BIO 373 1st Edition Lecture7 Outline of Last Lecture I Temperature Variation and Water Availability continued a Plants b Animals c Ectotherms d Endotherms e Variation in Water Availability i Water potential f Water Balance in terrestrial plants Outline of Current Lecture I Water Balance a Marine Animals b Terrestrial Animals II Energy a Sources of energy i Autotrophs ii Chemosynthesis iii Photosynthesis 1 Pathways Current Lecture Water Balance Marine Animals o Salt water Isosmotic to environment Use urea to raise osmotic potential Drink water with solutes lose solutes Na Cl from gill secretions and lose Mg2 and SO4 through urine to maintain osmotic potential o Fresh water Hyperosmotic to environment Water potential is lower so flows from outside to inside Tendency to gain water To maintain osmotic potential they gain osmotic through gills These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Some diffusion loss from gills and excrete dilute urine Terrestrial Animals o Adaptations to dryness Amphibians have thin permeable skin Tend to lose water easily so need to find a good water source Some have evolved a thicker skin Some produce a mucous layer outside the skin Insects have a waxy cuticle as a boundary layer for water loss Lose water through excretion and gas exchange Reptiles have very thick impermeable skin as a boundary later Kangaroo rat obtain water through food and oxidative metabolism of breaking down food Lose water through gas exchange and some sweat glands Very dry feces so little water lost but very dilute urine Energy Maintain chemical reactions grow reproduce interaction with environment Sources of energy o Autotrophs photosynthesizers Water and light chemical energy Energy captures is stored as carbon carbon bonds to make carbohydrates o Chemosynthesis Use inorganic substrates as electron donors for carbon fixation o Photosynthesis Plant responses to variation in light Light reactions and dark reactions Utilize one or the other depending on conditions o Plant responses to variations in light levels In high light they reach saturation and have enough light for max photosynthetic rate In lower light plants continue photosynthesis and have more photosynthetic tissue Carotenoids orange red Chlorophyll a and chlorophyll b greens RuBisCo enzyme that catalyzes photosynthesis Very abundant Plant responses to variation in water Lead water potential is increasing o Photosynthetic rate is increasing o Need water to open stomata and intake CO2 needed for photosynthesis Plant responses to variation in temperature Right temperature for enzyme function o Increase the temperature increase the rate Optimal growth temperature Can acclimate to different temperatures Plant responses to nutrient availability Nitrogen enzymes need Photosynthetic pathways C3 pathway o O2 beats CO2 to RuBisCO binding site so a new pathway is utilized o Photorespiration is detrimental so why do plants use it Maybe it is beneficial for protecting photosynthetic machinery from damage of intense light C4 pathway o Plant is trying to maintain increased CO2 by utilizing the enzyme PEP case to fixate CO2 so that the increase CO2 prevents O2 from binding RuBisCO o C4 plant abundance increases as higher temperatures Energetically costly pathway so at high temperatures the plant has more energy to use CAM pathway o Response to dryness o Crassulacean acid metabolism CAM o Minimizes water loss At night open stomata to obtain CO2 Not during the day because at night there s less light and less evaporation water loss Use PEP case enzyme to make C4 molecule and captures lots of CO2 makes acidic Day time obtain sunlight for light reaction but stomata is closed so there s no water loss Utilizes CO2 from the dark reaction