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 adaptations to extreme environments • Homeostasis and how is it achieved?
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 cells—limited to a few mm • Plants pump water s and transport nutrients to leaves through their vascular system • transpiration pull is the main pump • Evaporation at the leaf ‘sucks’ water up through the plant Water vapour diffuses from stomates Water evaporates from mesophyll cells Tension pulls water into the leaf veins And up the xylem vessels in the stem And up the root Water moves into the root—osmosis and into the xylem
When nutrients or water are scarce plants adapt: grow more roots and less shoots water and/or soil nutrients scarce –more allocation to root development Water and soil nutrients plentiful—larger shoots, more growth
Plants control water loss • Waxy leaf cuticle • Stomates on the underside—regulate evaporation • Spines and hairs help desert plants deal with heat and drought • still boundary layer that traps moisture and reduces evaporation
Oleander has its stomates situated within hairy pits on the leafs under surface
Plants have difficulty trapping CO2 without losing water Most plants and algae employ the C3mode of CO2 uptake—stomates must remain open for hours--not very water efficient RUBISCO has a low affinity for CO2 but the spongy mesophyll allows free air flow—maximize CO2 capture but high water loss
Many plants adapted to arid conditions eg. grasses use the 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 enzymes have different T-optima Desert plants/succulents Eg Crassulaceae CAM means Crassulacean Acid metabolism
marine fish also live in ‘dry’ environment Water and salt balance is a critical problem for fish Marine fish live in water more concentrated than their body tissues —tend to lose water and must drink to offset water loss. Freshwater fish live in a dilute medium –tend to take on water & lose salts through gills —produce dilute urine and take up salts by active uptake.
Tigriopsis is a tiny copepod crustacean that lives in splash pools and experiences dramatic fluctuations in salt concentration It responds to these changes with rapid changes in blood chemistry and metabolic rate.
Tigriopsis responds to high salt stress by producing large quantities of amino acids that make its blood more concentrated—requires energy Sharp increase in metabolic rate, as amino acids are metabolized In response to a sudden dilution of their environment, they metabolized the amino acids.
Adaptations for life in hot environments The scarcity of water in the desert make evaporative cooling very costly Reduce activity, or go underground during the day and be more active at night when it is cool Many desert plants orient their leaves away from direct sunlight, and others shed their leaves and become dormant during hot and dry periods. The kangaroo rat has both physiological and behavioural adaptations for desert environments
CO2 released into lung and exhaled Hemoglobin in RBC binds O2 CO2 carried away in blood O2 released to tissues Large animals have evolved muscular pumps to circulate fluids and nutrients around their bodies
Insects pump O2 to their body tissues using a tracheal system The tracheal system opens to the outside through spiracles Trachea divide into tracheoles which divide into finer air capillaries
Gas exchange and ion exchange occurs across the surface of the gills in fishes and other aquatic animals Filaments and folds increase surface area O2 diffuses from water into blood Blood flow is counter current to water flow O2 rich water
Counter-currents can also be useful for retention—eg heat Arrows indicate direction of heat transfer Heat is shunted directly from artery to vein in the leg bypassing the foot and allowing its temperature to drop to conserve body heat
Halophilic bacteria can adapt to high salt concentrations by producing enzymes with high salinity optima. Comparison of salinity optima for respiratory enzymes in a halophilic and halophobic bacteria
Acetylcholinesterase Isozymes in rainbow trout Winter adapted trout, T-opt is 2C Summer adapted trout, T-opt is 17C Temperature adaptation in cold-blooded animals often involves changing enzymes as temperature changes
Homeostasis/regulation often occurs through negative feedback systems A thermostat is a typical negative feedback system What do we mean by the term positive feedback? Negative feedback—if T is too high heater switched off, if too low heater switched on. The feedback is considered negative because the response is opposite to the deviation.
Maintaining a constant internal temperature warmer than the external environment is costly—the bigger the gradient the bigger the cost This West-Indian hummingbird, conserves metabolic energy by setting its thermostat down at night Set-point 40C Set-point 20C