grow in the direction of gravity negative: opposite direction (stems) enhancing apical dominance: high auxin concentrations inhibit the growth of axillary buds christmas tree shape promoting the formation of later and adventitious roots: promotes the formation of lateral and adventitious roots Angiosperm Classiﬁcation and Diversity Amborella Trichopoda: The Sister of All Other Angiosperms sister to all remaining angiosperms last remaining primitive angiosperms Monocots and Eudicots sister taxon to the magnoliids number of cotyledons monocots: one cotyledon eudicots: two cotyledons leaf venation monocats: parallel veins eudicots: netlike veins (reticulate venation) stem anatomy monocots: cortex and pith are indistinguishable eudicots: arranged in a ring and the cortex (outside) is distinguishable from the pith (inside) secondary growth plant gets larger in diameter due to thickening of the stems and roots more common in eudicots
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