Physiological Ecology

Species Distribution

The Fundamental Tasks of Living  Physiology is the study of how organisms work.  How nutrients are acquired & transported.  How wastes are eliminated.  Ecology is concerned with how species deal with their environments and how the environment limits distribution.  Both directly affected by physiology.

Do Species Distributions form Patterns?  Each place has a unique assortment of plants and animals.  Animals and plants are adapted to their environments.

Do Species Distributions form Patterns?  Which two pictures were taken closest to each other?  A & B  A& C  A & D  B & C

Do Species Distributions form Patterns?  Many factors influence the distribution of organisms:  Land or water  Amount of nutrients available  Amount of sunlight available  pH  Other species present

Do Species Distributions form Patterns?  The two most important factors in a terrestrial environment:  Moisture  Temperature

 From the way the Valdivian forest looks compared to the other locations, which labeled point on the graph would you expect to represent its annual temperature and precipitation?

Whittaker Diagrams  The Whittaker Diagram suggests that the average temperature and precipitation of a particular location controls what type of vegetation may grow there.

Temperature vs Water  Temperature and precipitation combine to control the amount of water available to plants and hence, its overall health.  Physiological tolerances describe what a plant can tolerate.  Max/min temperatures  How much water is required

Temperature vs Water  Water enters a plant through the roots.  Travels up through the plant  Is lost at the leaf surfaces – Transpiration  Water is also lost through evaporation from the soil surface.  The total amount of water available to plants in any ecosystem is a balance between incoming precipitation and outgoing evapotranspiration.

Potential Evapotranspiration  The amount of water loss from an ecosystem at a given temperature is known as the Potential Evapotranspiration (PET).  To avoid desiccation, a plant will need to access an amount of water that is equal to or greater than PET.

Climate Diagrams  The PET can be read from the temperature line on the climate diagram, because, as you saw, potential evapotranspiration (in mm) is approximately twice temperature (in °C).  Where the precipitation graph line lies above the temperature line, precipitation is greater than PET. If precipitation lies below temperature, precipitation is less than PET.

Tolerances Define Species Ranges  Every species has a limited tolerance to different environmental variables that determine its geographic range, including not only temperature and precipitation, but also the many other variables we mentioned earlier. The sum of these conditions is sometimes referred to as a species’ niche.

Tolerances Define Species Ranges  The speed of a desert night lizard increases up to 35 °C, then drops.  Physiology plays a large role in determining the range of areas where you will see any given species.

Tolerances Define Species Ranges  Temperature and precipitation are very important, but sometimes they don’t tell the whole story.  For example spruce require an environment where precipitation is above PET throughout the year.  In Georgia, precipitation is above PET, but spruce don’t occur.  Competition? Soil drainage? Nutrients?

Law of the Minimum  Liebig, working in the 1800’s, suggested that growth and reproduction are limited by the rarest resource.

Shifts in Species Ranges  The geographic range of a species can change over time.  As the ice receded after the last ice age, organisms moved back into the area.  Measured using pollen in core samples.

 Spruce tree distribution over the past 21,000 years. Ranges were reconstructed from depth-specific pollen grain counts in lake sediments. Blue indicates glaciated areas. Green indicates spruce range, with darker green suggesting higher spruce density. Data courtesy Williams et al and the National Climatic Data Center.

Physiological Ecology  Each species has an optimal environment and tolerance to a variety of conditions.  If conditions change a species can  Migrate with climatic conditions  Go extinct  Adapt to the new conditions

Physiological Ecology  Adaptation to new conditions can occur:  As individuals acclimate or  As populations evolve

Adaptation & Acclimation

Adaptation and Acclimation  Dams result in warmer water downstream.  Temperature is an important factor for many species.  Will it affect the trout living in the stream?

Trout Physiology  Enzymes are proteins that catalyze reactions.  Change shape during the process.  Affected by temperature.  High temps denature enzyme – doesn’t work.  Low temps decrease flexibility – doesn’t work.

Trout Physiology  Trout living above the dam (cool) and below the dam (warm) have enzymes that have different optimal temps.  Genetic adaptation or individual acclimation?

Acclimation  Experiment to determine if individual fish acclimate.  The optimal temperature for the enzyme adjusts upward over a few weeks.  No reproduction involved – not genetic.

Adaptation through Evolution  Acclimation occurs in the short-term.  No reproduction  What happens over several generations?  Each generation of fish receives a new mix of alleles.  Some may be better for high temperatures.  They may adapt to high temperatures through natural selection.

Managing Dams  Large dams pull water from deeper under water resulting in cooler summer temperatures and warmer winter temperatures.

Managing Dams  Mixing deep and shallow water alleviates the problem, but doesn’t eliminate it.  Still working to restore native fishes.  Small dams can often just be removed.

Homeostasis

 Homeostasis occurs when an organism maintains relatively constant internal conditions.  Temperature  pH  Salinity  Some organisms can tolerate a wide range of conditions, some narrow.

Surface Area to Volume Ratio  Organisms interact with their environment through the surfaces of their bodies.  Much of the exchange of heat and water occur across the skin.  The amount of skin, or surface area, is a key to homeostasis.

Surface Area to Volume Ratio  Surface area – exposed surface.  Sphere: πd 2  Cube: 6w 2  Volume – internal capacity.  Sphere: π/6 d 3  Cube: w 3

Surface Area to Volume Ratio  A thermoregulating kangaroo rat gains and loses heat via several processes which we account for using the heat balance equation. These heat inputs and outputs must balance (summing to near zero) for the animal to maintain homeostasis.

Surface Area to Volume Ratio  Heat can be gained an lost through:  Radiation from sun  Metabolic heat  Re-radiation  Conduction  Convection  Loss of heat with water (latent heat)

Surface Area to Volume Ratio  Ectothermic animals rely on the environment to regulate their temperature.  Large surface area in contact with warm ground & exposed to sun.

Adaptations for Controlling Internal Temperature  Change behavior  Seek shade/sun  Use color  Dark to absorb heat, light to reflect heat  Insulation

Water Balance  Ingestion  Animals can take in water by ingesting it – from water they drink or in foods they eat.

Water Balance  Secretion  Water lost through excretion of metabolic wastes and elimination of fecal waste.

Water Balance  Absorption – most aquatic animals can absorb water through their skin.  Bodies saltier than the freshwater they live in so water enters their bodies.

Water Balance  Metabolism of food  During cellular respiration, sugar (glucose) is broken down into carbon dioxide, water, and free energy.

Water Balance  Evaporation – loss of water from the surface of the organism.  Provides cooling

Adaptations for Water Conservation  Desert dwelling tenebrionid beetles use behavior to harvest moisture from fog.  Abdomen up, water condenses and rolls down grooves to mouth.

Trade-offs in Water Balance  Kangaroo rat tradeoff between water balance and heat balance.  Plants have a tradeoff between photosynthesis and water balance.

Why be a Mammal?  Mammals are endothermic & homeothermic.  They produce their body heat internally and maintain a steady temperature.  Requires lots of energy!  Optimal temperature for metabolism is always available.

Metabolism

 All organisms require energy to fuel their metabolism and nutrients to build their bodies.

Photosynthesis  Energy arrives as sunlight.  Plants use photosynthesis to make glucose from carbon dioxide & water using energy from the sun.  Bonds in glucose store energy.  6 CO H 2 O + sunlight → C 6 H 12 O 6 + 6O 2 + 6H 2 O

Respiration  When organisms need energy, they can break the bonds in glucose during cellular respiration.  C 6 H 12 O 6 + 6O 2 → 6 CO H 2 O + free energy

Photosynthesis  Light Reactions  Sunlight hitting chlorophyll molecules energizes electrons to power creation of first NADPH, then ATP.

Photosynthesis  Light Independent Reactions  Rubisco uses the energy stored in NADPH and ATP from light reactions to carry out carbon fixation.

Photorespiration  Rubisco can bind to oxygen instead of carbon dioxide.  Destroys the sugar.  Depends on concentrations of carbon dioxide vs oxygen.

C 4 Photosynthesis  Some plants that grow in hot climates separate light dependent and light independent reactions into different cells.

Water Potential  Plants take up water through their roots and lose water through pores in the leaves.  Pores in the leaves of plants ( stomata ) open to take in carbon dioxide for photosynthesis.  Release oxygen and water.  Transpiration

Water Potential  Water moves from an area of higher water potential to lower water potential.  Increased humidity in the air will make water move more slowly through the plant.

Cavitation  At low humidity, the tension in the water column. As the molecules pull away, air bubbles can form.  Interferes with a plant’s ability to take up water.

Soil Type Affects Water Potential  Attraction of water to soil decreases its mobility.  Finer particles (clay) of soil have more surface area for water molecules to adhere to – lower water potential.  Requires more suction to pull water out of soil.

Solutes Affect Water Potential  Adding solutes to the water decreases water potential.

Controlling Water Flow  Water can only flow from high to low water potential if there is an open route.  Add a valve to the top of the straw.  Partially closing the valve allows the plant to avoid cavitation at lower humidity.  Closing the valve stops the flow.

Controlling Water Flow  Leaves have a waxy coating to prevent water loss.  Stomata can open/close like valves to conserve water.

Xylem  The xylem is a series of tubes that carry water through the plant.  Tradeoff between having narrow tubes to prevent cavitation and wider tubes to carry more water.

CAM and Water Conservation  CAM is a third type of photosynthesis where light dependent reactions and light independent reactions are separated in time.  Stomata open at night to let carbon dioxide into the leaf. High humidity at night reduces risk of cavitation.  Stomata closed during the day. Light dependent reactions can now occur using the carbon dioxide taken up at night.

Ingestion by Heterotrophs  Heterotrophs can’t make their own food.  Take in food from the environment.  Herbivores  Carnivores  Decomposers  Specialists vs Generalists  Tradeoff between availability & efficiency

Plant Nutrient Acquisition & Mycorrhizae  Plants acquire nutrients from the soil.  Increased surface area will help gather more water and nutrients.  Plants solve this problem by associating their roots with fungi in a mutualism called mycorrhizae. The plant provides the fungus with sugars and in return the fungus grows out into the soil and transports nutrients to the plant.