Unit 2 - C4 CAM, Pop Growth Flashcards
In what part of photosynthesis is water used?
in the light reactions - photosystem II
What does water break apart into when it is oxidized by chlorophyll?
1/2O2, 2H+, 2e-
Where do the products from water splitting go?
1/2O2: escapes as O2 through the stomata
2H+: stay in the lumen until they travel through ATP synthase
2e-: 1 electron is taken up by chlorophyll+
Can the Calvin cycle run at night?
no because the products of the light reactions ATP and NADPH are used to power the Calvin cycle & the Calvin cycle needs a constant supply of these products
____% of the plants on Earth undergo “normal photosynthesis”
90
What is the tradeoff that comes with normal photosynthesis?
fast growth = water loss
-bigger leaves, grow fast (high RGR)
-smaller leaves, grows slower (high WUE)
What is another name for normal photosynthesis? Why?
C3 photosynthesis; CO2 is fixed into a 3 C sugar initially
What are 2 major problems of photosynthesis?
(1) in order to get CO2 for photosynthesis, plants need gas exchange (open stomata –> transpiration)
(2) Rubisco (enzyme that fixes/reduces CO2) can also fix/reduce O2
When Rubisco fix/reduces O2 instead of CO2, what happens instead of the Calvin cycle?
photorespiration
What are 2 reasons why photorespiration is bad?
(1) wastes/consumes ATP
(2) instead of producing sugar, CO2 is released
Under what conditions does Rubisco bind to O2 instead of CO2 & therefore undergo a lot of photorespiration?
(1) when it is hot
(2) when there’s not a lot of CO2 available
When is intercellular CO2 low?
when stomata are closed - when its dry & water is scarce; cells are flaccid and seal up the stomata
What specific environmental conditions facilitate photorespiration?
hot, dry conditions
What are long term solutions to photorespiration?
plants have evolved forms of photosynthesis that avoid the Rubisco-O2 problem–C4 and CAM photosynthesis
What do C4 and CAM do in particular to avoid the Rubisco-O2 problem?
instead of converting CO2 into a 3C sugar (PGA), they first fix CO2 into a 4C sugar called MALATE
How does C4 photosynthesis separate C-fixation from the Calvin cycle?
spatially
In C4 photosynthesis, Rubisco _____ comes into contact with _____ (no photosrespiration).
NEVER; O2
In C4 photosynthesis, what happens in the mesophyll cell?
light reactions & CO2 is fixed into 4C malate
In C4 photosynthesis, what happens in the bundle sheath cell?
Calvin cycle
What type of cells are cut off from all gas exchange happening at the surface of the leaf and are therefore responsible for Rubisco never coming into contact with O2?
bundle sheath cells
What happens in C4 photosynthesis once malate is moved from the mesophyll cell to the bundle sheath cell?
malate is then converted back into CO2 to be used as normal in the Calvin cycle
Does C4 photosynthesis limit water loss?
not really
Under what conditions is C4 photosynthesis ideal?
when its hot, but there is enough water around
Under what conditions is CAM photosynthesis ideal?
when its hot and dry
How do CAM plants limit water loss?
they only open their stomata at NIGHT
_____ plants:
-aloe, pineapples, orchid, cacti
CAM
Why do CAM plants open their stomata only at night?
to limit water loss; they only open when its wetter and cooler than normal
Where does CAM photosynthesis take place?
ALL in the mesophyll cells
What do CAM plants do with malate?
take in CO2 at night & convert it to malate & store it in the vacuole until the sun comes up
Where do CAM plants store malate?
in the vacuole
During the day, what happens to the malate stored in the vacuole of CAM plants?
its converted back into CO2 for use in the Calvin cycle
In CAM photosynthesis, does Rubisco always have access to adequate CO2 (even if stomata are closed)?
yes
Does Rubisco come into contact with O2 at all during CAM photosynthesis?
yes
How does CAM photosynthesis divide C-fixation and the Calvin cycle?
temporally
Is CAM photosynthesis efficient?
not very efficient, slow growth of plants & lots of energy spent
What requires more energy C4, CAM, or C3/normal photosynthesis?
C4 & CAM are more energy intensive than C3 photosynthesis
How is temperature related to the prevalence of C4 species?
directly/increasing
How do you expect the prevalence of C4 plants to change in the future given climate change?
increased survivorship; rainfall is variable but places with more rain will benefit C4 species
Are there more C4 or CAM photosynthesis plants?
C4
What organisms are classic r-selected in the Sonoran Desert?
scorpion, big-headed ants
What organisms are classic k-selected in the Sonoran Desert?
cougar, pronghorn
Parental investment of K-selected organisms?
lots / high
Offspring # of k-selected organisms?
few
Time to maturity for k-selected organisms?
long
Lifespan of k-selected organisms?
long
Size of k-selected organisms?
large
Energy cost of k-selected organisms?
high / energetically intense offspring
K-selected organisms are often viewed as few “_______” offspring.
expensive
Parental investment of r-selected organisms?
little
Time to maturity of r-selected organisms?
short / early maturity
Life expectancy of r-selected organisms?
short
Size of r-selected organisms?
small
Energy cost per r-selected offpsring?
low
R-selected organisms are often viewed as many “_____” offspring.
cheap
___-selected species have high survivorship.
K
What is the best example of an organism that has r and k-selected traits?
turtle
How does a turtle have r and k selected traits?
-no parental care of babies (r)
-large offspring pools (r)
-large organisms (k)
-live a long time (k)
Describe a type _____ survivorship curve.
-very high survivorship to old age
-babies live almost until their maximum life expectancy and then there is rapid decline
type I
Describe a type _____ survivorship curve.
-organisms that do not experience age related mortality
-straight, negatively sloped line
type II
Describe a type _____ survivorship curve.
-sharp decline right at the beginning
-lots of juvenile mortality, BUT if you can make it past a certain age you will usually achieve maximum lifespan
type III
What survivorship curve best fits k-selected species?
type I
What are examples of organisms that follow a type I survivorship curve? What do they all have in common?
humans, otters, bears, elephants, whales; they are all k-selected organisms
What survivorship curve fits neither r nor k selected species?
type II
What are examples of organisms that follow a type II curve?
songbirds, sparrows
What are examples of organisms that follow a type III curve? What do they all have in common?
oysters, insects, amphibians; they are all r-selected organisms
What survivorship curve best fits r-selected species?
type III
survivorship curve of big horned sheep:
-starts off as type III with rapid mortality of young sheep but after the age of 1 year old, most sheep survive until their maximum life expectancy and the curve follows a type I pattern
WHY IS THIS? POSSIBLE EXPLANATIONS?
-when sheep are young (w/out horns) they are really easy prey BUT after they reach a certain size they are able to defend themselves (grown with horns)
Do all populations grow at the same rate?
no
What can be an important factor in the potential rate of increase initially?
the # of offspring an organism has (the lower # the slower start; higher numbers lead to more rapid population growth)
________: dN/dt - the # of individual added (or lost) to a population in a given time period (year)
population growth rate
What does dN/dt stand for with regards to population growth rate?
change in population / change in time (final N - initial N / final t - initial t)
_____: r - the average # of offspring an INDIVIDUAL has over a given time period
per capita growth rate
How is per capita growth rate different from population growth rate?
population growth: # of individuals added overall
per capita growth: # of offspring added PER individual
What is the term for “how many offspring an individual has per year”?
per capita growth rate
How does dN/dt relate to r?
dN/dt = r No (intial population)
What is the term for “change in population per time”?
population growth
What is the equation for per capita growth rate?
r = population growth rate / No (initial population size)
Population growth models
______ growth:
-no limitations on resources
-not sustainable/realistic
-J shaped curve
exponential
How does population growth rate change over time with an exponential growth curve?
constantly increases
How does per capita growth rate change over time with an exponential growth curve?
it does NOT change; stays constant
Population growth models
_____ growth:
-limited resources limit population growth over time
-S-shaped curve
logistic growth
How are you able to tell population growth rate given a graph?
by the slope of the line
What does a steeper slope suggest about the population growth rate?
a faster pop GR
What are two ways to interpret a per capita value of 0.1?
(1) 1 in 10 organisms in a population has an offspring every year
(2) Each individual will have an offspring every 10 years
What type of growth curve eventually approaches a carrying capacity K?
logistic growth curve
_______: the maximum size of a population that an ecosystem can sustain
carrying capacity (K)
How does population growth rate change over time with a logistic growth curve?
varies greatly, depends on slope of line
-starts off slow, speeds up, slows down again
What would the shape of a graph of population growth rate vs time look like? What does this suggest?
upside down U
-start off with a slow growth rate
-in the middle, fastest growth rate
-end with a slow growth rate
When is population growth rate the highest for a logistic curve?
at the inflection point
What equation gives the size of the population where growth rate is the highest?
K / 2 –> inflection point
What does a negative per capita growth rate suggest?
more individuals are dying than are being born (death rate > birth rate)
How does per capita growth rate change over time with a logistic growth curve?
varies greatly (can be positive or negative; depending on birth and death rates
Do the increases in predator & prey populations line up perfectly?
no, there is a lagging effect
______ feedbacks:
-promote changes that lead back toward equilibrium
-overshoot, undershoot, overshoot
negative
What is a classic example of a negative feedback loop?
predator/prey dynamics
Is prey food availability an important factor in determining a predator-prey cycle?
yes
How would you best describe the climate of the Sonoran Desert?
hot & dry
Is precipitation variable in the Sonoran desert?
yes; inter annual variation (VERY unpredictable)
In what season does the Sonoran Desert get most of its rain?
winter
When is the growing season for plants in the Sonoran Desert and why?
winter because its wetter & cooler
What is the general trend in temperature over the years in the SD?
gradually increasing
What is the general trend in precipitation over the years in the SD?
decreasing (BUT a lot of variability of how much water in different places)
Why is being close to a water source important in terms of temperature?
water moderates humidity
When the Sonoran desert DOES get rain, what are the events like?
more INTENSE
Do hotter temperatures benefit high RGR or high WUE species?
not really
Which species (High RGR or WUE) will be less negatively impacted if overall there is less water around?
high WUE
Which species (high RGR or WUE) will be less negatively impacted by large, infrequent rain events?
high RGR
What is the process by which a species becomes BETTER SUITED to its environment & is the result of natural selection acting upon heritable variation over several generations?
adaptation
What are some ways in which organisms are adapted to their environment?
in their structure, physiology & genetics, in their locomotion and dispersal, in their means of defense and attack, in their reproduction and development
What are 3 adaptations that plants have used for low Nitrogen levels? *think Pumice Plain
(1) N-fixing plants - evolutionary evolved relationship; mutualistic interaction; involves bacteria
(2) parasitic plants - suck out nutrition from another plant; ex: invasive roots that go into another plant
(3) carnivory - plants eat insects; trap & digest them for protein
What is the main adaptation of welwischia?
dormancy - goes dormant for a long time waiting for it to rain & then comes back to life
