Biology 5B Post Midterm 2 Notes
Biology 5B Post Midterm 2 Notes Bio5B
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Date Created: 06/15/16
CIRCULATION: 1. Compare and contrast open and closed circulatory systems ● Open: insects & other arthropods, and most molluscs ○ blood surrounds the organs directly ○ body fluid is called hemolymph ● Closed: blood is confined to vessels and is distinct from interstitial fluid ○ more efficient at transporting fluids to tissues and cells 2. Compare and contrast the circulatory systems of fish, amphibians, nonbird reptiles, and mammals or birds ● Fish: single circulation with a 2 chambered heart ○ blood leaves the heart through 2 capillary beds before returning ● Amphibians, reptiles, and mammals have double circulation ○ oxygenpoor and oxygenrich blood are pumped separately from the right and left sides of the heart ○ Amphibians: lung and skin capillaries are on the same circuit ■ 3 chambered heart (2 atria and 1 ventricle) ○ Nonbird reptiles: 2 aortas; 1 acts to bypass the left side of the heart ■ 3 chambers in the heart because the 2 ventricles are not completely separated ■ ventricle is more complex and able to send oxygenated and deoxygenated blood to different vessels ○ Mammals and Birds: ■ separation between circuits ■ 4 chambers in the heart ■ high pressure to system and low pressure to lungs ■ left side of the heart only receives oxygenated blood and the right side of the heart receives only deoxygenated blood 3. Distinguish between pulmonary or systemic circuits and explain the function of each ● Pulmonary circuit: in doublecircuit system ○ takes oxygen poor blood and sends it to the lungs to get more oxygen ○ after, the blood flows back to the heart then through the systemic circuit ● Systemic circuit: sends blood to organs and muscles in the rest of the body 4. Trace the path of a red blood cell through the human heart pulmonary circuit and systemic circuit ● blood begins to flow with the right ventricle pumping blood to lungs by the pulmonary artery ● in the lungs, blood collec2and removes CO2 ● oxygenrich blood from lungs enters the heart by the pulmonary veins at the left atrium and is pumped through the aorta to the body tissues by the left ventricle ● blood leaves left ventricle through the aorta and travels to tissues on the system ● blood returns to the heart through the vena cava and flows into the right atrium then to the right ventricle 5. Define cardiac cycle and explain the role of sinoatrial node ● heart contracts and relaxes in a rhythmic cycle ● systole: contraction/pumping of blood phase ● diastole: relaxation/filling of blood phase ● Sinoatrial node: specialized muscle tissue in the wall of the right atrium of the heart that acts as a pacemaker by producing a contractile signal at regular intervals 6. Related the structures of capillaries, arteries, and veins to their function ● Arteries: branch into arterioles and carry blood to capillaries ○ thicker walls than veins to accommodate the high pressure of blood pumped from the heart ● Capillaries: where chemical exchange between blood and interstitial fluid ○ have thin walls and are lined with the endothelium and basement membrane to facilitate the exchange of materials ● Veins: return blood from capillaries to the heart ○ have endothelium, smooth muscle, and connective tissue (like arteries) 7. Define blood pressure and cardiac output ● Blood Pressure: hydrostatic pressure that blood exerts against the wall of a vessel (pressure changes throughout the cardiac cycle) ○ Systolic pressure: pressure in the arteries during ventricular systole(phase of the heartbeat when the heart contracts and pumps blood from the chambers); highest pressure in arteries ○ Diastolic pressure: pressure in arteries during diastole(when heart refills with blood after contraction) ● Cardiac output: volumes of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume (mL/minute) ○ cardiac output = (heart rate) x (stroke volume) GAS EXCHANGE 1. Discuss the advantages and disadvantages of water and of air as respiratory media ● less oxygen available in water than in air ● getting oxygen from water requires greater efficiency and more work than air breathing ● Oxygen easy to obtain but respiratory surfaces have difficulty remaining moist 2. Be able to calculate the partial pressure of gases ● Pgasncentration x barometric pressure 3. Describe the exchange of gases in the lungs and in tissues ● Gases diffuse down pressure gradients as a result of differences in partial pressure ○ from a region of higher partial pressure to a region of lower partial pressure ● in lungs and tissues,2and CO2iffuse from where their partial pressures are higher to where they are lower ● Mammals: ○ air is inhaled through nostrils and passes through pharynx by the larynx, trachea, bronchi, bronchioles, and alveoli, where gas exchange occurs 4. Understand how oxygen binds to hemoglobin ● When O moves to blood or any water based liquid, only a small amount of that is 2 soluble in the liquid ○ to move a larger amount of O through blood, it binds to respiratory 2 pigments (proteins that transport oxygen) ● Arthropods and molluscs have hemocyanin with copper to bind with O 2 ○ Central ion of hemocyanin is copper ● Most vertebrates and some invertebrates bind O with hemoglobin 2 ○ hemoglobin can carry 4 molecules of O2 ○ 1 O2that binds causes the molecule to change shape ○ The changes shape allows the second molecule of O 2to easily bind ○ This causes the 3rd opening to bind even easier to 2 ○ the 4th opening binds to 2 ○ Cooperativity: binding in a nonlinear fashion ○ Increasing affinity: increasing attraction of heme f r O 2 5. Draw and explain the hemoglobinoxygen dissociation curve and the effect of pH ● a small change in partial pressure of oxygen can result in a large change in delivery of O 2 ● CO2produced during cellular respiration lowers blood pH and decreases affinity of hemoglobin for 2 (Bohr shift) ● Decreased affinity: ○ increase in temperature ○ increase in CO partial 2 pressure ○ decrease in pH ● increased affinity: ○ decrease in temperature ○ decrease in CO2partial pressure ○ increase in pH 6. Explain what features could be different about animals with extremely well developed functional capacities. 7. Know something about the variety of respiratory systems across the diversity of animals ● animals require large, moist respiratory surfaces for exchange of gases between cells and air/water ○ surfaces: skin, gills, tracheae, and lungs ● Gills: outfoldings of the body that create a large surface area for gas exchange ○ ventilation: moves respiratory medium over respiratory surface ○ aquatic animals move through water or move water over their gills ○ uses a countercurrent exchange system: blood flows in opposite direction to water passing over gills ● Tracheal system in insects: tiny branching tubes that penetrate body ○ tubes supply oxygen directly to cells ○ respiratory and circulatory systems are separate ○ larger insects ventilate their tracheal system ● Lungs: derived from the gut during development ○ closed circulatory system transports gases between lungs and body ○ size and complexity of lungs are correlated to animal’s phylogenetic background, thermoregulatory strategy and metabolic rate OSMOREGULATION 1. Distinguish between the following terms: isoosmotic, hyperosmotic and hypoosmotic; osmoregulators and osmoconformers; stenohaline and euryhaline animals ● Osmolarity: solute concentration of a solution ○ determines the movement of water across a selectively permeable membrane ○ (number of moles solute)/(liters of solvent) ● isosmotic: solutions with the same osmotic pressure ● hyperosmotic: when one solution has a higher solute concentration than a surrounding solution ● hypoosmotic: when one solution has a lower osmotic pressure than a surrounding solution ○ net flow of water is from the hyposmotic to the hyperosmotic solution ● Osmoregulators: expend energy to control water uptake and loss in a hyperosmotic or hyposmotic environment ● Osmoconformers: isosmotic with surroundings and do not regulate their osmolarity ● Stenohaline: animals that cannot tolerate substantial changes ● Euryhaline: animals that can tolerate a great deal of changes 2. Define osmoregulation, excretion, anhydrobiosis ● Osmoregulation: balances the uptake and loss of water and solutes ○ based on controlled movements of solutes between internal fluids and external environment ● Anhydrobiosis: adaption where some aquatic invertebrates in temporary ponds lose almost all body water and survive in dormant state ● Excretory system: regulates solute movement between internal fluids and the external environment ○ Filtration: pressurefiltering of body fluids ○ Reabsorption: reclaiming valuable solutes from the filtrate to the blood or body fluids ○ Secretion: adding toxins and other solutes from body fluids to the filtrate ○ Excretion: removing the filtrate from the system ● Kidneys: organs of excretion and osmoregulation in vertebrates 3. Compare the osmoregulatory challenges of freshwater and marine animals ● Marine animals: ○ invertebrates: osmoconformers ○ vertebrates: osmoregulators ○ Bony fishes: hyposmotic to seawater ■ lose water by osmosis and gain salt by diffusion and from food ■ balance water loss by drinking seawater and excreting salts ● Freshwater animals: ○ constantly take in water by osmosis from their hyposmotic environment ○ lose salts by diffusion and maintain water balance by excreting large amounts of dilute urine ○ salt lost by diffusion are replaced in foods and uptake across the gills 4. Describe some of the factors that affect the energetic cost of osmoregulation ● osmoregulation based on controlled movement of solutes between internal fluids and external environment 5. Using a diagram, identify and describe the function of each region of the nephron ● Nephron: functional unit of the vertebrate kidney ● Filtration occurs as blood pressure forces fluid from blood in the glomerulus into lumen of Bowman’s capsule ● Bowman’s Capsule: surrounds and receives filtrate from the glomerulus ● proximal tubule: where reabsorption of ions, water, and nutrients takes place ○ Molecules are transported actively and passively from filtrate to interstitial fluid then capillaries ○ Some toxins are secreted into filtrate ● Loop of Henle: ○ Descending: water is removed because it is not permeable to salt ■ filtrate becomes more concentrated and is the most concentrated at the bottom of the loop before the collecting duct ○ Ascending: salt diffuses from the tubule into the interstitial fluid ■ filtrate is more dilute ● Distal Tubule: regulates the K+ and NaCl concentrations of body fluids ○ controlled movements contributes to pH regulation ○ urea and water are passively reabsorbed ● Collecting duct: permeable to water, water leaves to interstitial area ○ salts are actively reabsorbed ○ filtrates through the osmolarity gradient and more water exits the filtrate by osmosis ● Vasa recta: capillaries in glomerulus that serve the loop of Henle 6. Explain how the loop of Henle enhances water conservation ● urine had a higher osmotic potential than blood ● loop of Henle and collecting ducts are responsible for osmotic gradient that concentrates the urine ● descending, water is lost and filtrate becomes more concentrated ● ascending, salt is lost and becomes more dilute ● maintains a high salt concentration in the kidney 7. Describe some of the hormonal controls involved in the regulation of kidney function ● Antidiuretic hormone (vasopressin): increases permeability of tubules for water ○ increases water reabsorption in distal tubules and collecting ducts of the kidney ○ increase in osmolarity triggers the release of ADH, helping conserve water ● Aldosterone: increases reabsorption of Na+ by increasing active transport ● Atrial natriuretic peptide: increases urine production by reducing Na+ and water reabsorption PLANT DIVERSITY & NONSEED PLANTS 1. Describe four shared characteristics and four distinct characteristics between charophytes and land plants ● Shared: ○ Multicellular ○ Eukaryotic ○ Photosynthetic ○ Autotrophic ○ Cells walls made of cellulose ○ Many biochemical details ● Derived: ○ Alternation of generations (with multicellular, dependent embryos) ■ produces gametes ■ haploid stage where fertilization occurs ○ Walled spores produced in sporangia ■ Sporophyte makes walled spores in organs called sporangia ■ walls have sporopollenin, makes them resistant to harsh environments ○ Multicellular gametangia ■ gametes made in organs called gametangia ■ archegonia: female gametangia; makes eggs and are the site of fertilization ■ antheridia: male gametangia; where sperm is made and released ○ Apical meristems ■ where plants sustain continual growth ■ cells differentiate into various tissues 2. Distinguish between the phylum bryophyta and bryophytes ● Bryophyta: formal taxonomic name for the phylum that consists solely of mosses ● Bryophytes: all nonvascular plants (liverworts, mosses, and hornworts) 3. Diagram and label the life cycle of a bryophyte (nonvascular plant) ● Gametophytic Stage: ○ Sporophytes are present only part of the time and embryonically attached to the gametophyte ○ spore becomes gametophyte composed of protonema and gameteproducing gametophore ○ Rhizoids anchor gametophytes to substrate ○ height is restricted by lack of vascular tissues ○ mature gametophytes make flagellated sperm in antheridia and an egg in each archegonium ○ sperm swim through water and fertilize egg ● Sporophytic Stage: ○ sporophytes grow out of archegonia, and are the smallest and simplest sporophytes of all extant plant groups ○ sporophyte has a foot, seta (stalk), and sporangium (capsule), discharges spores through peristome ○ hornwort and moss sporophytes have stomata for gas exchange but liverworts do not 4. Explain why most bryophytes grow close to the ground and are restricted to periodically moist environments ● diverse in moist forests and wetlands ● some mosses are found in sandy soil to retain nitrogen in the soil ● some harbor nitrogenfixing cyanobacteria that increase the availability of nitrogen in the ecosystem ● many can live in the very cold and dry habitats because they can survive the loss of most of their body water and then rehydrate when moisture is available 5. Describe three traits that characterize modern vascular plants and explain how these traits have contributed to success on land ● Seedless vascular: evolved tissues: xylem and phloem ○ provided structural support and let plants grow tall ○ they have flagellated sperm and are restricted to moist environments ○ life cycles with dominant sporophytes with welldeveloped roots and leaves ● Vascular tissue provides transport and structure: ○ xylem: conducts most of the water and minerals and includes dead cells called tracheids ■ allows increase in height ○ Phloem: consists of living cells and distributes sugars, amino acids, and other organic products ● Roots: organ that anchor vascular plants ○ enable plants to absorb water and nutrients from soil ● Leaves: organ that increases surface area of vascular plants ○ captures more solar energy that is used for photosynthesis 6. Explain how vascular plants differ from bryophytes ● bryophytes lack innovations of vascular plants, like roots and true leaves ● similarities: multicellular embryos and apical meristems 7. Understand the basic concepts behind the evolution of roots and leaves ● Roots: organs that anchor vascular plants ○ let plants absorb water and nutrients from soil ○ may have evolved from subterranean stems ○ Bryophytes don’t have roots, they have rhizoids with no tissues or vascular units ● Leaves: organs that increase surface area of vascular plants ○ captures more solar energy that is used for photosynthesis ○ Microphylls: leaves with single vein ○ Megaphylls: leaves with a highly branched vascular system 8. Diagram and label the life cycle of a seedless vascular plant 9. Understand what is meant by alternation of generations and a representative life cycle showing it ● Produces gametes (2N) ● haploid stage where fertilization occurs 10. What adaptations allowed plants to colonize the land? ● development of spores with durable protective walls ○ allows spores to tolerate dry conditions/ survive harsh conditions ● waxy cuticle to reduce water loss across cell walls ● development of vascular system allowing plants to access water deep in the soil ● Stomata: pores in the cuticles of leaves that open and close ● Specialized cells with thickened cell walls for rigid support 11. Know vocabulary ● Charophyceans/Chlorophytes: green algae ○ plants evolved from these ● Sporopollenin: layer of durable polymer in charophyceans that prevent exposed zygotes from drying out ● Vascular plant subgroups: ○ Seedless plants ■ Lycophytes: club mosses and relatives ■ Pterophytes: ferns and relatives ○ Seed plants (clade) ■ seed: embryo and nutrients surrounded by protective coat ■ Gymnosperms: naked seed plants, conifers ■ Angiosperms: flowering plants ● Protonema: threadlike chain of cells that forms the earliest stage of bryophyte life cycle ● Gametophore: modified branch in moss that has gametangia ● Gametangia: organ or cell where gametes are formed in algae, ferns, and others SEED PLANTS: 1. Explain why pollen grains were an important adaptation for successful reproduction on land ● Microspores develop within pollen grains, containing male gametophytes ● Pollination: transfer of pollen to the part of a seed plant containing the ovules ● Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals ● If pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule 2. Describe the life histories of a pine and a flower plant; indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation ● Pine: ○ dominance of the sporophyte generation ○ development of seeds from fertilized ovules ○ transfer of sperm to ovules by pollen ○ Pine tree is sporophyte and produces sporangia in male and female cones ○ Small cones make microspores in pollen grains; microspore becomes male gametophyte ○ Large cones have ovules, make megaspores that becomes female gametophyte ● Flower Plant: ○ seed plants with reproductive structures called flowers and fruits ○ flower: unique structure that is specialized from sexual reproduction ■ has both male and female structures ○ male gametophyte are in pollen grains made by microsporangia of anthers ○ female gametophyte or embryo sac, develops with ovule contained within an ovary at the base of stigma 3. Describe which structures are haploid and which are diploid in both gymnosperms and angiosperms 4. Identify and describe the function of the following floral structures: sepals, petals, stamens, carpels, filament, anther, stigma, style, ovary, and ovule ● Sepals (calyx): cover immature flower bud ● Petals (corolla): brightly colored and attracts animals to serve as pollinators ● Stamens: microsporophylls; produce microspores within the anthers ● Carpels (pistils): megasporophylls; makes megaspores and eventually seeds ● Filament: fine hairlike stalk that the anther sits on top of ● Anther: part of stamen that produces and contains pollen ○ on top of a long stalk that looks like a fine, thin hair ● Stigma: one of the female parts of the flower ○ sticky bulb that is in the center of flower ○ part of the carpel of the flower that receives the pollen grains and where they germinate ● Style: long stalke that the stigma sits on top of ● Ovary: usually at the bottom of the flower ○ has seeds inside and turns it unto fruit ○ contains ovules ● Ovule: part of the ovary that becomes the seeds 5. Explain how fruits may be adapted to disperse seeds ● Fruit has a mature ovary but can have other flower parts ● protects the seeds and aids in their dispersal ● seeds can be carried by wind, water, or animals, to new locations 6. Explain how land plants have changed over the course of evolution with respect to their dependence on water ● Bryophytes: embryonic attachment to the mother plant ● Pteridophytes: cells joined in tubes for water and nutrient transport; vascular tissues ● Gymnosperms: seed stage; embryo packaged with a food supply in a protective coat ● Angiosperms: flowers; nutrients in seeds ● Decreasing reliance on liquid water for fertilization ● Increasing dominance of sporophyte generation PLANT STRUCTURE: 1. What is developmental plasticity and what function does it serve? ● Developmental plasticity: the ability to alter form in response to its environment ○ more marked in plants than in animals ● plant species have by natural selection accumulated adaptations in morphology 2. What are the 3 basic plant organs? ● Roots ● Stems ● Leaves 3. What are the functions of roots? What are the 3 types of roots? What is the function of root hairs? ● Root and shoot system: ○ root system: rely on sugar produced by photosynthesis in shoot system ○ shoot system: rely on water and minerals absorbed by root system ● Function: ○ anchoring the plant ○ absorbing minerals and water ○ storing organic nutrients ● 3 Types of roots: Taproot system, Adventitious roots, Fibrous root system ○ Taproot system: consists of one main vertical root that gives rise to lateral roots or branch roots ○ Adventitious roots: arise from stems or leaves ○ Fibrous root system: thin lateral roots with no main root ■ found in seedless vascular plants and monocots ● Root hairs: in most plants, absorption of water and minerals occur near root hairs ○ large number of root hairs increase surface area available for water and nutrient uptake 4. What do stems consist of? What are the 2 types of buds? What is apical dominance? ● Stem: organ that has alternating system of nodes and internodes ○ nodes: points where leaves are attached ○ internodes: stem segments between nodes ● Types of buds: axillary and apical ○ Axillary bud: potential to form a lateral shoot, or branch ○ Apical bud: terminal bud, located near shoot tip and causes elongation of young shoot ● Apical dominance: helps maintain dormancy in nonapical buds 5. What do leaves consist of? What is the function of leaves? What are simple, compound, and doubly compound leaves? ● Leaves mainly consist of: ○ flattened blade ○ petiole: stalk that joins the leaf to a node of the stem ● Leaves are the main photosynthetic organ of most vascular plants ● Simple leaf: single, undivided blade ○ sometimes deeply lobed ● Compound leaf: ○ multiple leaflets arising from petiole ○ no axillary bud at base ● Double compound leaf: leaflets divided again into smaller leaflets 6. What are the different modified roots, stems, and leaves? ● Root Modification: ○ Prop roots: support tall, top heavy plants (corn) ○ Storage roots: carrots, beets ○ “Air” roots: pneumatophores (mangrove) ○ Buttress roots: mainly rainforest trees ○ “Strangling” roots: some figs ● Stem Modification: ○ Rhizomes: horizontal stem below the surface ○ Bulbs: vertical underground shoots consisting of enlarged bases of storage leaves ○ Stolons: horizontal shoots along soil surface (runners) ■ allows asexual reproduction ○ Tubers: enlarged ends of rhizomes or stolons for food storage ● Leaf Modification: (see number 5) ○ Simple leaf ○ Compound leaf ○ Double compound leaf ○ Tendrils: leaves that provide support of weight and climbing (curly hairlike) ○ Spines: protection, reduces surface area (decreases water loss to the outside), shade (cactus) ○ Storage leaves: retain and store food and water ○ Reproductive leaves: adventitious plantlet; fall and root ■ produce plants at tips ○ Bracts: base of flower, surround flower that attract pollinators ■ compensate for small flowers or absent petals 7. What are the 3 categories of plant tissues? What do they do? What are the 2 vascular tissues and what do they do? ● Dermal tissue system: protective skin ● Vascular tissue system: carries out long distance transport of materials between roots and shoots ○ xylem: conveys water and dissolved minerals upward from roots into the shoots ○ phloem: transports organic nutrients from where they are made (photosynthesis) to roots and growth sites ● Ground tissue system: all other functions; photosynthesis, storage, support, etc. 8. What are the major types of plant cells? What are their characteristics and functions? ● Parenchyma: thin and flexible primary walls ○ initial undifferentiated cell type for all plant cells during development ○ least specialized ○ retain the ability to divide and differentiate ○ perform most metabolic functions ○ phloem cells, leaf photosynthetic cells, some storage tissues ● Collenchyma: grouped in strands that help support young parts of plant shoot ○ thicker and uneven cell walls ○ provide flexible support without restraining growth ○ mechanical support ● Sclerenchyma: highly specialized for mechanical rigidity ○ thick secondary walls, strengthened with lignin for rigidity ○ elongate when mature, resistant to bending, cannot grow ○ often dead at maturity ○ xylem cells (fluid conduction and support), fibers and sclereids (support) ● Waterconducting cells of the xylem: tracheids and vessels elements; both are dead at maturity ○ Vessel elements align end to end to form vessels (long micropipes) ● Sugarconducting cells of the phloem: primarily conducts sugars ○ Sieve plates: porous end walls that let fluid flow between cells along sieve tube ○ each sieve tube element has a companion cell with nucleus and ribosomes that serve both cells PLANT GROWTH: 1. What are meristems? What are the two general types of meristems? What are the two types of lateral meristems? ● Meristems: embryonic tissue and allow for indeterminate growth ○ Apical meristems: located at the tips of roots and shoots and at the axillary buds of shoots ■ elongate shoots and roots (primary growth) ○ Lateral meristems: add thickness to woody plants (secondary growth) ■ Vascular cambium: adds layers of vascular tissue called secondary xylem (wood) and secondary phloem ■ Cork cambium: in stems/trunk, replaces epidermis with periderm, which is thicker and tougher 2. Distinguish between primary and secondary growth ● Primary growth: elongates roots and shoots ● Secondary growth: increases thickness in roots and shoots 3. How do roots grow? What does the primary growth of roots produce? How do lateral roots form? ● Root tip is covered by root cap that protects the apical meristem as the root pushes through soil ● Growth occurs behind the root tip in 3 zones of cells: ○ zone of cell division ○ zone of elongation ○ zone of maturation ● Stele: vascular system of root or stem ○ angiosperms: stele of root is in a vascular cylinder ● Primary growth of roots produces epidermis, ground tissue, and vascular tissue ○ ground tissue fills cortex (place between vascular cylinder and epidermis) ○ endodermis: innermost layer of cortex ● Lateral roots arise from within the pericycle (outermost cell layer in vascular cylinder) 4. What is a shoot apical meristem? How do leaves develop? How do axillary buds develop? How do branches develop? ● Shoot apical meristem: domeshaped mass of dividing cells at the shoot tip ● Leaves develop from leaf primordia along the sides of the apical meristem ● Axillary buds develop from meristematic cells left at the bases of leaf primordia 5. How are stem tissues in eudicots and monocots? ● Lateral shoots: develop from axillary buds on the stem’s surface ● Eudicots: vascular tissue consists of vascular bundles that are arranged in a ring ● Monocots: vascular bundles are scattered throughout the ground tissue, rather than forming a ring 6. How are leaf tissues organized? ● =Epidermis: reduces water loss ● Stomata: lets CO2 exchange between air and photosynthetic cells in a leaf ● Stomatal pores flanked by 2 guard cells ○ regulate opening and closing ● Spongy mesophyll: below palisade mesophyll, in the upper part of the leaf ○ where gas exchange occurs ● vascular tissue of each leaf is continuous with vascular tissue of the stem ○ moves sugars to rest of plant and gets water and nutrients ● Veins: leaf’s vascular bundles and are leaf’s skeleton 7. What produces the tissues in secondary plant growth? What meristems are involved? ● Secondary body plant: has tissues produced by vascular cambium and cork cambium ● Secondary growth found in gymnosperms and eudicots, few monocots 8. Describe how secondary growth occurs in sequentially older parts of the stem (what does cambium produce? What does the cork cambium produce, what does this replace?) ● Cambium produces secondary xylem on the inside of the ring and secondary phloem on the outside, pushing xylem and phloem apart ● Cork cambium produces the cork ○ one of the many layers of bark between the cork and primary phloem ○ replaces the epidermis 9. Locate the primary and secondary xylem and phloem, the vascular cambium, cork cambium, bark, cork, and cortex in a crosssection of stem. PLANT TRANSPORT 1. What are the mechanisms for transport in plants? What is the difference between diffusion and active transport? ● Transport occurs by ○ shortdistance diffusion or active transport ○ longdistance bulk flow ● Transport starts with absorption of resources by plant cells ● Movement of substances into and out of cells: regulated by selective permeability of plasma membrane ● Diffusion: passive transport ● Active transport: pumping of solutes across membrane ○ requires energy (ATP) ● most solutes pass membrane through transport proteins ○ aquaporins channel water in/out of cell 2. How does active transport of solutes occur in cells? What do proton pumps do? How is a membrane potential created? ● Proton pumps: most important transport protein for active transport ○ in plant cells, creates a hydrogen ion gradient that is a form of potential energy that is used to do work ○ contribute to a voltage (membrane potential) 3. What drives the active transport of solutes into the cell? what is cotransport? ● membrane potential and proton gradient can drive the transport of solutes into the cell ● membrane potential made by proton pumps contributes to absorption of K+ by root cells ● Cotransport: when a transport protein couples the diffusion of one solute H+ with the active transport of another NO ● sucroseH+ cotransporter couples movement of sucrose against concentration gradient with movement of H+ down electrochemical gradient 4. What is water potential? Why is physical pressure a factor in osmosis? ● Water potential: measurement that combines the effects of solute concentration and pressure ○ determines the direction of movement of water ○ water flows from regions of higher water potential to regions of lower water potential ● physical pressure of cell wall pushes back on expanding protoplast 5. How do solutes and pressure affect water potential? ● Psi = Psi (s) + Psi (p) ● solute potential of a solution is proportional to the number of dissolved molecules ○ more solutes = more negative ○ solute potential: osmotic potential ○ pressure potential: physical pressure on a solution 6. In what potential direction does water move? ● Water moves in the direction from higher water potential to lower water potential 7. What affect do solutes and physical pressure have on water potential?How does this affect the movement of water? ● Addition of solutes reduces water potential ● Physical pressure increases water potential ● Negative pressure decreases water potential 8. What is plasmolysis? What affect does this have on plants? ● Plasmolysis: process where cells lose water in a hypertonic solution ○ occurs when protoplast shrinks and pulls away from cell wall ● If flaccid cell is in solution with lower solute concentration, cell gains water and becomes turgid ● Loss of turgor makes plants wilt 9. What are the major pathways of water and mineral transport? ● Transmembrane route: out of one cell, across cell wall, and into another cell ● Symplastic route: by the continuum of cytosol ● Apoplastic route: by the cell walls and extracellular spaces 10. What is bulk flow? ● movement of a fluid driven by pressure ● needed for efficient long distance transport of fluid 11. Where do most of the water and mineral absorption in a plant occur? ● Most water and mineral absorption occurs near root tips, where epidermis is permeable to water and root hairs are found ● Transpiration drives transport of water and minerals from roots to shoots 12. Why is it that the mineral and solute concentration is greater in the roots than in the soil? ● Active transport 13. What is the role of the casparian strip? ● Waxy casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder 14. What are the 3 major pathways of transport in plants? Describe each one ● Transmembrane route: out of one cell, across cell wall, and into another cell ● Symplastic route: by the continuum of cytosol ● Apoplastic route: by the cell walls and extracellular spaces 15. What components of the xylem and phloem facilitate transport of water, nutrients, and sugars? ● Xylem sap: bulk flow of water and minerals from steles of roots to stems and leaves ○ when transpiration is low at night, root cells keep pumping mineral ions into the xylem of the vascular cylinder lowering water potential ○ water flows from root cortex, making root pressure ○ positive root pressure is weak and a minor mechanism of xylem bulk flow ○ guttation: drops of xylem sap on tips or edges of leaves of some vascular plants 16. How are water and minerals transported from the soil to the xylem? ● endodermis regulates and transports needed minerals from soil into xylem ● water and minerals move from protoplasts of endodermal cells into cell walls ● diffusion and active transport are involved in movement from symplast to apoplast 17. What role does the Casparian strip play in transport of water and minerals into the xylem? How does it affect the pathway of transport? ● waxy casparian stip of endodermal wall blocks apoplastic transfer of minerals from the cortex to vascular cylinder 18. How is root pressure generated? ● water flows in from the root cortex 19. Describe the transpirationcohesiontension mechanism. How does transpiration produces negative pressure (tension) in the leaf and effect does this have on transport of water in the xylem? ● water is pulled upward by negative pressure in the xylem ● water vapor in the airspaces of a leaf moves down water potential gradient and exits the leaf by stomata ○ lowers the water potential in mesophyll ● transpiration makes negative pressure (tension) in leaf, which exerts a pulling force on water in the xylem, pulling water into the leaf 20. What role do cohesion and adhesion in water molecules play in water transport? ● Transpirational pull is facilitated by cohesion of water molecules to each other and adhesion of water molecules to cell walls ● water molecules are attracted to cellulose in xylem cell walls through adhesion and helps offset force of gravity 21. Describe the structure of stomata. What controls the opening and closing of guard cells? What role does this play in transport? ● Stomata: each is flanked by a pair of guard cells that control the diameter of the stoma by changing shape ● changes in turgor pressure open and close stomata ● results primarily from the reversible uptake and loss of K+ ions by the guard cells 22. What are the stimuli for stomata opening and closing? ● Open during the day and close at night to minimize water loss ● Stomata opening at dawn is triggered by light, 2depletion, and an internal clock in guard cells ● Drought, high temperature, and wind can cause stomata to close during the daytime ● abscisic acid: hormone produced in response to water deficiency and causes the closure of stomata 23. How is sugar loaded into sievetube elements? ● Sugar travels from a sugar source to sugar sink ● sugar can move by symplastic or both symplastic and apoplastic pathways ● requires active transport ● proton pumps and cotransport of sucrose and H+ let cells get sucrose 24. Describe bulk flow by positive pressure in a sieve tube. How is positive pressure generated and what role does it play in the transport of sugar? ● Phloem sap moves through a sieve tube by bulk flow driven by positive pressure 25. What are some (all?) of the tradeoffs that occur as a result of water transport within the plant? ● Transpiration: ○ plants lose a large amount of water and if it is not replaced, the plant will lose water and wilt; turgor is lost throughout the plant ○ but also results in evaporative cooling which can lower the temperature of a leaf and prevent denaturation of enzymes involved in photosynthesis and other processes
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