• Study of the abundamce and distribution of organisms and the interaction with the biotic and abiotic components of their environment
• is a Quantatative Science
• not environmentalism
• complex systems create messy data

Types of Ecological Studies

Theoretical

Theoretical predictions of ecological interactions 

ex. Niche Theory (role in environment), Lotka-Volterra models

Types of Ecological Studies

Modeling

Highly controlled environment; eliminate/manipulate specific variables

ex. physiological studies

Collection of field data; "natural" systems; non-manipulative

ex. nutrient budgets, landscape patterns of vegetation distribution

Examine long-term fossil records for insights

ex. paleolimnology

Large, system-level manipulations

ex. ELA, Hubbard Brook Experimental Forest, Limnocorrals

a Process:

that changes a population over time

that causes change in population phenotypes over time

that causes change in gene frequencies in a population's gene pool

Causes of Evolution

Genetic Drift

A random change in gene (allele) frequency in a population; typically associated with SMALLER populations

ex. founder effect, bottleneck effect

Causes of evolution

Gene Flow

Movement of alleles between local populations due to the migration of individuals; relative gene frequencies are a function of the balance of major migration processes

ex. immigration, emigration

Causes of Evolution

Natural Selection

States: In large populations of randomly mating organisms in the absence of evolutionary forces; allele frequencies will remain constant over time

**The process of inhertiance itself does not by iteself cause changes in gene frequencies

Random mating - no mate preference

No mutation - no new alleles

large population size - no genetic drift

No immigration emigration- no loss/gain of alleles

All gentypes have equal probability of surviving and mating - no natural selection

**Demonstrates that evolutionary forces frequently act on sexually reproducing populations;NOT INHERITANCE**

Stabalizing Selection

Extreme phenotypes in a population have lower rates of reproduction

The average phenotype remains most common from one generation to the next

Directional Selection

most phenotypes have lower reproduction and survival compared to the "exceptional" phenotypes

Result: the population average changes in a particular Direction over time

Distruptive Selection

Average phenotypes have lower reproduction and survival compared to the extremes in the population

Result: phenotypes become less common and the population becomes phenotypically more diverse (bi-modal)

Works on INDIVIDUALS not populations

Cascades to the genotype: genetic info for phenotype is ultimate recipient

Phenotypes controlled by multiple alleles not single

Survival of the fittest: Selecting AGAINST specific phenotypes

No perfect organism

Evolution and Ecology

Population growth and density

Evolutionary responses to high or low population densities

Ex. Dispersal under high densities; schooling/flocking (low density)

Evolution and Ecology

Predator-prey interactions

Responses of both predator and prey phenotypes to changes in each other's phenotype

ex. long-term co-evolved stable predator-prey populations; unstable predator-prey dyanmics with introduction of a non-native predator

One or both organisms benefit from an interaction

ex. commensalism/mutualism; leaf cutter ants and "farmed fungus"

Coexisting species exploiting the same resource can face pressure to use alternative resource.

ex. adaptive radiation

Phenotypic variation among individuals in a population are a result of: genotype and environmental conditions

ex. plant size of a single species can vary with altitude

Finch Ecology and Natural Selection

Rainfall vs Mortality

Seed Abundance vs Seed Hardness (Drought)

Beak Size vs Survival (Drought)

Large inter-annual variation in rainfall leads to large inter-annual variation in food availability for finches (seeds)

1) Decreased Rainfall, Increased Finch mortality

2) Seed abundance decrease, Seed hardness increase

3) Increased Finch size + increased Beak size = Increased survival

Chuckwalla Ecology

Climate vs Elevation

Body Size vs. Environmental Conditions (winter rainfall)

Common Garden Experiment

1) Average winter rainfall increased with elevation in desert mountains.  Variation in winter rainfall decreased with elevation.

2) Chuckwallas grow to larger size where winter rainfall is higher (increase rain, increase variation)

3) Both males and females from higher elevation populations grew to a larger size

Conclusion: Genetically more likely to grow at higher elevations

Latitudinal Variation

Higher latitudes have greater seasonal climate fluctuation

Global-scale patterns of air movement leads to preciptiation patterns and thus the distribution of biomes.

Temperature and precipitation together have large impact

Global Wind Directions

Coriolis Effect

Northern Hemisphere: Winds deflected to the right

Southern Hemisphere:  Winds deflected to the left

Environments which are distinguished primarily by the predominant vegetation associated with particular climates.

Global distribution primarily determined by world-wide climate patterns

Characteristics: geographic distribution, soils, climate, dominant vegetation types, biology of organisms, growing season length

Tropical Rain Forest

Distribution: 0°-10° N & S

Temp: 25°-27°C (little seasonal varation

Rain: 2-4 meters/year

Soil: highly weathered and leached, low organic nutrients

Growing Season: year around, not productive due to soil

Tropical DRY Forest

Distribution: 10°-25° latitude

Temp: 25-30°C (more variable than TRF)

Rainfall: Extensive Dry season; 1-2 meters/year (alternate between very wet/dry

Soil: more nutrient rich than TRF, but susceptible to erosion

Vegetation: Trees can go dormant in dry season, many of the same species as TRF

Tropical Savanna

Distribution: 10-20° N & S; Just outside zones of TDF

Temp: 18-30°C

Rainfall: 300-500 mm/year; drought causes fires from lightning

Soil: low permeability to rainfall; retains water near surface

Vegetation: Grass favored to trees due to saturated upper soils

Desert

Distribution: ~30° N&S; some lie in rain shadows of mountains or interior of continents; 20% of earth's land surface

Cold and Hot deserts

Rain: Evapotranspiration > Precipitation

Soil: Very little organic matter; low leaf litter

Organisms: low abundance, high diversity; physiological, behavioral and morphological adaptations

Mediterranean Woodland/Shrubland

Distribution: 30-40° N&S

Temp: cool and moist fall/winter, hot and dry summer

Rain: 200-500 mm/year, drought in dry season leads to wildfires

Soil: moderate fertility and sensitive to erosion

Vegetation:  Trees adapted to fire (thick bark)

Temperate Grassland

Distribution: 30-50° N&S

Temp: Cold Winter and hot dry summer

Rain: 300-1000 mm/year; max precipitation occures in early growing season; fires in summer

Soil: Fertile and deep with lots of organic matter

Organisms: Migrating large herbivores, herbaceous vegetation

Temperate Forest

Distribution: 30-55° N&S

Temp: Cool moist fall and winter, hot and dry summer.  Moderate temp variation

Rain: 650-3000mm/year

Soil: Fertile, rich in organic matter

Vegetation: Coniferous or deciduous trees

Coniferous: seasonal drought; summer=dry 

Boreal Forest

Distribution: 50-65° N (northern only)

Temp: long cold winters, bried summers

Rain: 200-600 mm/year;

evapotransporation < Precipitation

Soil: low fertility, thin acidic soils; thick layer of recalcitrant organic matter (pine needles)

Vegetation: dominated by evergreen conifers, limited growing season

Tundra

Distribution: Above arctic circle

Temp: -30-10°C cold and dry

Rain: 200-600 mm/year

Soil: Rich in OM - peat and humus accumulation, permafrost under uppersoils (slow breakdown)

Vegetation: perennial herbaceous vegetation; lichens are common

Organisms: caribou, reindeer, moose, migratory birds

Kelp Forests and Coral Reefs

Kelp Forests dominate in temperate areas

Coral Reefs dominate in tropics

El Nino Southern Oscillation- ENSO

Upper level disturbance created by changes in distribution of surface temperatures in the ocean causes weather alterations on a global scale

El Nino Conditions

More dense cold sub-surface water under less dense warm water

Similar general nutritional and physiological demands; ultimately derived by primary life in ocean

ex. plants need light and nutrients, animals need oxygen for cellular respiration

Terrestrial Systems

Gravitational Forces

Organisms must invest in rigid supporting structures (bones/cellulose) to grow upright TOWARD LIGHT SOURCE

Terrestrial Systems

Light

Amount of overhead vegetation is the strongest factor influencing the amount of sunlight getting to the ground

ex. forest and prairie systems; <10% of light energy reaches soils (although varies seasonally)

Terrestrial Systems

Variability

Face MORE variable conditions; day2day/seasonal variation.

ex. Climate, water availability

*Intertidal communities (low tide pools): experience similar variability as terrestrial systems

Terrestrial Systems

Soil and soil structure

Soils are main factor controlling water a nutrient abailability for plants

Formed by local parents materials chemically and physically weathered

Variety: locally and regionally dependent

Size distribution and characteristics determine soil class

Terrestrial Systems

Soil composition

Clays: poor porosity; saturation

Sands: high porosity

Silts: higher nutrient content

Silty Loam: best for farming; good nutrient levels and porosity.

Terrestrial Systems

Soil Horizons (OABC)

Organic horizon: OM (litter/fragments); depth depends on biota

A horizon: Mineral soil with refractory OM; soluble material leached from A to B

B horizon (Depositional): material leached from A deposited to B; distinct banding patterns

C horizon: Weathered parent material; lies on bedrock

Terrestrial Systems

Ion Exchange in Soils

Temperate soils contain more negatively charged sites on soil particles

**Total number of negatively charged sites in a soil matrix = cation exchange capacity**

Highly weathered or old soils are typically alumino-silicate clays that are acidic and nutrient deplete due to gradual replacement of cations from protons added by rainwater

Aquatic Systems

Water in a non-renewable resource

Global water cycle

Aquatic Systems

Hydrologic Cycle

*Important on Global Scale*

Driven by SOLAR energy

Solar heating + wind = evaporation+ wind = deposition

75% of Earth's surface

97% oceans

2% polar ice + glaciers 

others <1%

Oceans from the largest reservoir for the global hydrologic cycle

Atomsphere contains a relatively small amount of water

Ground water is being rapidly depleted by wells

Water is denser than air, harder to move

currents move you around (plankton)

Sinking

Transmission of gasses (ie. O2 is used faster than can be diffused into water from atmosphere)

More dense as a liquid than a solid (non linear relationship)

ocean water is more dense than freshwater at the same temperature (due to salinity)

Thermal Stratificiation

Upper: epilimnion

mid: metalimnion/thermocline

low: hypolimnion

Northern: clockwise

southern: counterclockwise

Gyres: large scale circulation patterns

Humboldt Current: El Nino

Salinity: 35 ppt, lower salinity near equator from increased rainfall.

Phytoplankton are the primary producers

Biomass organisms per unit area is low, but entire biomass is immense

Marine and transient system (dominated by marine)

Organsims have mechanical, physiological, or morphological adaptations to hold onto surface and deal with dessication

Sandy Zone: less diverse; snails, clams

Rocky Zone: more diverse; sea stars, barnacles

Estuaries: river meets ocean

Salt Marsh: low lying sandy area in north temperate areas; associated with river; herbacous vegetation (ex. Spartina spp.

Mangrove Swamp: assocaited with river mouth in tropic areas; salt-tolerant trees with prop roots

Water moves longitudinally

heavily modified by humans; dams, channels etc

Headwater: allochthonous (production comes from trees), low order, canopy, no temp change. Course particle organic matter in fall. contains "shredders;" invertebrates that process OM.

Intermediate: invertebrates, grazers, moderate temp change

Downstream: Autochthonous, fine particulate matter, larger fish

small scale currents

formed by glaciers, volcanoes, tectonics, reservoirs

Lake Baikal: 20% of earth's freshwater, tectonic lake

Human input of nutrients; causes algal blooms (blue-green)

Causes toxins/taste/odor issues

Low dissolved oxygen concentration: algal blooms respire, low diffusion rates of O2 out of H2O

Metabolic function, ways to get energy

Tradeoff between temperature maintenance and water requirements

Ecophysiology

Tolerance Limits

Related to Conditions an organism faces

Beyond the upper and lower limits, fitness suffers

Limits are related to condition NOT resources (nutrients)

Ecophysiology

Limiting Factor

Related to Resources

A limiting factore is a resource that is the shortest supply relative to demand for the organism's survival, growth, and reproduction

ex. plant need water, light, nitrogen; if soil is poor then Nitrogen is the limiting factor

Temperature Relations

Terrestrial Environments

Macroclimates: conditions in a climatic zone; ex. deserts are hot and dry

Microclimates: small scale spatial variation

ex.

Altitude: lower temp, higher alt.

Aspect: north vs. south

Vegetation: shade

Ground color: local geology

Boulders and burrows

Greater thermal stability:

higher specific heat- absorbs more heat with less temp change

high latent heat of vaporization- evaporative cooling

latent heat of fusion- gives up heat as it freezes

Volume Dependent: more water = greater stability

Acclimation: short-term adjustment to a change in conditions; WITHIN AN INDIVIDUAL

Adaptation: evolution via natural selection that changes phenotype of a POPULATION

Metabolic rates of many organisms increase with temperature, only to a point

Q₁₀= (R2 + 10C)/R1

Regulation of body temperature 

(3)

Poikilotherms: inverts; body temp varies directly with environmental temp

Ectotherms: cold-blooded organisms; rely upon external energy sources to regulate body temp

Homeotherms: mammals; metabolic activity keeps body temp constant

H_s= H_m ± H_cd ± H_cv ± H_r - H_e

H_s: stored heat content

H_m: Metabolic heat

H_cd: heat of conduction; transfer of heat with contact

H_cv: heat of convection; heat flow between body and air

H_r: heat of radiation; heat coming from EMR

H_e: heat of evaporation; always negative

Behavioral: basking (+Hr), burrowing (-Hr, ±Hcd), sun orienting (± Hr)

Morphological: leaf size (±Hcv), height (±Hcv, ±Hr, ±Hcd), color (±Hr)

Physiological: sweating (-He), panting (-He), countercurrent heat exchange (+Hcd, +Hcv)

Range of temperatures within which organisms operate "normally"

Arctic species have large range due to high seasonal variation

Metabolic reactions occur in an aqueous environment

Water travels down concentration gradients (high to low)

Contrast between water content externally relative to organism's internal content can determine the magnitude of evaporative water loss or gains

Water Relations

Terrestrial

Humidity: water vapor content of air

Water Vapor Pressure (WVP): Increased humidity, increases WVP

Saturation water vapor pressure (SWVP): pressure @100% humidity

Water vapor pressure deficit (VPD): Difference between WVP and SWVP; VPD= gradient in water concentration from organism to air (organism ~100%)

GREATER VPD = STEEPER GRADIENT

High VPD, low WVP

High VPD, increased rate of evaporation

W_IA = W_D + W_F + W_A - W_E - W_S

W_IA: Internal water content of animal

W_D: Water intake (drinking)

W_F: Water intake from food

W_A: Water absorbed from air

W_E: Water loss via evaporation

W_S: Water loss via secretion

Arid Environments

Animals: metabolic water from cellular respiration, water in food, behavorial adaptations

Plants: Deeper tap roots (ex. phreatophytes; groundwater plant), redistribution of water through root system (lateral transfer)

Animals: Hide with waxes, hyrdocarbons, concentrated waste products

Plants: Thick leaves (less SA for transpiring), fewer stomata, dormancy during drought, wilting, alternate photosynthetic pathways

Soil → Plant → Air

Water potential Gradient (Ψ)

Expressed as negative values: pure water=0, dry air= -100, more negative means lower water potential

W_IP = W_R + W_A - W_T - W_S

W_IP: Internal water content of plant

W_R: water intake via roots

W_A: Water absorbed from air

W_T: water loss via transpiration

W_S: Water loss via secretions, seeds, fruits

Water Relations

Aquatic Environments

Diffusion: water from high to low

Osmosis: diffusion of water through semi-permeable membrane

Isosmotic: cells contain equal water as environment

Hypoosmotic: cells have higher concentration

Hyperosmotic: cells have lower concentration

W_I = W_D - W_S ± W_O

W_I: internal water content

W_D: Water intake via drinking

W_S: water loss via secretion (urine)

W_O: water loss or gained via osmosis

marine inverts: isosmotic; no energy spent overcoming osmotic gradients

Sharks, rays: hyperosmotic (higher concentration of solutes in body); water moves into body, high amounts of urea, Na diffuses through gills

Marine bony fish: hypoosmotic; drink seawater, but use chloride cells on gills to eliminate Na and Cl

Opposite of marine fishes

Hyperosmotic: bodily fluids contain more salt than outside environment

water diffuses through gills, disposed via dilute urine

Actively take up Na and Cl and in food

Energy taken in used from growth and reproduction

ex. light, organic/inorganic molecules

Trophic Biology

Photosynthetic autotrophs

Light (energy) + CO2 (carbon)

to make organic molecules for energy

Trophic Biology

Chemosynthetic Autotrophs

Trophic Biology

Hetertrophs

Bacteria: Photo, Chemo, Hetero

Protista: Photo, Hetero

Plants: Photo, Hetero

Fungi: Hetero

Animals: Hetero

**base of most foodwebs**

Photosynthetically Active Radiation (PAR): 400-700nm (visible light), 45% of light energy, UV too powerful

Measured as photon flux density (μmol/m²/s)

Photosynthetic Pathways

Varies with temperature and water availability

Photons absorbed → ETC → ATP + NADPH → Carb synthesis

C₃ Pathway

most common; higher plants, all algae

water is used for this pathway, plants located in moist areas

CO2 binds with RuBP → RuBP carboxylase catalyzes product → PGA C₃ acid formed

C₄ Pathway

arid/warm environments

Segregation: light dependent (mesophyll) and light independent (bundle sheath cells)

stomata stay open less due to concentration of CO2 in bundle sheath (diffusion gradient)

CO2 + PEP → PEP carboxylase (high CO2 affinity) → C₄ acid diffuses under bundle sheath → converted to Pyruvate + CO2 → C₃ cycle → Pyruvate diffused back to mesophyll

CAM pathway

Succulent plants in arid areas

stomata open at night to perform C-fixation (limit water loss)

At night CO2 is combined with PEP to form C₄ acids and stored until day then is converted to pyruvate + CO2

CO2 binds to PGA to form sugars

Pyruvate held at night then repeated

Few bacteria do this

 Oxidize inorganic forms of nutrients:  NH4+, H2S 

Other bacteria - oxidize NO2-, Fe2+, H2, CO

Heterotrophs

nutrient requirements vs. chemical composition of food

Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus make up >90% of biomass

Plant tissues have lower N and P than animal

Herbivores have lower assimilation efficiency than carnivores

Herbivores and their food

plant defenses

Morphological: thorns, bark

nutritional value: plant tissues contain varying C:N

Inedibility/digestibility: lignin/cellulose

Toxins: phenolics (reduce digestion by binding to plant proteins), Alkaloids (nictoine, caffiene)

Greater toxic plants than temperate.

due to: year around growing season causes higher diversity and faster evolutionary rates. 

Consume dead organic matter

earthworms, fish, stream insects

C:N ratios of food sources are high (inhibits fungal and bacterial growth)

some toxins, secondary metabolites exist

Consumer and food source are elementally similar to each other

Defenses: mechanical, behavioural, Aposematic coloring

Mullerian mimicry: co-mimicry of several species that are noxious

Batesian mimicry: harmless forms mimic a toxic species (snakes)

Functional responses: the rate at which organisms can take in energy is limited (number per unit time)

Predictable patterns in response curves

Theorectical functional response curve

Type 1

Food intake proportional to prey abundance; filter feeders

Theorectical functional response curve

Type 2

Slope is continually decreasing; curve is due to shift from "looking for an item" to "handling time"

Most common for Animals (individual foraging rates)

Theorectical functional response curve

Type 3

Sigmoid; switch to less common food when it reaches a threshold density; learning behavior

(multiple food choices)

Predicts on what, when and where an organism will eat

predator chooses is related to:

1) energy gains from item

2) how abundant it is

3) the costs of getting an item

Optimal Foraging Model

equation

Matthews et al. 2010

3-spine stickleback

Purpose

Examined how divergence in habitat use within the same species can lead to differences in foodweb ecology

1) size differences can lead to disruptive selection on generalist predators

2) leads to diversification

Matthews et al. 2010

Purpose

Examined how divergence in habitat use within same species can lead to differences in food web ecology

1) Size differences in prey can lead to disruptive selection on generalist predatores

2) leads to diversification

Examined how differences in feesing ecology and habitat use differ in populations of 3-spine stickleback fishes 

Matthews et al. 2010

Materials Methods

fish from 6 different lakes

1. one lake of a limentic type only

2. one with an intermediate

3. two with both types

4. two with benthic type only

Used stable isotopes to exmain proportion of littoral food (Carbon-13) in the diet and trophic position (Nitrogen-15)

Morphology: Measured Gill Raker length

Matthews et al. 2010

Predictions

1)Proportion of littoral C increases with body size in benthics only

2) Trophic position increases with body size in pelagics only

3) proportion of littoral C declines with increasing gill raker length in pelagics only

4) Trophic position increases with gill raker length in pelagics only

Matthews et al. 2010

1) Proportion of littoral C increases with body size in benthics and declines in pelagics

2) Trophic position increases with body size in pelagics only

3) proportion of littoral C declines with increasing gill raker length in pelagics only

4) Trophic position increases with gill raker length in pelagics only

Murphy et al. 2008

purpose

-Examined the influence of ENSO dynamics on the abundance and biomass of krill in Antarctic waters

*Does this cascade to upper-level predators?

-Links large-scale physical processes to local-scale ecological dynamics

Murphy et al. 2008

Variation in ENSO affects krill recruitment and predator dynamics (cyclic in nature)

Krill numbers have declined over the last 30 years; increasing SST → decrease krill abundance/biomass → decrease in fur seals

*External forces (climate) can have large and lasting effects for complex food webs*