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Lecture 3

Lecture 3-Sept 12.docx

4 Pages

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BIOL 2000
Joseph Rasmussen

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Sept 12, 2013 Adaptations to Terrestrial and Aquatic Environments  Some adaptations of plants for life on land  Osmotic adaptations of fish for marine life  Adaptations of animals to desert environments  Physical adaptations required for large size  Biochemical adaptation’s to extreme environments  Homeostasis and how is it achieved? Plants evolved  Plants evolved root, vascular systems and stomates to obtain water and nutrients, and pump them through their bodies • Microorganisms live in water and depend on diffusion to feed and cleanse their cell- limited to a mw  Plants pump water and transport nutrients through their vascular system  Transpiration pull is the main pump  Evaporation at the leaf “sucks” water up through the plant  Water vapor o Diffuses from stomates  Water evaporates from mesophyll cells  Tension pulls water into the leaf veins  And through the xylem vessels in the stem  Then through the root o Osmosis and into the xylem Water loss  Controlled by o Waxy leaf cuticle o Stomates on the underside- regulate evaporation  Spines and hairs help dessert plants deal with heat and drought  Still boundary layer that traps moisture and reduces evaporation Plants have difficulty trapping Co2 without losing water (C3 mechanism)  Most plants and algae employ the C3 mode of CO2 uptake o Stomates must remain open for hour- not water efficient  RUBISCO has a low affinity for CO2 but the spongy mesophyll allows free air flow- maximize CO2 capture but high water loss  Adaptation to Arid conditions (C4 mechanism)  PEP-carboxylase has much higher affinity for CO2 than RUBISCO  Stomates mostly closed and mesophyll tightly packed to reduce air circulation keeps CO2 levels in the leaf low and conserves water  Photosynthesis can be highly efficient without water loss, but only occurs in the bundle sheath CAM plants are even more water efficient than C4 Metabolism  Stomates open at night only when transpiration is low  OAA is formed and stored within cell vacuoles  During the day stomates close and OAA is recycled to release CO2 to the Calvin-Benson cycle  Day and night enzyme have different T-optima Marine fish  They live in a dry environment  Water and slat balance is critical problem for fish  Marine fish live in water more
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