Biology 1060 Exam 3 Study Guide
Biology 1060 Exam 3 Study Guide Bio 1060
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This 19 page Study Guide was uploaded by Margaret Notetaker on Tuesday April 5, 2016. The Study Guide belongs to Bio 1060 at Saint Louis University taught by Dr. Thole in Spring 2016. Since its upload, it has received 227 views. For similar materials see General Biology II in Biology at Saint Louis University.
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Date Created: 04/05/16
Margaret S Biology 1060 (General Biology II) Exam 3 (Plants) Study Guide Exam 3 is on Friday, April 8 , 2016 This Guide covers everything except the last 2 days of class. Things To Know: The Difference Between Plant and Animal Cells • Plant cells have: cell walls, large vacuoles for water storage, chloroplasts, no ability for movement, plasmodesmata connecting cells, and are photoautotrophs (make their own food from the sun), and animal cells don’t have these things • Plants undergo plastic development (are constantly regenerating their own organs) • Plants and animals are both organized cellsàtissuesàorgans Basic Plant Evolution • All of the Following (Until Future Notice) Is In Reference to Vascular Plants: Plant Structure: • Shoots: above-‐ground o Stem o Leaves o Flowers • Roots: below-‐ground • Apices exist at the tip of roots and shoots Meristems: • Plant stem cells o Always dividing o Totipotent (can give rise to any cell because they are undifferentiated) o Responsible for primary growth • Found at apex of shoot and root Cell Types: • Parenchyma Cells o Responsible for primary walls (thin, non-‐lignified) § Lignin makes cells more rigid and aggregates in the secondary cell wall (within the primary cell wall) o Always alive at maturity o Totipotent o Photosynthesis and gas exchange (make up stomata) o Make up phloem • Collenchyma Cells (not present in all plants) o Uneven, non-‐lignified cell walls o Function as support for young plant organs (celery strings) • Sclerenchyma Cells: o Primary and lignified secondary cell walls o Often dead at maturity o Consist of fibers (which contain secondary cell walls of lignin), sclereids (ex. grainy cells in pears), and xylem (tracheids and vessels that move water) Tissue Types: • Dermal Tissue: “skin” of plant, covers surface area of leaves o Parenchyma cells o Epidermis is usually 1 cell thick o Often has outer cuticle of wax to retain water o Includes stomata (guard cells) which facilitate gas exchange and minimize water loss, trichomes which protect the plant and minimize water loss as well as produce smells, and roots/root hairs which absorb water • Vascular Tissue: circulatory system of plant, exists in the form of veins that are visible in leaves and are made up of xylem and phloem o Xylem (sclerenchyma cells) and phloem (parenchyma cells) o Xylem and phloem are veins in leaves o Xylem transports water and minerals upwards only, and are dead at maturity to facilitate osmosis/diffusion § Xylem cells have lignified cell walls o Phloem transports food (glucose) up and down plant, and cells are alive at maturity • Ground Tissue: everything besides skin and circulatory system o Parenchyma, sclerenchyma, and collenchyma cells o Makes up most of plant body Plant Organs (Non-‐Reproductive): must be plastic (constantly regenerating) because plants can’t move away from danger/towards favorable conditions! • Leaves o Undergo photosynthesis (absorb sun’s rays, contain chloroplasts) o Evolved to achieve maximum photosynthetic capacity (started as photosynthetic stems which lost their apical meristems) o Stem of the leaf is called petiole o Contain veins as vascular tissue which allows water to leave via transpiration and carbs from photosynthesis to go to the rest of the plant o Eudicots have net-‐like veins, monocots have parallel veins o Simple leaves are a blade and petiole, but compound leaves have leaflets, and needle leaves (ex. Pines) are neither simple or compound o Various modified leaves have specific other functions (protection, storage, pollinator attraction, etc.) • Stems o Support plant and transport nutrients and water o Are mostly made of shoots and leaves (and flowers but that comes later): § Shoots are made of nodes and internodes: nodes are the portion of the stem that contains leaves and axillary buds (axillary buds are backup meristems located just above each leaf branch along the stem, they allow for branching in seed plants); internodes are the portion of stem between leaves o Shoots from the top down: § The tip: just meristem § Just Under: meristem and procambium § Just Under: pith and primary xylem § Just Under: Secondary xylem, pith, primary xylem § Some plants have wood under this, but some don’t (they are herbaceous) o Have special leaf organization that allows for different optimal leaf arrangements for each plant species o 3 Zones: Division, Elongation, Maturation § Zone of Division: apical meristem (tip of shoot) § Zone of Elongation: just below meristem, cells get longer § Zone of Maturation: lowest part of plant, contains fully grown and differentiated cells o Conduction (movement of water, minerals, and food) is from source (production site) to sink (usage site) o Stems have vascular tissue in bundles § Monocot stems have randomly scattered vascular bundles § Eudicot stems have vascular bundles arranged in a ring around internal ring of ground tissue (pith), they also have small extra layer between xylem and phloem called vascular cambium which makes more xylem and phloem when the stem grows wider § Both types of stems have xylem towards center of stem in each bundle and phloem towards the outside of the stem o Apical meristem = primary growth (getting taller) o Lateral meristems = secondary growth (all other kinds), there are 2 types of lateral meristems: § Vascular cambium: only in eudicots, makes more vascular tissue (in trees, this is right under the wood) § Cork cambium makes bark around outside of stem in some plants (trees) o Wood is excess secondary xylem produced by the vascular cambium, which also produces secondary phloem o o Rings within trees are dependent on water availability, they will be wider with more of it § Narrow ring = slow growth, usually in the center, heartwood § Wide ring = fast growth, usually in the outer layers, supwood • Roots o Root meristems have protective layers called root caps (are bottom tip of root) that are necessary for the root to grow o Root meristems are zones of cell division, and there are zones of elongation and maturation as you work your way up just like shoots, but in reverse o 2 types of roots: § Tap roots: 1 clear main root § Fibrous roots: no clear main root o Endodermis of roots surrounds dermal tissues (Suberin on endodermis makes up outer layer called Casparian strip, which is watertight) § Xylem and phloem in roots are not arranged in bundles § Vascular system here is enclosed in the stele of the root, which is surrounded by the cortex § Monocots have an extra layer of pith in the middle of the root § No vascular cambium in roots § New root apical meristems form from the pericycle (just within the vascular tissue) o Roots do not undergo secondary growth (don’t get wider) Roots vs. Shoots: • Size o Roots: relatively large o Shoots: relatively large • Protection to meristem o Roots: root cap o Shoots: none • Lateral organs o Roots: lateral roots o Shoots: leaves and branches • Primary growth o Roots: yes: apical meristem o Shoots: yes: apical meristem • Secondary growth o Roots: none o Shoots: yes in eudicots • Branching o Roots: present o Shoots: present Seeds: • The endosperm provides nutrients to the developing inner embryo • In monocots, the majority of the seed is endosperm • Main difference between mono/eudicots: o Monocots have 1 cotyledon (miniature leaflet inside embryo) o Eudicots have 2 cotyledon • Embryogenesis determines axes and all 3 tissue layers of plant • • Seeds are crucial to land adaptations: for protection, dormancy in unfavorable conditions, providing food, and embryo dispersal • Seeds germinate based on environmental cues like light, temperature, and moisture Vascular Transport • Transpiration means that water/sugars move towards parts of the plant with more negative potentials (or lower water potentials) • All water transport is passive (diffusion or osmosis) • ΨW + ΨS + ΨP + ΨG = Ψ o ΨW is water potential o ΨS is solute potential, which is always negative o ΨP is pressure potential, which is always positive o ΨG is the pressure from gravity, but is mostly neglected because it only has an effect in very tall trees o The units for Ψ are MPa • Turgor pressure helps the plant withstand gravity (cell wall pushes on the outer membrane), turgor pressure always positive o Flaccid cell lacks turgor pressure, when plants aren’t watered this leads to drooping • Hypertonic solution: has a greater concentration of solutes than the inside of the cell, so water will flow out of the cell • Hypotonic solution: has a lesser concentration of solutes than the inside of the cell, so water will flow into the cell and the cell may eventually lyse (burst) • Isotonic solution: there are equal concentrations of solute on the inside and outside of the cell, so there is no net movement of water • Pure Water Flaccid Cell Pure Water Turgid Cell Ψ = 0.0 MPa ΨP = 0.0 MPa Ψ = 0.0 MPa ΨP = 1.0 MPa ΨS = -‐1.0 MPa ΨS = -‐1.0 MPa Ψ = -‐1.0 MPa Ψ = 0.0 MPa Water goes into the cell (hypotonic) No net movement of water In these solutions, animal cells burst, but (isotonic) plant cells don’t because of their rigid cell walls; eventually the imbalanced turgor pressure will cause osmosis to even it out • Solution Cell ΨS = -‐0.7 MPa ΨS = -‐0.2 MPa ΨP = 0.0 MPa ΨP = 0.5 MPa Ψ = -‐0.7 MPa Ψ = 0.3 MPa Water flows out of the cell in this case, because the water will always flow to the area with the lower potential, in this case, the solution. The cell membrane might eventually undergo plasmolysis (the membrane on the inside shrinks away from the outer cell wall). This is an example of a hypertonic solution, because water flows out of the cell (ignore the negatives and just pay attention to where the water flows for these problems). • After equilibrium is achieved (isotonicity), ΨW of the cell = ΨW of the solution, so in the example above, at equilibrium, both the Ψ of the cell and the solution will be -‐0.7 MPa. • Pressure potentials ( ΨP ) are always positive, as noted above • Water potential is measured for individual cells, tissues, root and shoot systems, and entire plants Plants Need Water, CO2, Elements, and Essential Nutrients From Soil • Essential nutrients are required for a specific structure/function necessary for normal growth and development o Macronutrients are needed in large quantities ; are building blocks of key molecules o Micronutrients are needed in small quantities; function as cofactors for specific plant enzymes • Water carries nutrients into roots indirectly through uptake regulated by endodermis o Endodermis is right under root surface and contains aquaporins and ATP, prevents water leakage • Proton pump in roots moves protons to outside to allow negatively charged nutrients in (secondary active transport) • Carnivorous plants trap and digest insects to get nutrients • Parasitic plants get nutrients from other plants • Mycorrhizal associations are mutualistic relationships between plant roots and soil fungi; they increase nutrient availability for plants • Nitrogen-‐fixing bacteria also help plants obtain nitrogen, some species of plant have nodules to house the bacteria in their roots More Stuff About Vascular Tissues • Phloem are alive and contain sieve tubes and companion cells o Sieve tubes are phloem and are made of conducting cells (parenchyma) o Companion cells maintain, load, and unload sugar into and out of sieve tubes • Phloem sourceàsink is food moving from leaves or storage roots to other parts of the plant • In xylem, water enters roots, travels up and leaves through leaf stomata • In phloem, minerals enter through roots, carbs from photosynthesis/water move up and down the plant • Translocation: movement of sugars through phloem (stem/grown leavesàroots, flowers, and baby leaves) • Radioactive CO2 watching shows it moving to younger leaves • Phloem transport of sugar includes active and passive steps: o Active: loading/unloading of sugar created via photosynthesis in mesophyll cells around the phloem, proton ATPase helps secondary active transport (protons move in to cells to provide energy) o Pressure-‐Flow Hypothesis (passive): sugar transport is driven by a difference in pressure potential (ΨP); water flows into the phloem from the xylem, it will always flow from an area of high ΨP (source) to an area of low ΨP (sink); pressure is what governs the sourceàsink movement and the bulk flow of sugar (driven by pressure) is passive • Xylem vs. Phloem: o Xylem: water moves to lower potential, always passive o Phloem: sugar moves to lower potential, active and passive o Phloem contains amino/organic acids, protein, hormones, RNA, and ions in addition to sugar Plant Hormones • ABA: helps maintain dormancy in seeds as well as stomatal closure during times of drought (it is a stress hormone) • Auxin (IAA: Influences Almost Anything): o 1 plant hormone discovered o Principle production sites are shoot apical meristems, young leaves, and developing fruits and seeds o Auxin is transported to roots, where it undergoes polar transport to develop cells that will become vascular tissue o Auxin causes apical dominance (when the apical meristem is attached, it is the only meristem that will grow, but when the apical meristem is removed, axillary buds start developing) o Auxin suppresses growth of axillary buds by inhibiting synthesis of cytokinin o Roots have a lot of auxin, shoots have a little auxin but a lot of cytokinin • Ethylene: gaseous, allows fruit to ripen • Gibberellins: control stem elongation • Cytokinin: promote cell division Perception Process: • 1 Step: Receptor cells (could be photoreceptors, mechanoreceptors, or chemical receptors) perceive an external stimulus (could be light, gravity, touch, etc.) and transduces the information to an internal signal • 2 Step: Hormone travels throughout the plant after being released by the receptor cell • 3 Step: The receptor cell receives the signal, transduces it to an internal signal, and changes its activity according to that signal Tropisms • Tropisms are growth responses involving bending towards/away from a stimulus o Negative tropism: movement away from stimulus o Positive tropism: movement toward stimulus • Types of tropisms: o Phototropism (growth towards light) § Plants do this thanks to auxin, which aggragates on a shaded side of the plant and causes elongation, which bends the plant overall towards the light § Darwin did a famous experiment with a foil cap over a plant tip, Went did the second that officially proved auxin’s existence § o Gravitropism (growth in response to gravity) § Roots have positive gravitropism (grow down) § Shoots have negative gravitropism (grow up) § Gravity-‐sensing organelles called amyloplasts are found in root caps, and when the plant is tilted, they shift and auxin is transported to the downwards side, where the concentration is so high it inhibits cell growth, leading to an overall downward growth § o Thigmotropism (growth in response to touch) § The cells in contact with the stimulus grow faster than the ones that aren’t § Tendril coiling is caused by this § Sensitive plant is a specific type that reacts dramatically by closing its leaves in response to touch; this is possible due to rapid changes in turgor pressure When Plants Grow: • Plants have Circadian Rhythms just like people o Constans (CO) is a gene that depends on a 24 hour time scale, works together with light to produce flowers • Plants bend toward blue light (white light contains blue light) because a photoreceptor called phototropin absorbs it • Phytochrome is a hugely important photoreceptor with 2 forms: o Pr: dormant form: absorbs red light, changes to Pfr in red light o Pfr: active form, absorbs far red light, changes to Pr in far red light § Can enter the nucleus to express certain genes • o If there is more far red light absorbed, phytochrome kicks in and stimulates continued growth upwards o If there is more red light absorbed, the plant grows on its own without needing to elongate incessantly in search for red light • Because of all this, plants kept in the light have shorter stems and more optimally placed leaves, while plants in the shade elongate more and as a result have longer, thinner internodes (portion of the stem between leaves) as well as fewer leaves • In the understory of the rainforest, 10% of plants are exhibiting Pfr (active form) while in an open environment, 60% of plants will be exhibiting Pfr (active form) • Important to remember: o Lots of light = red light = plant will absorb all red photons and grow normally, bending towards this light o Shade = far red light = the plant will absorb photons that above plants don’t absorb (not optimal for photosynthesis like red light is), and this plant will elongate more in search of light • An experiment showed that whatever light a seed is most recently exposed to has the greatest effect on germination: o If seeds are more recently exposed to red light, almost all will germinate o If seeds are more recently exposed to far red light, only about 50% of them will germinate o This process is called photoreversibility: the expression of the genes Pr and Pfr can be influenced/reversed by light When Plants Flower: • Flowers are adult plant reproductive structures, flowering depends on light cues o Cues include: day length and vernalization • Vernalization: cold treatments that either are or stimulate winter cause plants to flower, and without a cold treatment these plants will continue preparing for winter and never flower o o In this diagram, the plant on the left has not experienced a cold treatment and is producing flowers to prepare for winter, while the plant on the right has experienced a cold treatment which is why it is elongating and flowering o Flowering Locus C (FLC) is a floral repressor gene that turns off after vernalization via epigenetic regulation § Plants that haven’t seen winter have no repression of FLC (which represses flowering), and so they do not flower § Plants that have seen winter have mechanisms in place to repress FLC and flowering occurs § This happens because chromatin is remodeled after the first winter, and FLC is always repressed after that • Photoperiodism: the ability of an organism to detect day length o Long day plants: flowering is only promoted when day length exceeds a certain duration in a 24 hour cycle; these plants often flower in spring and early summer o Short day plants: flowering requires day length that is less than the critical length; these plants often flower in late summer and early fall o Day-‐neutral plants use other indicators besides day length to regulate flowering o Leaves perceive photoperiodism signal by measuring length of night § In the laboratory: even a quick flash of light in the middle of the stimulated “night” can cause short day plants not to flower in otherwise short day conditions § The quick flash of light can also cause long day plants to flower in short day conditions (it all depends on the continuous length of the night) Reproduction • Angiosperms are flowering plants, and therefore undergo sexual reproduction • All flowers are made up of 4 parts: sepals, petals, stamen, and carpels o Stamen is made of an anthers and filaments o Carpels have 3 parts: stigma (the tip of the carpel), style (provides transport from stigma to ovary), and ovary (contains ovules) • • Some plants pollinate themselves, but most rely on wind or pollinators to do it for them; ones that rely on pollinators are brighter • General flower characteristics: o A complete flower has all 4 whorls (sepal, petals, stamen, carpels) o A perfect flower has both male and female parts o Imperfect flowers have either only male or only female parts o A flower can be any combination of complete/incomplete and perfect/imperfect, except imperfect and complete o Monoecious: one plant has both male and female flowers (this plant would be incomplete and imperfect) o Dioecious: one plant has either all male or all female flowers (still incomplete and imperfect) Angiosperm Life Cycle • Pollination: movement of pollen from the anther to the stigma o Pollination is any mechanism where pollen travels to where it needs to be to fertilize o Pollen lands on the stigma, then stimulates the growth of pollen tubes through the style (2 for each style) • Self-‐Pollination: plant’s own pollen lands on its stigma (usually plants that do this have some evolutionary need to keep their genes as they already are) • Cross-‐Pollination: pollen from one flower lands on the stigma of a different flower (outcrossing), these plants reproduce this way because they need greater genetic diversity • Fertilization: fusion of haploid gametes, next step after pollination • Pollen moves via o Wind o Insects o Bees/Birds o Other Animals o All of these except wind are pollinators, which put pollen on their bodies and transport it to the next plant • Angiosperms are highly dependent on pollinators, of which bees are the biggest group o Butterflies pollinate red/orange flowers with tubes underneath that hold nectar (they are attracted to those because they drink nectar with long tongues) o Birds like tubule flowers too o Some flowers smell like rotting meat to attract flies o Bats pollinate flowers that flower at night with strong odors to help the bats find them • Bees: o Typically pollinate yellow or blue flowers, and many have stripes or lines of dots that indicate the location of nectar like a bullseye for bees • Sometimes plants evolve to look/smell like the female of an insect species; this is an example of extreme coevolution • Fig wasp pollination: another very specific example of coevolution • Details of fertilization/pollination: o Pollen grain lands on the stigma of carpel o The pollen must germinate and grow tubes through the style and into the ovary o Pollen sperm travels down to fuse with the ovule o After fertilization, most angiosperms’ ovaries develop into fruit • Double Fertilization: o Gametophyte: haploid female gametophytes have 8 cells: one is the egg to be fertilized, 2 others fuse to form a diploid central cell (in the diagram below, they are shown in step 1 unfused and called “polar nuclei”) o Male gametophytes have 3 cells: 1 is generative (produces ATP to fuel the growth of the pollen tube), the other 2 cells carry out both of the fertilization steps: 1 fertilizes the egg (ovule) to become a diploid (2n) zygote and the other fertilizes the central cell to become a 3n endosperm • • Post-‐fertilization: 1) zygote divides mitotically to be an embryo, 2) the triploid central cell divides mitotically to become an endosperm, 3) the ovule becomes a seed with a tough coat, and 4) the ovary wall develops into fruit o The endosperm provides nutrients to the developing embryo • During embryogenesis, 3 other major events happen for angiosperms: o Development of a food supply o Development of a seed coat o Development of fruit surrounding seed • As the fertilized egg becomes an embryo, the ovary wall becomes a fruit • The number of carpels a flower originally had is revealed in the cross section of a fully developed fruit • Fruits have extreme diversity (for example where the seeds are)
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