Ecology: Week 3 Lecture 5 - Terrestrial Adaptations PDF

Ecology Week 3 Lecture 5 – Adaptations to Terrestrial Environments  Water Balance Water is essential to organisms: needed for photosynthesis, provides a medium for nutrients But: terrestrial organisms live in air with a lower water content than their bodies, thus...

Ecology Week 3 Lecture 5 – Adaptations to Terrestrial Environments  Water Balance Water is essential to organisms: needed for photosynthesis, provides a medium for nutrients But: terrestrial organisms live in air with a lower water content than their bodies, thus constantly lose water Problem: how to maintain water balance?  Salt Balance “Salt balance and water balance go hand in hand” WHY? Salts are located in water When water leaves organism via evaporation, salt concentration increases Solute concentration affects water movement via osmosis  Osmoregulation Osmoregulation: The mechanisms that organisms use to maintain proper salt balance Water balance: Plants Plants lose water by transpiration, mostly from the stomates but also from all exposed surfaces. Water flows through xylem Most uptake in plants is through the root system. Water balance: Plants Plants lose water by transpiration, mostly from the stomates but also from all exposed surfaces. Water flows through xylem Most uptake in plants is through the root system. How to defy gravity?  Osmosis Osmosis is the passive movement of water across a differentially permeable membrane, from areas of low solute concentration to high concentration Force generated by osmosis = Osmotic potential  Active or Passive process? E.g., requires energy expenditure? Solutes will move out at same time; counteracted by: Semipermeable membrane Active transport of solutes back in Cohesion-Tension Theory: Transpiration pulls water in a continuous column Why does this work? Osmotic potential creates root pressure; max 20m against gravity  Water molecules Polarized, forms bonds – Cohesion among water molecules via these hydrogen bonds – High surface tension (the highest of all common liquids except mercury) – Capillary forces (e.g., xylem walls) 11 Why do plants need to move water? -Transport ions (including nutrients) -Photosynthesis  Ion movement in plants Ions enter through roots and xylem, are transported to cells, stored in vacoules Central vacuole  Photosynthesis 6CO2 + 6H2O  C6H12O6 + 6O2 Carbon dioxide Water Sugar Oxygen 15 16 Water absorbs longer wavelengths better  17  Photosynthesis ? 6CO2 + 6H2O  C6H12O6 + 6O2 Carbon dioxide Water Sugar Oxygen  Photosynthesis - Phloem transport sugars 6CO2 + 6H2O  C6H12O6 + 6O2 Carbon dioxide Water Sugar Oxygen How can plants control water uptake? -solute concentration in roots -opening/closing stomates  Soils and Water Cohesive forces also make water stick to soil: strength is termed water potential of the soil. When water potential of a substance is negative, it will pull pure water (water potential = 0) into it To obtain water: root osmotic potential < water potential Stomates affect water (and CO2) 22  Mangroves and water balance Live in coastal mudflats Saltwater = high external osmotic potential  Mangroves adaptations 1) Excrete toxic salts through leaf pores 2) Active transport, plus organic compounds (amino acids and small sugar molecules) roots.  Water/Salt Balance: Animals For terrestrial animals, water balance is less problematic: – Water not massively lost through transpiration – Closed systems, thus easier to retain mineral ions What are water pathways for animals? Pathways of water gain and loss for animals C6H12O6 + 6O2 ⇔ 6CO2 + 6H2O  Kidneys Control water and salt balance by controlling urine concentration In humans, solute concentration in urine 4X that of blood; in kangaroo rats, 14X  Temperature Increasing temperature causes – Molecules move faster – Chemical reaction rates accelerate  – Productivity increases 10°C = 2-4 X faster metabolism  Enzymatic Activity Life processes depend on biochemical reactions, mostly catalyzed by enzymes At lower temperatures, reactions proceed slower so more substrate, more enzymes, or functionally different enzymes are needed. Thus whole organisms are fine-tuned to the temperatures they normally experience 29 (Acetylcholinesterase: critical to nerve functioning)  Temperature Movement Radiation is the emission of electromagnetic radiation (photons); moves through vacuum or clear substance Conduction is from molecular vibration; occurs between bodies in contact with each other Convection is the movement of heat in liquids or gases (type of conduction) Evaporation removes heat from a surface as water changes from liquid to gas 31  Heat Balance Heat Gains: Heat Losses: 32  Temperature Most physiological processes require liquid water, or temperatures between 0 and 100 C However, any given species can only handle a restricted range, with upper and lower lethal limits, and an optimum Outside of limits, enzymatic reactions don’t function properly-> 33  Extreme Heat What happens at very high temperatures (>45 C)? - Proteins open up (denature)  Extremophiles Thermophilic bacteria  Extreme Cold What happens when living cells freeze? – Biological reactions cannot occur without solutes in a liquid – Ice crystals destroy delicate organelles 36  Extreme Cold Adaptations include: – Insulation – Hibernation – Delayed ice formation Freezing point depression (cf. salt on roads) 37  Challenges for polar fish Pure water freezes at 0 °C and seawater freezes at -1.9 °C due to solutes – Thus vertebrate tissue can actually freeze in liquid seawater Adaptation: – Glycerol (natural antifreeze); 10% in blood will decrease freezing point by 2 °C 38  Homeostasis Homeostasis: ability to maintain constant internal conditions in face of varying external environment. – Salt, water, heat – Uses negative feedback 39 Homeothermy 40  Animals and temperature Physiologically, animals can be divided into homeotherms and poikilotherms. Homeotherms have stable, non-varying internal temperature. Poikilotherms have internal temperature fluctuations, tracking external environment 41  Ectotherms and endotherms Another way to distinguish organisms and their temperature physiology: – endotherms: animals which produce their own heat internally through their metabolism. – ectotherms: animals dependent on the environment as a heat source and heat sink. 42  Birds and mammals tend to be homeothermic endotherms (previously termed “warm- blooded”) Amphibians, fish, reptiles, and insects tend to be poikilothermic ectotherms (“cold- blooded”)  Endothermic Fish Lamnid Sharks Zina Deretsky, National Science Foundation  Opah (Moonfish) Endothermic and homeothermic; Maintain same internal temperature in deeper/colder water Ectothermic Mammal Naked Mole Rat - live in desert tunnels, low O2 Homeothermic Ectotherm? 47 Poikilothermic Endotherm 48  Endothermy costs High energy cost to maintain body temperature to optimize metabolic rate. Can be counterbalanced with adaptations: – Reduce heat loss: insulating fur, feathers and fat – Enhance heat loss: sweating, panting and increasing blood flow through the skin. Benefits? 49  Endothermy benefits Enzymes/ biological reactions can all be optimized to same temperature Animals can be active at times and places where ectotherms are forced to be inactive. – For example, earliest mammals were probably active at night 50  Endotherms Endotherms tend to be larger: – easier to control heat with lower surface area to volume Endotherms also tend to be terrestrial: 1 - Low O2 in water 2 - Convection high 3 - Low temp variation 51  Aquatic Endotherms (Marine Mammals/ Aquatic Birds) Adaptations? – breathe oxygen from the air – have thick fur or feathers – high levels of insulation from fat deposits – unusual blood circulation patterns – eat high energy foods Bill Nye's Climate Change Summary https://www.youtube.com/watch?v=EtW2r rLHs08 54