Lec 4-6 Flashcards
Physiological processes are affected by _________
Temperature
Why are physiological processes affected by temperature?
Enzyme-catalyzed processes rely on steady temperatures
Physiological processes affected by temp
Photosynthesis
Cellular respiration
Enzymes catalyze reactions faster at __________ temperatures
HIGHER
Low temperatures therefore _______ support physiological processes well
Do NOT
Enzymes at extremely high temperatures?
Get DENATURED
High temps do NOT support processes
Physiological Age
Developmental time
Measured as number of degree-days above threshold temp
Developmental time
Time it takes to reach a certain stage of development
Depends on temperature in certain organisms (many insects are examples)
Developmental time is _________ when temperature is HIGHER; ________ when temperature is COOLER
FASTER; SLOWER
Grasshopper eggs require _____ degree-days above a threshold temperature of ____ in order to develop
70; 16
At daily mean of _____, grasshopper eggs take _____ days to develop
23C; 10
70/(23-16) = 10 days
Degree-days equation
degree-days/(daily mean temp - threshold temp)
Mechanisms by which organisms gain or lose heat
Solar Radiation
Sensible Heat
Latent Heat
Metabolic Heat
Solar Radiation
Sun’s energy input
Sensible Heat
Convection
- Heat exchange between a gas or liquid circulating around a solid
- COOLING mechanism
- All water circulates around organism’s body, heated by body, rises, leaves body cooler behind
Conduction
-Heat exchange between two solids in contact with each other
Latent Heat
Heat exchange that occurs during a CHANGE OF PHASE
Evaporation
- Conversion of liquid to gas
- COOLING
Condensation
- Conversion of gas to liquid
- WARMING
Adaptations of PLANTS to HEAT
Decrease solar radiation
-Pubescence, waxy cuticle (reflects sun rays), curled or vertical orientation (less sun able to strike)
Increase sensible heat (CONVECTION)
-Compound leave to increase surface area-to-volume ratio for more air contact and heat exchange
Increase latent heat (EVAPORATION)
- Evaporation is TRANSPIRATION in plants
- Requires LARGE water supply, so plants have deep/wide-spreading roots or be able to store water (succulents)
Adaptations of PLANTS to COLD
Annual life history strategy:
-Seeds resistant to cold, so annual plants survive cold seasons by existing exclusively as seeds
Supercooling
-Production of excess sugars within cells, which increases their solute concentration and lowers their freezing point
“Types of animals” with respect to temperature
Ectotherms
Endotherms
Heterotherms
Animal Temperatures: Ectotherms
Regulate the amount of solar radiation they receive to maintain a fairly constant body temperature
-Examples include fishes, amphibians, reptiles, and most invertebrates
Ectotherms with HIGH SA-V ratio better able to exchange heat with surroundings (smaller)
- As body size increases, SA-V decreases
- -Large ectotherms UNCOMMON
- –Dinosaurs likely endotherms
Animal Temperatures: Endotherms
Regulate temperature METABOLICALLY (use metabolic heat)
-Maintain CONSTANT body temperature
VERY effective: Trade-off = High energy consumption
Examples: Birds and mammals
Tolerate temperature extremes:
- Insulation
- –Fur, feathers, fat (all reflect solar radiation)
- Shivering
- –Involuntary muscle activity to increase heat production
- Evaporative Cooling
- –Sweating, panting, breathing
Animal Temperatures: Heterotherms
ACTUALLY ENDOTHERMS
ENDOTHERMS that are able to relax control of metabolism during inactive periods, allowing body temp to drop near environmental temperature
Torpor: Metabolism relaxed daily
- –Bats during the day
- –Hummingbirds at night
Hibernation: Metabolism relaxed seasonally
- –NOT bears
- –Many rodents - squirrels, mice, hamsters
Importance of Light for Organisms
Light is the energy source for photosynthesis in ALL ecosystems
Light provides a cue that environmental conditions are changing
Light and Photosynthesis
Stages of Photosynthesis:
1) Light Reactions:
- -Light energy is used to oxidize water into oxygen, providing the electrons required to generate high-energy ATP and NADPH
2) Calvin Cycle:
- -ATP and NADPH energy is used to reduce carbon dioxide (GAIN e-) into glucose and other carbohydrates, which are high in chemical energy
PAR:
- -Photosynthetically Active Radiation
- -Solar radiation wavelengths that provide the energy for photosynthesis (specifically light reactions)
- –All visible light wavelengths EXCEPT green
- —-Plants appear green because that’s the energy being reflected, all others are absorbed
Light Response Curves:
–Graphs showing the relationship between light levels and photosynthetic rate
Compensation Point:
- -The minimum PAR required for positive net photosynthesis
- —The point at which CO2 uptake for photosynthesis is balanced by CO2 loss from cellular respiration
Saturation Point:
- -The maximum PAR that plants can use for increased rates of photosynthesis
- –When plants are saturated with sunlight
Photoinhibition:
- -Reduced photosynthesis rates at very high lights levels, due to damage caused by excessive solar radiation
- -Too much light is generally not a problem for most plants
SHADE-TOLERANT PLANTS
- -Those plants able to maintain positive net photosynthesis even in very low light conditions
- -Plants found in forest understories where most light is blocked by the canopy above
Adaptations of Shade-Tolerant Plants
1) General characteristic:
- -Low compensation point (exceptionally)
- -Low saturation point (handle shade well, not)
- -Susceptible to photoinhibition
2) Mechanisms of shade tolerance:
- -Allocation of more resources to the light reactions than to the Calvin Cycle
- -Allocation of more resources to the leaves than to the stems or roots
- -Thinner but wider leaves
Light as an Environmental Cue
Circadian Rhythms:
- -Daily pattern of activity that correspond to a 24 hour cycle of light and dark
- -Best demonstrated by diurnal and nocturnal oorganisms
- -The adaptive value of circadian rhythms can be physical or biological
Physical:
- -Insects are ectotherms, so they are diurnal to “soak up the sun”
- -Rabbits are nocturnal to avoid the heat of the day
Biological:
- -Plants are diurnal and open their flowers during the daw when their pollinating insects are active
- -Owls are nocturnal because their prey are active at night
Photoperiodism:
- -A response to changing daylengths throughout the year
- -Not seen in equatorial organisms
Changes in light levels are the most reliable cues of upcoming seasonal changes
Importance of Water for Organisms
Polarity of water ad the hydrogen bonds that forms between water molecules lead to water’s life-supporting properties:
1) Water molecules stick to each other (COHESION) and to other molecules (ADHESION)
- Necessary for the transport of water up plant stems
2) High specific heat capacity
- Helps organisms maintain fairly constant body temperatures
- Moderates the temperature o f the environments in which organisms live
- High boling point and low freezing point, so liquid at ambient Earth temperatures
3) Excellent solvent for dissolving solutes
- Common aqueous solutions include the cytosol of cells, the blood of animals, and the sap of plants (H2O + sugar)
- Water also trasnports solutes well because it flows easily (is not viscous)
- -Solution where water is solvents: AQUEOUS SOLUTION
Types of Plants with respect to water
Mesophytes
Xerophytes
Hydrophytes
Opening of stomata on leaves is necessary for photosynthesis, allowing ____ to enter plant
CO2
H2O is lost through open stomata, dduring the process of ___________
Transpiration
A plant’s _________ relates the amount of CO2 entering a plant to the amount of H2O lost
Water Use Efficiency (WUE)
_________ means much CO2 taken in with minimal H2O lost
High WUE
Major enzyme that brings CO2 into Calvin Cycle:
Rubisco
Rubisco:
a) is efficient
b) is NOT efficient
c) brings in O2 into Calvin Cycle
d) Brings in CO2 to Calvin Cycle
e) b, c, and d
f) All of the above
e) NOT efficient, brings O2 and CO2 into Calvin Cycle
Rubisco inefficiency yields NO photosynthetic output and wastes the CO2 present because the Calvin Cycle is “occupied” by O2: Consequence - WUE is ______-
LOWERED
Most plants are _____ plants and must deal with problem of PHOTORESPIRATION
C3:
-Undergo normal photosynthesis (Mesophytes and Hydrophytes)
Photorespiration:
-CO2 and O2 produced
Xerophytes
Evolved alternative photosynthetic pathways to increase WUE:
- C4 pathway
- CAM pathway
Examples of C4 plants
Corn and Sugarcane
In C4 plants, CO2 is first bound to a different enzyme, PEP carboxylase (PEPcase), which has ____________
NO affinity for O2
This bound CO2 is transported to the bundle sheath cells, the only cells in which the Calvin cycle occurs
CO2 is unloaded in the bundle sheath cells and becomes so concentrated that any O2 is ______________
“swamped out”
The C4 strategy
Increases WUE by efficiently utilizing all of the CO2 taken into the plant
Still loses some H2O
NONE of CO2 is wasted
Examples of CAM plants
Cactus and Pineapple
CAM plants open stomata at _______
Night
When there is LESS transpirational pull on H2O (not losing water to surroundings)