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Lecture

Lecture 1 - 23 and Nature article readings

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Department
Biology
Course
BIO120H1
Professor
James Thomson
Semester
Fall

Description
Lecture 1 Content Abiotic Factors (for success)  Resources (are exhaustible): nutrients and space  Conditions (are not exhaustible): Temperature, pH o Vary across space and time  All organisms perform best at certain levels. o We expect organisms need a range of tolerance o From Survival  Growth  Reproduction Most important factors that limit distribution?  For terrestrial Plants (most important to least): o Temperature (this and soil are most important) o Soil moisture o Nutrients (N most important, then P, K) o Disturbances (esp. fire) o Disease, pollinators, etc etc)  For Terrestrial animals o Food and water o Temperature o Habitat quality o Predation, disease o Tend to follow plants Variations in the Above Factors  Temperature is a function of latitude o High latitude are colder, and seasons depend on temperature o Lower latitudes are warmer, and seasons depend on rainfall  Rainfall depends on atmospheric circulations Lecture 2 Content Heat Balancing  Size o SA:Volume ratio o SA determines the equilibration rate o Volumes provides the inertia o THUS, big things with huge ratios will equilibrate slowly compared to smaller things o Bergmann’s rule  Homeotherms are larger at higher latitudes (colder)  Duh, cause you don’t want the outside environment affecting their inner environment quickly. Low SA:V ratio  Shape o Allen’s rule  Appendages (anything outside the body) is reduced in cold climates  So technically why isn’t everything a sphere? Lowest possible SA:V  Well we need some SA for function  Hot environments you want to lose heat therefore want large SA, you typically find flat animals in hot environments  (flying snake)  (pika’s very minimum SA:V ratio as they form a sphere and curl up into a ball, small ears as well, good for cold habitats so you don’t lose heat as quickly)  Insulation (more important than size/shape) o Hairs, feathers, blubber  Vascularization o Like the hare, can use blood vessels in ear to dump heat into the environment  Countercurrent circulation o Used to conserve heat o So if you have a small distance from arteries and veins, (appressed vessels) then returning blood can be warm due to gradient  If vessels are not appressed then returning blood is chilled  Convection and Evaporation Lecture 3 Content Why doesn’t natural selection produce perfect species?  Weasel body shape o NS does not produce perfection o Short furred, but very long and thin  High SA:V, and they curl to a flat disk (higher SA compared to balls)  Yet they live in cold climates Why? o Remember, Constraints and Tradeoffs  Weasels trade off a low SA:V shape/size so that they can fit in narrow burrows to get food  Like the pocket gopher  Basically, being thin has more fitness gains, then the fitness cost of an expensive metabolism to staying warm due to higher SA:V ratio o THUS, NS can’t maximize everything, but gives you the best option  2 reasons o 1) Tradeoffs  Being good at (x) doesn’t mean being bad at (y) o 2) Constraints  NS can only build on what is already there  Example: can’t just make wings out of nothing for humans  NS can tinker, but cant redesign Kangaroo Rats  Osmotic Balance (conserving water in hot dry envivronments) o 1) Bipedal, thus less heat gain from conduction from the ground o 2) Super efficient kidneys and metabolic sufficient  Can make fat into water so they don’t need to go drink water, just need fat as a food source o 3) Nocturnal  Spends hot days underground o 4) Cache seeds  They put seeds underground that recapture water vapor from exhalation from the k-rats! When Physiological Stress becomes Overwhelming  Enter dormant stage with minimal metabolism (refer to Torpor)  Hibernate  Store Food  Migrate  Both migration and Hibernation are driven by food supply than abiotic stress Lecture 4 Content Plant Ecophysiology of Carbon Balance  Autotrophs depend on net photosynthesis o CO2 + H2O  Carbohydrates + O2 o Must take in light, gases and water into photosynthetic tissue  Requires a range of temperature, osmotic balance, enzymes, and nutrients from soil (N,K,P) o Ultimately, the anatomy and physiology of plants will reflect constraints Plant Structure  Photosynthetic structures o Normally the leaves, but can be stems o Leaf size and shape  Are thin and flat (thus high SA:volume ratio)  Benefits, would be great SA for photosynthesis  Costs, would be bad for overheating, and water lost  Can also influence gas exchange through laminar flow vs. turbulent flow  Plants don’t want stream line flow (laminar) because there is a boundary layer, that decreases the velocity of air  Want turbulent flow so you get eddies, that eliminate the boundary layer  Thus, keeps the plant cool and lots of gases for exchange  You’ll see leafs with holes, used for turbulance o Stomata  Will open and close  Closes so that the leaf won’t lose water, but then it can’t cool the leaf either. Shuts off all photosynthesis  Opens to cool the leaf, but loses water to the environment  Examples: o Deserts you have plants with very small leaves (microphylly) like the Palo Verde (green stick)  It photosynthetic bark and trunks, so that it can grow without heat load/water loss from the leaves o Cacti  Shallow roots, but wide spread out. REALLY far  Reasoning is that water is episodic in desert, so if you have wide spread out roots you can get the most once it rains.  Saguaro Cactus  Accordion-pleated trunk to allow expansion  Can absorb 800L of water to store it for growth Plants Evasive Strategies  Deciduous habit o Dropping leaves during dry or cold reasons to reduce water stress and tissue damage Epiphytes  Grow on trees, thus can’t put roots into the soil, causing water/nutrient stress o Thus needs an environment with lots of rain o You see convergent evolution with epiphytes and cacti  They have water storage abilities  Sponge, Tank, succulence (like cacti) Mesophyll and Sclerophyll Large Leaves Small Leaves Thin, and flexible, papery Thick needles or scales High SA:V Low SA:V Frequently deciduous, last only for 1 season Frequently evergreen, for several seasons Maples, oaks, etc Coniferous tress, pines, firs, spruces Paradox  Plants with Sclerophyll leaves common in 4 situations o 1) Boreal forests (high altitude and latitude)  Thus, very cold and moist soils o 2) Pine Barrens  Hot summers, dry sands, acid soils o 3) Maine bogs  Cool summers, wet, avid soils o 4) Mediterranean heaths  Dry hot summers  Wow so many climates wtf? o A) small leaves (low SA:V) good for dry habitats, so you don’t take in heat from the environment  Seen in (2,4) o B) Winter green needles allow photosynthesis in warm spells  Seen in (1) o C) Converses nutrients in poor soils, by not dropping leaves and making new ones, thus saves nitrogen  Seen in (all) Lecture 5 Content Population Ecology  Collection of individuals o Population size = N  N is added by sex, subtracted by death o Population Density = N/Area Population Models  To predict what happens to the population as a function of t  Nt= how many individuals in a population now  Nt+1= how many individuals in a population one step later  So N t+1 F(N)t  N0= starting time  Use Differential Equations when growth is smooth and continuous reproduction  Use Difference Equations when time steps are discrete units, for episodic reproduction So how does N t+1hange?  Due to death, birth, emigrate and immigrate  So N t+1 Nt – D + B – E + I  Simply it, we assume no immigration and emigration  Treat birth and death during on time step as per-capita rates (how many (x) in a population) that are fixed constants  λ = population change over one time so a “growth rate)  If λ >1 then birth exceeds death o If its <1 then deaths exceed births o If it = 1 then birth and deaths are the same  Nt+1= λ x N t  This is the Geometric Growth! Another Version t  Nt= N 0 λ o Geometric growth is λ > 1  Graphing: same curves, but step functions  And obviously if λ <1 then population has death exceeding births therefore population dies exponentially  Nt= N 0 rt o Exponential growth if r > 0 (if r=0 then population is 0) o Graphing: if r is Positive then growth increases exponentially, depending on the size of r, the higher the number the steeper the slope (growth rate)  If r is negative then death exceeds birth, so population dies exponentially  Conclusion o Both exponential and geometric models have similar outcomes and can both be called exponential growth o HOWEVER,  Both models use a constant growth rate, therefore the population size will EXPLODE. Very bad  But all populations have the potential for positive population growth, and negative population growth o But no species has ever mainted a positive or negative λ for a long period o Mechanisms in nature will stop this growth (density dependent models) o Density dependent will regulate growth o Density independent will cause reduction Classically d,d, growth modeled by logistic equation  Start with rN, (exponential growth) but added stop factor (K-N)/K o rN*[(K-N)/K]  K = carrying capacity of the environment o Resources required for the population to grow  So at N = 0 then there is no breaking at low density populations, because K = 1, o But as N approaches K then K becomes 0 which will break growth  If you solve this equation for t, it gives us a sigmoid growth curve o So you start with exponential growth, but at an inflection point, the population will start reaching the carrying capacity, slowdown in growth and plateau (figure 1)  However, not always sigmoid, only when starting with a low population size N0 o But everything will level off at K (figure 2)  So when is the population growth rate the highest? o When N=K/2 (inflection point)  This is where population growth is maximized  that doesn’t mean that population is the best  Best place is actually when population is at 0 because most resources Logistic Model: Good and Bad Features  Good because it is simple (only one extra parameter (K) beyond exponential) o Can be used to consider multispecies competition  Bad because it’s too simply, only one kind of density dependence o Always a gradual approach to carrying capacity Alternative forms of Braking  1) [(K-N)/K]^z o When z >1 then braking increases as it approaches K o If z<1 then braking decreases as it approaches K  2) Time-delayed o Adds time lag o So time lag before population responds to carrying capacity  The population will overshoot o As time delay increases (t – Ʈ) the population will never reach carrying capacity, just overshoot it and crash. Lecture 6 Content Typical Life-History for Higher Plants and Animals  Start life at a small size  Grow for a period without reproducing (resource accumulation)  Then mature and spend resources on reproduction  Not all organisms have the same capacity for sex/death  Use Age-structured population growth models o Still for a single population, but now reproduction and survivorship vary with age  So age specific rates (no longer constant) o Implication for  Evolution of life histories  Conservation of populations  Human Affairs Fecundity Schedules  b x number of daughters born to female of some age during the interval x to x+1 o Shape of this curve will be different based on species  The tradeoff of is that as fecundity increases, then more resource accumulation used for that, less for survival therefore increase death chance.  R 0s the number of daughters a female has in her lifetime (net reproductive rate) o Thus R = 0L * bx x  Makes sens due to Lx will help discount all the mothers that die early before reproduction  Generation time T o Average age at which a female gives birth o T= Ʃ*x*L * bx/ R x 0  X is female age, so you know how many offsprings are produced at that age when multiplying it by Lx and bx. Then divide that by the total lifetime reproduction to get generation time. t t  Remember R = λ0(λ is growth rate at a time interval, instead of a generation unlike R0)  Organisms with higher λ have higher fitness, so why aren’t all plants annuals and mammals like mice? Live short and fast lives? o Because reproduction is costly, longer reproduction periods allow times to accumulate resources Life Tables  v xs reproductive value, expected number of future daughters left to an individual of some age. o Humans this is typically highest at late teens. And lowest at older ages and really young years  So we use v xor captive breeding/releasing, and dispersal to new habitats  Want to maximum v bexore doing the above Antagonistic Pleiotropy  Theory of senescence o Why do we die?  Pleiotropy o One gene has multiple functions  Antagonistic Pleiotropy o Gene that has one effect may have opposite effects at different ages o So positive when young, negative when older o Force us to reproduce early o Accumulations of these genes cause death (p53 gene that prevents tumours when young, but later kills stem cells) Lecture 7 Content Classifications of Species Interactions  Types of interactions are classified as + or – by who suffers and benefits o Consumer-resource (+/-)  Predator-prey  Plant-herbivore  Host-parasite o Competition (-/-)  Both species share the same resource o Mutualism (+/+)  Both sides are helped  Lotka-Volterra Equations for two species competing for resources o Logistic model already has a braking term for intracompetition, now just add a second one for interspecific competition between species o r N1*[1K -N1-α 1 )12 2, r 1 *2(K2-N -α2N 2/K21 1 2 o So in the above example α N i12br2king from species 1 by species 2 o α = competition coefficient o If a=0 then no competition o If =1 then same competition o If <1 small competition o If >1 big competition  Some possible outcomes o Two species may coexist (only if both species inhibit their own growth more then they inhibit each others) o Species 1 may always when (N1=K1, N2=0) o Species 2 may always when (N2=K2, N1=0) o May depend on starting of N  Complete competitiors or Law of Competitive Exclusion o You would assume that you can never coexist  But various external factors will prevent even unstable competition from going to completion  Example: Gause Experiments  Saw both coexistence and comeptitve exclusion o Predator-prey was unstable  Predator eat up all pray then starve  UNLESS habitat complexity was added Competitive Effects manifested in Nature  Two species are less likely to habitat same area  Natural selection select for higher competitive ability or for reducing resource-use overlapping  You won’t get competitive exclusion unless both species get near carrying capacity o And environmental effects will always prevent near carrying capacity  Cycling of L-V Models for predator-pre o Prey reproduces, lots of food for preds, now preds reproduce, a lot, killing off almost all prey, lack of food for preds, pred starves  Example: Lynx and hare o But in reality its more complex  Quality of plant, hares also may be cycling with plants (therefore probably not just the lynx that cause hare to crash)  Social stresses in overcrowded populations  Niche differentiation theory o Coexistence by niche differentiations to prevent competition exclsuion o So, competition increases if big overlap of niche  Called niche partitioning  Example: Warblers, all in same coniferous trees, but not high ’s due to co-existence through resource partitioning  Using different parts of the trees o For this to occur  1) Limiting similarity  Niches had to be different  2) Resource partitioning  Dividing of resources  3) Assembly rules  If A is established in an area first B cannot establish  4) Character displacement  Coexisting similar species evolve differently  All happen at high densities without abiotic factors so not really reality o However, proven as a wrong theory too simple  Island Theory o So L-V model, but on different islands, thus, different islands are at different stages, and dispersal possibilities  So globally it’s a stable population o This is called metapopulation structure  Allows predator-prey coexistence o Requires 2 things  1) A must sometimes go extinct in a patch OR new patches must be created from time to time  2) B must be better disperser then A  So B must be able to disperse away from A o So co-existence possible due to different life histories K Strategy (can outcompete) R Strategy (can get to different islands) Slower growth Faster growth Larger body size Smaller Body size Lower reproduction rate Higher reproductive rate Better competitive ability Better dispersal ability More investment in individual offspring (heavy Produce more but lighter seeds seeds) Iteroparity more likely Semelparity more likely Shade tolerance (if a plant) Share intolerant (if a plant) Introduction to the Basic Drivers of Climate What is Climate?  Largely determined by temperature and precipitation  Longer term climate changes are due to changes in the intensity and distribution of solar radiation on the earth's surface Sunlight is a key component of climate  Areas near the equator are most directly exposed to the sun's rays therefore receive the most solar energy  Sunlight intensity changes over years due to the earth's orientation changing in space  Seasonal variations occur due to the earth tilted on its axis by 23.5 degrees Sunlight intensity affects global winds....  Warm air is less dense then cold, therefore warm air rises  Warm air can carry water vapor in wet areas, because it is less dense then water molecules, therefore they can fit within the warm air's mass  When the air cools, the density increases, therefore less space for water.  Water molecules condense to form clouds and precipitate  As the warm air rises, cold air from adjacent areas comes rushing in the fill the void left behind. (Hadley Cells did all of the steps before)  This pushes the warm air away from the equator and towards the poles, where it is colder and denser around 30 degrees north/south latitude  The new warm dry air will absorb moisture from the ground. (Dry habitats with very little rain)  60 degrees north and south the air rises again and cools, causing precipitation. (Ferrell Cell)  The cold and dry air flows to the poles where it absorbs moisture creating cold and polar regions (Polar cells)  All and all the convergence zone will shift seasonally due to the tilt of the earth, and gets pushed around, it’s not a simple equator Prevailing Wind patterns  Hadley cells causes the north/south movement of winds  Winds are also generated by rotation of the earth (coriolis effect), o Creating eastward and westward winds. o These winds affect ocean currents  Warm tropical waters (near the equator) carry heat pole-wards along the east side of continents. (Tradewinds, northeast and southeast trades)  Cold waters from the poles send their cold toward the tropics along the west coast.  Horse latitudes is where the wind is weak and unpredictable  Roaring 40’s is where there is no continents to block winds therefore they are huge endless waves  Both wind and ocean currents redistribute heat across earth, 60% due to circulation of air and 40% due to ocean currents Regional Climate Patterns  Proximity to large bodies of water influence climate on a regional scale.  Coastal areas have less seasonal variation compared to continental interiors. o The milder winters and cooler summers  Due to water's ability to hold heat for longer periods of time. Compared to land where it doesn’t hold heat well.  Mountain ranges can act as physical barriers to force air to rise and cool, and moisture of the air is lost on the windward side of the mountain.  On the leeward side, the air descends and warms, absorbing moisture from the ground. Much less precipitation falls on the leeward side of the mountain. This creates the rain shadow  Rain shadows can create both dry as hell places, or not as dry, grassland places. Microclimates  Created by variation in physical structure of the area o Also by vegetation o Strong relationship between microclimatic conditions and ecosystem structure El Nino-Southern Oscillation  Due to a disruption in oceanic currents and air masses o Normal conditions, warm water pools in the western pacific  El Nino the heat covers most of the pacfic  During El-Nino the trade winds (easterly tropical winds) decrease. o Thus, warm water covers ocean surfaces in the tropics. (Instead of pooling in western pacific)  Thus this redistribution of heat leads to evaporation, condensation, and precipitation in the eastern pacific and Americas.  This results to flooding in the Americas and Europe, drought for Australia, and parts of Africa  Marine life is affected as well o Normally upwelling of water (wind driving cold, dense nutrient rich water to ocean surfaces) causes these areas to have high levels of primary production by phytoplankton.  Thus, increased food o El Nino events can cut off the supply of nutrients, thus phytoplankton productivity decreases.  Thus decrease populations of marine mammals, fishes, and birds  Chain reaction Terrestrial Biomes Terrestrial Biomes  Distinguished by their vegetation  Determined by temperature and rainfall (moisture) o Which will determine the types of plants that grow in that area  Height, Density and Species diversity decrease from warm, wet climates to cool, dry climates.  Growth (primary productivity) increases with moisture and temperature o So warm and moist places get a lot of vegetation  Seasonality is secondarily important  As you get dryer, typically the height of the forest decreases.  Proportions of different life forms vary with climate o Life form spectra are more alike in similar climates on different continents then they are in different climates and same continent  Biomes = similar climate and dominant plant types Tropical Forest Biomes  Areas centered on the equator  Very little seasonal variation in climates  High rainfall and warm temperatures  Dominant plants are: phanerophytes (trees), lianas, and epiphytes  Contain, tall trees, tall shrubs and herbaceous vegetation (ground level)  Highest biodiversity and primary productivity o Sustained even with poor soils (due to decomposition rates in warm/moist conditions)  Mycorrhizae (fungal, associated with plant roots), rapidly uptake nutrient from litter decomposition  Contains many sub-biomes o Evergreen rainforest, seasonal deciduous forest, etc etc  Develop due to seasonal changes in rainfall and elevation Savanna Biomes  Located north and south of tropical rain forest biomes  Lower rainfall and longer dry seasons  Dominant plants are a mix of grasses and small trees  It’s the transition from tropical forests to deserts  Trees are normally drought deciduous  Fires play a major role in balancing trees and grasses o Tree and shrub population increase during periods between fires o Fire releases the nutrients tied up in dead plant litter o Soil is a good thermal insulator and protect rhizomes of grasses from damage  Primary productivity is 400-600g (compared to tropical which is (2000-3000g)  Decomposition is rapid and year round o High turnover due to large diversity of herbivores (up to 60% of biomass can be consumed in a year)  Dung beetles important for breaking down animal droppings Desert Biomes  Occur around the world between 15-30 degree north and south latitude, also where cold water is upwell (so inland of cold-water upwellings) o Where ocean currents bring cold water to the surface and air gets sucked into the land the air rises (thus, dry air)  Low rainfall  Lots of variability, hot, cold, high elevation, and rain shadow deserts o Obviously then there is a lot of variability in biodiversity, productivity, and organisms found in deserts  Dominant plant is shrubs with extensive roots and small leaves o In warm desert therophytes (annual plants) can make up most of the diversity  They survive through unpredictable dry periods as seeds  Stay in soil for several years until appropriate rainfall and temperature conditions occur  Primary productivity in deserts is low and extremely variable (0-120g) Grassland Biomes  Primarily in interiors of continents  Large seasonal temperature variations o Hot summers and cold winters  Precipitation varies, strong in summer o Thus, the type of community that develops and productivity will be determined by the variable precipitation  Productivity can be 400g -1000g  Grasslands grade (group of species) into deciduous forest biomes if there wetter, and desert biomes if there drier. o Shift depends on precipitation, disturbance, fire and drought  Three forces dominate the evolution of plant traits o 1) Recurring Fire o 2) Periodic Drought o 3) Grazing o Which led to the dominance of hemicryptophytes (grasses)  Some of the world’s largest terrestrial animals are found in grasslands Temperate Deciduous Forest Biome  Occur in mid latitudes  Cool winters, warm summers, high year round precipitation  Productivity is 600 -1500g.  Lots of litter for nutrient recycling  Lots of tall trees and shrubs, ground layer of herbaceous plants  High biodiversity due to the niche (particular range of conditions a species can tolerate) partitioning by the multiple forest layers. o More complex forests are associated with greater number of animal species Mediterranean Climate Biomes  30-40 degrees north and south latitude  Hot and dry summers, & cool and moist winters  Evergreen and sclerophyllous shrubs and trees have evolved independently in these areas, they are unrelated and example of convergent evolution  Productivity is 300-600g o Fires help aid nutrient cycling o Productivity decreases after 10-20 years due to accumulation of litter Northern Coniferous Forest Biome  Located at higher latitudes  Dominated by needle-leaved, drought tolerant, evergreen trees o Two layered forest o Overstory of trees and ground layer of herbs and mosses  Long, cold winters, and short cool summers  Low biodiversity o Over story made up of one or two species o Therefore low productivity 200-600g  Low temperatures lead to slow decomposition and higher litter accumulation o 60% biomass tied up in litter Tundra Biome  Beyond the boreal tree line  Very short growing seasons and temperatures are low  Very low productivity 100-200g  Low biodiversity o Dominated by mosses, lichens and shrubs o Shrubs are low growing due to low temperatures and windy conditions  Low nutrients in soil due to slow decomposition rates Physiological Ecology Introduction  Temperature one of the most significant factors (will limit distribution of species) o Organisms evolved to regulate their temperatures in their environments  Water availability is another significant factor  Acquisition of energy and nutrients is another significant factor o Autotrophs and Heterotrophs Physiological Optima and Critical Limits Physiological Optima and Critical Limits  Distribution of organisms are dependent on biotic (living organisms) and abiotic (non- living properties) environmental factors  Organisms maximize their fitness at an optimal environmental range, and can only survive a short period with environmental conditions exceed their critical tolerance limits o These ranges and thresholds will vary based on physiological adaptation and energetic o Critical limits can define species distributions, community structure, and how community respond to environmental changes o Defining a organism’s critical limits with variations in fitness between environmental factors can be diagrammed as a performance curve  Species limited by Geographical ranges o Limited by climate/vegetation o Limited to special habitats  Example: the Pronghorn, has a large climate tolerance, but narrow habitat range (grassland biome), they can’t jump or climb mountains/hills  Causes “idiosyncratic” (differences in same species due to habitat) o Limited by other organisms Thermal Performance Curves  Performance curves illustrate an organism’s performance across a range of environmental conditions (example temperature)  Eurythermal organisms have a wide thermal range  Stenothermal organisms have a narrow thermal range  Endotherms o At optimal range – thermal neutral zone (TNZ)  Metabolism is constant and minimized  Above and below TNZ  Metabolic rate is elevated to maintain body temperature  Ectotherms o They have no TNZ, but do have a optimal temperature zone o Behavioral regulation to maintain body temperature  Even before reaching upper and lower critical limits organisms perform less and less well o Pejus temperatures are where performance begins to decline  Performance optima occurs when physiological rates and metabolic efficiency are both maximized Mechanistic Bases of Thermal Performance Curves Lower Critical Thermal Limits  Organisms cannot survive the formation of ice inside of cells, but ice can form outside of cells as long as the ice grows in a controlled and directed manner o Allowing extracellular ice to form, but prevent intracellular ice  1) Compatible solutes (glycerol and glucose) are concentrated inside cells, lowering the freezing point of cytosolic fluid.  2) Ice formation is encouraged to occur in extracellular fluid by ice nucelators  When nucleated ice formation begins, the remaining solutes are concentrated in extracellular fluids, this makes a osmotic pressure gradient, so water moves out of cells, further concentrating intracellular fluid and reducing its freezing point  Other cells use antifreeze proteins to prevent freezing  When hibernating organisms also need to make sure enzymes and membranes stay in the range of marginal stability for proper function Ecological Implications Rocky Coast Example  Upper distribution limits for each band is set my abiotic tolerance limits o To the point there organisms are unable to live any higher on the rock given its performance curve!  Lower distribution limits set by biotic interactions o Competition for space and predation Reponses to climate change  Global mean temperature is on a trend of rising o This means that many organisms will be outside their optimal temperature ranges  For some organisms current habitat temperatures are well below their thermal optima o Thus they have suboptimal performance/fitness  So they are slowly becoming closer to their thermal optima  And opposite for organisms that are at/near there thermal optima  Species living in highest temperatures have the highest thermal tolerance limits, they are also experiencing a habitat near their thermal limits o Therefore most at risk Homeostatic Processes for Thermoregulation Introduction  Homeostasis allows an organism to regulate its internal environment, with a fluctuating external environment Types of Thermoregulation  Two primary responses for thermoregulation o Poilkilothermy and Homoeothermy  P-Therms or ectotherms can’t generate heat thus they need behavioral interventions o shifting betweens areas of lower and higher temperatures o changing body positions (conduction/radiation)  Some color choices for lizards is not for thermal regulation, it’s for camouflage o However some have also shown that melanistic species warm up more quickly than light colored species, allowing them to remain more active under cold conditions Thermoneutral Zone  Basal metabolism does not involve physiological thermoregulation  A range of temperature associated with basal metabolism is the TNZ o So when temperatures are higher or lower then TNZ, then physiological thermoregulation occurs.  Non-basal metabolic rate increases when an animal is thermoregulating to prevent overheating or overcooling o This will define what temperatures the organism can tolerate beyond TNZ. o Homeotherms use behavioral means to keep themselves at TNZ Heterothermy  Describes the variations in body temperature both spatial and temporal scales o For example, body temperature are warmest at the core but lower at the extremities o This allows for counter-current exchange o Temporal scales refer to how animals change in body temperature over time  Example: Increase/decrease of fat insulation during different seasons  Using fever as a response to pathogen presence  Changing basal metabolic rate to limit energy consumption o Reasoning is because energy resources might not also be enough to fuel the same BMR  Example: organisms going to topor, a state of reduced metabolic rate and hypothermia  Used so that an organism can focus using its energy for thermoregulation instead of BMR Conclusion  Being a homeotherm is not better because they do use more energy for thermoregulation. Thus, this constraint where they can live due to energy sources. o But Topor is an example of an adaptation to preclude this problem Population Limiting Factors Introduction to Population Growth Limitation  Populations grow geometric or exponential rates if you have unlimited resources o Geometric is like pulsed reproduction (mating season) o Exponential is reproduction at anytime (humans)  All populations begin exponential growth in favorable environments and low population densities (except Allee effect)  Obviously in nature population growth rate slows down due to depletion of resources o This is Logistic growth  The place where population growth rate stops = the carrying capacity (K)  The population a environment can support  Thus, birth rates = death rates because the population is constant Populations Cannot Grow Without Limit  Example: Lemming population o Predation limited the population growth  When lemming had a high population size, predation increased therefore preventing rapid population growth  Now there predators have more resources and there reproduction success increased, therefore more predator population o Now the predator population made the lemming population collapse, which causes the predators population to collapse o Cycle repeats Density Dependant Limitation  Factors include: o Disease, competition, and predation  Can be positive or negative correlation to population size o Positive is when these limiting factors increase with population size, and limit growth as population size increases o Negative is when population size is limited at low densities, but becomes less limited as it grows Density Independent Limitation  Factors include o Catastrophe and environmental stressors o Food or nutrient limitation, pollutants, climate extremes, seasonal cycles o Often abiotic  Lower quality of nutrients the higher environmental stress Allee Effects History and Definition  Allee effects are negative effects of having a low population density  Allee effect reduced at higher population densities  Undercrowding that reduced population growth  If populations are below a particular threshold, then they cannot maintain themselves are go extinct o If they are above a threshold, same as logistic (sigmoid curves/L shape curves), all approaching K (figure 2)  Allee effect has two manifestations o 1) Component Allee effects happens when a population has a positive association with some fitness component and population size o 2) Demographic Allee effects occur when component Allee effects produce a positive association between per capita population growth and population size  Population at small size will be “average individual fitness”, due to high populations have competition of resources and space  Thus, an Allee effect is a positive association between average individual fitness and population size over a finite interval o So fitness increasing as population size increase  If an Allee effect causes a critical population size (if below this size a population cannot persist) are called STRONG.  If an Alee effect does not result in critical sizes, they are called WEAK Mechanisms that cause Allee Effects  Mate limitation in undercrowing species  When breeding, feeding and defense are cooperative, larger social groups have increased reproductive success  Per-capita risk of predation is smaller in large prey populations then small  Multiple individuals can alter environmental or biotic conditions in a favorable way.  Genetic mechanisms o Small population size cause inbreeding repression, so population size declines  In the end: Small populations suffer from reduced average individual fitness. Evidence of Allee Effects Component Allee Effects  Predator Satiation (positive density dependence) o Predators that are satiated stop increasing consumption, and don’t track the abundance of the small prey population Demographic Allee Effects  Hard to find o 1) due to Allee effects in one component of fitness offset at low density by increase in other components of fitness, such as decreased competition for resources o 2) hard to detect populations at low densities Evolution  Negative effects of low density are expected and often result in strong selection for traits that reduce these mechanisms  Populations that are most likely affected by Allee effect are the populations that were a large population and suffered a recent reduction in size due to habitat fragmentation or catastrophic natural events. Survivorship Curves Introduction  A cohort is a group of individuals part of the same species, populations, and born at the same time.  However, survivorship curves can be very different depending on the environment o Thus, they are not normally considered a property of a species  The curve is affected by biotic (competition) and abiotic (temperature) factors  L x probability of being alive at age x  L 0 1.0 by definition  Thus, the survivorship curves is a graph of L vs x x o And of course L dexlines with x  Three basic patterns: o 1) Type 1 survivorship  High survivorship throughout life cycle  Humans in developed countries and animals in zoos, most die of old age  Seen in very competitive environments, therefore infants are raised with high competitive ability increasing likely hood of survival (K-selected) o 2) Type II  Constant proportion of individuals dying over time (negative linear line)  Mortality is therefore not dependent on age  Examples: turtles, rodents, and birds o 3) Type II  Very high mortality at a young age  Normally produce thousands of individuals whom die right away  Then survivorship is constant (fish, seeds, larvae)  Little effort for parental care (r-selected)  Typically done due to frequent disturbance or uncertainty in environments  Most populations are mix of three types Semelparity and Iteroparity Semelparity  Death after first reproduction is semelparity  Living to reproduce repeatedly is iteroparity  Semelparity has evolved from iteroparous ancestors  Species tend to approach it when high level of adult mortality appear in iteroparous life  All grain crops are annuals. o Due to way more yield Dilemma and Cost of Reproduction  Semelparous species produce more offspring in their single reproductive episodes then there other related species.  When organisms don’t need resources for future survival/reproduction, they can just put all of it into the single massive reproduction Theoretical Approaches  So what causes a species to evolve to want to use semelparity? o 1) When survival is low (often due to harsh seasonality), evolution abandons withholding resources for future reproduction that is unlikely (demographic model) o 2) When adult survival is highly variable, then evolution favors iteroparity because it won’t risk putting all reproductive effort into a single attempt (bet- hedging model) o 3) When most of the costs for reproductive effort can happen at low levels of reproductive effort. OR when the benefits of reproductive happen at high levels of reproductive effort. Basically, when reproduction output is increased by accumulating resources for a longer period (non-linearity model) Synchronous Semelparity  Plants that synchronously flower and die together  All seem to grow in environments where it is climatically more moderate then extreme environments where most Semelparous species live.  Can happen due to predator satiation (lets satisfy the preds, by releasing a huge butt load of resources that they won’t eat them all) Causes and Consequences of Dispersal in Plants and Animals Introduction  Dispersal is when individuals move away from the population where they were born in, to another one where they settle and reproduce. o 1) Natal Dispersal  First movement of an organism dispersing to another site to attempt reproduction o 2) Adult Dispersal  After reaching reproductive maturity, they move to another habitat o 3) Gamete Dispersal  For non-motile individuals, such as plants Active and Passive Dispersal  Active Dispersal o Movement of the entire organisms o Dispersal vary among species based on many factors  Society Structure  If you rely on a single adult male for reproduction, juvenile males born in a particular movement will disperse o It is density-dependent  Therefore depends on population size, resource competition, and habitat quality/size o High vagile (able to move from different habitats) animals are very efficient at active dispersal (birds, bats, large insects).  Highest capacity for long-distance dispersal  Passive Dispersal o Animals and plants that cannot move themselves, but use dispersal units called “dissenminules”  Dissenminules are adapted to move through the what is available in the environment, like wind, water, or another animal Why Disperse? Why Not?  Crowding in populations and food availability will influence dispersal  Environment as well  Climate change o If a population can no longer find a suitable environment to disperse too, they will become extinct  Ultimate causes of dispersal is avoidance of inbreeding and inbreeding depression o Because inbred results in decreased fitness  Can reduce competition for resources and mates, therefore increasing individual fitness  Increased mortality risk during dispersal due to increased energy expenditure, unfamiliar habitat or predation risk o Also reduced survival or reproductive success due to new environment and decreased ability to adapt to the new habitat The Effects of Dispersal on Individuals, Populations and Species  Survival, growth and reproduction at individual level o Tied to distance and frequency of dispersal  All mediated by local resource availability  For populations with high frequency of dispersal, this causes ongoing gene flow o Thus, populations will become genetically similar to one another and evolve as a single unit  Therefore, if you lack dispersal among populations then o Isolated populations will accumulate genetic attributes, through genetic drift (fluctuations in allele frequencies that occur by chance). o Thus, local adaptation happens o This normally happens due to landscape features that cause a population to become isolated Limits to Dispersal  Species are constrained by a range of environmental variables (temperature, resources, physical barriers) o Therefore, they cannot disperse if the new habitat will not meet their requirements for survival or reproduction Quantifying Dispersal  Direct Methods o Mark-recapture  Marking techniques or raido tracking devices  Easier to use on large animals  Indirect Methods o Infer dispersal without actually having to observe the dispersal movement o Molecular methods to measure gene flow  Differences in allele or genotype frequencies between populations reveal patterns and levels of dispersal Human effects on Dispersal  Organisms travelling by ballast water of ships (zebra mussels example) The Glorious, Golden, and Gigantic Quaking Aspen Aspen  Found at different elevations, environments, and geographic ranges  The white bark is a living tissue that helps in photosynthesis, unique for North American Trees o But its low fire resistance (=D), and easy food source  All structures arose from a single aspen seed o Often from a very distant past  Connected via root system  And comprise from a single clone  In spring aspens produce reproductive parts called catkins o Either male produce pollen or females produce eggs o Lots of these tiny seeds mature an float off on to air currents  Aspens can do asexual expansion o Spreading via roots and sending up shoots o Good for sharing water (one clone might be water, and another near good soil)  Aspens also live near avalanches, fires and mudslides o So they need colonal reproductive and regenerative capabilities o So if you find an area with LOTS of clones, most likely there were lots of environmental disturbances because if there wasn’t other organisms would have taken the area.  Why do the aspen leaves quake and tremble? o It is strong in one dimension (long part of the ellipsis) and not strong in the second part (narrow part of the ellipsis), so gentle winds can cause this quaking o Minimizes the risk of too much sunlight, reducing the risk of overheating o Reduce insect damage Lecture 8 Fender’s Blue Butterfly Example  Fender’s blue butterfly can only eat a rare planet species, the Kincaid’s Lupine  It was very abundant plant, but due to agriculture conversation its now very rare  Butterfly’s must find prairies with lupines, caterpillars also need the lupines or they die  Demo with Ecobreaker Simulation Model o Butterflies undergo annual cycles of reproduction but disperse randomly across the habitat, must discover prairie or they die without reproducing o It was a type 3 survival curve o Patches needed to b e large enough for butterfly dispersal o IF the small patches are near a larger reservoir patch, then butterfly’s can exist on them through migration Pika Example  Mining ghost town, great for Pikas  Love living in slopes with rocks where they live in  North patches were doing very well, even the small patches because they are all anchored by the big reservoir o Only reason why middle and south patches had pika’s was due to the SOURCE of the north patch  Middle patches were going through extinction/renewal, no reservoirs o It was a sink, not a source, existed only because of the source of the north  South patch is declining each year o Lots of extinctions, again it’s a sink due to the north source patch General conclusions on stability and coexistence  Model populations can be driven to extinction in several ways o Strong density-dependence (overshoot and crash) with time lag o Unstable competition o Unstable predator-prey relationship o Allee effects at low density  But all of these are countered by non-equilibrium conditions that prevent competition from going extreme, habitat patchiness, rescue by migration, and vibrations in life history strategies Conflicting views of causes of associations  Organismal hypothesis o Certain species found together because they are biologically integrated and depend on each other’s presence like a tissue of a organisms (Clements theory)  Individualistic hypothesis o Species distributed independently from each other, limited by:  Dispersal  Filtering by physical environment from abiotic ranges of tolerance o Basically depends on abiotic factors Direct gradient analysis (Robert Whittaker’s) to test Gleason and Clements Hypothesis  Look at 4 trends of species distribution o Clements theory you should find specie distribution all cutting off at the same time, and rising together o Gleason’s theory you should find curves with different tolerance levels, looks like species are distributed individually  This was found to be correct  Other evidence to support individualistic hypothesis (Gleason’s) o Curtis’s indirect gradient  Did not find strong clustering of species o Margret Davis  Pollen data to track migration of tree species, found that they migrate along different paths and times.  So not as a whole unit  Thus, terrestrial vegetation is continuous and not discrete, and strongest filtering is due to physical abiotic factors o But species interactions can affect distributions o Animal communities much less individualistic then plant communities  If you kill off a animal, HUGE ripple affect o THUS, similarities between plants are due to their similar abiotic tolerance not there reliance on each other Lecture 9 Community Dynamics: Predictable successional change in plant communities  Pioneer species get in first (from dispersal or seed bank in soil) o R-strategists (great at dispersal)  Short lived  As plants die, soil building process begins, shade thought to be critical here o Dead plants contribute to organic matter making more complex soil (most important factor is soil formation)  Thus more plants can establish in better soil  Vegetation changes spontaneously as the vegetation itself modifies the environment  Gores through non-equilibrium stages o Plants attract birds, and birds bring in more seeds o As tree canopy closes, soil is well developed and shades become important factor o Now plants are either shade tolerant or spring plants that do all there photosynthesis in the spring  Ends at climax stage where its stable and at equilibrium no more change o K-strategists o Takes around 300 years Drivers of terrestrial succession  Soil development o So accumulation of organic matter (nitrogen and pH buffering, water retaining capacity)  Really important for primary succession  Shading o Shade tolerant species replace shade intolerant species  Really important for secondary succession Succession where no climax equilibrium is attained  Boreal Forest o Leads to spruce-fir forests, but do not replace itself  You don’t find young spruces, you find nothing o Forest just dies not a continuous climax  Acid Sandy Soils o Pine-oak litter makes the soil more acid, not richer  Fire prone ecosystems Gap phased succession  Succession happens at a scale of individual trees  So big tree dies, you get a gap, now new species can come in, because that tree leaves a major canopy gap. Understanding of Patterns of fire  Habitats are mosaic of patches in different stages of re-growth following a disturbance  Intermediate disturbance hypothesis for maximum species diversity o Ecobeaker demo  So diversity increases at beginning, then decreases and ultimately reaches very little  Fire resets succession in areas its affecting  Thus you form the mosaics Lecture 10 Trophic Ecology: Who Eats What?  Levels o Primary Producers = Plants o Primary Consumers = Herbivores o Secondary Consumers = Carnivores o Tertiary Consumers = Carnivores who eat secondary consumers o Detritivore = eat dead organic matter Trophic Cascades  World is green because carnivores keep down herbivores, so they don’t limit plant growth  Indirect effect = one trophic level exerts influence on a second by affecting the third o plants being aided by carnivores o indirect effect of carnivores eating herbivores o So carnivores have a positive effect on plants, but negative effect on herbivores  Cascade is an affect that drastically affects communities  Lizard Example o Lizards and spiders both eat the beetles (herbivores) o Lizards also eat spiders o Beetle eats the plants o Probably a cascade, but who?  So lizards help spiders eat the beetles, but occasionally eat spiders too  There affect on beetles is more then on spiders  Dragonfly Example o With no fish there are a lot more dragonflies  Thus eating all the bees for pollination of the plant (St. John’s wort)  Thus, if a pond has fish there is much more bees for pollination  So indirect methods can be as strong as direct effects Species difficulties of herbivory  Plant tissues are hard to convert into animal tissues  Plant tissues also heavily defended against herbivores mechanically and chemically  Arms Race o Plants get better at defending, but herbivores get better at adapting o Thus insect herbivores is responsible for much of the biodiversity  Due to specialization being common  Milkweed Example o So milkweeds squirt out white sap when damaged o This will cause insects to avoid the plant  So generalized insects will be deterred o Monarch butterfly larva cut leaf midrib, and reduce the sap pressure before eating o They actually don’t even detoxify the poison;  they make themselves poisonous and distasteful from eating milkweed Challenges and Solutions for Vertebrate Grazers and Browsers  Some plants (Geminoids) are defended mechanically o So by silica crystals in leaves, grinds down teeth like sand paper o Meristem’s are then protected by being deep underground  Some adaptations for eating plants o Use of fermenting chambers: o Rumen (foregut), Cecum (hindgut)  Bacteria inside secrete enzymes necessary to digest the plants o Grinding Molars  Teeth used to resistant grinding of grasses  Pika Example o Accomastylis rossi are toxic for pika’s and bitter o Trifolium parryi pika’s love o Pika’s store the toxic ones and eat it all during winter  They becomes less toxic if stored overtime  They don’t store the trifolium because they rot  Thus they would need to make 3000 trips during the winter to eat trifolium because they can’t be stored for very long o More trips = more chance of predation Janzen-Connell Hypothesis  Plant species diversity in rainforests is so phenomenal o Because attacks from specialist insects and fungi o Seedlings have a very low chance of success around the of the mother tree o Strong density dependence prevents any species from monopolizing habitat o Very little seasonality  Thus insects populations are high throughout the year, making many specialist insects Last Note  Interaction with organisms and abiotic factors can cause species diversity as seen before, but the environment isn’t complex enough to explain the diversity we see today  Ultimately it’s the interactions with other organisms that produce unlimited diversification  So the biotic factors Lecture 11 Glacier Lily Example  Flowering of plants is most abundant in very rocky surfaces  Life History o Iteroparous o Long resource accumulating phase o The corn is 30-40cm below the soil so it can persist from year to year  Seed Dispersal o Not very far (20cm) o No secondary dispersal from ants  Elaiosome attract ants, which help dispersal of seeds  This isn’t found in glacier lilies  Seed Germination o Seeds live longest in organic rich and deep soil, thus need moist soil  BUT, glacier lily’s found in rock areas, that’s where soil is dry and not very deep  Distribution of Species o Should find more plants in thin soil, not rocky areas o Weak dispersal, thus we should find seedlings near flowering plants o Patterns:  1) Vegetative plants and flowering plants were found in the same distribution pattern  2) Flowering plants and seedlings were found in different patterns  Not expected because seedlings have no dispersal, so how are they so far from flowering plants?  3) Soil is most moist away from rockiness areas, but plants distribution is around rockiness areas  4) Gopher activity is highest in soil moisture areas, they avoid rock areas  Understanding of patterns o Seeds are produced in rocky areas, but most die o Few seeds that reach moist deep soil areas will survive and produce seedlings, but these are killed by gophers o Thus, glacier lilies best survive in rocky areas with limited dispersal  Also explains why they have no elaiosome, because they don’t want large dispersal to avoid gophers. Aspen and Meadow Example  If you remove gophers, aspen invade the meadow o They increase their stems where gophers were removed  So same as above  Rock-Refuge effect o Gophers cut the stems of aspen o But aspen prefer moist soil areas o But to avoid gophers they centered on rock outcrops What to take away from above examples?  Gophers are keystone species in aspen-meadow mosaic o They keep the diversity of the community, because without them aspen clones will just dominate and decrease diversity in the meadows  Indirect Effects o Gophers hurt lilies, but indirectly prevent succession from turning meadows into a forest  Negative direct effect on lilies  Positive indirect effect on lilies  Giving them more sun by preventing aspen domination Climate Change  Greenhouse gases causing earth to warm  Hadley cells getting stronger and larger, beyond 30 degrees latitudes  Organisms migrating to higher latitudes and altitudes o To cooler areas Lecture 12 Introductions  Evolution o 2 Dimensions  1) Ecological (Darwin)  2) Genetic o Individuals DO NOT evolve  Your genotype is unique to you and dies with you, will never occur again o Thus to study evolution must look at populations o Answers “why’ questions  Ultimate questions o Assumptions about evolution verified by scientific studies  Organisms have changed through time gradually not instantaneously  Lineages split or branch by speciation, which results in biodiversity  Thus all species have a common ancestor  MOST evolutionary change is due to natural selection  Thus, biodiversity and adaptation are products of evolution  Biodiversity and Adaptation o Biodiversity  Between species, the variety of life on earth  Genetic diversity is within species o Adaptation  A trait that contributes to fitness making the organism better to survive or reproduce OR  A evolutionary process that leads to the origin and maintenance of such traits Theory of Evolution  Evolutionary mechanism o Microevolution  Seeing evolution in action o Determine both ecological and genetic mechanisms o Test models with experiments  Evolutionary History o Macroevolution  Looking at trees of life o Determine common ancestry and phylogenetics o Uses comparative data, non-experimental pattern based Water Hyacinth Example  Aquatic weed, that clones reproduction, can also reproduce sexually  They reproduce sexually when roots can hit the soil, (due to decreased water levels) o Clone reproduction when water levels are high, and also I non-native ranges  Missing a short-styled morph of water hyacinth o Found in lowland south America o Diversity is much higher in the Amazon, and small form only found in native ranges o Very little diversity in non-native ranges  Founder Event o A small number of individuals establish a new population from the source population o This population as decrease genetic diversity, and possess a small sample of the genetic diversity from the source population o HUGE founder event when human introduced WH into alien ranges (non-native ranges) Rat Tail Example  Rat tail has evolved a perch so that the birds can pollinate it o Known as an unbranched inflorescence axis  Old-world birds don’t hover, thus need a perch to stand on for feeding/pollination  If you cut off the perch the birds walk on the floor and feeds o HOWEVER, plant gets no reward because the perch actually puts birds near the sex organs for pollination o Thus, removal of perch lowers fertility and increases self-fertilization  Thus, the perch is an adaptation promoting increased chance of reproductive success Lecture 13 The Theory of Evolution – How it developed  Living things change gradually from one form into another over time o Replaced view of a static world o It’s a phenomenon with NO purpose  Example: like gravity  It is not the bring about human species, it just is  Lamarck o First to use the term o Linear view of evolution (rather than branching)  Simplest forms evolve to complex forms o Got the mechanism wrong  Said it was:  The inheritance of acquired characters  Example: giraffe’s neck  Got longer because progressive increase in neck during life time as an INDIVIDUAL was passed on to offspring o DUH its wrong because remember evolution occurs at a POPULTAION level, so genetic pool of the POPULATION changes, not due to individuals  August Weisman Germplasm Theory o Proved Lamarck was wrong o 1) inheritance only by germ cells, soma cells don’t act as agents of heredity  So genetics cannot be passed on by changes in soma o 2) genetic information only flows in one direction, from DNA to protein  Never reverse  Thus, increased neck length is a protein aspect, thus can’t be passed off back into DNA  Darwin and Wallace o Darwin returns from Beagle and spends 20 years accumulating evidence of evolution o Wrote but did not publish theory of NS o Began work on NS book o Published paper with Wallace o Published The origin of species The Origin of Species  Key components o 1) All organisms descended with modifications from a common ancestor o 2) The mechanism of medication is natural selection operating on variation among individuals within a population  Development of Darwin’s ideas o Went on the Voyage with the beagle to go explore and collect things o Read Lyell’s book on “Principles of Geology”  Geology is a continuous and GRADUAL process  First thing to introduce a dynamic world not a static one o Species vary  Looking at Galapagos mockingbirds  Found variations in patterns, so now he doubts fixity of species  4 similar species around the islands  Couldn’t find a CLEAR boundary between the species o So he found out species aren’t fixed entities, they can merge, to become sub species o Is no PERFECT species, what is a “typical” human? o Variation is what matters, species aren’t fixed entities o Selection  He reads Malthus’s Essay on the Principle of Population  Favorable variations will be preserved and unfavorable ones would be destroyed o Thus, individuals that can get limited resources will be more likely to survive. That population of individuals will have variations that will be favorable to fitness, thus preserved. The Essence of Darwin’s world view  Variation among individuals is not imperfection, but the material’s that NS uses to better adapt forms of life o So think of populations not individuals o Variation is the fuel for evolution to occur, without genetic variation evolution cannot occur  Requirements for Darwin’s theory to work o 1) Variation among individuals within a population o 2) Heredity  Inheritance of genes o 3) Selection  Some forms are better at surviving and reproduction then others in a given environment o ALL must be accepted and true Lecture 14 Darwin travels to Tropical Ecosystems  Brazil o Very high species diversity  But individuals of the same species are widely separated  Largely evergreen o Many more biotic interactions and mutualisms o Year round warmth means increase in insects  Thus pest pressures become big  Such high species diversity, how do plants disperse? Next tree could be 300km away, so wind is no good o Animals and insects that travel long distances are good for pollinators  Example: Bees as long distance pollinators  Can travel up to 23km per day  Pest Pressures o So tropical tree seedlings are less likely to establish near maternal parents  Survival increases greatly as distance from the mother tree increases  Mutualisms o Ant-Plant in Acacia example  Holes for nesting sites for ants  Produce nectar too  Protein for food on beltian bodies  Reason = without the ants the acacia die because of beetles. The plants use ant as a defense o Devil’s garden  Ants defend their host plant by using formic acid as a herbicide  So any plant that grows in the area the plants will kill  Epiphytes o Found commonly in tropics o Dispersed by bird poop  Colored evolution o Red leaves to attract pollinators when the flower is so small Darwin travels to Patagonia  Environment where abiotic factors dominate landscapes  Saw abrupt tree lines o This displayed that strong physical factors prevented tress from dispersing pass a particular point  Saw familiar and unfamiliar species o Bumblebee with darker colors o Flightless birds o Small camels called Gunanco Darwin travels to Galapagos Islands  15 main islands of volcanic origin o Very young only 5 -10 millions years old  Vegetation is colonized by species capable of long distance dispersal from the south American mainland  Distinct species on different islands o Used as evidence for speciation  Isabela Island o Prickly pear cacti  Got there because birds eat their fleshy fruits  Poop on island  Galapagos finches o Very different bills o Showed a adaptive radiation  Evolution of ecological and phenotypic diversity as a result of speciation  From a single ancestor, the above process allows exploitation of a range of habitats and resources  Four Components of adaptive radiation  1) Recent common ancestry from a single species  2) Phenotype-environment correlation  3) Trait utility  4) Rapid speciation Darwin travels to Australia  Vegetation have high levels of endemisim (meaning they are restricted to a particular geographical habitat  Biological uniqueness due to a long history of isolation from land masses  Very dry forests o Gum Tree  Adpated to dry conditions  Koala adapted to eat gum tree  Banksia o Rodent pollinated  Grown on the ground Community Ecology Introduction  Ecological community is a group of potentially or actually interacting species all living in the same location, bound together by a shared environment  Food webs are the core concepts of the field  Keystone Species = species that when present or absent profoundly affect other species In the community Resource Partitioning and Why it Matters Similar Species Compete for Limiting Resources  Interspecific Competition = Different species commonly compete for resources  Two species cannot coexist on the same limiting resource if they use it the same way o The superior competitor will always win (complete competitors) Dividing the Resource Pie  Using a resource different or at different times  One way o Partition resources by what species consume  Morphological adaptations allowing different resource use  Example: Bumblebees and accessing different lengths of corolla in flowers  Different in plants  Plants differ in forms of nitrogen preference  Differences in rooting depth and light-use  Solution for Coexistence o Competitive exclusion will be less likely with resource partitioning o By using the resource differently or at different times interspecific competition decreases and intraspecific competition increases  Thus, they limit their own population growth more then they limit other competitors. Thus, long-term coexistence.  Competition and Evolution differences o Competition limits growth, thus decrease reproductive success  Thus, competition will be a driving factor to drive evolution traits that cause different resource use to increase reproduction  Example: different shaped beaks of birds on the Galapagos islands Resource Partitioning, Species Extinction, and the Functioning of Ecosystems  If a species shows high degree of resource partitioning then when that species is gone, then the capacity to use that resource pie is also gone. o Thus, this will impact the whole ecological community Predation, Herbivory, Parasitism Predation  Antagonistic interaction = Benefit one, detriments the other  All of the above (title) are antagonistic interactions  Influences organisms at two ecological levels o Individual  Prey has a abrupt decline in fitness (decreased lifetime reproductive success) o Community  Decrease in prey population  Adaptation o Life-Dinner Principle  Arms race between two species (predator and prey)  If the predator fails to catch the prey it won’t have a large decline in fitness contrasted to if it does catch the prey  Both Prey and Predator have selective pressure to evolve better to avoid being eaten or to eat better Parasitism  Parasite consumes nutrients from another organisms, decreasing fitness to the host o Pathogens = parasites that can cause disease in the host  Two categories o 1) Endoparasites = live inside the body of their hosts o 2) Ectoparasites = live and feed outside the body of their hosts  Parasites do not kill their hosts  Parasitoids do kill o Difference between them and predators is that parasitoids feed on living tissues, while predators kill the living specie before consuming it Parasite Transmission  Direct transmission – parasite moves from one host to another of the same species without intermediate organisms  Vector transmission – Parasite uses an intermediate organisms Dynamics of Predation Introduction  Bottom-up control is where resources are limited, thus populations would decline as individuals try to compete for this limited resource o helps keep populations around the carrying capacity  Top-down control would be predation on prey population Population Cycles in a Pedator Prey System  Often as cyclic swings in population. o population peaks every 3-4 years  Basically as prey population increases, food availability decreases, they turn to other food sources to prevent starvation but population declines  When prey population increase, predator population also increases  Therefore, both resource availability and predator pressure can affect prey population Experimental Studies of Snowshoe Hare Populations  Blocks with food supplementation increased hare population density 3 folds.  Fertilizer increased plant biomass, but did not correspond with increase in hares o Thus its resource quality rather then availability that act as a bottom-up control for hares  Predator exclusion increased population density of hares two fold.  When predators were excluded and food supplementation given, the hare population increased 11 fold. Foraging Behavior  Ideal circumstances an individual will encounter high quality food items on a regular basis.  These food provide most nutritional benefit with the fewest cost o costs could be handling time, presence of chemicals, or reduce nutritional quality  organisms switch to other less desirable alternatives when food is scarce o when they switch is not clear, depends on abundance of the food, potential costs with each food, and exposure to predators while eating Increasing Complexity: Host-parasite Interactions  Example: the parasite ectoparasite Sarcotes Scabel a mite infected foxes  Cause a decline in fox population  Did not affect the voles population, same oscillation pattern as before. o however population in hares and grouse increased due to decreased strength of top down control from predation  parasites can sometimes use prey as a intermediate hosts, and predators as a primary hosts o this can cause sometimes unusual foraging behavior, making the prey more susceptible to predation o this causes a decline in both prey and predator populations Keystone Species Paine’s Milstones  Studied an rocky intertidal ecosystem where the community was dominated by same species of mussles, barnacles, and starfish. o Pisaster type if starfish was the top predator o Diversity of organisms declined as number of predators declined  Hypothesized, some species might be playing a greater role then others in controlling the diversity in these communities  Compared a area
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