ECOLOGY 2129 Chapter 1 Ecology â branch of science dedicated to ...
ECOLOGY 2129 Chapter 1 Ecology – branch of science dedicated to the study of relationships between organisms and the environment. – Physiological ecology o Emphasizes the physiological, functional, and anatomical mechanisms by which organisms solve problems posed by physical and chemical variation in the environment – Behavioural ecology o Focuses on the ways that plants and animals use behaviou to deal with environmental variation – Population ecology o Centers on the factorsinfluencing population structure and process o Includes adaptations, extinction, distribution, abundance of species, population growth and regulation variation in the reproductive ecology of species – Community ecology o Observing ecological community as an associatin of interacting species o Concentrates on organisms inhabiting area – Ecosystem ecology o Includes the ecological community in an area plus all of the physical and chemical factors influencing the community o One goal is to understand the controls on nutrient cycling and energy flow through ecosystems – Landscape ecology o Studies exchanges among ecosystems – Geographic ecology o Long term, large scale regional processes Levels of ecological organization 1)Biosphere largest spatial scale e.g. relating atmospheric CO2 to global temperature 2)Region 3)Landscape 4)Ecosystem 5)Community 6)Populations 7)Individuals Ecotones transition from one type of ecosystem to another e.g. transition from agricultural field into the surrounding forest boundaries can also be created through wild fires, insect outnbreaks, and other large scale disturbances Scientific Method science means “to know” ask questions and then attempt to find answers example: MACARTHER • study of warblers • question: how can several species of insecteating warblers live in the same forest without one species eventually excluding the others through competition? • Hypothesis : several warbler species are able to coexist because each species feeds on insects living in different zones within trees • Determine validity by testing predictions that follow from the hypothesis
• Test by observation, experiment, and modeling Example: SCHINDLER • Study of eutrophication – what determines phytoplankton abundance • Question: what distinguishes lakes that are chlorophyllrich from lakes that are chlorophyll poor? What nutrients contribute to amplified eutrophication • Test IN FIELD – apply different combinations of different nutrients to various sections of lakes and observe • Must test in field rather than in a lab because of several factors o Underlying mechanisms driving ecological shift require the ability of microflora and fauna to shift in species composition as nutrient levels shift o Exchange of nitrogen and carbon with the atmosphere cannot be reproduced in lab • Determined that phosphorus was primarily responsible for amplified eutrophication
What do ecologists want to know about? total biomass • how much and why? • Biotic effects o neurotoxins produced by cyanobacteria o oxygen starvation due to bacterial activities o impacts on biotic communities • Harvestability o Forestry o Crops • Changes in biomass can affect biogeochemical processe o Effects on climate – transpiration by plants cooler climates and more precipitation o Effects on erosion and nutrient concentration ecosystem functioning • ecosystem – biological community plus all of the abiotic factors influencing that community • primary production fixation of energy by autotrophs in an ecosystem o gross primary production = total amount of energy fixed by all autotrophs in ecosystem o net primary production – amount of energy left over after autotrophs have met their own energetic needs – gross primary production minus respiration by primary producers = amount of energy available to the consumers in ecosystem • primary productivity (at a relatively local scale) o production of new organic matter, or biomass, by autotrophs in an ecosystem o CO2 organic matter o Base of food webs o Greater productivity leads to greater herbivore densities, but herbivores can also alter productivity • Primary productivity at a broad scale o Productivity varies spatially o Human impacts • Water cycling o Ecosystem wide importance – affects loss of nutrients through erosion, influences primary productivity o for individual plants – vascular transport o transitory precipitation can have massive effects on ecosystem functions
•
•
decomposition o replenishment of nutrients for primary production o breakdown of organic matter accompanied by the release of CO2 and other inorganic compounds, a key process in nutrient cycling biogeochemical cycles o nitrogen cycle – including nitrogen fixation o atmospheric constituents o pollination
species diversity • global scale o influenced by factors such as climate, evolution, etc. • local scale o effects on ecosystem functioning greater diversity = greater evaporation e.g. fields with weeds greater diversity = greater rate of regeneration of NPP following disturbance (e.g. drought) population size of a species • estimates of abundance have direct bearing on the legal status of species • abundant species vs at risk species o abundant species effect system e.g. grazing o disease vectors – lyme disease, rocky mountain spotted fever • hyper abundant species o can lead to widespread pesticide use o mountain pine beetle infestation • harvestable populations o abundance estimates/determines quota o bad estimates can be disastrous distribution of a species • geographic distribution, regional distribution • economic consequences o harvestable populations – are they capable of providing sustainable economic benefit? • Affects local species diversity • Influences biotic interactions
Chapter 2 Factors that influence ecological characteristics – independent factors – History, evolution – Physiological tolerance – Limiting resources – Biotic interactions (including competition, predation, and herbivory)
history, evolution • study of how organisms in a particular area are influenced by factors such as climate, soils, predators, competitors, mutualists, evolutionary history • slow changes on ecological(short) time scales • e.g. peppered moth (natural selection) physiological tolerance • often an optimal response curve to factors such as temperature
•
conditions that
L a k e T a h k e n it c h
1 .2
L a k e T a h k e n itc h , O r e g o n
P o p u la t io n g r o w th r a t e (d o u b lin g s p e r d a y )
P o p u la t io n g r o w th r a te (d o u b lin g s p e r d a y )
• limiting resources • resources – essential for individual growth o e.g. nutrients, light, water, space, etc o a resource can be consumed • Liebig’s law of minimum o The limiting factor is the one that an organism must concentrate the most relative to environmental concentrations (that it needs the most) o Amount required / amount available • If a factor limits population growth, rate of growth declines, biomass declines, and distribution is limited L i m i t i n g f oa c t E.g. photosynthesis – light reaction is limited by light, dark reaction is o rs E f f e c t o n p o p u limited by CO2 la tio n g r o w th r a te o f v a r io u s n u t r ie n t a d d it io n s t o t h e w a t e r o f • Limiting factors L a k e T La hi mk e in t i it cn hg f a c t o r s Eof f e c Effect on population growth rate of various nutrient additions to the water of t o n p o p u la t io n g r o w t h r a t e o f v a r i o Lake Tahkenitch u s n u t r ie n t a d d it io n s t o th e w a te r o f
1 .2
0 .6
L a k e T a h k e n itc h , O r e g o n
0 .6
0
C o n tr o l
1 .0 N
0 .0 5 P
1 0 .0 C
0 C o n tro l
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1 .0 N + 0 .0 5 P
1 .0 N + 1 0 .0 C
1 0 .0 C
1 .0 N +
0 .0 5 P + 1 0 .0 C 1 .0 N +
1 .0 N + 0 .0 5 P + 1 0 .0 C
0 .0 5 P +
1 .0 N +
N u t r i e n t a d d i t i o n s ( m g / L ) i n d i f f e r e n c e 0e . 0x5 pP e r i m1 0 .e0 nC t a l 1 t0 r. 0e Ca t m0 . 0e 5 nP t s+ 1 0 .0 C
N u tr ie n t a d d itio n s (m g /L ) in d iffe r e n c e e x p e r im e n ta l tr e a tm e n ts
o
impact of nitrogen and carbon addiction is minimal to none, therefore its capacity to limit population growth is nonexistent – NOT the primary nutrient limitant effect of phosphorus is great – if you add nitrogen AND phosphorus it gets even a bit better, but since error bars probably overlap, it is hard to conclude that the nitrogen plus phosphorus is statistically significant o EXAMPLE lake of the woods, effect of nutrient additions i m i t i n Lg i fmoa ic t ti on gr s f a c t o r s E ffe c t o f n u tr ie n t a d d i t i phosphorus is primary limiting factor o n s o n p o p u la t io n E ff e c t o f n u t r ie n t a d d it io n s o n p o p u la tio n g r o w t h r a tge r oo wf tSh . r ca at e p or fisecondary limiting nutrient is nitrogen cS o. rc na up rt ui cmo r in n u tLu am k ei n L a k e o f t h e W oo of dt hs e W oo d stertiary is carbon
L
1 .2
0 .6
P o p u la tio n g r o w th r a te (d o u b lin g s p e r d a y )
P o p u la tio n g ro w th ra te (d o u b lin g s p e r d a y )
niche is defined by the totality of environmental a species can tolerate influences geographic range enormously
1 .2 L a k e o f t h Le aWk eo o fd ts h, eO Wn to ao rd i so , O n t a r i o
0 .6
0
0
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1 .0 N
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1 0 .0 C
1 .0 N + 0 .0 5 P
1 .0 N + 01. 0. 05 NP +
1 0 .0 C
1 .0 N + 0 .0 5 P + 1 .0 N + 1 0 . 0 5C P + 1 0 . 10 . C0 N + 0 . 0 5 P + 1 0 .0 C 0 .0 5 P + 1 0 .0 C
N u t r i e n t a d d i t i o n s ( m g / L ) p e r e x p e r i m e n t a l t r e a 1t m0 . 0e Cn t
N u tr ie n t a d d itio n s (m g /L ) p e r e x p e r im e n ta l tr e a tm e n t
o EXAMPLE – mussel – limited by space availability, cannot be too high where water wont reach or predators will eat, cannot be too low where they cant gain nutrients – must attach to rock and be wet enough
biotic interactions – competition • interspecies – between species; intraspecies – within species • fundamental vs realized niche o fundamental excludes the effect of biotic interactions like competition o realized is smaller than fundamental, as resources are less available and the spaces that they can occupy are inhibited by negative impacts of biotic interactions o one species will dominate over another so realized niche of the dominated species shrinks, while the fundamental niche of the dominating species remains the same • example: c4 = water use efficiency grater in c4 plants (can close stomata in leaves while continuing to do photosynthesis) so c4 plant will slowly drive out c3 plants in hot and dry places
• •
–
example: new guinean bird distribution o species divide the habitat they occupy according what other species are already there o when species are all present on the same island, they subdivide the habitats among them o different colours represent a different species o in some areas, a particular species is able to occupy any habitat, but when there’s competition, they will only occupy a certain area according to its competitive capability predation and herbivory • example: Yellowstone national park in the US; an enclosure to keep out big grazers from an area containing plants o big grazers have a major role in shaping the structure of the ecosystems and the species diversity o there are so many big grazers because the wolves have been killed by humans so the grazers have no serious predators so the populations have reached epidemic proportions • example: sugar maple distribution in N.A. o why doesn’t this range extend further north,south, or west?
Temperature wintertime temps are too low along and above the northern border – you can test it by transplanting trees from within the range to areas beyond the range Precipitation – western range margin is limited by lack of precipitation in the prairies
o
o southern border may be limited by hot temperatures, also may be limited by competition – a more dominant species that can’t endure winter is present south and will beat out sugar maple
P ro b le m
o Solar radiation – maximal at 0•. maximal at 30•N and 30•S o Climatic variation is caused by uneven heating of its surface by the sun
E n e r g y – g l o b a l s c a le
P ro b le m
a te r
M n
nw
K
e nt ra t i oni
example: one adds a solution of Mn, K, and Si to a seawater sample containing phytoplankton. The concentrations of these elements changes according to • O n e a d d s a s o lu tio n o f M n , the graph. What conclusions can we draw? – silicon is K , a n d S i to a s e a w a te r probably a limiting nutrient s a m p l e c o n t a i n i n g p h y to p la n k to n . T h e c o n c e n tra tio n s o f th e s e Large scale patterns of climatic variation e le m e n ts c h a n g e s a c c o rd in g to th e g ra p h . W h a t Major Physical Properties of Terrestrial Ecosystems c o n c lu s io n s c a n w e d ra w ? Energy – global scale
Si Conc
•
T im e a fte r n u trie n t a d d itio n
Hadley cell – air moving from 30 latitude back to the equator – sun heats air at equator , warm moist air cools, condenses, heavy rainfall (tropics) – stops rising spreads north and south, dry high altitude air cools and sinks back to earth at 30•latitude dawing moisture from lands, creating desert
G ro w th ra te
Polar cell air warms at 60• latitude • P o p u l a t i o n g r o w t h r a t e and cools at poles – primarily s o f a p l a n t s p e c i e s v a r i e responsible for the weather patterns s a c c o rd in g to th e associated with most northerly and 0 c o n c e n t r a t i o n o f t w o southerly areas, bringing cold from n u t r i e n t s s h o w n o n t h e poles rig h t. In te rp re t th e s e Ferrel cells – mid latitudes – driven re s u lts . partially by effects of Hadley and C o n c e n tr a tio n
polar cells – warm,
o moist air flowing from Hadley cells rises as it meets cold air flowing from the polar cells – as this air mass rises, moisture picked up from desert regions at lower latitudes condenses to form the clouds that produce the abundant precipitation of temperate region o air movement would be north.south if it weren’t for the west to east rotation of the earth
o Wind – between 30 to 60 flows mainly from the west (westerlies), higher than 60 seems to come from the east (polar easterlies) o Seasonality varies with latitude – as you move towards equator: Mean increases for temperature Variance decreases More land mass in northern hemisphere, easier to change temperatures of terrestrial systems because land will heat and cool faster than water o Coriolis effect – phenomenon caused by the rotation of the earth, which produces a deflection of winds and water currents to the right of their direction of travel in the Northern Hemisphere and to the left of their direction of travel in the Southern hemisphere o Advection of heat Transfer of heat in a fluid • Ocean currents • Atmospheric circulation Precipitation Maximal precipitation at 0 degrees Minimal precipitation at 25•N and 25•S Orographic effects • Mountain ranges, air is forced upward, cools and condenses, releases rain at low elevations and snow at high elevations, by the time the air reaches the other side of the mountain range it is very dry, so the land on the leeward side o the range does not get a lot of precipitation At equator we have relatively substantial amount of tropical storm patterns that emerge – Hadley cell is just beginning Typhoons in south east asia have accumulated energy from all the way across the pacific ocean which is way bigger than the atlantic so typhoons are way bigger and more devastation than hurricanes that hit the gulf coast of north America Hurricanes track coreolis effect – as they move northwest towards the gulf coast, they start to turn to the north east, away from land again, sometimes it hits the land sometimes its diverted before contact o Evapotranspiration The sum of water evaporated and transpired from plants in a community and its Influence on rates of primary production AET – actual evapotranspiration • Total amount of water that evaporates and transpires off a landscape during the course of a year • Is measured in mm of water per year • Is affected by both temperature and precipitation • Highest levels of primary production are those that are warm and receive large amounts of precipitation • Lowest levels of AET either because of little precipitation, are very cold, or both o E.g. hot deserts and tundra exhibit low levels of AET PET = potential ET from saturated surface • If evaporation was happening as fast as possible and transpiration was happening as fast as possible AET = actual ET ET, given that water may be limiting, integrates water supply and heat • Given the amount of water that there is, how much actually happens • Water deficit: PETAET
geographical distribution of factors limiting primary productivity
N e m a n i e t a l 2 0 0 3 S c ie n c e 3 0 0 :1 5 6 0
Climate diagrams Developed by Walter as a tool to explore the relationship between the distribution of terrestrial vegetation and climate Summarize a great deal of useful climatic info, including seasonal variation in temp and precipitation, the length and intensity of wet and dry season, and the portion of the year during which average minimum temp is above and below 0• STRUCTURE o X axis: months of the year (jandec for northern hem; juljune for S. hem) o Left Yaxis: temperature o Right Yaxis: precipitation o Zeroes of left and right Yaxes are even o Every 10• Celcius that the scale goes up is equivalent to 20 mm of precipitation that the scale goes up o Climate diagrams for wet areas such as tropical rain forest compress the precipitation scale for precipitation above 100 mm so that 10•C changes are equivalent to 200 mm of precipitation o months where average low temp is above freezing can be indicated o mean annual temp is in upper left corner o mean annual precipitation is in upper right corner o elevation of the site in meters above sea level is also in upper right corner READING IT o Adequate moisture for plant growth occurs when precipitation line is ABOVE temp line o When temp line is ABOVE precipitation line – potential evaporation rate exceeds precipitation so it is a dry period
C lim a t ic c h a n g e s 1 9 8 2 1 9 9 9
T e m p e r a tu re
Nutrients
nutrients in the soil o poor in tropics (all leached into the biomass), and in regions where the underlying rock in insoluble (granite) o Rich in regions with soluble underlying rock (sediments)
Light
aspect escarpments are capble over receiving a lot of light to its understory
Biological Consequences of Physical Factors Spatial Distribution of Organisms
Global Scale (Biomes) o Mixedwood plain (south eastern ontario) Very high biological diversity, high population densities Rich soils, mild climate Vegetation: mostly deciduous (maples and oaks), some conifers (white pine) Fauna: Deer, squirrels (carnivores exasperated) o Boreal Shield (stretchs across northern Ontario, Quebec, and Manitoba) Soils very nutrient poor (insoluble granite) Many bogs due to poor drainage Glaciation shaped landscape Dry due to rocky mountains (many forest fires) Vegetation: Conifers (Fir, Spruce), Deciduous (birch, aspen) Fauna: Moose, beaver (carnivores remain)
Biomes: Prediction depends principally on temperature and water availability Primary Productivity incorporation of CO2 into the plant biomass result of all of the photosynthesis that occurs in a plant community Factors Controlling Primary Productivity Global Scale positively related to temperature and precipitation
substrate (nutrient availability)
Local Moisture, sun, nutrients (NPK)
Regional
Physical Properties of Aquatic and Marine Ecosystems Trophic Status Concentrations of Nutrients Oligotrophic Low Mesotrophic Medium Eutrophic High *Result of… 1) Substrate: runoff through sedimentary rock are nutrient rich, runoff through granitic is nutrient poor 2) Human Activities agriculture (usually non point source) water use (usually point source) Ex. If P concentrations above 20 mg/m3 create too more chlorophyll, calculations may be made to check the maximum allowable P for a particular lake. Lake Volume= area x avg. depth Maximum P= lake volume x [P] threshold Relative to 1 person= Max P/(human impact in mg) *** can be mitigated by simple calculations dilution of discharge loss of nutrients from discharged water into soil sedimentation of particulates agricultural impacts are much more intense Factors that Vary within a particular lake Density of water o Temperature Ice less dense than 4 deg. Water (ice on surface) o Salinity Oxygen solubility increases at LOW temp Salt solubility decreases at LOW temp *In eutrophic lakes, Oxygen Levels decrease at deeper depths due to oxygen consumption by decomposers of fallen dead algae AND less respiration from rooted plants on the seafloor
o Vertical Stratification
Chemical Properties
increased oxygen
Ex. Light intensity problem A species energy production drops below respiration energy consumption for a river if the light intensity goes below 10 j/m2. Surface light: 320 J/m2s Coefficient of loss: 1.5 m1 Compensation point? Z= 1/k (ln(I0)ln(Ik)) = (ln(320)ln(10))/1.5 =2.31m Therefore the species cannot persist under 2.31 m *All of these effect euphotic zones of lakes Euphotic zone: zone of light availability (photosynthetic activity)…. Vary with trophic status Aphotic zone: zone of no light availability (no photosynthetic activity) Factors that vary within marine ecosystems Morphometry extent of euphotic zone? How large is watershed? How long is fetch? (affects thermocline and wave height) o Wind forces warm waters down and pulls colder waters up (el nino, la nina) Consequences 1) Vertical Distribution of Plants Macrophytes phytoplankton 2) Vertical Distribution of Fish 3) Geographic Distribution of Phytoplankton in freshwater in the ocean
Population all individuals of a given species Population= F(environmental conditions) Abundance: total numbers of individuals
Population Density: number of individuals per unit space
Calculating Population Estimate Count species in quadrats or transects Abundance Total= (total area/quadrat area) * (Sum of species/number of quadrats) *Uncertainty can be variation among quadrats (spatial dist. of species: random, uniform, clumped) Variance: reveals uncertainty of population sample… ́ 2 2 ∑ ( X −X ) S= n−1 Sampling Populations
Mobile Organisms o Use MarkReleaseRecapture method o Able to predict populations depending the populations of marked organisms recaptured o Population= (Sample 1 Marked)*(Sample 2 total)/(Sample 2 Marked Recaptured)
on
Prediction of Abundance of Species based on Environmental conditions estimation by availability of limiting nutrient estimation by habitat characteristics 2 R =¿ estimate of how strong predictions are in terms of being the function of population abundance (1 being perfect prediction)
*there are many factors that affect population dynamics (biotic interactions, temporal variation, etc) Population Growth Population= Nt = Nt1 + birth – mortality + immigration – emigration **Within a Community we can eliminate Immigration and emigration to 0 Discrete Generations Geometric Growth N(t) = N 0 λt growth happens in generation stages ❑ λ = N(t)/N(t1)
Continuous Growth (Exponential) N(t) = N 0 ert growth is continuously occurring
❑ ❑ λ = e r , therefore ln( λ )= r
linearization of the exponential growth gives r the slope and t variable
Logistic Population Growth N dN/dt= r max N 1− K
(
)
population growth cannot continue forever at large population sizes growth will be slowed by competition and/or increased mortality
intraspecific
K (carrying capacity) depends on resource availability, r depends on the characteristics of the organisms in its environment Many Factors affect the r value (ex. Growth rates vs. body size: The larger you are the slower grow, and oppositely the smaller you are the faster your
your population will population will grow)
*Logistic growth typically seen when a species is introduced into a new locale (ex. Sheep of Tasmania, pheasants to protection island) or when they are in a bacterial culture where environmental conditions are predictable and constant. Delayed Logistic growth
(
dN/dt= r max N t 1−
N t−d K
)
Population growth can depend on previous populations and the carrying capacity (K).
Hypotheses of Regulation and Growth
extinctions are rare (in nature) populations converge towards a particular value
When Population Density is High birth rate decreases (ex. Less eggs per clutch, less number of clutches)
oscillate around
Mortality rate increases (ex. High initial density yields less survivors) Emigration increases (ex. High initial density yields more spread emigration of species)
** and vise versa when populations density is low Density Dependence VS. Inverse Density Dependence
Density Independent Factors
factors that kill the same proportion of the population no mater what the density is EX. Fire, extreme weather, accidents (environmental stochasticity) Do not pull the population towards a stable density
Ex. Thrips population depend predictably on the weather Density Independent and Dependent Factors interact in the real world Ex. Allele effects such as reproductive failure occurs among very small populations Mortality Rates Depend on Density Age Climate Birth Rates Rates Depend on Density Age Year (some species can reproduce earlier than others) Juvenile Survival Rates Depends on: Density (ex. Sheep birth weight decreases with high density) Temperature (ex. Deer birth weight increases with increasing temperature) Predicting Abundance
∗( probability of survival ) ( fecundity adult )
N t , a=N t −1,a−1∗( probability of survival )+ N t−1,a−1∗ Total Abundance= N t =
∑ Na
Prediction of Abundance Requires initial abundance age structure mortality as a function of age, density and environment age, density, and environmentdependent fecundity survival rates of young Human population Growth Exponential Growth: constant through time Logistic Growth: diminishes through time HyperExponential Growth: increases through time *On weight vs. population density graph we are off of the trend (have densities similar to that of mammals with body sizes of 1kg) Malthus Prediction: Our exponentially growing population will eventually out grow our resources (crops) and limit our growth. productivity per hectare of has increased, more than population until NOW (not everywhere ex. Africa) Projected Future Growth 1 person added every second, 1 hectare of agriculture lost every 7.67 seconds HYPEREXPONENTIAL growth of humans due to increased birth rates and decreased mortality rates o Ex. Reduced rates of infectious diseases such as AIDS The demographic transition Mortality decrease: due to improved hygiene and clean water (simple medical and civil innovations) Natality decrease: due to improved economic conditions (financial security, based on cost benefit considerations) Average Income (per capita GNP): increased GNP/income decreases birth rates Income equality/inequality causes rates to vary from general curve Perfect equality : wealth shared Perfect Inequality : 1 person owns all the wealth Gini Coefficient : area of the deviation from the 1:1 line as a proportion of the different between perfect equality and perfect inequality • LOW value= more equality • HIGH value= more Inequality Education Ex. Countries in poverty experience increased births Reducing Population Growth Contraception voluntary (ex. India giving out birth control) o didn’t work
coersive (ex. China one child law) o did work but with human rights issues
Social Programs (ex. Sri Lanka) can work but costly Ecological Footprints area of productive land required to support each person with resources to sustain their lifestyle o Ex. Food, transport, manufactured goods, energy etc.
I=PAT o o o o
I: environmental impact P: population size A: affluence T: technology
Environmental scarcity occurs from either 1) demand induced scarcity: population growth in a region demands more 2) supply induced scarcity: supplies degrade to low levels 3) structural scarcity: occurs from unequal social distribution of resources OFTEN ALL OCCUR SIMULTANEOUSLY AND INTERACT Canadian Footprint: 5.3 Hectares/ person North America dominates rest of the world in terms of average footprint if the rest of the world followed these standards we would need 3 worlds for sustainability Stern Report Summary: States that early action on reducing the rate of climate change now will undoubtedly outweigh the potential costs in the future. Right now climate change is manageable however in the future if no action is made it will be too overwhelming to overcome. Fresh water supply by 2025 more than 3 billion people will live in 48 countries under water stress Maximum Carrying Capacity for Humans current population: more than 6 billion Optimistic Capacity: 15 billion Level off at about 9 billion
Biotic Factors on Population Interspecific Interactions: species interaction with other species Intraspecific interactions: species interaction within its population 1) Resource Competition a. When a resource is in limited supply i. Result of niche overlap (this competition creates difference between fundamental niche and the realized niche) ii. Within a niche, the presence of other species competitors decreases the population of both (realized niche shrinks)
2) Interference Competition a. Direct harm to other individuals Theory of Limiting Similarity: if two species niche overlap is too great, competition drives one to extinction called competitive exclusion *Explained in LotkaVolterra equations
(
Logistic equation: dN/dt= r max N 1−
N K
)
When a competitor is introduced the population growth decreases in the strength of the competing species
proportion to
d N1 =r max1 N 1 ( ( K 1−N 1−α 12 N 2 ) /K 1 ) dt d N2 =r max 2 N 2 ( ( K 2−N 2−α 21 N 1 ) / K 2 ) dt α 12 : is the effect of individual of species 2 on the rate of species 1
pop. growth of
α 21 : is the effect of individual of species 1 on the rate of species 2
pop. growth of
Ex. If deer is a weak competitor to moose, deer could have a α 21 = 0.5 which means that 100 deer would have the same competitive impact as 50 moose. When we equate growth to zero we can determine the equilibrium size of a species when the competitor is absent.
population
N 1=K 1−α 12 N 2 N 2=K 2−α 21 N 1
therefore when N 1=¿ 0, N 2=
K1 and when N 2=¿ 0, α 12
N 1=
K2 α 21
*When one species isocline is entirely above another, the lower species disappears (competitive exclusion)
immigration/emigration stable age structure
LotkaVolterra
Example
Mathematical the describe with
Models simplify phenomenons they assumptions
LotkaVolterra no
is no different
genetic factors are constant no time lags in population impacts no environmental variation (constant carrying capacity) all competition coefficients are linear with population density of competitor logistic growth
* the intensity of competition varies with resource availability Tilman Resource Mechanism most successful competitor is able to reduce the availability of a limiting resource to a loser level R*
*Evidence of Tilmans theory is seen with the Asterionella and Cyclotella both coexist at balanced supplied of silicate and phosphate, only Cyclo. survives in HI phosphate low silicate, and vise versa for Aster. Niche Partitioning: species have sufficient phenotype pasticity to alter their resource usage to avoid competition. Classic Example:
Finches in the galapacos o All evolved from a common ancestor to the isolated islands
that somehow made it
6 forms of Competition 1) 2) 3) 4) 5) 6)
Consumptive: exploitation of food Preemptive: competition for space Overgrowth: growing over or on another rindividual (selfthinning, canopy vs. understory) Chemical: allelopathy Territorial: aggressive defense or intent to defend a unit of space (similar to preemptive) Encounter: interaction between mobile organisms that harm one or both.
Ghost of Competition past: many species may no longer compete today due to evolutionary change (character displacement) Diffuse Competition: many, weak, pairwise interactions that are hard to detect individually as density of plants increases (biomass), diffuse competition increases
Competitive Release: increased productivity, distribution, and abundance for a species that has just driven a competing species to extinction. Diamonds Assembly Rules 1) Some pairs of species should never coexist (by themselves or as a part of a larger group) 2) Species occurring together should have a lower niche overlap than species do at random due to character displacement Ex. Tested on the islands for New Guinean birds, drosophila, as well as cogeneric bird species in rainforest aren’t found in same habitat.
Predation & Herbivory Herbivory organisms consuming plant species o affect plant communities o affect other organisms habitats New niches for herbivores may have caused the evolution of most of the worlds species World stays Green from 3 possible ways… 1) Bottom up control of herbivory by plants a. Using chemical defenses (phototoxins etc) 2) Top down control of herbivores by predators 3) Herbivore populations cannot track the plant resource Predation organisms consuming prey organisms able to track prey (seen is Lotka Volterra Models) prey and predators coexist and their populations fluctuate cyclically is the environment offers refugia Disturbance and Succession Succession Primary Succession : the chronological change of a biotic community in a newly established area Secondary Succession : chronological change of a biotic community following disturbance Early Successional Species strong dispersers/competitors for nutrients
allocate resources to roots function for climax species: enrich soil with N *low nutrients, high light Later Successional Species less good at dispersal but increasingly good competitors for light allocate resources to shoots *more nutrients, less light Intermediate Disturbance Hypothesis species richness is a maximum when the frequency of disturbance are at a medium
works in theory, however statistical data cannot support the theory
Island Biogeography Area Effects: strong implications on conservation and biodiversity varying area alone can effect species richness Islands are great for studying (isolated and have boundaries) The theory of Island Biogeography 1) Individuals can immigrate more easily to islands that are close to mainland
2) Extinction rates are lower on large islands a. Increased arealower extinction ratesmore species
3) Species richness on islands represents a tradeoff between immigration and extinction affected by a. Island size b. Distance from mainland
*Important, because ecologists apply these concepts to conservation Applying the Theory of Island Biogeography to Conservation Diamond Proposes park designs to be: 1) larger 2) more connected (emulate increased size through migration) Simberloff argued that smaller more spread out would be better to more diversity of species. HOWEVER… disease can eradicate small populations edge effects of small areas have big impacts *Over the long term, species persistence is better in large parks Habitat Remnants can interact through Metapopulations Metapopulations: an assemblage of local populations linked by colonization and extinction
In theory, improving landscape connectivity should help conserve species. Global Biodiversity Patterns: Species richness is highest at the equator, why? MAJOR Hypotheses Rapoports Rule: species do not have to worry about season variability
capture
however species richness does not trend to mean climate directly
Glacial History: Many northern regions were covered in ice and not able to sustain life and diversify other factors more relevant Climate: species richness will increase with greater energy availability (heat/light) does a good job of explaining 7090% of variability in species richness Habitat Heterogeneity: increased habitat variability allows for different species to adapt to a region this is good theory for small areas, however climate over powers this theory on a larger scale Mid Domain Effect: species are limited by boundaries of each pole therefore naturally the center of both (equator) will contain the highest diversity of species. this pattern tested on islands does follow the effect however it is mainly a cause of edge effects
Climate Change Denier Strategies
repeat false arguments until they seem credible “truthiness tactic” use selective citations from literature distort scientific evidence in propogranda suggest scientists are apart of a conspiracy target audiences without scientific background
Claim 3 things 1) climate change is not happening 2) if it is happening it is not by humans 3) if it is by humans then its natural and good for us Scientific community must not continue to argue with deniers or else they will continue to fuel the fire on confusion as though the dispute over global warming has not been verified.
• Test by observation, experiment, and modeling Example: SCHINDLER • Study of eutrophication – what determines phytoplankton abundance • Question: what distinguishes lakes that are chlorophyllrich from lakes that are chlorophyll poor? What nutrients contribute to amplified eutrophication • Test IN FIELD – apply different combinations of different nutrients to various sections of lakes and observe • Must test in field rather than in a lab because of several factors o Underlying mechanisms driving ecological shift require the ability of microflora and fauna to shift in species composition as nutrient levels shift o Exchange of nitrogen and carbon with the atmosphere cannot be reproduced in lab • Determined that phosphorus was primarily responsible for amplified eutrophication
What do ecologists want to know about? total biomass • how much and why? • Biotic effects o neurotoxins produced by cyanobacteria o oxygen starvation due to bacterial activities o impacts on biotic communities • Harvestability o Forestry o Crops • Changes in biomass can affect biogeochemical processe o Effects on climate – transpiration by plants cooler climates and more precipitation o Effects on erosion and nutrient concentration ecosystem functioning • ecosystem – biological community plus all of the abiotic factors influencing that community • primary production fixation of energy by autotrophs in an ecosystem o gross primary production = total amount of energy fixed by all autotrophs in ecosystem o net primary production – amount of energy left over after autotrophs have met their own energetic needs – gross primary production minus respiration by primary producers = amount of energy available to the consumers in ecosystem • primary productivity (at a relatively local scale) o production of new organic matter, or biomass, by autotrophs in an ecosystem o CO2 organic matter o Base of food webs o Greater productivity leads to greater herbivore densities, but herbivores can also alter productivity • Primary productivity at a broad scale o Productivity varies spatially o Human impacts • Water cycling o Ecosystem wide importance – affects loss of nutrients through erosion, influences primary productivity o for individual plants – vascular transport o transitory precipitation can have massive effects on ecosystem functions
•
•
decomposition o replenishment of nutrients for primary production o breakdown of organic matter accompanied by the release of CO2 and other inorganic compounds, a key process in nutrient cycling biogeochemical cycles o nitrogen cycle – including nitrogen fixation o atmospheric constituents o pollination
species diversity • global scale o influenced by factors such as climate, evolution, etc. • local scale o effects on ecosystem functioning greater diversity = greater evaporation e.g. fields with weeds greater diversity = greater rate of regeneration of NPP following disturbance (e.g. drought) population size of a species • estimates of abundance have direct bearing on the legal status of species • abundant species vs at risk species o abundant species effect system e.g. grazing o disease vectors – lyme disease, rocky mountain spotted fever • hyper abundant species o can lead to widespread pesticide use o mountain pine beetle infestation • harvestable populations o abundance estimates/determines quota o bad estimates can be disastrous distribution of a species • geographic distribution, regional distribution • economic consequences o harvestable populations – are they capable of providing sustainable economic benefit? • Affects local species diversity • Influences biotic interactions
Chapter 2 Factors that influence ecological characteristics – independent factors – History, evolution – Physiological tolerance – Limiting resources – Biotic interactions (including competition, predation, and herbivory)
history, evolution • study of how organisms in a particular area are influenced by factors such as climate, soils, predators, competitors, mutualists, evolutionary history • slow changes on ecological(short) time scales • e.g. peppered moth (natural selection) physiological tolerance • often an optimal response curve to factors such as temperature
•
conditions that
L a k e T a h k e n it c h
1 .2
L a k e T a h k e n itc h , O r e g o n
P o p u la t io n g r o w th r a t e (d o u b lin g s p e r d a y )
P o p u la t io n g r o w th r a te (d o u b lin g s p e r d a y )
• limiting resources • resources – essential for individual growth o e.g. nutrients, light, water, space, etc o a resource can be consumed • Liebig’s law of minimum o The limiting factor is the one that an organism must concentrate the most relative to environmental concentrations (that it needs the most) o Amount required / amount available • If a factor limits population growth, rate of growth declines, biomass declines, and distribution is limited L i m i t i n g f oa c t E.g. photosynthesis – light reaction is limited by light, dark reaction is o rs E f f e c t o n p o p u limited by CO2 la tio n g r o w th r a te o f v a r io u s n u t r ie n t a d d it io n s t o t h e w a t e r o f • Limiting factors L a k e T La hi mk e in t i it cn hg f a c t o r s Eof f e c Effect on population growth rate of various nutrient additions to the water of t o n p o p u la t io n g r o w t h r a t e o f v a r i o Lake Tahkenitch u s n u t r ie n t a d d it io n s t o th e w a te r o f
1 .2
0 .6
L a k e T a h k e n itc h , O r e g o n
0 .6
0
C o n tr o l
1 .0 N
0 .0 5 P
1 0 .0 C
0 C o n tro l
1 .0 N
0 .0 5 P
1 .0 N + 0 .0 5 P
1 .0 N + 1 0 .0 C
1 0 .0 C
1 .0 N +
0 .0 5 P + 1 0 .0 C 1 .0 N +
1 .0 N + 0 .0 5 P + 1 0 .0 C
0 .0 5 P +
1 .0 N +
N u t r i e n t a d d i t i o n s ( m g / L ) i n d i f f e r e n c e 0e . 0x5 pP e r i m1 0 .e0 nC t a l 1 t0 r. 0e Ca t m0 . 0e 5 nP t s+ 1 0 .0 C
N u tr ie n t a d d itio n s (m g /L ) in d iffe r e n c e e x p e r im e n ta l tr e a tm e n ts
o
impact of nitrogen and carbon addiction is minimal to none, therefore its capacity to limit population growth is nonexistent – NOT the primary nutrient limitant effect of phosphorus is great – if you add nitrogen AND phosphorus it gets even a bit better, but since error bars probably overlap, it is hard to conclude that the nitrogen plus phosphorus is statistically significant o EXAMPLE lake of the woods, effect of nutrient additions i m i t i n Lg i fmoa ic t ti on gr s f a c t o r s E ffe c t o f n u tr ie n t a d d i t i phosphorus is primary limiting factor o n s o n p o p u la t io n E ff e c t o f n u t r ie n t a d d it io n s o n p o p u la tio n g r o w t h r a tge r oo wf tSh . r ca at e p or fisecondary limiting nutrient is nitrogen cS o. rc na up rt ui cmo r in n u tLu am k ei n L a k e o f t h e W oo of dt hs e W oo d stertiary is carbon
L
1 .2
0 .6
P o p u la tio n g r o w th r a te (d o u b lin g s p e r d a y )
P o p u la tio n g ro w th ra te (d o u b lin g s p e r d a y )
niche is defined by the totality of environmental a species can tolerate influences geographic range enormously
1 .2 L a k e o f t h Le aWk eo o fd ts h, eO Wn to ao rd i so , O n t a r i o
0 .6
0
0
C o n tr ô le
C o n trô le
1 .0 N
1 .0 N
0 .0 5 P
0 .0 5 P
1 0 .0 C
1 0 .0 C
1 .0 N + 0 .0 5 P
1 .0 N + 01. 0. 05 NP +
1 0 .0 C
1 .0 N + 0 .0 5 P + 1 .0 N + 1 0 . 0 5C P + 1 0 . 10 . C0 N + 0 . 0 5 P + 1 0 .0 C 0 .0 5 P + 1 0 .0 C
N u t r i e n t a d d i t i o n s ( m g / L ) p e r e x p e r i m e n t a l t r e a 1t m0 . 0e Cn t
N u tr ie n t a d d itio n s (m g /L ) p e r e x p e r im e n ta l tr e a tm e n t
o EXAMPLE – mussel – limited by space availability, cannot be too high where water wont reach or predators will eat, cannot be too low where they cant gain nutrients – must attach to rock and be wet enough
biotic interactions – competition • interspecies – between species; intraspecies – within species • fundamental vs realized niche o fundamental excludes the effect of biotic interactions like competition o realized is smaller than fundamental, as resources are less available and the spaces that they can occupy are inhibited by negative impacts of biotic interactions o one species will dominate over another so realized niche of the dominated species shrinks, while the fundamental niche of the dominating species remains the same • example: c4 = water use efficiency grater in c4 plants (can close stomata in leaves while continuing to do photosynthesis) so c4 plant will slowly drive out c3 plants in hot and dry places
• •
–
example: new guinean bird distribution o species divide the habitat they occupy according what other species are already there o when species are all present on the same island, they subdivide the habitats among them o different colours represent a different species o in some areas, a particular species is able to occupy any habitat, but when there’s competition, they will only occupy a certain area according to its competitive capability predation and herbivory • example: Yellowstone national park in the US; an enclosure to keep out big grazers from an area containing plants o big grazers have a major role in shaping the structure of the ecosystems and the species diversity o there are so many big grazers because the wolves have been killed by humans so the grazers have no serious predators so the populations have reached epidemic proportions • example: sugar maple distribution in N.A. o why doesn’t this range extend further north,south, or west?
Temperature wintertime temps are too low along and above the northern border – you can test it by transplanting trees from within the range to areas beyond the range Precipitation – western range margin is limited by lack of precipitation in the prairies
o
o southern border may be limited by hot temperatures, also may be limited by competition – a more dominant species that can’t endure winter is present south and will beat out sugar maple
P ro b le m
o Solar radiation – maximal at 0•. maximal at 30•N and 30•S o Climatic variation is caused by uneven heating of its surface by the sun
E n e r g y – g l o b a l s c a le
P ro b le m
a te r
M n
nw
K
e nt ra t i oni
example: one adds a solution of Mn, K, and Si to a seawater sample containing phytoplankton. The concentrations of these elements changes according to • O n e a d d s a s o lu tio n o f M n , the graph. What conclusions can we draw? – silicon is K , a n d S i to a s e a w a te r probably a limiting nutrient s a m p l e c o n t a i n i n g p h y to p la n k to n . T h e c o n c e n tra tio n s o f th e s e Large scale patterns of climatic variation e le m e n ts c h a n g e s a c c o rd in g to th e g ra p h . W h a t Major Physical Properties of Terrestrial Ecosystems c o n c lu s io n s c a n w e d ra w ? Energy – global scale
Si Conc
•
T im e a fte r n u trie n t a d d itio n
Hadley cell – air moving from 30 latitude back to the equator – sun heats air at equator , warm moist air cools, condenses, heavy rainfall (tropics) – stops rising spreads north and south, dry high altitude air cools and sinks back to earth at 30•latitude dawing moisture from lands, creating desert
G ro w th ra te
Polar cell air warms at 60• latitude • P o p u l a t i o n g r o w t h r a t e and cools at poles – primarily s o f a p l a n t s p e c i e s v a r i e responsible for the weather patterns s a c c o rd in g to th e associated with most northerly and 0 c o n c e n t r a t i o n o f t w o southerly areas, bringing cold from n u t r i e n t s s h o w n o n t h e poles rig h t. In te rp re t th e s e Ferrel cells – mid latitudes – driven re s u lts . partially by effects of Hadley and C o n c e n tr a tio n
polar cells – warm,
o moist air flowing from Hadley cells rises as it meets cold air flowing from the polar cells – as this air mass rises, moisture picked up from desert regions at lower latitudes condenses to form the clouds that produce the abundant precipitation of temperate region o air movement would be north.south if it weren’t for the west to east rotation of the earth
o Wind – between 30 to 60 flows mainly from the west (westerlies), higher than 60 seems to come from the east (polar easterlies) o Seasonality varies with latitude – as you move towards equator: Mean increases for temperature Variance decreases More land mass in northern hemisphere, easier to change temperatures of terrestrial systems because land will heat and cool faster than water o Coriolis effect – phenomenon caused by the rotation of the earth, which produces a deflection of winds and water currents to the right of their direction of travel in the Northern Hemisphere and to the left of their direction of travel in the Southern hemisphere o Advection of heat Transfer of heat in a fluid • Ocean currents • Atmospheric circulation Precipitation Maximal precipitation at 0 degrees Minimal precipitation at 25•N and 25•S Orographic effects • Mountain ranges, air is forced upward, cools and condenses, releases rain at low elevations and snow at high elevations, by the time the air reaches the other side of the mountain range it is very dry, so the land on the leeward side o the range does not get a lot of precipitation At equator we have relatively substantial amount of tropical storm patterns that emerge – Hadley cell is just beginning Typhoons in south east asia have accumulated energy from all the way across the pacific ocean which is way bigger than the atlantic so typhoons are way bigger and more devastation than hurricanes that hit the gulf coast of north America Hurricanes track coreolis effect – as they move northwest towards the gulf coast, they start to turn to the north east, away from land again, sometimes it hits the land sometimes its diverted before contact o Evapotranspiration The sum of water evaporated and transpired from plants in a community and its Influence on rates of primary production AET – actual evapotranspiration • Total amount of water that evaporates and transpires off a landscape during the course of a year • Is measured in mm of water per year • Is affected by both temperature and precipitation • Highest levels of primary production are those that are warm and receive large amounts of precipitation • Lowest levels of AET either because of little precipitation, are very cold, or both o E.g. hot deserts and tundra exhibit low levels of AET PET = potential ET from saturated surface • If evaporation was happening as fast as possible and transpiration was happening as fast as possible AET = actual ET ET, given that water may be limiting, integrates water supply and heat • Given the amount of water that there is, how much actually happens • Water deficit: PETAET
geographical distribution of factors limiting primary productivity
N e m a n i e t a l 2 0 0 3 S c ie n c e 3 0 0 :1 5 6 0
Climate diagrams Developed by Walter as a tool to explore the relationship between the distribution of terrestrial vegetation and climate Summarize a great deal of useful climatic info, including seasonal variation in temp and precipitation, the length and intensity of wet and dry season, and the portion of the year during which average minimum temp is above and below 0• STRUCTURE o X axis: months of the year (jandec for northern hem; juljune for S. hem) o Left Yaxis: temperature o Right Yaxis: precipitation o Zeroes of left and right Yaxes are even o Every 10• Celcius that the scale goes up is equivalent to 20 mm of precipitation that the scale goes up o Climate diagrams for wet areas such as tropical rain forest compress the precipitation scale for precipitation above 100 mm so that 10•C changes are equivalent to 200 mm of precipitation o months where average low temp is above freezing can be indicated o mean annual temp is in upper left corner o mean annual precipitation is in upper right corner o elevation of the site in meters above sea level is also in upper right corner READING IT o Adequate moisture for plant growth occurs when precipitation line is ABOVE temp line o When temp line is ABOVE precipitation line – potential evaporation rate exceeds precipitation so it is a dry period
C lim a t ic c h a n g e s 1 9 8 2 1 9 9 9
T e m p e r a tu re
Nutrients
nutrients in the soil o poor in tropics (all leached into the biomass), and in regions where the underlying rock in insoluble (granite) o Rich in regions with soluble underlying rock (sediments)
Light
aspect escarpments are capble over receiving a lot of light to its understory
Biological Consequences of Physical Factors Spatial Distribution of Organisms
Global Scale (Biomes) o Mixedwood plain (south eastern ontario) Very high biological diversity, high population densities Rich soils, mild climate Vegetation: mostly deciduous (maples and oaks), some conifers (white pine) Fauna: Deer, squirrels (carnivores exasperated) o Boreal Shield (stretchs across northern Ontario, Quebec, and Manitoba) Soils very nutrient poor (insoluble granite) Many bogs due to poor drainage Glaciation shaped landscape Dry due to rocky mountains (many forest fires) Vegetation: Conifers (Fir, Spruce), Deciduous (birch, aspen) Fauna: Moose, beaver (carnivores remain)
Biomes: Prediction depends principally on temperature and water availability Primary Productivity incorporation of CO2 into the plant biomass result of all of the photosynthesis that occurs in a plant community Factors Controlling Primary Productivity Global Scale positively related to temperature and precipitation
substrate (nutrient availability)
Local Moisture, sun, nutrients (NPK)
Regional
Physical Properties of Aquatic and Marine Ecosystems Trophic Status Concentrations of Nutrients Oligotrophic Low Mesotrophic Medium Eutrophic High *Result of… 1) Substrate: runoff through sedimentary rock are nutrient rich, runoff through granitic is nutrient poor 2) Human Activities agriculture (usually non point source) water use (usually point source) Ex. If P concentrations above 20 mg/m3 create too more chlorophyll, calculations may be made to check the maximum allowable P for a particular lake. Lake Volume= area x avg. depth Maximum P= lake volume x [P] threshold Relative to 1 person= Max P/(human impact in mg) *** can be mitigated by simple calculations dilution of discharge loss of nutrients from discharged water into soil sedimentation of particulates agricultural impacts are much more intense Factors that Vary within a particular lake Density of water o Temperature Ice less dense than 4 deg. Water (ice on surface) o Salinity Oxygen solubility increases at LOW temp Salt solubility decreases at LOW temp *In eutrophic lakes, Oxygen Levels decrease at deeper depths due to oxygen consumption by decomposers of fallen dead algae AND less respiration from rooted plants on the seafloor
o Vertical Stratification
Chemical Properties
increased oxygen
Ex. Light intensity problem A species energy production drops below respiration energy consumption for a river if the light intensity goes below 10 j/m2. Surface light: 320 J/m2s Coefficient of loss: 1.5 m1 Compensation point? Z= 1/k (ln(I0)ln(Ik)) = (ln(320)ln(10))/1.5 =2.31m Therefore the species cannot persist under 2.31 m *All of these effect euphotic zones of lakes Euphotic zone: zone of light availability (photosynthetic activity)…. Vary with trophic status Aphotic zone: zone of no light availability (no photosynthetic activity) Factors that vary within marine ecosystems Morphometry extent of euphotic zone? How large is watershed? How long is fetch? (affects thermocline and wave height) o Wind forces warm waters down and pulls colder waters up (el nino, la nina) Consequences 1) Vertical Distribution of Plants Macrophytes phytoplankton 2) Vertical Distribution of Fish 3) Geographic Distribution of Phytoplankton in freshwater in the ocean
Population all individuals of a given species Population= F(environmental conditions) Abundance: total numbers of individuals
Population Density: number of individuals per unit space
Calculating Population Estimate Count species in quadrats or transects Abundance Total= (total area/quadrat area) * (Sum of species/number of quadrats) *Uncertainty can be variation among quadrats (spatial dist. of species: random, uniform, clumped) Variance: reveals uncertainty of population sample… ́ 2 2 ∑ ( X −X ) S= n−1 Sampling Populations
Mobile Organisms o Use MarkReleaseRecapture method o Able to predict populations depending the populations of marked organisms recaptured o Population= (Sample 1 Marked)*(Sample 2 total)/(Sample 2 Marked Recaptured)
on
Prediction of Abundance of Species based on Environmental conditions estimation by availability of limiting nutrient estimation by habitat characteristics 2 R =¿ estimate of how strong predictions are in terms of being the function of population abundance (1 being perfect prediction)
*there are many factors that affect population dynamics (biotic interactions, temporal variation, etc) Population Growth Population= Nt = Nt1 + birth – mortality + immigration – emigration **Within a Community we can eliminate Immigration and emigration to 0 Discrete Generations Geometric Growth N(t) = N 0 λt growth happens in generation stages ❑ λ = N(t)/N(t1)
Continuous Growth (Exponential) N(t) = N 0 ert growth is continuously occurring
❑ ❑ λ = e r , therefore ln( λ )= r
linearization of the exponential growth gives r the slope and t variable
Logistic Population Growth N dN/dt= r max N 1− K
(
)
population growth cannot continue forever at large population sizes growth will be slowed by competition and/or increased mortality
intraspecific
K (carrying capacity) depends on resource availability, r depends on the characteristics of the organisms in its environment Many Factors affect the r value (ex. Growth rates vs. body size: The larger you are the slower grow, and oppositely the smaller you are the faster your
your population will population will grow)
*Logistic growth typically seen when a species is introduced into a new locale (ex. Sheep of Tasmania, pheasants to protection island) or when they are in a bacterial culture where environmental conditions are predictable and constant. Delayed Logistic growth
(
dN/dt= r max N t 1−
N t−d K
)
Population growth can depend on previous populations and the carrying capacity (K).
Hypotheses of Regulation and Growth
extinctions are rare (in nature) populations converge towards a particular value
When Population Density is High birth rate decreases (ex. Less eggs per clutch, less number of clutches)
oscillate around
Mortality rate increases (ex. High initial density yields less survivors) Emigration increases (ex. High initial density yields more spread emigration of species)
** and vise versa when populations density is low Density Dependence VS. Inverse Density Dependence
Density Independent Factors
factors that kill the same proportion of the population no mater what the density is EX. Fire, extreme weather, accidents (environmental stochasticity) Do not pull the population towards a stable density
Ex. Thrips population depend predictably on the weather Density Independent and Dependent Factors interact in the real world Ex. Allele effects such as reproductive failure occurs among very small populations Mortality Rates Depend on Density Age Climate Birth Rates Rates Depend on Density Age Year (some species can reproduce earlier than others) Juvenile Survival Rates Depends on: Density (ex. Sheep birth weight decreases with high density) Temperature (ex. Deer birth weight increases with increasing temperature) Predicting Abundance
∗( probability of survival ) ( fecundity adult )
N t , a=N t −1,a−1∗( probability of survival )+ N t−1,a−1∗ Total Abundance= N t =
∑ Na
Prediction of Abundance Requires initial abundance age structure mortality as a function of age, density and environment age, density, and environmentdependent fecundity survival rates of young Human population Growth Exponential Growth: constant through time Logistic Growth: diminishes through time HyperExponential Growth: increases through time *On weight vs. population density graph we are off of the trend (have densities similar to that of mammals with body sizes of 1kg) Malthus Prediction: Our exponentially growing population will eventually out grow our resources (crops) and limit our growth. productivity per hectare of has increased, more than population until NOW (not everywhere ex. Africa) Projected Future Growth 1 person added every second, 1 hectare of agriculture lost every 7.67 seconds HYPEREXPONENTIAL growth of humans due to increased birth rates and decreased mortality rates o Ex. Reduced rates of infectious diseases such as AIDS The demographic transition Mortality decrease: due to improved hygiene and clean water (simple medical and civil innovations) Natality decrease: due to improved economic conditions (financial security, based on cost benefit considerations) Average Income (per capita GNP): increased GNP/income decreases birth rates Income equality/inequality causes rates to vary from general curve Perfect equality : wealth shared Perfect Inequality : 1 person owns all the wealth Gini Coefficient : area of the deviation from the 1:1 line as a proportion of the different between perfect equality and perfect inequality • LOW value= more equality • HIGH value= more Inequality Education Ex. Countries in poverty experience increased births Reducing Population Growth Contraception voluntary (ex. India giving out birth control) o didn’t work
coersive (ex. China one child law) o did work but with human rights issues
Social Programs (ex. Sri Lanka) can work but costly Ecological Footprints area of productive land required to support each person with resources to sustain their lifestyle o Ex. Food, transport, manufactured goods, energy etc.
I=PAT o o o o
I: environmental impact P: population size A: affluence T: technology
Environmental scarcity occurs from either 1) demand induced scarcity: population growth in a region demands more 2) supply induced scarcity: supplies degrade to low levels 3) structural scarcity: occurs from unequal social distribution of resources OFTEN ALL OCCUR SIMULTANEOUSLY AND INTERACT Canadian Footprint: 5.3 Hectares/ person North America dominates rest of the world in terms of average footprint if the rest of the world followed these standards we would need 3 worlds for sustainability Stern Report Summary: States that early action on reducing the rate of climate change now will undoubtedly outweigh the potential costs in the future. Right now climate change is manageable however in the future if no action is made it will be too overwhelming to overcome. Fresh water supply by 2025 more than 3 billion people will live in 48 countries under water stress Maximum Carrying Capacity for Humans current population: more than 6 billion Optimistic Capacity: 15 billion Level off at about 9 billion
Biotic Factors on Population Interspecific Interactions: species interaction with other species Intraspecific interactions: species interaction within its population 1) Resource Competition a. When a resource is in limited supply i. Result of niche overlap (this competition creates difference between fundamental niche and the realized niche) ii. Within a niche, the presence of other species competitors decreases the population of both (realized niche shrinks)
2) Interference Competition a. Direct harm to other individuals Theory of Limiting Similarity: if two species niche overlap is too great, competition drives one to extinction called competitive exclusion *Explained in LotkaVolterra equations
(
Logistic equation: dN/dt= r max N 1−
N K
)
When a competitor is introduced the population growth decreases in the strength of the competing species
proportion to
d N1 =r max1 N 1 ( ( K 1−N 1−α 12 N 2 ) /K 1 ) dt d N2 =r max 2 N 2 ( ( K 2−N 2−α 21 N 1 ) / K 2 ) dt α 12 : is the effect of individual of species 2 on the rate of species 1
pop. growth of
α 21 : is the effect of individual of species 1 on the rate of species 2
pop. growth of
Ex. If deer is a weak competitor to moose, deer could have a α 21 = 0.5 which means that 100 deer would have the same competitive impact as 50 moose. When we equate growth to zero we can determine the equilibrium size of a species when the competitor is absent.
population
N 1=K 1−α 12 N 2 N 2=K 2−α 21 N 1
therefore when N 1=¿ 0, N 2=
K1 and when N 2=¿ 0, α 12
N 1=
K2 α 21
*When one species isocline is entirely above another, the lower species disappears (competitive exclusion)
immigration/emigration stable age structure
LotkaVolterra
Example
Mathematical the describe with
Models simplify phenomenons they assumptions
LotkaVolterra no
is no different
genetic factors are constant no time lags in population impacts no environmental variation (constant carrying capacity) all competition coefficients are linear with population density of competitor logistic growth
* the intensity of competition varies with resource availability Tilman Resource Mechanism most successful competitor is able to reduce the availability of a limiting resource to a loser level R*
*Evidence of Tilmans theory is seen with the Asterionella and Cyclotella both coexist at balanced supplied of silicate and phosphate, only Cyclo. survives in HI phosphate low silicate, and vise versa for Aster. Niche Partitioning: species have sufficient phenotype pasticity to alter their resource usage to avoid competition. Classic Example:
Finches in the galapacos o All evolved from a common ancestor to the isolated islands
that somehow made it
6 forms of Competition 1) 2) 3) 4) 5) 6)
Consumptive: exploitation of food Preemptive: competition for space Overgrowth: growing over or on another rindividual (selfthinning, canopy vs. understory) Chemical: allelopathy Territorial: aggressive defense or intent to defend a unit of space (similar to preemptive) Encounter: interaction between mobile organisms that harm one or both.
Ghost of Competition past: many species may no longer compete today due to evolutionary change (character displacement) Diffuse Competition: many, weak, pairwise interactions that are hard to detect individually as density of plants increases (biomass), diffuse competition increases
Competitive Release: increased productivity, distribution, and abundance for a species that has just driven a competing species to extinction. Diamonds Assembly Rules 1) Some pairs of species should never coexist (by themselves or as a part of a larger group) 2) Species occurring together should have a lower niche overlap than species do at random due to character displacement Ex. Tested on the islands for New Guinean birds, drosophila, as well as cogeneric bird species in rainforest aren’t found in same habitat.
Predation & Herbivory Herbivory organisms consuming plant species o affect plant communities o affect other organisms habitats New niches for herbivores may have caused the evolution of most of the worlds species World stays Green from 3 possible ways… 1) Bottom up control of herbivory by plants a. Using chemical defenses (phototoxins etc) 2) Top down control of herbivores by predators 3) Herbivore populations cannot track the plant resource Predation organisms consuming prey organisms able to track prey (seen is Lotka Volterra Models) prey and predators coexist and their populations fluctuate cyclically is the environment offers refugia Disturbance and Succession Succession Primary Succession : the chronological change of a biotic community in a newly established area Secondary Succession : chronological change of a biotic community following disturbance Early Successional Species strong dispersers/competitors for nutrients
allocate resources to roots function for climax species: enrich soil with N *low nutrients, high light Later Successional Species less good at dispersal but increasingly good competitors for light allocate resources to shoots *more nutrients, less light Intermediate Disturbance Hypothesis species richness is a maximum when the frequency of disturbance are at a medium
works in theory, however statistical data cannot support the theory
Island Biogeography Area Effects: strong implications on conservation and biodiversity varying area alone can effect species richness Islands are great for studying (isolated and have boundaries) The theory of Island Biogeography 1) Individuals can immigrate more easily to islands that are close to mainland
2) Extinction rates are lower on large islands a. Increased arealower extinction ratesmore species
3) Species richness on islands represents a tradeoff between immigration and extinction affected by a. Island size b. Distance from mainland
*Important, because ecologists apply these concepts to conservation Applying the Theory of Island Biogeography to Conservation Diamond Proposes park designs to be: 1) larger 2) more connected (emulate increased size through migration) Simberloff argued that smaller more spread out would be better to more diversity of species. HOWEVER… disease can eradicate small populations edge effects of small areas have big impacts *Over the long term, species persistence is better in large parks Habitat Remnants can interact through Metapopulations Metapopulations: an assemblage of local populations linked by colonization and extinction
In theory, improving landscape connectivity should help conserve species. Global Biodiversity Patterns: Species richness is highest at the equator, why? MAJOR Hypotheses Rapoports Rule: species do not have to worry about season variability
capture
however species richness does not trend to mean climate directly
Glacial History: Many northern regions were covered in ice and not able to sustain life and diversify other factors more relevant Climate: species richness will increase with greater energy availability (heat/light) does a good job of explaining 7090% of variability in species richness Habitat Heterogeneity: increased habitat variability allows for different species to adapt to a region this is good theory for small areas, however climate over powers this theory on a larger scale Mid Domain Effect: species are limited by boundaries of each pole therefore naturally the center of both (equator) will contain the highest diversity of species. this pattern tested on islands does follow the effect however it is mainly a cause of edge effects
Climate Change Denier Strategies
repeat false arguments until they seem credible “truthiness tactic” use selective citations from literature distort scientific evidence in propogranda suggest scientists are apart of a conspiracy target audiences without scientific background
Claim 3 things 1) climate change is not happening 2) if it is happening it is not by humans 3) if it is by humans then its natural and good for us Scientific community must not continue to argue with deniers or else they will continue to fuel the fire on confusion as though the dispute over global warming has not been verified.
