Gas Exchange 3/26/12. Biology: life study of. What is Life? Ch. 44 pg Properties of Life Cellular Structure: the unit of life, one or many

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1 Biology: life study of What is Life? Properties of Life Cellular Structure: the unit of life, one or many Metabolism: photosynthesis, respiration, fermentation, digestion, gas exchange, secretion, excretion, circulation--processing materials and energy Growth: cell enlargement, cell number Movement: intracellular, movement, locomotion Reproduction: avoid extinction at death Behavior: short term response to stimuli Evolution: long term adaptation The basic metabolic interdependence of terrestrial organisms CO 2 gas exchanges H 2 O O 2 CH 2 O H 2 O Gas Exchange Ch. 44 pg Photosynthesis light CO 2 + H 2 O O 2 + CH 2 O chlorophyll Respiration CH 2 O + O 2 CO 2 + H 2 O + energy 1

2 Leaf Cross Section cuticle upper epidermis palisade mesophyll vein xylem vein phloem spongy mesophyll lower epidermis gas exchange CO 2 O 2 Metabolic Mode Day In Out Autotrophic Night Out In Heterotrophic stoma and guard cells SEM of Spongy mesophyll shows each leaf cell is close to air The exchange of gases is regulated by the opening size of the stoma (mouth) between the two guard cells of leaf epidermis. flaccid turgid 2

3 Factors influencing stomatal diameter enlarging stoma abundant water abundant light low internal CO 2 turgid reducing stoma water deficit darkness high internal CO 2 abscisic acid hormone flaccid H 2 O Woody stems lack stomata, so exchange gas through lenticels openings in the bark Gas Exchange in Plants Understand why Photosynthesis and Respiration are complementary. Understand where gas exchange happens in a plant, what regulates gas exchange, and how the structure of plant leaves helps exchange gasses in the cell. 3

4 Gas Exchange in Animals Aquatic organisms O 2 CO 2 Gas Exchange Diffusion Stentor Paramecium As size increases, more respiratory surface is needed Size Matters: Surface/Volume Ratio unfold the cube s surfaces 1 cm surface = 6 cm 2 volume = 1 cm 3 S/V=6.0 unfold the cube s surfaces 2 cm surface = 24 cm 2 Conclusion? volume = 8 cm 3 S/V=3.0 Larger organisms have less surface area relative to volume than do smaller organisms. Food and wastes cannot be exchanged by diffusion alone. Circulation is necessary! 4

5 Diffusion Rate In order maximize diffusion: 1. Increase surface area 2. Decrease the thickness of the respiratory surface 3. Increase the partial pressure gradient of the gas across the surface (conc. grad.) Gas exchange through diffusion requires an extensive capillary system Bristleworms (Nereis) have capillary beds in the parapodia for gas exchange Gas Exchange External Gills Mexican Axolotl Ambystoma mexicanum Nudibranch These amphibians can also exchange gasses through their skin 5

6 Gas Exchange Internal Gills Calico scallop Argopecten gibbus Ciliated surfaces move water across gills for gas exchange, Water movement necessary in aquatic animals with internal gills Sea cucumber Cl. Holothuroidea Norton Presentation Maker, W. W. Norton & Compa 6

7 Sea Cucumber Breathing Gas Exchange in Fish oxygenated water operculum deoxygenated, carbonated water Perca flavescens 7

8 Gill filament shows countercurrent exchange design: oxygenated water water and blood flow in opposite directions deoxygenated water Countercurrent is more efficient than concurrent exchange water concurrent countercurrent blood Percent O 2 Saturation water blood In countercurrent exchange, there is always a difference in partial pressure, so oxygen always move into capillaries. Not so in concurrent circulation Percent O 2 Saturation blood water Countercurrent flow maximizes: Oxygen removal from water Blood oxygen content Questions What is the name of the cells that open and close to allow for gas exchange in plants? Guard cells List two things that cause guard cells to open. Abundant H 2 O and light, low [CO 2 ] What 3 things can be manipulated to increase oxygen diffusion? Surface Area, Resp. thickness, part. pressure 8