Ecology

Oikos= House                Logos= to study

The study of how organisms interact with the environment

               - to understand distribution and abudance of organisms

                - Recognize/explain patterns of nature

Biotic Vs. Abiotic

Two components of the Environment

Biotic-  Living

Abiotic- Non-Living

Biotic Interactions- between organisms

Abiotic Interactions- Between organisms and nonliving environment

Levels of Ecological Study

organismal- single organism.  Focuses on interaction between indivistual and environment (ex. what an organism eats, reaction to stimulus)

population-all organisms of a species.  Focuses on how organisms compete with each other.  Tries to understand mechanisms in regulating population growth, and interactions between members.

community-  all species in an area and interactions.  Focuses on interspecific interactions(within species).  Ex. increase or decrease fitness.

Also on community structure

              ex.  When disturbed, how fast/well do they respond and recover

ecosystem- community and abiotic elements.  Focuses on nutrient cycles/energy flow.  Ex.  How enegy transfers through ecosystem.

Climate Vs. Weather

Climate:  Prevailing long term weather conditions that historically describes terrestrial/aquatic systems. 

Weather- short term atmospheric aquatic conditions

"Climate is what you expect, weather is what you get"

Climate and Weather

-can directly and indirectly affect organisms

          ex. temperature influences metabolism

                Wind causes moisture loss

                sunlight determines if photosynthesis happens

Causes for global variation in climate:

  (temperature vs precipitation, Hadley cell, Ferrel & Polar cells)

Temperature:  controlled by solar energy

                              -hotter temperatures at the equator because the sun is hitting the earth at a 90 degree angle

                         - as you move further from the equator and toward the poles, the angle of the sun becomes shallower and the concentration of photons is not as strong, thus resulting in colder temperatures.

vs.

Precipitation:  determined by temperature and air circulation

Seasonality

Cause by the 23 degree tilt of the earth and revolution of the earth around the sun.

results in:

-Boreal (northern hemisphere) and Austral (southern hemisphere) summers and winters

-transitional falls and springs

-effect of earth's tilt more pronounced with lattitude

Causes of regional variation in climate

(topographic influence)

Also known as MicroClimates wich are caused by topographic influences such as mountains and oceans. 

mountains: cause air to rise and cool and release moisture

slopes facing water = wet side. 

opposite slope is drier = "rain shadow"

Oceans:  Modify temperature due to high specific heat of water (acts as a buffer)

            - results in cooler summers and warmer winters

Factors regulating terrestrial & aquatic ecosystems

Terrestrial:   -Temperature

                   - Precipitation

Aquatic:  -Sunlight

             -Nutrients (more limiting in aquatic systems)

Terrestrial System:  -soil retains nutrients

                            -large regions characterized by distinct vegetation which have distinct temp. and precip.

Freshwater Ecosystems

(Lentic Vs. Lotic)

Lentic Systems:  still, slowly flowing water

                            -horizontal structure

           - lakes, ponds, bogs, marshes, swamps

Lotic Systems: rapidly flowing water; unidirectional

                              -stream, river

Lentic Ecosystems

Lakes and Ponds:

littoral zone:  shallow enough for rooted for vegetation

linnetic zone:  too deep for vegetation to grow

photic zone: enough light for photosynthesis

aphotic zone: not enough light for PS

benthic zone: the bottom of the lake or pond

The following are considered Wetlands:

Marsh: no woody plants (trees), slow moving water

Swamp: has trees

                                 ^both usually connected to a lake or stream and are productive

Bog:  stagnant water, very acidic due to decomposition.  very little productivity

Lotic Ecosystems

Unidirectional due to gravity

Streams-   Rivers= big streams     Creeks= little streams

Cold streams= high in O2

Rapid agitation= little nutrients

early formation:low temp., low nutrients, high O2

mid:  warmer temp., higher nutrients, lower O2

late:  Warmest temp., highest nutrients, lowest O2

^Estuaries: where river meets ocean

                      -a mixture of fresh and salt water

                      - very productive habitat

Marine Ecosystems

Horizontal Zones (determined by depth):

Intertidal: daily covering/uncovering by tides

Neritic:  portion of ocean over continental shelf

Oceanic:  portion over deep ocean, past continental shelf

Vertical zones

photic zone

aphotic zone - 70% of the world's habitat

Behavior

Response to Stimulus

Proximate cause: how a behavior happens

Ultimate cause: why a behavior happens

Example:  Flashlight is shone in your eyes

Proximate ---> neuron triggers muscle in eye...etc.

Ultimate------> you blink to adjust to change in lighting

Variation in behavior

(innate vs learned; stereotypical vs flexible)

Innate: Unmodified by learning

Vs.

Acquired by learning

Highly Stereotyped: little variation

vs.

Highly Flexible: condition dependent

FAP's

Fixed Action Pattern

Highly stereotyped, innate behavior

3 distinct characteristics:

                           -once initiated, it runs to completion

                           -Inflexible (almost no variation)

                           - Species specific

ex.  sneezing

Set off by releaser stimuli

                         -small amounts of simple info.

                  ex. robin birds like to attack orange things

FAP's respond to threatening situations

            ex. kangaroo rat and rattlesnake rattle

Learning

(6 types)

Simple Learning

Conditioning:  learning through time and repetition

                       ex. Pavlov's dog.  Put on metronome while feeding the dog multiple times.  Eventually the dog will salivate when you just put on the metronome.

Imprinting: Fast and irreversible (etched into memory)

                  -occurs during a critical time window

                  - ex. hatching geese/ penguins

Complex Learning

Behavior modified by life experience: 

                                    -Demonstrates a spectrum of complexity along both behavioral axes

                                    -ex. birdcalls

Mistake based learning:     Learning by mistake

                                    ex.  bluebird eating monarch butterfly.  Insects with "unrewarding flowers"

Cognition:  The ability to form concepts and gain insight.  Recognition of manipulation of facts about the world. 

                  -ex monkey with dangling bananas.  Stacks boxes to get them.

                  - ex.  blackbirds bending wire to obtain bugs at the bottom of a tube. 

Observational:  Watching others perform the task first and then attempting it yourself.

                         - ex.  Octopuses and glass jar/ rubber stopper experiment.  Sees the other octopus in separate tank who knows hot to get the crab and then mimics.

Communication

Signal from one individual that modifies the behavior of another

communication can be: visual, auditory, tactile, olfactory

Ex. honeybee dance

Deception- ex.  vice butterfly looking like monarch butterfly so other animals think it has the same defenses as the monarch and not eat it.

Orientation

(Taxis)

Movement that results in a change of position

Taxis:simple orientation

Photo------------------------->  light

Phono-------------------------> sound

Geo---------------------------> gravity

Chemo------------------------> smell

Migration

(3 types)

Prolonged movement over geographic distance

 (usually associated with seasons)

Piloting:  use of visual references

 ex. gray whales migration use coastline to pilot up and down the West coast

Compass Navigation:  use of sun, stars, magnetic fields

ex.  Wandering Albatross- at sea for nine years of its life but always know how to return to their natal island.

True Navigation:  compass navigation plus knowledge of where you are. 

ex. European Starling migration experiment.  Moved birds from Scandinavia to Switzerland. Young birds flew south to Spain, more mature birds new to go Northwest to France, the usual destination of their migration.

Altruism

(Kin selection, Hamilton’s rule, eusociality, reciprocal altruism)

"Self Sacrificing Behavior"

Behavior that imparts a cost to self and a benefit to another.

2 types

1.  Kin Selection:  Altruism occurs if the cost is less than the benefit due to relatedness

          Hamilton's Rules:  Br>C  

                                       B=benefit

                                       r=coefficient of relatedness

                                       C= Cost

ex Prarie dog sentinels are more likely to raise an alarm for a predator if they have offsprings or siblings in a coterie.  Less likely for cousins and very unlikely if they have no kin (if they raise the alarm they draw attention to themselves, lowering their own chance for survival)

** Eusociality- altruism in social groups that have sterile individuals and females are more closely related to each other rather than their own offspring. 

    ex.  most common in ants and bees

2.  Reciprocal Altruism:  self sacrificing behavior with unrelated individuals

       - most common between individuals with past history of altruism

              ex.  vampire bats helps regurgitate some food for other hungry/sick bats or hugs it when they are cold.

                    ^if one didn't reciprocate when it was helped it is usually shunned.

Population Ecology

the study of:

Population size change over time

Population distribution change over time

Population abundance over time

Population

( Density, Dispersion, Reproductive Strategy)

Group of individuals of the same species that

              -live in a localized area

              - utilize a common pool of resources

Density:  # per unit area of volume

Dispersion: distribution within that area or volume

                 -Clumped: aggregated around resources

                 -Uniform distribution: Evenly distributed

                             (usually results from competition)

              -Random: lacking any discernable pattern

Reproductive Strategy: 

                        Semelparity: breed once and die

                         Iteoparity:  breed multiple times in a lifetime. 

Can be seasonal (same time each year) or continuous (anytime during the year)

Demography

Factors that influence population size & structure over time

4 main components

1. Births...................Increase

2. Deaths.................Decrease

3. Immigration..........Increase

4. Emmigration.........Decrease

ex. United States vs. India population

Survivorship Curves

Survivorship and Fecundity

proportion of surviving to a particular age class.

Type 1:   Young survivor ship- high, old-low

                      ex. humans

Type 2:  Constant throughout life

                        ex. coral

Type 3:  Young age survivorship- low, old age - high

                           ex. plants

Fecundity:  # of offspring produced

                      ^females are constraining factor.  So analysis is limited to number of female offspring produced by female parents.

Inverse relationship with survivorship

ex.  insects, low survivor ship, high fecundity

         (^ short life span but produces a lot of offspring)

ex.  elephants or humans, high survivorship, low fecundity  (long life, only one or two offspring born at a time, and over a longer period of time.

Community Ecology

Considers all individuals (all species) in a given area

Population<Community<Biome

The study of specie interactions and the consequence it has on the interacting species' fitness.

Mutualism

Mutualism: (+/+) both species gain from interaction. 

                               May seem like they are both helping each other out, but are really looking out for their own fitness (selfish)

                          ex.  ants (protect tree from grazers) and acacia trees (provide home and some food)

                      ex.  Cleaner shrimp (gets a meal) and fish ( gets parasites removed and teeth cleaned)

**^Mutualistic interactions are rare**

Comensalism

Commensualism:(+/0)  when an organism helps another organism's fitness with no cost to itself. 

                   ex.  Moras hiding under large whales for protection from predators

ex.  Birds nesting in a tree

Amensalism

Amensalism:(0/-)  when an organism's interaction has a harmful effect on another organism's fitness, but has no effect on it's own fitness.

              ex.  rhino stepping on insects

              ex.  penicillum excreting penicillin as byproduct that kills bacteria

Consumption

Consumption: (+/-) interaction  where one organism will increase it's fitness at the expense of the other interacting organism's fitness.

3 basic types

Herbivory: organism consumes plant tissues.

Parasitism: when an organism consumes small bits of tissue from host organism

                               ex.  Leeches

                                 ex.  ticks

Predation: when an organism kills and consumes another organism

2 defense mechanisms against consumption

         Constitutive: always present ex. camouflauge

                                                      ex. thorns

         Inducible:  produced in result to predators

ex.  Muscle thinkens it's shell in response to a crab's pinch

ex. Cottonwood tree secretes salicotin when a beaver starts to gnaw on it.

Mimicry

       Mullerian:  2 species with similar defenses resemble each other

             ex.  Porcupine and hedgehog

      Batesian:  species without defenses resemble a species that does

                ex.  Vice butterflies resembling Monarch butterflies, which are inedible to most birds.

Competition

Competition: (-/-)  Both species experience a fitness decrease.

Fundamental Niche:  total possible use of the environment by a species

Realized Niche:  actual observed use of the environment used by species reduced by competition.

Species in overlapping niches compete with each other

G.F. Gause- Hypothesized that 2 species with the same niche cannot co-exist

2 types of competition

              -symmetric:  Each species experience the same decrease in fitness

              -asymmetric: one species has greater fitness decrease than the other (more common than symmetric)

control of predator/prey interactions

(Top down vs bottom up)

Top down:  predators control prey abundance

Bottom up:  The amount of prey determines the abundance of predators.

Indirect interactions

trophic cascade, keystone spp.

Two species that do not directly interact influence on each other

           ^consequence of interaction with another species

Trophic Cascade

                       direct                      direct

ex. Producer---------> Herbivore ----------> Carnivore

             ^ ------------------------------------------^                                          indirect

Producers have a positive effect on the carnivores because they help feed the herbivores

Carnivores have a positive effect on the carnivores because they help eliminate the herbivores. 

         ex.  wolves, deer, and aspen trees

         ex.  Sea star removal and muscles overtaking barnicles and algae

Keystone Species:  species with effects on communities that are disproportionate to their biomass ( small biomass but big effect)

   -tend to be top level predators

                      ex. sea otter

Species Richness Vs. Species Diversity

Species Richness:  # of species, unweighted (all individuals contribute the same)

Species Diversity: # of species and abundance, weighted

Cause of Species Diversity

(three hypotheses)

Global Patterns:  many terrestrial ecosystems show pattern of decreasing diversity with lattitude.

                         ex.  vascular plants going from the equator to the poles has a steady decrease. 

                         ex. number of mammals from dense tropics to northern Alaska has a steady line of decrease.

Poductivity hypothesis:  high productivity supports more species

           - supported by natural patterns

           - contradicted by experimental studies

                        - rodents actually decrease when ecosystem's productivity increases. 

Area hypothesis:  Large areas support more species

                        -supported by observational/ experimental studies

Intermediate Disturbance Hypthesis: local species diversity is maximized when ecological disturbance is neither too rare nor too frequent.

-At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem.

-At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct

- at intermediate levels of disturbance, diversity is thus maximized because both competitive K-selected organisms and r-selected species can coexist.

Role of ecological diversity

(effect on NPP)

Net Primary Productivity (NPP) - amount of plant material available to herbivores and decomposers

        -how fast a certain unit is created per space per unit time (makes it comprable to different areas around the world)

Productivity may increase with species richness, however the variation of primary production decreases with species richness ( as there are more of one species the less there is in variation)

Diversity increases productivity/efficiency helps recover quicker for better stability.

          Resistance:  measure of how much disturbance affects a community

           Resilience:  Measure of how quickly a community recovers from disturbance.

- Diverse communities able to use more of the resource base resulting in higher productivity

-Diverse communities more likely to have redundant species (can step in and assume role when a similar species are reduced/lost)

Clements Vs. Gleason

Frederick Clements: 

                      -saw communities as superorganisms

                      - species work cooperatively

Henry Gleason:

                      - Communities= collection of individual species with unique physiological tolerances

                       - individualistic view of community dynamics

Succession

(primary vs. secondary)

The recovery of a community after a disturbance

Primary succession:  all species and soil/propagules removed.  Area has not been occupied by any biotic organism

                 ex.  lava flow, glaciers

**Remember example of Glacier Bay!**

Secondary succession:  some of all species removed but soil/propagules left in tact ( a footprint of what lived there)

         ex.  fire, strong storm

pioneer community = fast growing short lived plants weeds, mosses

Late successional community = long lived, slow growing, superior competitors.  Trees

Climax community = stable, persistent community

                                ex.  redwood forest

Species interactions during succession

(3 types)

Facilitation:  one species makes conditions more tolerable for another

  ex.  Alder tree facilitates growth  of the Sitka spruce

          (however spruce grows faster with prescence of Alder and eventually outshades the Alder tree)

Inhibition: one species prevents the establishment of another

Tolerance:  species neither helps or prevents the establishment of another species.

Island Biogeography

Study of spatially isolated communities

True islands:  chunks of terrestrial habitat surrounded by water

Virtual islands:  Fragments of habitat surrounded by inhospitable habitat

                       ex.  farmland in the Amazon

Species Area Relationship

For certain taxa, species diversity increases predictably with island area

Slope increases the slope you are getting more species with less land

 (y- axis = # of species) ( x-axis = area)

log(# of species) = z (slope) = log(Area) + log (smallest area for species to exist)

Equilibrium Theory

Rates of Colonization

Rates of Extinction

S = # of species

1. increase is S, decrease in colonization rate

2.  increase in S, increase in extinction rate

3.  increase in area, decrease in extinction

4.  increase in distance/isolation from mainland, decrease colonization rate