ecology quiz 2! Flashcards
6.1 what is photosynthesis?
process by which energy from the sun (shortwave radiation) drives a series of chemicals rxns that result in fixation of CO2 into carbs and the release of O2 as the byproduct
6.1 what is photosynthetically active radiation?
amount of light available for photosynthesis
6.1 what is the rxn for photosynthesis?
6CO2 + 6H2O –> C6H12O6 +6O2
6.1 what are the two metabolic rxns?
light dependent and light independent
6.1 light dependent rxn begins with…? and ends with?
- chlorophyll molecules within the chloroplast absorb light energy (chlorophyll is a light-absorbing pigment)
- absorption of photon of light raises energy level of chlorophyll molecules - excited molecule is not stable and electrons rapidly move to ground state, thus releasing absorbed proton energy
- energy is transferred to another acceptor molecule - resulting in photosynthetic electron transport, which then results in synthesis of ATP and NADPH
6.1 ATP & NADPH ARE ____ energy substance and ___ reductant essential for ______?
high, strong, light-independent
6.1 what happens in light-independent rxns?
- CO2 is incorporated into simple sugars
- the rxn does not require sunlight but is dependent on the product of light dependent rxn
6.1 steps of light-independent rxn?
- RuBP combines with CO2 to form two molecules of a three-carbon compound called PGA (3-PGA) (phosphoglycerate)
- plant converts the 3-PGA into energy rich sugar molecule = G3P
- some of the G3P is used to produce simple sugars while the other is used to synthesize new RuBP to continue process
6.1 Synthesis of G3P from 3-PGA requires what?
ATP & NADPH
6.1 availability of light energy can ____ light-independent rxn but why?
limit - because solar radiation is used to make the product of light-dependent rxn in which is used in light-independent rxn for the making of simply sugars and the synthesis of G3P and regeneration of RuBP
6.1 Photosynthetic pathway involving inital fixation of CO2 into 3-PGA is called?
calvin cycle / C3 cycle
6.1 what is the rxn called when co2 and RuBP combine to make 3-PGA?
carboxylation and is catalyzed by rubisco
6.1 what is the drawback of the C3 cycle?
rubisco can also act as an oxygenase - so as a catalyst, the oxygenation of RuBP results in the release of CO2, referred to as photorespiration - in all it reduces efficiency of C3 photosynthesis
6.1 where does cellular respiration happen and involves what?
mitochondria and involves oxidation of carbs to generate energy
6.1 rxn of cellular respiration?
C6H12O6 + 6O2 —> 6CO2 + 6H2O + ATP
6.1 leaves use both ____ during photosynthesis and produce ___ during respiration - difference is what?
CO2, O2, rates of net gain in carbon
6.1 what is net photosynthesis?
difference between rate of carbon intake in photosynthesis and carbon loss in respiration
6.1 process of photosynthesis occurs in _____ within ______ ?
chloroplast within mesophyll cells
6.2 availability of light to the leaf = ?
influences rate of photosynthesis
6.2 what happens at night in abscence of PAR? and then what?
only respiration occurs and net uptake of CO2 is negative
but as sun rise, value of PAR increases, meaning rate of photosynthesis increases and eventually reaches level where rate of CO2 uptake in photosynthesis = rate of CO2 loss in respiration
AT THIS POINT, RATE OF NET PHOTOSYNTHESIS = 0
6.2 What is light compensation point?
level of light where photosynthesis and respiration balance each other
6.2 as light levels ___ LCP, rate of net photosynthesis increases with PAR and eventually photosynthesis _________
exceed, becomes light saturated
6.2 what is the light saturation point?
amount of light at which plants achieve maximum rate of photosynthesis ; no further increase in photosynthesis occurs
6.2 plants that are adapted to shady environments, photosynthetic rates ____ as light levels exceed saturation
decline
6.2 negative effect of high light levels is called?
photoinhibition and it can result in “overloading” processes in light-dependent rxns
6.3 process of photosynthesis occurs in cells within the leaf called?
mesophyll cells and they are the specialized tissue between epidermal layers of leaf
6.3 CO2 must move from ____ into the leaf
outside atmosphere
6.3 in land plants, CO2 enters leaf through its ____ by ____.
stomata - pores on leaf
diffusion
6.3 what is diffusion
movement of substance from high to low concentration
6.3 what happens when concentration is equal?
equilibrium is reached and no more net exchange occurs
6.3 what two factors control diffusion of CO2 into leaf?
stomatal conductance and diffusion gradient
6.3 what is diffusion gradient
difference between concentration of CO2 in air adjacent to leaf and concentration of CO2 in leaf interior
6.3 what is stomatal conductance? and what are its 2 components?
flow rate of CO2 through stomata
1. stomatal density
2. size of stomatal opening (arpeture)
6.3 stomatal aperture is under _____, stomata open and close in response to _____
plant control, environment and biochemical factors
6.3 As long as concentration of CO2 in air outside leaf is ____ than that inside of leaf and stomata are open —>
greater, CO2 will continue to diffuse through the stomata into the leaf
6.3 why do concentration of CO2 inside and outside leaf not come to equilibrium?
concentration inside leaf declines as CO2 is transformed into sugars during photosynthesis - as long as photosynthesis occurs, gradient remains
6.3 what would happen if photosynthesis stopped?
if it stopped and stomata stayed open as well, CO2 would diffuse into leaf until internal CO2 = outside concentration
6.3 when photosynthesis and demand for CO2 are reduced, stomata….
closes which reduces flow into leaf
6.3 as CO2 diffuses in stomata, water vapor inside leaf _____ through same opening
diffuses
6.3 what is transpiration
water loss through stomata - loss of water vapor from plant to outside atmosphere
6.3 water vapor diffuses from?
high to low concentrations
6.3 Lower relative humidity of air means what to the diffusion gradient?
it will be larger and more rapidly the water inside the leaf will diffuse through stomata into surrounding air
6.3 does the leaf have to replace water lost to atmosphere?
yes otherwise it’ll wilt and die
6.4 what is turgor pressure?
forced exerted outward on a cell wall by water contained in the cell (osmosis)
6.4 growth rate of cells & efficiency of physiological processes are high____? but when water content declines ____
highest when their cells are at maximum turgor pressure
when it declines, turgor pressure drops and water stress occurs
6.4 what to do to maintain maximum turgor pressure?
water lost to atmosphere in transpiration must be replaced by water taken up from soil
6.4 what is water potential?
a measurement used to describe gibbs energy of water at any point along soil-plant-atmosphere continuum
6.4 water potential goes from?
areas of high water potential to low
6.4 when relative humidity of atmosphere is 100%, what is at 0atm?
atmospheric water potential
6.4 what happens as relative humidity of atmosphere drops?
atmospheric water potential becomes negative
6.4 as long as relative humidity of air is below 99%, gradient of water potential between lead and atmosphere will ____?
drive process of diffusion
6.4 water vapor moves from?
high water potential (interior of leaf) to low water potential (atmosphere) ; state of high to low gibbs energy
6.4 water being lost to atmosphere through stomata =?
water content of cell decreases - which increases concentration of solutes in cell
6.4 decrease of cell water content =?
decrease in water potential of cells
6.4 what factors determine water potential in plant?
- turgor pressure
- increasing solute concentration
- surfaces of larger molecules
6.4 how does turgor pressure affect cell water potential?
it increases water potential - represents hydrostatic pressure
6.4 how does increasing concentration of solutes affect wate potential?
lowers water potential - more concentrated a solution = lower osmotic potential
6.4 what is osmotic potential?
attraction of water across membrane
6.4 how does surfaces of larger molecules affect water potential?
it exerts attractive forces of water - tendency of water to adhere to surfaces reduces gibbs energy of water molecules which reduces water potential
6.4 what is matric potential?
tendency of water to adhere to surfaces
6.4 total water potential is the sum of?
osmotic, matric, and hydrostatic pressure
6.4 is sum of water potential positive or negative?
can be both but typically negative and movement of water proceed from high to low potential so movement of water from soil to root, root to leaf, leaf to atmosphere depends on maintaining a gradient of increasingly negative water potential.
6.4 how does the gradient of water potential increase
negatively increases
atm < leaf < root
6.4 water loss through transpiration continues as long as?
- amount of energy striking leaf in enough to supply necessary latent heat of evaporation
- moisture is available for roots and soil
- roots are capable of maintaining a more negative water potential than soil
6.4 if gradient cannot be maintained, the stomata does what?
closes to prevent further water loss through transpiration - closure results in stooping uptake of CO2
6.4 to carry out photosynthesis, stomato must ___ but when it does it _____ water which it does have to replace
be open, lose water
6.4 what happens if water is scarce?
plant must balance the opening/ closing of stomata - so that it takes up enough CO2 while minimizing water loss
6.4 what is water-use efficiency?
ratio of carbon fixed (photosynthesis) per unit of water lost (transpiration)
6.5 process of carbon uptakes differs how in terrestrial and aquatic autotrophs?
aquatic lacks stomata
6.5 CO2 diffused from ____ into surface water and is mixxed through water column, what happen once it dissovled?
atmosphere
CO2 reacts with water to form bicarbonate
6.5 some aquatic species use ___ as a carbon source, but they must first convert it to CO2 using the enzyme ___
bicarbonate
carbonic anhydrase
6.5 what two ways does aquatic organisms convert bicarbonate into co2
- active transport of bicarbonate into cell followed by conversion of co2
- exertion of enzyme into adjacent water and subsequent uptake of converted co2 across membrane.
6.5 why as CO2 is taken up, its concentration in water adjacent to organism declines?
diffusion of co2 in water is slower than air - can easily become depleted in water - reducing rate of uptake/photosynthesis
6.9 demand for water is linked with?
temperature
6.9 as air temp rise…?
saturation pressure rises
which increases gradient of water vapor between inside life and outside air and rate of transpiration,
and as a result - amount of water required by plant to offset losses from transpiration will increase with temp
6.9 what do plants exhibit in response to changes in water availability?
acclimation and developmental plasticity
6.9 what do plants do when atmosphere is dry?
they partially close and open stomata for shorter time periods
6.9 plants close their stomata during hottest part of day when ____
relative humidity is low
6.9 closing stomato reduces ____ through transpiration but also reduces ____ diffusion into leaf and dissipation of heat through evaporative cooling.
loss of water
CO2 diffusion
6.9 leaf curling/wilting allows leaves to what?
reduce water loss and heat by reducing surface area exposed to solar radiation
6.9 what an example of developmental plasticity?
plants respond to low soil water availability by increasing allocation of carbon to the production of roots while decreasing production of leaves
6.9 what happens when plants increase production of roots?
they can explore a larger volume and depth of soil for extracting water
6.9 reduction in leaf area =?
decreases amount of solar radiation the plant intercepts and surface area that is losing water through transpiration
6.9 what does mesic mean?
wet environment
6.9 describe C4 plants
they have modified photosynthesis which increases water-use efficiency in warmer/drier environments
6.9 what is the C4 photosyntehtic pathway?
it involves mesophyll cell and bundle sheath cells
CO2 initially reacts with PEP to form 4-carbon compounds in mesophyll cells
compounds are then transported into bundle-sheath cells where they are converted into CO2 and undergo C3 photosynthesis pathway
6.9 Rxn between CO2 and PEP is catalyzed by? and produces what
PEP carboxylase
produces OAA but then OAA is turned into 4-carbon molecules of acid which are then transported to bundle sheath cells - enzymes there break down acids to form CO2
6.9 how does extra step in fixation of CO2 give C4 plants advantage?
pep does not react with oxygen
2. conversion of acids to co2; co2 in bundle sheath reaches higher concentration than in mesophyll
(higher con. = increase effiecny of rxn of CO2 and RuBP)
6.9 what is the adaptive advantage of C4 pathway?
the plants exihibit a greater water-use efficiency - advantage for those in hot/dry climate where water is a factor for limiting plant growth
they fix more carbon in photosynthesis
6.9 C4 has a higher _____
energy expenditure bc of need to produce PEP and the PEP carbolyase
6.9 what is the CAM pathway?
separated process of CO2 uptake and fixation when growing under arid conditions - takes up CO2 at night when stomata is open and converts it to simple sugars during the way when stomata is closed.
6.9 describe how plants adapt to dif soil moisture environments
- in xeric conditions, they habe lower stomatal conductance (lower number/size of stomata) - which results in lower rate of transpiration and functions to decrease rate of photosynthesis
6.9 reduction of stomatal conductance function to increase…?
water-use efficiency
6.9 what is xeric?
dry environment
6.9 plant species adapted to drier conditions have greater ____ of carbon to the production of roots relative to leaves.
what does it allow plant to explore?
allocation
larger volume/depth of soil for extracting water
6.9 decline in leaf area in xeric conditions is a combined effect of what?
reduced allocation of carbon to production of leaves and changes in leaf morphology - low SLA
6.9 Some leaves have hair that scatter ____ and others have wax coats/resins that ____ and reduce its ____
solar radiation
reduce light
absorption
6.9 what do features of leaves function to do?e
- reduce amount of energy striking lead which enhances dissipation of heat through convection, thus reducing loss of water through transpiration
6.9 reduced leaf area ___ carbon gain from photosynthesis, resulting in….?
decreases
reduction of plant growth
7.8 what is a poikilotherm?
organism whose body temp varies according to temperature of its surroundings
7.8 what is a homeotherm?
animal with fairly constant body temp
7.8 most organisms body temp is regulated through…?
behavior, physiology, and morphology
7.8 what does regulation truly imply?
maintaining avg body temp or variation in body temp with certain bounds - requires mechanisms for organism to sense and respond to its thermal environment
7.8 what are the two categories of thermal regulation that emphasize source of thermal energy used to influence body temp?
ectothermy & endothermy
7.8 what is ectothermy?
process of maintaining body temp through exchange of thermal energy with surrounding environment
7.8 what species use ectothermy?
called ectotherms
poikilotherms use this
7.8 what is endothermy?
process of maintaining body temp through internally generated metabolic heat
7.8 what species use endothermy?
endotherms
homeotherms use this
7.8 endotherms have the ability to raise their ____ in excess of their immediate needs, using resulting metabolic heat to maintain body temp
metabolic activity
7.9 each species have minimum and maximum what?
temperatures
7.9 poikilotherms have ___ metabolic rate and high ability to exchange heat between body and environment, what do they carry out?
low, aerobic respiration
7.9 what do poikilotherms do under stress
their inability to supply sufficient oxygen to the body requires that energy to come from anaerobic respiration, which limits them to short burst of activity and rapid physical exhaustion
7.9 poikilotherms are able to undergo temperature acclimation. which allows what?
allows relationship between body temp and performance to shift, involves shift in enzyme system
7.9 animals in water reach ___ with their surrounding temp faster than terrestrial animals
equilibriumm
7.9 since seasonal water temps are relatively stable, fish/aquatic invertabrates….
maintain constant temp any given reason - they adjust by acclimation or physiologically adjust to a change in environment conditions
7.9 water temps changes ____ so poikilotherms may adjust ___
slowly,slowly
7.9 what is the process of thermal acclimation?
involves change in upper/lower tolerance of temperature
7.9 to main body temp, amphibious poikilotherms rely on…
behavioral thermoregulation (basking in sun)
7.9 what is operative environmental temperature?
body temp that occurs when the snake occupies each of these environments
7.10 homeotherms meet thermal constraints by
being endothermic
7.10 how is homeotherms body temp maintained?
through oxidation of glucose and other rich molecules in respiration process
7.10 organisms basal metabolic rate is measured by?
rate of oxygen consumption
7.10 rate of respiration for homeotherms in proportional to?
their body mass
7.10 what is the thermonuetral zone?
range of environmental temperatures within which the metabolic rates are minimal
* outside this zone, metabolic rate increases
7.10 how do homeotherms maintain high level of energy production?
through aerobic respiration - they can sustain high levels of activity for long periods
7.10 ______ of external temp, homeotherms can exploit wider range of thermal environments
independent
7.10 what do homeotherms use to regulate exhcange of heat between body and environment?
insulation, shivering, evaporative cooling
7.10 insulation can keep heat in but can also?
keep heat out
7.10 thickness of mammals fur changes with season =?
but small mammals are limited because?
acclimation
thick coat would reduce ability to move
7.10 in hot environment, animal either rids itself of excess body heat or prevents heat from being absorbed, how?
- reflect solar radiation from light-colored fur
- grow heavy coat of fur that heat doesn’t penetrate
7.10 what happens when insulation fails?
shivering occurs - form of involuntary muscle activity that increase heat production
7.10 evaportive cooling is employed to reduce body heat, how?
when body heat is above upper critical temp, evaporative cooling is accelerated by sweating & panting
7.11 endothermy allows ____ to remain active regardless of what? and what does it cost?
homeotherms
variation in environmental temperatures
cost energy bc maintenance of internal body temp requires high metabolic rate and heat loss to surrounding environment must be continuously replaced (metabolic cost weigh heavy)
7.11 environmental temps dictate activity of ____
poikilotherms (ectothermy)
7.11 poikilotherms dont need to burn carloies to provide metabolic heat so they….?
allocate more of their energy intake to biomass production than metabolic needs
7.11 because ectotherms do not depend on internal generated body heat…
they can curtail metabolic activity in times of food/water shortage and extreme temps
7.11 important feature influencing ability to regulate body temp is…
animal size
7.11 poikilotherms absorb heat across their body surface BUT they also must?
absorb enough energy to heat its entire body mass
7.11 as organisms size ___, SA:V ratio ___
increases
decreases
7.11 ectothermy impose constraint on maximum body size for ____ and restricts ____ of larger poikilotherms to _____
poikilotherm
distribution
warm regions
7.11 what constraint does size impose of homeotherms?
- so there body mass produces heat through respiration while heat is lost to surround environment across body surface
- small organism = larger SA:V ratio = greater relative heat loss to surround environment
SO to maintain constant body temp, heat loss must be offset by increase metabolic activity
- small organism = larger SA:V ratio = greater relative heat loss to surround environment
- small homeotherms have higher mass-specific metabolic rate and consumer more food than larger ones, so their mass-specific metabolic rate rises so rapidly that they do not meet their energy demands
7.11 define altricial state?
when they are born blind, naked, and helpless and start life as ectotherms
