Lecture 10: Physiology Flashcards
Human influences around the globe
Habitat loss
Habitat fragmentation
Species exploitation
Movement of species
Changing nutrient cycles
Global climate change
AAAS Initiative on Climate Change
- Human caused climate change is happening
- We face risks of abrupt, unpredictable and irreversible changes
- Responding now will lower risk and cost of taking action
Effects of climate change for humans
Heat waves: dangerous for vulnerable populations
Drought: widespread crop failure and disrupt food system
Loss of low lying communities including island countries
Greater frequencies of extreme events and new kind of events (destructive as emergency resources being depleted)
How are we seeing shift in species and community properties from anthropogenic (human caused) pressures on Earth?
Plant species richness has decreased
Changes in diversity over time
Small, but consistent changes in _____ can cause major disruptions to ecosystem structure
temperature
How are humans changing the world and how does
that influence how we study ecology?
Mechanistic understanding of ecosystems will allow us to:
manage ecosystems
predict changes before they occur
Fragmentation, invasive species, global perturbations can be “natural experiments” to aid in our understanding
Combining “natural” with controlled experiments ca make progress in understanding, prediction, and management
Biology is ____ and ____
powerful and sensitive
exponential growth and ability to adapt makes biology powerful
Why are we having trouble dealing with climate change despite our knowledge?
Caused by collective actions of many individuals
Benefits of changing behavior will not come directly to individuals who change behavior
Solutions toward climate change
Developing social norms, form committees, governmental structures at higher levels to help
Using technology, cooperation, and understanding natural systems
Factors to influence Individual’s Physiology
Temperature
Water
Obtaining energy
Physiology
individual dependence on and species’ adaptations to the environment
Optimum
value of environmental variable at which an
important physiological process is maximized (growth, reproduction, survival)
Stress
condition in which an environmental change results in a decrease in the rate of an important physiological
process
Ameliorating (improve stress) through:
tolerance and avoidance
Tolerance
find a way to deal with/live through the challenge
Ex of drought tolerance and avoidance in Plants
Drought tolerators: work well at repairing xylem that are
damaged during drought
Drought avoiders: shut down stomata and go into quiescence in drought
Avoidance
find a way to get away from the challenge
Acclimation
Adjustment in an individual organism to lessen effect of a stressor
Short term, reversible process
Ex of cold tolerance and avoidance for bears
Tolerance: thick fur, fat, dark skin
Avoidance: hibernate to avoid cold
Adaptation
Traits with a genetic bases in an population that lessen the effect of a stressor
Long-term processes irreversible for an individual
Through specialized for environment, genetic, evolution
Example of adaptations from humans to environment
People in andes have higher red blood cell count for greater lung capacity
People in Tibet have higher breathing rate
Adaptations to high altitude and low oxygen
Adaptations often involves _____ influencing ____
tradeoffs
growth, survival, or reproduction
Example of tradeoff from adaptations
Increasing high red blood cell count may increase survival but comes cost to growth
Adaptive red blood cell count is intermediate value to balance trade off
Climate envelope
range of climate conditions under which a species occurs
influences fundamental and realized niche
Fundamental niche
all of the (abiotic) environments in which a
species could live
How does challenges of hot temperature within physical limits effect organisms?
rapid water loss
proteins denature
Realized niche
the actual distribution of the species
Differs from fundamental niche because of disturbance, dispersal ability, interactions with other organisms (competition and facilitation)
How does challenges of cold temperature within physical limits effect organisms?
Organism have physical limit so too cold causes cells to freeze and burst, chemical reactions slow, enzymatic activity ineffective, and lipid membrane of organelles can solidify
Temperature is a stress since
Enzymes function most effectively at intermediate temperature
Membranes functioning within cells
Influences water loss rate
Changes in an organism’s temperature are influenced by
energy balance (inflow outflow of energy)
Energy can flow in/out via
conduction
convection
latent heat transfer
solar and infrared radiation
Conduction
direct transfer of energy from warmer, more rapidly moving molecules to cooler, more slowly moving
molecules
Convection
movement of energy through moving air or
water
Plant energy balance with energy input and outputs
Energy inputs:
Sunlight and infrared radiation
Conduction and convection from ground, air if warmer
Energy outputs/losses
Emission of infrared radiation
Conduction and convection from ground, air if cooler
Transpiration
Latent heat transfer
phase transitions in water
Solar and infrared radiation
Transfer of electromagnetic
energy
Plants exist in environments outside their _____
optima
Leaves are sensitive to
temperature/heat
cause adaptations to cool plants
Cooling adaptation for leaves
Pubescence (reflect more solar radiation to alter temp, lower SR and IR)
Ex. desert shrub harrier in summer
Decreases boundary layer for greater convective cooler (lower H conv)
Ex. many thin small leaves
Evaporation (increase H ET)
High latent heat of vaporization; water absorbs large amount of energy before evaporating to leave organism to be much cooler
Transpiration controlled by plants: stomates closed and open
Example of how Snow Lotus adapt to extreme cold
Wooly plant of Himalayas
Pubescence: increase boundary layer, decrease convective cooling, trap solar radiation)
Grow close to ground: away from wind, decrease convective cooling
Ectotherm
Regulate heat through energy exchange with environment
Most animals
Endotherm
Regulate heat through internal heat generation
Represent H met
Birds and mammals, some fishes and insects
For thinking about adaptations or acclimations need to know
Organism’s stress (getting hotter or colder than optimum)
Adaptation free flow of energy
If organism losing heat to environment across surface area…
Layer of air around organism will heat up
Air will slow down this transfer (boundary layer)
How can organisms manipulate boundary layer to conserve heat?
Protect boundary layer
Have fur, stand out of wind
How can organisms manipulate boundary layer to get rid of heat?
Disrupt boundary layer
Stand in wind, move around, shed fur
All else being equal, are these boundary layer adaptations more effective in small or large organisms?
Small organisms
Small organisms have _____ for
higher surface area to volume ratio
greater ability to move heat across surface area
When surface area/ volume approximately a sphere: 3/r
r increases, SA/V decreases
Ectotherms have greater
Greater tolerance in body temperature variation
often same temperature as surrounding
active modulation possible
Active modulation in ectotherms
Surface area: volume critical
SA:V decreases as animals get bigger
Low SA:V more difficult to modulate heat through environmental modulation
Large ectotherms unlikely; little ability to exchange heat with environment
Characteristic of ectotherms
Bask in the sun
Susceptible to predators: Good camouflage
Fine tune with distance to ground
How do ectotherms adapt to cold temperatures?
Avoidance strategy: migration, burrow in the soil
Tolerance: maintain high concentrations of antifreeze proteins in cells
(Generally invertebrates; vertebrates can’t tolerate freezing as well)
Endotherms greatly expanded geographic ranges and seasonal activity, but cost is
high demand for food supply to support metabolic heat production
Metabolic rate in Endotherms
function of external temperature, rate of heat loss
Small endotherms have ______ per unit biomass compared with bigger endotherms
higher basal metabolic rates
Thermoneutral zone
Seen in endotherms
Range of environmental temperatures well suited to basal metabolic rate
Only minor behavioral and morphological adjustments made to adjust temperature within zone
Differences in thermoneutral zone: effect of fur, feathers, fat
increases boundary layer
reduce convection
reducce conduction (air, water is good insulator)
Topor/ hibernation
Endotherm adaptation where alter lower critical temperature during cold periods by entering dormancy
Slows down other functions and just use metabolic rate to keep temperature from killing them
Need to be able to get enough reserves during warm temperature periods to pay for this: difficult in polar regions
