Ecology Final Notes
Lecture 1: Biodiversity and Ecology
- Biodiversity = the variety and variability among living organisms and the complexes in which they occur. Levels are gene, species, and community/ecosystem types.
- Gene BioDiv = polymorphism, heterozygosity, and molecular variation.
- Species BioDiv = morphological, biological, phylogenetic. (1.5-10, 30? Million species)
- community/ecosystem BioDiv = all the types of terrestrial/aquatic ecosystems.
- Ecosystem = living and nonliving parts of environment which energy flows and matter cycles.
Lecture 2: Asking and Answering Questions in Ecology
- A hypothesis cannot be proven, only falsified or supported.
- Observational approach – correlation doesn’t equal causation
- Experimental approach – manipulated var = changed, response var = measured
- Replicated good in case of bad luck and to get good estimate
- Must change just one variable
- Natural experiment
o Natural change in variable, very real, low work, but low control, difficult to find replicate series
- Field experiment
o Ecologist changes variable, very real and generality, low control, high variability in replicates, lots of $, constraints on scale
- Semi-field
o Better control, lower variation in replicates, mimic natural conditions, do very extreme treatments not allowed in field.
- Lab experiment
o Very high control, low replicate variation, numerous treatments, but low reality and restricted to small species.
- Theoretical approach – Modeling with stats, concepts
Lecture 3: Ecology and Evolution
- Evolution = change over time (change in gene frequencies and heritable traits)
- Test evolution with common garden experiment to see if it led to differentiation
- Phenotypic Plasticity = change over time that is not genetic (w/in lifetime). Genes stay the same but expressed differently in response to environment.
- Causes of Evolution
o Nat Selection = variation in heritable trait, differential survival/reproduction, changes from mutation/genetic recombination (doesn’t create ‘new’ things)
o Sex Selection = from differential mating success
o Chance = Bottleneck, founder effect, drift.
- Adaptation = product of natural section (test by asking if it is heritable and increases relative fitness)
- May be maladaptation based on context and [constraints] on being perfect (trade-offs).
- Macro = differences among species, families, kingdoms. Micro = differences among pop’s.
- Key Points
o Who is most fit depends on ecological context which is always changing.
o Evolution is more than just selection (chance, plasticity)
o Mutations don’t always cause change in fitness so aren’t evolutionary mech.
Lecture 4: Physiological Ecology I: Dealing with the physical environment
- Conditions are infinite. Resources get used up.
- Physical environment includes: Salinity (sea, estuary, freshwater), Acidity (pH), Nutrients (micro important, but can have too much), Soil (many definitions, comes from rock and influenced by climate, topology, time, living things. Has different textures and water capacities. Losing 2x faster than formation due to erosion, runoff).
- Know the response curves. They set limits of tolerances which are organism-dependent.
- Look at indicator species with response curves, can also look at history.
- Niche = multidimensional hypervolume, where organism fits into ecological community.
- Coping with change:
o Regulation = rapid change (shivering, sunning); reversible
o Acclimation = long-term exposure induced change (tanning); reversible
o Phenotypic Plasticity = different expression of genes, change in development, morphology, physiology; diff-impossible to reverse.
o Adaptation = Over many generations there are changes from selection
Lecture 5: Physiological Ecology II: Climate and Biomes
- Climate = long term average of pattern of weather (includes seasonality)
- Climate affects and determines tolerances, resources, niches, distribution and abundance.
- Climate on 4 spatial scales
o Global: Sunlight/latitude example, seasonality, deserts at 30 degrees from warm and cold air with moisture.
o Regional: Water as a buffer for temp, humidity. Mountains influencing patterns.
o Local: Stuctures affecting temp, shade, air circulation, (city heat domes, slope)
o Microclimate: Climate over small spatial scale like fallen log.
- Biomes: large scale ecosystem units with uniform vegetation determined by climate.
o Tundra = belowground storage, low nutrient requirements. Taiga = needle-like evergreen leaves, high nutrient retention. Temperate Forest = anti-freeze compound, deciduous leaves. Grasslands = high allocation to roots, C4 photosynthesis, Shrubland = thick leaves, flammable oils, roots sprouting cork. Desert = seed dormancy, reduced leaves, CAM photosynthesis, deep roots. Tropical Rain Forest = drip tips, focus on canopy growth. Dry Forest = decidous, broad-leaved trees.
Lecture 6: Population Ecology I: Demography
- Population = group of interbreeding individuals of same species at same area.
- Not easy to answer what an individual is sometimes (clonal plants)
- Measuring density = Plots, mark-recapture, indicators.
- Distribution can be uniform, random, clumped.
o Clumped due to facilitation or patchy resource distribution. Uniform due to competition or territoriality.
- Sex Ratio = tells us about potential birth rate (females limiting)
- Age Structure = tells about potential population growth.
- Life Table
o Cohort = group of individuals born at same time period. Know all terms.
- 3 types of survivorship graphs depicting time of majority of mortality.
- Ro = net reproductive rate; total of Ixbx.
Lecture 7: Population Ecology II: Population growth and regulation
- Ro doesn’t tell us anything about generation time, just the average number of offspring a female will have in her lifetime.
- “r” = birthrate – deathrate. Accounts for Ro and generation time.
- dN/dt = rN = exponential growth
- K = carrying capacity b/c resources are limiting (logistic growth).
- dN/dt = rN [(K-N)/K]
- Population growth stops at K b/c competition, toxic waste buildup, disease, predation
- Can also have inverse density-dependence (strength in numbers, etc.)
- Chance also affects growth (density-independent)
- Assumptions of logistic growth are: no movements, continuous breeding, K is constant, no time lags.
Lecture 8: Population Ecology III: Life history traits
- Life history = lifetime pattern of growth, development, and reproduction.
- Can’t max fitness because of trade-offs.
- “r species” = early/single reproduction, small offspring, lots of offspring, low care for them, short life, temporary environment, unpredictable, pioneers.
- “k species” = opposites – good competitors
- Appear at different parts of logistic growth cuve.
- Reznick’s guppies (microevolution)
o Age-specific mortality of 2 different predators selects for observed differences in life histories between populations of guppies.
o Looked at investment in growth, number size of offspring, size at maturity.
- Asexual plants successful because low cost, habitat specificity, resource storage and physiological integration.
- Physiological integration is sharing of resources amoung ramets. (acts as buffer to environmental stress and divison of labor benefits.)
Lecture 9: Population Ecology IV: Applied population ecology
- Time lags happen when: overshoot K, then start crashing and undershoot K.
- Sustained yield means constant yield without causing population crash.
- Want population to be at max growth rate for max sustained harvest
- Max sustained yield = K/2 = inflection point
- Aquatic organisms have long gen times so easily over exploited.
- MVP depends on threshold to population growth, sex ratios, random events, immigration/emigration.
Lecture 10: Intro to community ecology and species interactions
- An ecological community is a collection of populations of different species that occupy a given area. They may interact directly, indirectly, or not at all.
- Characteristics
o Composition – which species/groups are present and their abundance
o Diversity – How many species/groups present (richness and evenness)
o Structure – density/dispersion/vertical structure
o Complexity
- Introduced species: Are successful b/c they avoid competition, are a generalist predator on easy prey, avoid natural predation and parasites, are a good/generalist mutalist.
Lecture 11: Competition I
- Competition (-/- activity). Individuals sharing a potentially limiting resource. Can be very different organisms (plant/microbes competing for soil nutrients).
- Interference = physically deny access to resource (direct)
- Exploitation = abundance of resource is reduced so that it’s unavailable (indirect)
- Expt to look at competition = before and after competitor added to plot, look at growth; do density series with competitor and look at reproduction;
- Fundamental niche = niche that plant could occupy w/out competition
- Realized niche = niche that plant occupies in reality
- Can look for past competition by looking at patters used to get resource
o Example of beak size in separate and overlap birds and how they split together.
o Evolution occurring in response to species interactions to resist competition.
Lecture 11: Competition II
- Alpha = competition coeffecient
- Need to know equations (1 but for both species)
- Need to know outcome possibilities (sp1 wins, sp2 wins, coexistence, stble, unstable)
- For competition assume no change in genetics, environment, no immigration, emmigration
Lecture 12: Predation I
- Predator = an organism that kills and eats prey (plants too_
- Herbivore = an organism that consumes living plants or their parts
- Parasitoid = organism whose young live w/in and consume a host, killing it
- Parasite = consume part of host blood or tissue w/o killing it (plants too)
- Know equations for predation (2)
- C = how efficiently predator catches prey
- B = how efficiently captured prey converted into predator reproduction
- D = environmentally-induced death of predator
- Predator density lags behind prey in biomass vs. time of 2 species
- Predators can regulate prey populations (oscillations)
- Regulation dependent on tightly connected factors
- Functional response of predators to prey is consumption
- Numerical response of predators to prey is conversion of prey to baby predators
- Prey switching occurs below/above point where predator preference for prey changes in regards to prey abundance.
- As prey decreases, predation rate affected by search/handling time
- Predator-prey interactions can be a source of strong selective pressure on both species.
- Prey effected by evolutionary race more than predator b/c lives are at stake, not lunch
- Prey adaptations: physical protection, chemical protection, camouflage, mimicry, and strength in numbers or a distraction/warning call.
Lecture 13: Predation II
- To max energy intake, benefits of foraging must outweigh costs.
- Foragers should pursue most profitable prey first followed by next profitable
- Profitability = the total energy in a prey item divided by time it takes to get that energy.
- Specialists are very good at handling but have longer search times
- Generalists have longer handling times but much shorter search times
- Predator should broaden its diet until decrease in avg quality of prey offsets any decrease in searching time due to greater abundance of prey included w/in diet.
- Increased productivity favors specialization, increased competition favors generalization
- Energy gain in a patch slows w/ length of stay.
- Know graph of how predator decides to leave patch
- Want steepest slope to give max energy/time in patch
- Shorter travel time = less time before giving up in patch
- If patches vary in quality, foragers should reduce resources to same marginal rate of return before leaving, so they’ll stay longer in higher quality patches.
- Quality of patch also determined by number of other foragers in it as well as predators.
Lecture 14: Mutualism I
- Mutualism is an interaction b/w species where both benefit (+/+)
- Fitness is increased and at population level N1 has a pos. correlation w/ N2.
- A mutualism is an exchange of goods and/or services
- When the benefit depends on context = conditional mutualism. Trees don’t get mutualistic benefits from ants at cooler parts of year and in the sun.
- Expt to test for mutualism: make Ho of what is exchanged in interaction, remove one species from other, observe change in growth, reproduction, biomass, % mortality, presence of parasite/predator.
- Cheating conflict in cleaner fish: can cheat by removing just mucus
- Will do if client is sedated. Client warns first then eats them or seeks different cleaning station.
- Pollination example of mutualism. Food source and seed dispersal. Can have cheating if don’t take pollen, just steal food.
- Seed cachers can be mutualistic if have bad memories. Mast years keep squirrel #’s down.
- Specific mutualism (one species paired with one species) vs. Diffuse mutualism (one species interchangeable with set of species).
- Obligate mutualism (species dependent for survival on mutualism) vs. Facultative mutualism (Not necessary for survival).
- Symbiotic mutualism (physiological connection) vs Non-symbiotic (free living).
- Specific facultative not observed b/c no strong pressure to be specific if just a bonus.
Lecture 15: Mutualism II
- Looking at community structure when alter mutualisms.
o Argentinian ant and S. African shrublands – large seeds not dispersed and ant outcompetes while not consuming large seeds, so small seeded shrub thrives
o Cleaner fish doesn’t have community level ramification on coral reef
o Plant growth stunted w/o mycorrhizae.
- Keystone mutualist removal affect whole community.
- Mutualisms may affect diversity, composition, abundance in community; competition, predation, dispersal; may allow organisms to colonize/persist in habitats they can’t otherwise inhabit.
Lecture 16: Complex Species Interactions I (density mediated indirect interactions)
- Direct interactions = unmediated effects of one species on another
- Indirect interactions = effect of one species on another mediated through 3rd species
- Density mediated i.i = effects due to changes in density
- Trait mediated i.i = effects due to changes in traits
- Multiply signs of direct interactions to get indirect effect (+ or -)
- Know example of Predator mediated coexistence of competitors
- If one predator key to coexistence of many competing species = Keystone Predator
- Starfish and shellfish – when take away starfish dominant shellfish outcompete others, so you lose diversity – starfish is keystone predator
- Know example of indirect mutualism between predators
- Trophic cascade = predator – consumer – resource (interactions among 3 species)