BIO307 - Ecology

Ecology

the scientific study of the relationship between organisms and their environment

Heterogeneity

non-uniformity; natural systems are highly non-uniform at multiple scales

Climate

Uneven heating of the Earth’s surface drives air movement and weather systems

Uneven heating

Angle of incidence of sun’s rays is positively correlated with the amount of heating; heat spread over larger areas with low angles of incidence at poles

El Niño/La Niña

Changes in atmospheric pressure affect ocean currents, decade-scale

Milankowitch cycles

Changes in Earth’s orbit and tilt of its axis, long-term glacial/interglacial cycles of 100,000 year periods

Hadley cells

creates high precipitation areas at equator with rising hot air and deserts 30º out with falling cool air.

Ocean currents

Affects regional climate, the ocean has a stabilizing affect on local climate

Aspect

direction of a surface or slope

N/S slopes

Generally warmer and less vegetated on S slopes in N-hemisphere.
Tilt causes S slopes to get more direct sunlight, snow melts faster, too fast for plants too use.

E/W slopes

Generally warmer and more vegetated on W slopes versus.
Land has more time to heat up before W slopes get direct sunlight, better for photosynthesis.

Soil Depth

Shifts with slope position, water storage

Albedo

Reflectance of a surface
high albedo high reflectance
implications with drying and nutrients

Soil texture

the triangle, water retention

Aquatic environments are ___ to T due to ___

less, high capacity of water

Water has ___ albedo

Low, absorbs lots of radiation

Thermal Stratification (vertical)

T varies with depth, seasonal turnover, thermocline

Benthic Zone

bottom and sides of stream channel
lowest ecological region

Hyporheic Zone

substrate below and adjacent to stream

Riparian Zone

adjacent terrestrial area

riffles

shallower, faster zones

pools

deeper, slower zones

Biomes

Characteristic types of vegetation determined by large-scale climactic variation

Climate diagrams

0’s match and T:P is 1:2
P below T is a drought period, Insufficient precipitation to facilitate plant growth

Rules to robust experimental design

1. Designed to test a particular hypothesis

   • testable hypothesis

   • can infer causation within scope of inference

2. Must include replicated experimental units

   • to which treatments are applied

   • no pseudoreplication

3. Treatments must be assigned randomly

   • random assignment

4. Must control for variation

   • minimize effect of outside factors

   • keep other factors same for all replicates/treatments or at least account for it

Inferring Causation

• BACI: Before/After, Impact/Control site for observational studies while following rules

• Treatments must be established with respect to the independent/explanatory variable in order

Evolution

change over time in the heritable characteristics of a population;
change in allele frequency over time

Mechanisms of Evolution

1. Mutation

2. Natural Selection

3. Genetic drift

4. Gene flow

5. Non-random mating

Proximate (Immediate) Cause

how the behavior occurs; mechanistic

Ultimate Cause

why the behavior occurs; evolutionary or historical reason

Evolutionary Approach to Behavior

ability to survive and reproduce is in part dependent on behavior so nat sel should favor individuals whose behaviors make them fitter

Gene-Environment Interxn

Most aspects of animal behavior controlled by both genes and evironment

Optimal Foraging Theory

Animals will maximize the amount of E gained per unit of feeding time and minimize the risks involved

Marginal value theorem

Food may be depleted in a patch after spending some time there;
GUD: density of prey items where it is energetically favorable to move to a new patch

Mating Behaviors

Males may provide females with direct or indirect benefits;
Compared to males, females invest more time and energy, and have less offspring;

Selection should favor mating behaviors that:

• protect the female’s investment (choosing a good mate → females are pickier)

• allow males to mate with as many females as possible

Life History

a record of events relating to an organism’s growth, development, and reproduction as well as its survival.

Life History Strategies

the overall pattern in the average timing and nature of life history events;

determined by division of t and E between growth, repro, and survival;

Individuals within a species show variation;

Nat sel favors individuals with life history strategies which make them fitter

Phenotypic plasticity

One genotype may produce diff phenotypes under diff env conditions;

Can produce continuous range of growth rates;

Can produce discrete types –– called morphs

Differences between asexual and sexual reproduction

Asexual reproducers have a more rapid growth rate compared to sexual reproducers;

Sexual reproducers are better at adapting to changing env conds;

In asexual reproduction, favorable gene combinations are far less likely to be broken up;

ex: Daphnia

Semelparous

only reproduce once; then DIE

Iteroparous

can reproduce multiple times; little whores

r-selection

selection for high pop growth rates;

uncrowded or newly disturbed environments;

High fecundity, low survivorship

K-selection

selection for slower growth rates in pop that are at or near K;

in crowded conditions, efficient reproduction is favored;

Low fecundity, high survivorship

Trade-Offs

organisms allocate limited E to one structure/function at the expense of another

Grime’s triangle model

Tolerance versus Avoidance

Staying put and dealing with it versus moving away from change

Fundamental Principle of Environmental Variation

geographic ranges of species are related to constraints imposed by the environment

Stress

environmental change results in decreased rates of physiological processes;

lower potential for survival, growth, or reproduction;

distinct from disturbances (discrete event)

Acclimatization

organisms adjusting to stress through changes in behavior or physiology;

NOT adaption (change in pop over time)

Absolute density measures

# per area/volume;

total count or census of small area → subsampling;

transect line with quadrats along it

Relative density measures

sampling with a constant but unknown relationship to true data;

Catch per Unit Effort (CPUE)

Metapopulation

A group of population linked by dispersal (gene flow)

Dispersal

movement from birthplace;

distance, patch size, transport methods

Population vortex

when population decreases, genetic variation reduces and reduces ability of pop to respond to env change;

feedback loop;

high frequency of inbreeding

Env stochaticity

unpredictable changes in the environment that can cause extinction of small populations

Exploitation competition

species compete indirectly through their mutual effects on the availability of a shared resource

Interference competition

species compete directly for access to a resource

Competitive exclusion

If the niche of a weaker competitor is shared with a stronger competitor, the stronger competitor will likely drive the weaker one to extinction

Competition exclusion principle

two species that use the same limiting resource in the same way cannot coexist

Lotka-Volterra Competition Model

N_x = pop. density of species x

r_x = intrinsic rate of increase of species x

K_x = carrying capacity of species x

α = effect of species 2 on species 1

β = effect of species 1 on species 2

Intermediate disturbance hypothesis

Disturbance can kill some while creating opportunities with others;

Highest diversity at intermediate level of disturbance

Character displacement

Nat sel results in competing species becoming more diff over time

Generalist predator

eat a broad range of prey items, w/o showing preference

Specialist predator

do show a preference, narrower range of prey

Herbivore diet

can be grouped by what part of plant they eat;

generally narrow diet

Anti-predator adaptions

large size, rapid vs agile movement, body armor, toxins, aposematic (warning) coloration, crypsis/camouflage/mimicry, living in groups

Anti-herbivory adaptions

• compensatory growth –– herbivory triggers growth

• physical defenses –– tough leaves, thorns, spines, pernicious hairs, saw-like edges

• secondary compounds –– compounds that reduce herbivory. Some are toxic to herbivores, others attract predators or parasites/oids.

Constitutive defenses

Always on;

Often phys but chem too

Induced defenses

Stimulate by herbivore attack;

Often chem but phys too

Endemism

Species that are native and unique to a geographic area;

Seen in islands and island-like things

The latitudinal gradient hypothesis

Terrestrial: species richness is highest at equator and decreases towards the poles

• higher rate of species diversification in tropics

• evolutionary timeline is greater in tropics (glacial)

• Higher productivity results in more abundant resources in the tropics

Marine: reversed, highest towards the poles and decreases towards the equator

Filter analogy

Local community structure is a function of a series of abiotic and biotic filters

Ecosystem engineers

species that affect the environment

Topographic relief gradient

More species in mountainous regions, especially mammals

Biodiversity hotspot

a biogeographic region that is both a significantly reservoir of biodiversity and is threatened with destruction

Complementarity hypothesis

As species richness increases so does ecosystem function

Redundancy hypothesis

As species richness so will ecosystem function to a leveling off point

Idiosyncratic hypothesis

relationship will vary because some species have stronger effects than others

1º production

autotrophic fixation of carbon

2º production

heterotrophic assimilation of organic matter

Net primary production equals

gross primary production subtracted by respiration

Eutrophication

increased nutrients in lakes;

aging of lakes;

natural process exacerbated by humans

Streams are ___ limited

“storage”

Lakes are often ___ limited

P

wetlands are generally ___ limited

N

River Continuum Concept

explains the predictable gradient that rivers exhibit;

based on nutrient availability, E sources, and downstream transport of organic matter;

RCC → biotic components of ecosystem, predictable

Wetlands

Salt marsh more productive than freshwater;

often not very biodiverse

Detritus

Accumulates more in terrestrial vs aquatic ecosystems

Allocthonous

PP derived from outside of stream

Autocthonous

In-stream PP

2nd Law of Thermodynamics

During transfer of E, some is lost;

Energy decreases w/ increased trophic levels

Relationship between E and biomass across trophic levels

In terrestrial ecosystems, E increases with biomass and both decrease with trophic levels;

In aquatic ecosystems,
E decreases with biomass
E decreases with trophic levels
biomass increases with trophic level

Herbivores and plants: Terra vs Aqua

Terra herbivores consume lower prop of autotroph biomass;

Aqua plants require less cellulose, easier to digest;

Aqua plants more nutritious while terra more defensive;

Terra herbivores more constrained by predators

Trophic Cascades

A series of trophic interxns that result in changes in biomass ad species composition;

Bottom-up or Top-down

Factors affecting trophic levels

1. Energy: amount of PP, more = more levels

2. Disturbances: more frequent = less levels

3. Ecosystem size: bigger is better––larger ecosystem support larger pops, have more habitat heterogeneity, and higher species diversity

Biogeochemistry

The study of the phys, chem, and biological factors that influence the movement and transformation of elements

C:N ratios

Animals have lower C:N ratio than plants, herbivores must consume more than carnivore to get N

Soil Parent Material

Bedrock, Till (glaciers), or Loess (wind)

Leeching (Soil)

Movement of dissolved particles from upper to lower layers (or horizons)

HIPPO

Habitat loss

Invasive species

Pollution

Population (human)

Overharvesting