BIO 373 1st Edition Lecture7Outline of Last Lecture I. Temperature Variation and Water Availability continueda. Plantsb. Animalsc. Ectothermsd. Endothermse. Variation in Water Availabilityi. Water potentialf. Water Balance in terrestrial plantsOutline of Current Lecture I. Water Balancea. Marine Animalsb. Terrestrial AnimalsII. Energya. Sources of energyi. Autotrophsii. Chemosynthesisiii. Photosynthesis1. PathwaysCurrent LectureWater Balance- Marine Animalso 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 potentialo 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 gillsThese 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 Animalso 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 urineEnergy- Maintain chemical reactions, grow, reproduce, interaction with environment- Sources of energyo Autotrophs—photosynthesizers Water and light= chemical energy Energy captures is stored as carbon-carbon bonds to make carbohydrateso Chemosynthesis Use inorganic substrates as electron donors for carbon fixationo Photosynthesis Plant responses to variation in light--Light reactions and dark reactions- Utilize one or the other depending on conditionso 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 increasingo Photosynthetic rate is increasingo Need water to open stomata and intake CO2 needed for photosynthesis Plant responses to variation in temperature- Right temperature for enzyme functiono 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 pathwayo O2 beats CO2 to RuBisCO binding site so a new pathway is utilizedo Photorespiration is detrimental so why do plants use it? Maybe it is beneficial for protecting photosynthetic machinery from damage of intense light- C4 pathwayo 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 RuBisCOo C4 plant abundance increases as higher temperatures Energetically costly pathway so at high temperatures, the plant has more energy to use- CAM pathwayo Response to drynesso Crassulacean acid metabolism=CAMo 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