Ecology Final Review

C3 Pathway

• %%most common%% - most plants ~90%
• light independent reaction
    * but occurs in the presence and absence of light
    * occurs mostly in the day when NADPH and ATP are abundant
• northern grass
    * wheat
    * rice
    * barley oats
    * rye
    * ferns
    * algae
    * gymnosperms
    * bryophytes
• mesophyll cell
• fix C one time
• enzyme: ribulose 1,5 - bisphosphate carboxylase oxygenase (RuBisCo) (RuBP(SC))
    * takes Co2 and O2 and attaches it to RuB
• plants have high photorespiration rate
    * low water use efficiency (Wlie)
    * optimum temp is 20-25 degrees C (68-77F)
• %%C3 reactions occur in the stroma of the chloroplasts in the mesophyll cells%%
• PGA - phosphoglyceric acid (3 carbon compound)
• Step 1: c-fixation
    * RuBisCo attaches CO2 to RuBP and creates PGA 2x
• Step 2: Reduction
    * GAP (glyceraldehyde phosphate), PGAL (phosphoglyceraldehyde), G3P (glyceraldehyde 3-phosphate)
    * ATP, NADH
    * Sugar (need to repeat process 6 times to get a 6C sugar)
• Step 3: Regeneration
    * ATP
• photorespiration: competitive reaction with photosynthesis
• Calvin cycle:
• concentration ratio CO2/O2
• 25-50% rate of photorespiration
• higher temp → increases O2 affinity
• higher temp → lower sugar reduction in C3 plant
    * more O2 used
    * more photorespiration
• Water use efficiency
    * ratio of the rate of CO2 fixation to water loss by transpiration
    * low bc transpiration rate is high

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C3 Pathway Additional Explanation

• C3 plants
    * one that does not have photosynthetic adaptations to reduce photorespiration
• Calvin Cycle: chemical reactions by plants to reduce CO2 and other compounds into glucose
    * results in the three-carbon compound (3-PGA)
    * Calvin cycle steps
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        1. Carbon fixation
        * reduces CO2 using RuBisCO
        * CO2 binds to RuBP which is called carbon fixation
          * forms two-three carbon molecules of phosphoglycerate (3-PGA)
        * the enzyme that makes this happen is ribulose bisphosphate carboxylase/oxygenase (RuBisCO)
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        2. Reduction
        * 3-PGA molecules are converted into sugar - glucose
          * obtained energy from ATP and NADPH
            * these are formed during light-dependent reactions of photosynthesis
          * energy from ATP and NADPH transferred to sugars
        * electrons are transferred to 3-PGA molecules to form glyceraldehyde-3 phosphate (G3P)
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        3. Regeneration
        * requires ATP
        * some G3P molecules used to produce glucose
        * others recycled to regenerate the RuBP acceptor
• Products of the C3 cycle
    * ONE @@carbon molecule@@ is fixed at each calvin cycle turn
    * ONE %%glyceraldehyde-3 phosphate%% (G3P) is created in three turns of the calvin cycle
    * TWO ^^glyceraldehyde-3 phosphate^^ combine to form ONE ^^glucose molecule^^
    * THREE ==ATP== and TWO ==NADH== used during reduction of 3-phosphoglyceric acid to glyceraldehyde-3 phosphate and in the regeneration of RuBP
    * END PRODUCTS: EIGHTEEN $ATP$ and TWELVE $NADPH$ are consumed to produce ONE $glucose molecule$

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C4 Pathway

• 3% terrestrial
• southern grasses: corn, sugarcane, sorghum, millet
• Sedges, shrubs
• includes the calvin cycle
• TWO TYPES OF CELLS INVOLVED
    * mesophyll cell
    * bundle sheath cell
• Fix carbon TWICE
    * RuBisCO --- takes CO2 and attaches it to RuBP to produce PGA
    * PEPcarboxylate (PEPCO)
    * PEP - phosphoenol pyruvate (3C0
      * operates in the mesophyll cell (carbon fixation)
    * low photorespiration rates → increase yield and increase sugar
    * higher water use efficiency (WUE)
• optimum temp is higher temps 30-50C
    * distinct advantage over C3 plants in warmer and drier habitats

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CAM Pathway

• Crassulacean Acid Metabolism
• xerophytes typically use this pathway
    * plant adapted for survival in arid habitats
    * includes: cacti, crassulaceae (stonecrop plant family), agave, cactus-like euphorbs (like succulents), pineapples
• only in mesophyll cell (like C3 pathway)
• fix carbon TWICE (like C4 pathway)
    * use two different enzymes
    * one using RuBisCo (O2 and CO2)
    * PEP Carboxylate (PEPCO) - CO2
• low transpiration rate
    * plants live in harsh dry environments and don’t want to dry out
• optimum temperature
    * 35C+
• BIG DIFF THAN C3 AND C4 PATHWAY: %%CO2 is fixed initially at NIGHT%%
• change of pH between night and day time
• pH decreases at night (4-5) and increases in the day (6-7)
• some of these plants are %%obligate%%
    * only one way to fix carbon dioxide (which is at night)
• facultative - options
    * revert to one calvin cycle

Similarities between: C4 and CAM Pathway

• both use malic acid as intermediate
• both fix carbon twice
• RuBisCo, PEPCO

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Differences between C4 and CAM

• C4- Two cells involved (mesophyll cells and bundle sheath cells)
    * CAM- One cell (mesophyll cell)
• C4 Plants enzyme- mesophyll cell (PEPCO) bundle sheath cell (RuBisCo)
    * CAM enzyme- 1 cell (Mesophyll cell) at night PEPCO enzyme is operating; during day RuBisCo enzyme is operating
• C4 plants fix CO2 only in day
    * CAM fix CO2 night (PEPCO)
    * CAM fix CO2 day (RuBisCo
• C4 spatial separation
    * initial CO2 fixation - mesophyll PEPCO
    * Calvin cycle (sugar) - BSB, RuBisCo
      * CAM - temporal separation (all happening in mesophyll cell)
        * inition CO2 fixation - night
        * Calvin cycle (sugar) - day

Helpful links:

• https://byjus.com/biology/calvin-cycle/
• https://www.khanacademy.org/science/biology/photosynthesis-in-plants/photorespiration--c3-c4-cam-plants/a/c3-c4-and-cam-plants-agriculture

Plants response to too much water

• Stresses
    * limited gas exchange in submerged tissues
    * accumulation of toxic substances in soil due to anaerobic conditions
• Adaptations
    * Aerenchyma (can be party of a normal development of a plant; or can be induced by stressors)
      * interconnected gas filled chambers throughout the plants - straw, snorkel
      * helps ventilate the plant
      * can be in stem, root, leaf, etc
    * Adventitious roots (can be part of a normal development of a plant; or can be induced by stressors)
      * root which grows in a position where roots would not normally grow (grow from non-root tissue;)
      * can replace the function of the original roots where oxygen is available
    * Pneumatophores
      * specialized growth on the root system that helps with gas exchange and provides oxygen
      * “knees'“

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Aquatic Habitats

• variation in salinity reflects the relative “aridity”
• Substances (salts, water) move down their concentration gradients by diffusion
• Osmosis is movement of water down its concentration gradient across a semipermeable membrane
• Osmolarity
    * freshwater vs saltwater
      * saltwater (brackish) > 1000 mosm
      * freshwater <1000
    * relationship of an aquatic organism to its environment
      * isosmotic
        * internal concentration of water and salt equal to the concentration in the environment
      * hyperosmotic
        * lower internal concentration of water and higher internal concentration of salt compared to the environment
      * hypoosmotic
        * higher internal concentration of water and lower internal concentration of salt compared to the environment

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Population Crash

• a sharp decline in the population size
• may lead to local extinction of a population or species extinction
• Causes:
    * human persecution
    * scarcity of food resources
    * disease
    * emigration
    * habitat alteration
• ex: reindeer
• American Bison
    * 30 million
    * nearly extinct and hunted by 1880s
    * 1840 - est pop. 325
    * from 30 million to 325
      * why?
        * humans killed a lot of bison
          * why?
            * market hunting for hides
            * take bones, grind up and use as fertilizer
            * major reason: control indigenous populations (by decimating a major resource indigenous people used)
    * current population: ~500,000
    * yellowstone national park: ~5,000
      * “managed wild populations”
    * huge population crash due to humans
• St. Matthew Island
    * 1944 - intro reindeer
    * 29 ; 24 female 5 male
    * high quality food; lichen and moss
    * largest herbivore on island
    * 1957 daveklein - USFW
      * new pop: ~1350
      * healthy, thick reindeer
      * exceeded domestic herd rates by ~60%
      * went back in 1963
        * est. pop. ~6,000
    * 137.9 sq/mi = > 44 sq/mi
      * ratio to fawns and adults dropped
      * now they are skinny
      * too many reindeers
      * no natural predators
      * exhausted food resources of lichen
      * two harsh winter 63-64, 64-65
    * went back in 1966
      * population dropped to 42 reindeer
        * 41 female, 1 male believed to be sterile
    * great example of population crash by scarcity of food resources
    * early 1980s population is gone
    * island is still damaged by the intense grazing over a period of time
    * this population did not recover, sometimes other populations are able to recover from a population crash

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Life History

• lifetimes pattern of growth, development, and reproduction
• life history characteristics affect and are reflected in population life tables

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Life History Classification

• attempt to organize life history based on population characteristics such as a number of offspring, survival, relative offspring size, age at reproductive maturity

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r and K selection

• Mac Arthur and E. O. Wilson - 1967
• Erica Pianka - 1970, 1972

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r selected

• population attributes
• intrinsic rate of increase (r) is high
    * they grow very rapidly
• tend to live in variable and unstable habitats
• may be highly disturbed or temporary
• competitive ability is not strongly favored
• reproduction starts early for them
• body size is typically small
• reproductions single, semelparity
• offspring; many and small
• es: mosquito
• type III survivorship curve

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K selected

• population attributes
    * intrinsic rate of growth is low
      * do not grow at rapid rate, tend to stabilize around the carrying capacity
    * competitive ability is highly favored
    * live in constant or predictable environments
      * woodland, grassland, forest
    * development is slow
    * reproduction is later in life
    * tend to be larger animals
    * iteroparity and repeated reproduction
    * offspring, few and larger
    * low disturbance
    * long life expectancy
    * type I and type II survivorship curve

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Plant life history

• J. P. Grie - 1977
• Disturbance - any mechanism or process that limits plants by destroying plant biomass
• stress - external environmental conditions that limit growth of all or part of the vegetation
• 2 key variables

  
  1. intensity of disturbance (either high or low)

     
     1. grazing - herbivores
     2. fires
     3. farming
     4. landslide
     5. natural disaster
  2. intensity of stress

     
     1. limitations of moisture
     2. lack of nutrients
     3. extreme temperature
     4. salinity
     5. soil pH

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Ruderals

• rely on disturbance to minimize competition - low competitive ability
• high disturbance, low stress
• grow rapidly
• produce seeds in short period
    * between successive disturbance events
    * they want disturbance to knock down competitors
    * produces seeds quickly after disturbance events
• large portion of biomass is dedicated to reproduction
• ex: dandelion

Stress-tolerant

• high stress, low disturbance
• grow slowly, limited in growth by extreme environmental conditions
• competition limited by environmental conditions, low competitive ability
• conserve carbon - evergreen; may produce unpalatable chemicals to reduce herbivores eating them
• capable of exploiting temporarily favorable conditions
• ex: cacti

Competitive

• low disturbance, low stress

  selected for strong competitive ability

• ex: birch - deciduous forest

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Human Population Growth

• 1804 - 1 billion people living estimated
• pop. largely increased within last several hundred years
• 8 billion humans - est, November 15, 2022
• factors influencing the dramatic increase in the human population
    * technological innovations
    * improved sanitation
    * better medical care
    * increased agricultural output
• by 2050, ~9.7 billion people
• Age population pyramid
    * graphical representation of the distribution of a population by age group and sex
    * broader base - more children
    * death rate - slope
    * life expectancy - estimated and determined by the height
    * kink - indentation : increases but indentation and then comes back into another age group
      * means decrease birth rate increase death rate
      * because of : war, famine, disease
    * buldge : increase birth rate (baby boom)
    * expansive
      * triangle
      * rapid population growth
      * wide the base; faster the growth
      * large youthful population
      * dominated by infants and children
      * decreased working and elder population
      * high potential for growth in these populations - each birth cohorts gets larger
      * high birth rate
      * high death rate
      * low life expectancy
      * high dependency ratio
      * children and elderly to the working age groups
      * concerns: poverty, disease is common, civil unrest
        * plan for education/schools, housing

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12/1 Notes

Type of Human Growth Pyramid: Rapid/Expansive Pyramid

• triangle
• rapid population growth
• wide the base; faster the growth
• large youthful population
• dominated by infants and children
• decreased working and elder population
• high potential for growth in these populations - each birth cohorts gets larger
• high birth rate
• high death rate
• low life expectancy
• high dependency ratio
• children and elderly to the working age groups
• concerns: poverty, disease is common, civil unrest
    * plan for education/schools, housing

Type of Human Growth Pyramid: Stationary Pyramid

• rectangular or beehive shape age pyramid
• more uniformed population size across age groups
• more rectangular that it is, the slower the growth (less of a beehive shape)
• declining birth rate
• lower death rate (higher life expectancy)
• economically developed nations
• greater access to healthcare
• greater access to birth control
• delay in marriage/having children

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Type of Human Growth Pyramid: Constrictive Pyramid

• coffin shape (narrow at the base)
• low birth rate
• low mortality rate
• high life expectancy
• high number of elderly in population
• shrinking population
• fertility rates fall below replacement rate
• high dependency ratio mainly with the elderly
• highly developed
• wealthy nations
• access to modern healthcare
• higher standard of living
• medical care for the elderly
• concerns: meeting need like elderly services
    * they need to focus on elderly needs more than school and children since there are less children

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Demographic Transition Model

$<strong>* some nations can be in stages for years, decades or never even move, not all nations are guaranteed to reach stage 4. Many factors keeps nations in stage (social, economic, etc)</strong>$

• CBR (crude birth date)= #/1000
• CDR *crude death rate)= #/1000
• %%Stage 1 - high stationary%%
    * CBR, CDR - high
    * growth slow- fluctuates
• %%Stage 2 - early expanding%%
    * CBR - high
    * CRD - fall, decline
    * rapid increase in population
    * a lot of nations are in this stage (typically third world)
    * needs kids for livelihood (work in fields, etc)
• %%Stage 3 - late expanding%%
    * CBR drops (less births)
    * CDR low
    * kids are an expense
    * death rate typically is low
    * population growth still occurring
      * starts to decelerate
• %%Stage 4 - low stationary%%
    * CBR and CDR both low
    * population under these conditions are slow growth but steady

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Air Pollution

• ^^air pollution^^ - any gas or particulate matter added to the atmosphere that can produce a detrimental environmental effect on living organisms or non-living materials
• Sources of air pollution
    * Natural
      * ^^geogenic^^ (non-living sources) (volcanic eruption, fire, etc)
      * ^^biogenic^^ (living) (outgassing from soils, cows, etc)
    * anthropogenic - man-made
      * mobile
      * stationary/fixed sites
      * evaporative (VOC - volatile organic compounds)
      * agriculture/Forestry
      * waste disposal landfills
• ^^Point source^^
    * any single identifiable source of pollution from which pollutants are emitted
• ^^non-point source^^
    * pollution which originates from many places or from a widespread area
• ozone - O3
    * NOx + VOC + O2 → O3
      * (sunlight on top of the arrow)
• the case of lead
    * took ice samples
    * analyzed layers of ice to see the emissions
    * these emissions were taken in greenland with est 50,000 pop
      * ut has est 50,000 student
      * conclusion: pollution is not greenlands fault, it is our and other nations who pollute a lot. emissions have no boundaries and will spread everywhere. we have to be more responsible and watch our impact on other places
    *

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Global Distillation Effect - Grasshopper Effect

• net transfer/transport of pollution from lower latitudes (typically where it’s warmer) to high latitudes (poles, colder)
• steps
    * pollution emission
    * transport emission and multiple evaporation and condensation events
    * water condenses and comes back to surface
    * the emission is then somewhere else
• 

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