Lecture 3 + 4 Flashcards
____ is used by plants to time dormancy and flowering
Photoperiod
A ____ is an organism that relies on external sources of heat to determine the pace of their metabolism
Ectotherm
Species of bacteria and archaea that can live at temperatures of 100 degrees Celsius are known as ________?
Thermophiles
Temperature, humidity, amount of precipitation, and water pH are examples of __________.
Physiochemical features of the environment known as conditions
Organisms will consume _______ during the course of their growth and reproduction
Environmental resources
Resources
Nutrients, water, co2 are consumed by organisms while conditions are not (temperature, salinity, toxic substances)
Conditions
Physical-chemical aspects of the environment that influence organisms
- set the context for life and constrain its existence
- generally, not consumed by the organisms, BUT organisms often influence conditions in their immediate environment
ex. temperature, pH, salinity
Body temperature of warm blooded animals
Around 30-45ºC; work to keep their temperatures relatively high (but not too high), which offers many advantages. BUT it also has a high cost in terms of their need for energy (food)
Rates of biological processes tend to…
Increase with increasing temperature…up to a point
General trend for purely chemical reactions
higher temp, higher reaction rate (exponential)
General trend for enzyme catalyzed reactions
reaction rate increases with temp until max, then drops
Three responses of a population to a condition
- reproduction (highest point + performance, organism can survive, grow, and reproduce)
- individual growth (medium)
- individual survival (lowest)
In general, are warmer temperatures more favourable for life? And would we therefore expect to see more species in warmer environments?
- there is a general trend of greater number of species per area in tropics, fewer in temperate zone, and less in polar regions for terrestrial ecosystems and for lakes
- also for surface ocean waters. BUT deep oceans have incredible diversity and temperature is only 4ºC
Which of the following best describes the relationship of temperature and diversity across the Earth?
A) the cold temperatures at depth in the ocean slow down predators, allowing for longer life spans of most organisms and therefore an explosion of diversity through evolution.
B) temperature per se may not be the important factor, but rather disturbance over geological time scale, which is inversely correlated with temperature most places but not in the deep ocean.
C) temperature is only one factor affecting diversity; low resources also favour high diversity, and resources are low in the deep ocean.
D) temperature is only one factor affecting diversity; high resources also favour high diversity, and resources are high in the deep ocean.
B) temperature per se may not be the important factor, but rather disturbance over geological time scale, which is inversely correlated with temperature most places but not in the deep ocean.
C) temperature is only one factor affecting diversity; low resources also favour high diversity, and resources are low in the deep ocean.
Adaptation to the condition, as with any adaptation, can be…
Morphological, physiological, or behavioural
Morphological adaptations
-> are closely associated with physical aspects of an organism
Arctic and alpine plants: rough surfaces to minimize heat loss through convection (larger boundary layer of low wind)
Rocky mountain goat (and arctic species) have thicker fur in the winter, providing more insulation
Needles are better than broader leaves at handling the snow and ice that occur in cold climates
Physiological adaptation
-> are associated with processes and functioning with an organism
Antarctic springtails (an insect) tough out the Antarctic winter by undergoing a physiological change to minimize damage of freezing (high glycerol content in winter, low in summer)
Hibernation
Behavioural adaptation
Migration of snow geese
Hibernation
Burrowing depth
Important to ground squirrels, if they are too close to the surface, temperatures can fall below freezing, which is fatal
True of other animals, such as fiddler crabs that over-winter at depth in burrows in salt marshes
Temperature can affect competition
- certain species can outcompete others and drive them to extinction
- potential bell curve distribution
-> actual distribution if outcompeted at higher temperatures (shaded in on cold/left side area)
Temperature can affect infection with parasites
Ex. Fungi on grasshoppers, so temperature influences outbreaks of this agricultural pest
Will climate change increase the problem from the grasshopper outbreaks, as temperatures in more areas become too warm to control the fungi? Or are there counteracting forces?
We really don’t know. Warmer temps could result in many more situations where it is too hot for the fungi, resulting in more grasshopper outbreaks. Farmers could response by using more pesticides, grasshoppers evolve to resist the pesticides, resulting in large grasshopper outbreaks plus collateral damage to other organisms from the increased use of pesticides
Temperature is not the only ecologically important environmental condition
Intensity of condition
Concentration of arsenic (graph: level until drop in performance to zero, like a rollercoaster)
Increasing salinity (graph: zero to sharp increase, level, then rollercoaster drop in species performance)
Freshwater fish are
More salty than their environment
-freshwater teleosts gain water across their gills
-excrete excess water in their urine
-replace some lost solutes with salts from their food
- solutes are lost passively across the gills but are also taken up actively against a concentration gradient
- expend energy to filter solutes to minimize losses from their urine
Salt-water fish are
Less salty than environment
- marine teleosts lose water across their gills and in their urine
- which they must replace by drinking seawater
- take up solutes by drinking seawater
- must expend energy to excrete excess solutes across their gills and in their urine
American eel
Breeds and lives juvenile life in Sargasso Sea (35 ppt salinity). Adults spend most of their lives in freshwaters
Atlantic salmon
Breeds and lives juvenile life in freshwaters. Adults spend most of their lives in 35 ppt ocean water.
What about invertebrates that dominate animal life in the oceans (such as molluscs, cnidaria, crustacea, etc.)?
Most have body fluids with salt levels identical to the water around them
What about molluscs, cnidarian, and crustacean in freshwater?
Salt levels just slightly greater than in surrounding water. Maintaining seawater salt levels is too difficult.
The salt levels slightly higher than freshwater appear necessary to support metabolic functions, and is a manageable expense.
Saltmarsh cord grass, spartina alterniflora
Great competitor at high salinity, but it “prefers” freshwater. However, they are not found in freshwater/low salinity because they are outcompeted by freshwater marsh grasses.
Conditions are physiochemical features of the environment, such as
Temperature
Humidity
Salinity
Adaptation: spend less time out foraging during warm parts of the day
Behavioural adaptation
Adaptation: grow longer fur
Morphological adaptation
Decrease in metabolic rate
Physiological adaptation
Organisms whose major resources are photosynthetic radiation, water, nutrients, and carbon dioxide are known as ________.
Autotrophs – organisms that can produce its own food using light, water, CO2, and other chemicals
Heterotrophs
Organisms that eats other plants or animals for energy and nutrients
Which is NOT a type of heterotroph?
Fungi
A flea
Human that feeds on plant material
Bacteria that feed on hydrogen sulfide
Bacteria that feed on hydrogen sulfide
Which type of organism feeds on already dead material?
Decomposer
True or false: Plants face a trade-off between photosynthesis and water loss
True – open up stomata, facilitate gas exchange and transpiration
Why do all organisms need energy?
The second law of thermodynamics: increase in entropy (decrease in order) over time in the universe, and in any closed system
- but only if there are no external inputs of energy to the system
- organisms are highly ordered systems, maintaining that order through continual inputs of energy
For plants, algae, and photosynthetic bacteria, where does their energy come from and how is it stored?
Originates from sunlight and is stored as organic carbon molecules
For heterotrophs (animals, fungi, and most bacteria and archaea), where does their energy come from and how is it stored?
Originate from photosynthesis and the energy is the organic carbon molecules
Basic photosynthesis equation
CO2 + H20 -(+light)-> organic carbon + O2
True or false: Photosynthesis always generates O2 and fixes CO2 into organic matter
False because photosynthesis evolved in cyanobacteria using H2S rather than H20 as electron donor
CO2 + H2S -(+light)-> organic matter + oxidized S
Still carried out by photosynthetic sulfur bacteria and by cyanobacteria
Atmospheric O2 and Earth History
3-4B years ago: photosynthetic cyanobacteria evolve
0.5-2.5B: O2 consumed by terrestrial weathering
Cyanobacteria
aka blue-green algae
- not algae
- photosynthetic bacteria
Photosynthesis in eukaryotic organisms (i.e., those with cells that have organelles)
Evolved by “engulfing” cyanobacteria in algae first (plants evolved later)
Chloroplasts
Where photosynthesis occurs in the cells of algae and plants
- can be thought of as symbiotic cyanobacteria
First step in photosynthesis
Light Reaction
2H20 + 2NADP + 2ADP + 2P -(chlorophyll, light)-> 2NADPH + 2ATP + O2
2NADPH + 2ATP are stored chemical energy
- uses light energy to split H2O
- produces chemical energy (ATP, NADPH)
Dark Reactions (carbon fixation, light independent)
In the first dark reaction, stored chemical energy of NADPH and ADP converted to an organic molecule with 5 carbons, ribulose-1, 5-biphosphate (RuBP)
Then, the enzyme Rubisco (RuBP carboxylase-oxygenase) catalyzes the reaction of RuBP and CO2 to form sugars with 3 carbons
Dark reaction formula
CO2 + RuBP -(Rubisco)-> 2(C-3 sugar)
1C + 5C -> 2*C-3
Rubisco is just one protein. It makes up how much of the
total protein and nitrogen in the world’s algae and plant
leaves?
25% – chlorophyll also makes up a lot
Where is photosynthesis greatest on land and ocean?
On land, greatest in tropics
In ocean, low in tropics, greater at higher latitudes
Resources for photosynthesis
light
water
carbon dioxide
nutrients (principally nitrogen and phosphorous)
Phytoplankton of the oceans (algae and cyanobacteria)
- plenty of water
- plenty of co2
- availability of sunlight and nutrients is critical
Photosynthesis increases with…
Increasing light up to a point before light saturation
- different populations of algae (and plants) have different response curves to light, and are adapted to the light they tend to experience
Phytoplankton (algae, cyanobacteria) of the oceans need CO2 and nutrients (nitrogen and phosphorus)
- usually plenty of CO2, but nutrient concentrations are very low in large areas of the ocean (high in other parts)
- nutrients (and CO2) taken up across the cell surface
- some are big (100s of microns), others are small (1 micron)
Considering the need to take up nutrients, what are the advantages and disadvantages of being big or small?
Volume of sphere = (4/3)pir^3
Surface area = 4pir^2
When you double the radius, volume increases 8-fold but area increases only 4-fold. SA to volume ratio decreases by 2-fold (just as with a cube)
Tripling the radius decreases surface: volume ratio by 3-fold, etc.
Absorbing nutrients; SA and volume
Nutrients are taken up by enzymes attached to the surface of the cell
Rubisco and chlorophyll are distributed throughout the volume of the cell
Does an environment with very low nutrients favour bigger or smaller cells?
Small cells dominated because they have larger SA of the cell (for enzymes that take up N & P) compared to the volume of the cell that holds chlorophyll and Rubisco (for photosynthesis)
More abundant nutrients lead to larger cells, with proportionately more chlorophyll and Rubisco compared to surface enzymes for N & P uptake
For phytoplankton, a large portion of the cell is…
Composed of chlorophyll and Rubisco (with set chemistry that is relatively rich in organic N compared to organic C)
Little need for supporting structure (which for lands plants, is rich in C and very low in N), since they are floating in water
Ratio of organic C to organic N = 7:1 (by moles or atoms)
Plants on land
Water is often scarce
Need more structure (carbon-rich) than phytoplankton
- land plants are not floating and more structure allows them to be taller, compete better for light
Much higher C:N ratio
Transpiration
The evaporation of water from leaf interior when stomata are open
CO2 in, H2O out
Fundamental trade-off between
Obtaining CO2 and losing water
- when water is abundant, no problem with transpiring water, which is necessary to get CO2
- when water is scarce, this can constrain ability to get CO2 and limit photosynthesis
One mechanism that some plans have which gives them an advantage in this CO-water trade off is
C-4 photosynthesis
- all algae and photosynthetic bacteria and most plants use C-3 photosynthesis
- C-4 photosynthesis evolved to reduce the problem of PHOTORESPIRATION (but also conveys an advantage when water is short)
C-3 photosynthesis evolved when
The atmosphere had less O2 and more CO2 than it does today
- problem now is when a photo-system sees too much O2 or too little CO2: Rubisco catalyzes reaction of RuBP with O2 instead of with CO2
-> this photorespiration can greatly decrease the overall net efficiency of photosynthesis
Which of the following can lead to situations where a photo-system sees too much O2 or too little CO2 ?
A) Very high light levels, leading to very high rates of
photosynthesis that build up O2 faster than it can diffuse
out of a chloroplast.
B) Drought conditions, leading to a plant closing its stomata and limiting the supply of CO2.
C) Very high rates of photosynthesis by algae in a lake, sucking the CO2 levels in the water down to very low levels.
D) All of the above.
E) None of the above
D) All of the above
Plants that use C-4 photosynthesis greatly reduce photorespiration by
1) using a different enzyme than Rubisco in the initial dark C fixation reaction, forming a molecule with 4 carbons rather than C-3 sugars; unlike Rubisco, this enzyme does not catalyze reaction of RuBP with O2
2) then taking the 4-C molecules, moving them to specialized cells that do not have the light reaction part of photosynthesis (so low in O2); here, Rubisco catalyzes reaction of the 4-C substance and CO2 to produce C-3 sugars
C-4 plants use CO2 more efficiently
Therefore, they do not need to have their stomata open as much, and lose less water for the same amount of photosynthesis
C-4 photosynthesis evolved relatively recently (25-32 million years ago), and independently at least 30 times
- became ecologically important only in the past 6-7 million years
- only 3% of plant species have C-4 photosynthesis
- but those that do are often very productive, and so can be globally important: 30% of all photosynthesis by land plants
C-4 plants
60% are warm-region grasses, including some major agricultural crops (ex. switch grass, sugar cane, corn, sorghum)
- much higher rates of photosynthesis at higher light levels
C-4 plant abundance in Australian grasslands as a function of temperature (warmer tends to mean drier)
Almost linear increase, higher temp, the more % of C2 species in regional grass floras
C4 plants do well when and better than C3 plants when
- it’s warm and dry
- do better than C3 plants when CO2 is low
-> with human-driven climate change, don’t really know which ones are favoured. Co2 increase (C3 plants) and temperature increase (C4 plants)
CAM photosynthesis
An even better approach to conserve water during photosynthesis
Night: stomata opened
- open stomates and take up CO2 at night when humidity is highest and transpirational water loss is lowest
- CO2 is stored as a four-carbon organic acid in vacuoles
Day: stomata closed
- during the day, CAM plants close their stomates to limit transpirational water loss
- the stored organic acids release CO2 to the Calvin cycle
Comparing photosynthetic pathways
C3: no separation
C4: separated in space
CAM: separated in time
The ultimate source of energy for most life on earth is
The sun
What is the equation for photosynthesis?
6CO2 + 6H20 -> C6H12O6 + 6O2
C6H12O6 + 6O2 -> 6CO2 + 6H20
6CO2 + C6H12O6 -> 6H20 + 6O2
6CO2 + 6O2 -> C6H12O6 + 6H20
6CO2 + 6H20 -> C6H12O6 + 6O2
Plants take in CO2 and release O2. That C is kept to produce carbohydrates during photosynthesis
You learn that an organism is using abiotic environmental resources to assemble carbohydrates and proteins, and then forming them into tissues and organs. This organism is likely a:
Autotroph
If a plant is prevented from transpiring, what do you expect the outcome will be?
the plant will likely become overheated
Relationship between incident light and photosynthetic CO2 uptake rate
Logarithmic increase before reaching light saturation
- light compensation point
- light limitation
- light saturation
True or false: All elements of photosynthetic reactions take place only when light is actively shining.
False because think about dark reactions and CAM plants which have parts of their photosynthetic reaction at night
Which of the following evolved first.
CAM photosynthesis in algae
C4 photosynthesis in algae
C3 Photosynthesis in algae
CAM photosynthesis in plants
C4 photosynthesis in plants
C3 photosynthesis in plants
C3 Photosynthesis in algae
True or false: C4 photosynthesis is an important photosynthetic pathway for plants in environments with consistently high precipitation.
False. C4 photosynthesis is typically associated with plants that thrive in environments with high temperatures and intense sunlight, as well as in regions with seasonal drought.
- an adaptation to efficiently capture and concentrate carbon dioxide while minimizing water loss
Imagine a series of perfectly spherical cells going from small to large.
As the size of a cell increase the surface are to volume ratio __________.
Decreases
Imagine some lakes going from low nutrient to high nutrient concentration.
The phytoplankton in the nutrient poor lakes are likely to be __________ the phytoplankton in the nutrient rich lakes.
(Presume the trait of phytoplankton size is mostly determined by the environment)
Smaller than
A major distinction between the food sources of herbivores and carnivores is that:
- Plants are primarily sources of carbohydrates, while animals are primarily sources of protein
- Plants and animals are both primarily sources of fibre and fat
- Almost all plant materials shown are high in protein, while all animal products shown are high in fat
- There is no discernable difference between the two food sources
Plants are primarily sources of carbohydrates, while animals are primarily sources of protein
If you wanted to eat something with a high C:N ratio, which of the following would you select?
- A vegetarian salad
- A piece of steak
- A piece of fish
- Yogurt
A vegetarian salad
