NR306 – Ecology

Justus Von Liebig (1840)


-Organic chemist, worked with plants

-Developed law of minimum by working with plant nutrition (water, micro, macronut.)

-Growth of plant is dependent on food, presented in min. quantity

-Law of min. eventually extended to cover all requirements of plants and animals.

Influences on animal reproductive success/survival

-Limited by food, water, shelter (cc)

-Lack of water for spawning

-Too much, or too little water for nesting

Constraints on Liebig’s Work

-Applies to only steady state conditions, does not change over time.

-Factor interaction not considered: high availability of substance other than min. may modify rate of utilization of latter.

Law of Minimum
When a multiplicity of factors is present (operating on an organism) and only one is near the limits of toleration, and that is the controlling factor.;
Limiting Factors

Factors or other restraints in the physical and biological environment of an organism that

-restrict growth

-interfere with reproductive success

-may cause death

Presence or success of organism;depends on complex set of conditions –> law of min. 

Organisms in nature are controlled by:

-quantity and variability of materials, there is a min. requirement

-physical factors (temp., moisture)

-Limits of tolerance of organisms to components of environment (habitat, other organisms)

Eugene Odum – Limiting factors
those constraints or factors that significantly reduce the growth and reproduction of an organism
Aaron Moen – Wildlife Ecology
Those constraints that reduce the rate of biological process sufficiently to limit all other processes.

Factors that affect the extent of the relationship b/w an organism and its environment.

-Potentially limiting factors always present


-May be present with CC

Factor Compensation
Some organisms can adapt the timing of growth and reproduction to adjust to constraints in the environment.
A locally adapted species that generally has a wide geographic range.
Victor E. Shelford (1913)

-Animal ecologist

-Study both structural elements (plants, animals) of a community together. 

-Developed the Law of Tolerance

Law of Tolerance

-Bell shaped curve (too little or too much stress)

-A species has a range of tolerance or requirements with a minimum on one hand and a maximum on the other. 

Factor Interaction

When conditions are not optimum for a species with respect to one ecological factor, the limits may be reduced with respect to other ecological factors.

-Organisms in nature are not living at optimum range (physical factor).

-Reproductive periods (environmental factors)

Eugene Odum – L of T

For each organism there exists a specific tolerance range for any essential environmental factor below or above which the organism’s activity is adversely affected.

-Constraint growth and reproduction (pH for fish)

S. Charles Kendeigh – L of T

A species distribution is limited more by conditions of physiological stress than by the actual limits of tolerance.

-Death verges on the limits of tolerance

– Species existence would be jeopardized if too frequently exposed to limits of tolerance. 


Shelford and Frederick Clements (1877)

-Started with oyster beds (Karl Mobius)


Major natural unit of plants and animals

“Major life zone”


Living and non-living environment functioning as a self-organizing, self-sustaining system.


-Plants and animals interacting with the physical environment

Bioconisis = Community
Collection of living organisms which find everything for growth and development in a particular geographic area.
Optimum Environment

-It requires/demands the most favorable levels of all factor intensities.

-An improvement in an environmental condition tends to favor population development.


Implies that wide variations in factor intensities are of little consequences in the region of the optimum

-bell shaped curve, pollution

-Closer the factor is to limit of toleration, the greater the relative impact of the change on the organism’s behavior. 

Optimum Enviro. and L of T change with:

-Stage of life cycle



Time refers to:

-Time of day




Space refers to:




-Up and down



The nature of the action of the environment on living organisms.

-All of the common conditions acting on the organism.

-all, common, condition

Open System

-Lehninger (1965)

A system which exchanges matter with surroundings. Can also exchange engergy.

-Energy can enter or leave the system.

-May create unstable relationships b/w population # and resource availability.

Any entity possessing mass when at rest. 

The capacity to do work. 


Types of energy important to organisms





Open system and 


-Pops are dependent on matter and energy from outside sources.

-If flow and energy/matter is interrupted w/in the system, problems may develop.

Closed System

Any system that does not exchange matter with its surroundings. 

-Amount of matter is fixed within a system.

-Radient energy can enter and leave.

Closed system and


CS have site-bound energy that is tied to matter cycle in the system.

-State of equilibrium b/w pop and resource use inside CS.

To attach physically
Affix attached to the beginning of a word, produces a derivative word.
An affix occurring at the end of a word
habitat (selection)
Oliver Owen

Resource Classification System

“Natural Resource Conservation”

RCS – Inexhaustible (2)

No apparent finite supply or amount. Quantity will remain relatively constant. 



-Misusable (quality)

RCS – Immutable 

Incapable of much adverse change through man’s activities


-Atomic Energy

-Wind power


-Water power of tides

RCS – Misusable

Quality impaired.


-Solar power


-Waters of oceans, lakes, streams

-Water power of flow streams

RCS – Exhaustible (2 main)

Those that can be completely used up.




RCS – Maintainable

Those whose quantity and quality are dependent upon man’s use.

Renewable (flow): living biota

Non-renewable: Once gone, can’t be replaced

RCS – Renewable


Flow resources – rejuvenated

Living biota. Perpetual harvest depends upon proper planning and management.

-Water in place

-soil fertility

-products of land and water

-human powers

RCS – Non-Renewable

Once gone, can’t be replaced: can’t recreate it

-Species of wildlife


-oligotrophic lakes (few food)

RCS – Non-maintainable

Primarily mineral resources. Total quantity is static. Can’t be replaced when used. 


-Non-reusable (stock)

RCS – Reusable
Gems, precious metals, diamonds
RCS – Non-reusable


Fossil fuels/oil

non-metallic mineral



-Group of individuals of single species

-Structure, function, and adaptations to diverse environmental conditions or other pop’s

-Characteristics different than that of individual (age structure, sex ratios…)

-Species pop’s occupy same place at same time.


A group of individuals (plants, animals) or objects agreeing in common attributes and designated by having the same name.


-Heterosexual vertebrates


coined money, in the shape mentioned
A course or series of events that recur regularly

-Terrestrial vertebrates (mammals and birds), also reptiles, amphibians.

-NOT fish/invertebrates (Hanson).

one way out
one way in
Two way movement, governed by time of year
Turnover (wildlife)

The time it takes to replace all individuals in a pop.

-New individuals through birth and immigration.

Turnover Rate

Rate at which young individuals replace older individuals

-Annual measurement

-Stability  static conditions

Turnover rate – Numbers in wild

-Few orgs. live to old age in wild


-Individuals w/in pop change rapidly, even though total number remains constant from period to similar time period.

Study of freshwater systems

still waters




Flowing waters



fisheries – Coldwater




-white fish, grayling


Less than 20° C

fisheries – Warmwater






More than 20° C

Endemic species, indigenous to specific area


Think boars

Non-native (and stocked fish) adapted, which have become established in an area and naturally reproduce 

-“put and take” fisheries





Running upward. Adults travel upriver from sea to spawn. Return to sea.


-Salmon, steelhead





Migrate b/w fresh and salt water

-eels, carp




Live, lay elsewhere

Live in fresh water, migrate to salt water to lay eggs.




Both spawn and feed as adults in open water of ocean.

-Move around to different areas of the ocean.

Evolution (Species concept)
Diversity of nature is divisible into a finite number of definable species.
Ecology (Species population)
Group of similar organisms residing in a defined space at a certain time.
Biological Species
Group of actually/potentially interbreeding pop’s that are reproductively isolated from other groups.
Bone in head of fish, balancing organ, determines age of fish.
Why do populations fluctuate/cycle through time?
Depends on LF’s and CC
Cycles – Irruptive

Irregular growth patter, unstable numbers, erratic, unpredictable

-Favorable conditions that occur from time to time (weather, climate, good habitat)


-Normal cycle, stable, but can increase suddenly




Cyclic (periodic/less stable)


NO wildlife pop is constant in numbers

due to:

Why a pop fluctuates through time…

-gains from birth

-losses from death





Steady state (input = output)

Stable cycle

Relatively constant in number from period to similar period.

-Minor ups and downs from births and deaths (CC)

-Biomes with constant temp. and rainfall

Cyclic cycle


-Two types

Less stable, fluctuate at regular intervals.

Short (3-4, 2-5 years) and 10-year

-Biomes with low temp. and rainfall (arctic, temperate)

-Less complex communities

-Buffer species live longer, less importance (hare)

Short Cycle

3-4, 2-5 years

-Lemmings, mice overrun natural habitat

-Tied to cycles of natural predators (fox, owl)

-Time lag effect

Time lag effect

-Short year

Predator/prey relationship is offset. One controls the other. 
10-Year Cycle

-American game birds

-Not well studied, but well known

-Time involved 

Affect great # of species at same time

-Boreal forest

Growth Curves (Animals)

Way a pop responds to new environment through time, or the carrying capacity of the environment. 

-basic GC express the slope of a pop’s growth when organisms introduced to new environment

-Biotic potential (push up) and environmental resistance (push down)

An interval of time during which a sequence of recurring succession of events is completed.

Biotic Potential (GC)

Flies and DDT

-Good light, temp, chem. environment

-High repro rate

-Generalized niche

-Good food supply, habitat

-Can compete, defend themselves



Environmental Resistance (GC)

Decimating Factors

-Bad light, temp, chem. enviro.

-Low repro. rate

-Specialized niche

-Bad food supply, habitat

-Too many competitors, can’t defend

-Bad health

-Can’t migrate/adjust

Biotic Potential – define

Max. sustained rate of natality and min. rate of mortality.

-Rate of increase limited by physiological limitation of species, not environment

Environmental Resistance – define

Sum total of all decimating (Limiting) factors, operate to cause mortality.

-Prevents Biotic Potential from being realized.

J-Shaped Curve

Nr = dN/dt (# offspring/period of time)


Exponential, uncontrolled growth

S-Shaped Curve

S = Nr [(K-N)/K]


-When a species becomes established in new habitat with good CC

The two Growth Curves



-show type of pop growth exhibited in situations where

-CC of habitat is constant

-BP of species modified by density dependent factors.

Density Dependent factors

-Increase in intensity as pop numbers approach CC of the environment.

Mortality increases as pop increases.


population size at a point in time

o is point of starting


Maximum rate of increase

-# of organisms that will breed (females)

Number of individuals added for a time period
a specific time period (change in time)
growth rate for time period
carrying capacity
S-Shaped curve graph
P.F. Verhulst (1838)
-Developed original model for population growth. 

Raymond Pearl 


L.J. Reed (1920)

-Wrote paper that plotted US growth, fit the curve of Verhulst
Course Description

-Broad terminology and classification system

-Dynamics of energy flow and nutrient cycles at the community and ecosystem level

-Man’s role as a principle factor of change in the resources of natural systems

-Historical perspective which includes important people and dates

Coarse Goal
Students articulate/list environmental conditions and ecological principles that influence, control, and determine, the ecological factors that affect an organism’s presence in selected areas. 

-A fundamental truth that explains the relationship b/w 2 or more variables.

-It is descriptive and predictive, NOT prescriptive.

-Was synthesized from observation

-Can’t be disproved, but can be modified through time.

Principle: Descriptive
-Describes how nature behaves, what should happen under certain conditions
Principle: Predictive
-describes what may happen given a certain set of circumstances.
Resource Management Functions
planning, organizing, and implementing
-A building block of a theory, the mental image formed by the generalization of ideas.
A concept: 

-Describes some regularity, relationship w/in a group of facts

-an element of memory

-vehicle of thought

-entity by means of which thinking is carried on

-is not the meaning in the sense of things signified


-an explanation of a potential law of nature

-a belief or procedure proposed or followed as the basis of action.

-a plausible general concept or body of principles offered to explain phenomena

unproved assumption


a tentative assumption made in order to draw out and test its logical or empirical consequences.

-Proposition thought to be true because its consequences are true. 

-Has NOT been tested

Law of Minimum (who)
Justus Von Liebig
Law of Tolerance (who)
Victor Shelford
Combined concept of Limiting Factors
presence and success of an organism, etc. depends on a complex set of conditions (Law of Min, Law of Tolerance)
Physical Factors
Abiotic environmental conditions, such as precipitation, soil type, temp., and sunlight. 
Its composed of biotic and abiotic elements that interact and interrelate.
-The separation of organic matter into similar compounds.

Living systems consume and produce energy.

-Energy in plants = Primary Production


The maintenance of constancy w/in a biological system. In terms of interaction b/w organisms in a community or internal environment of an individual. 

-All living systems are in equilibrium with the environment

-The amount of living tissue produced per unit time by the population is a function of available resources and the environment. 
Food chains/food web

-Number of organisms forming a series through which energy is passed. 

1. First trophic level: green plant (autotroph), traps energy, makes food for consumer levels. 

Trophic Levels
-Energy passes through a system, it passes through trophic levels. In steady-state conditions, rate of energy production by one level MUST EXCEED the rate of energy utilization by succeeding level. 
Metabolism/size of indivduals
All chemical reactions, which take place in a living organism.
Trophic structure/ecological pyramids
Pyramid shaped diagram representing a series of organisms, allocated to certain trophic levels. For complete ecosystems isolated from other systems: little material is gained or lost b/w them
Sedimentary Cycles

Cycle involving movement of more earth bound elements: 



-volcanic activity

-mountain building

Nonessential Elements

Elements that pass back n forth b/w organisms and environment, many involved in sedimentary cycle. 

No known value to organism, but concentrated in tissues, similarity to vital elements.

-Atomic bombs = radioactive isotopes of these elements and get into environment and food chains. 

Organic Nutrients
Amino acids, carbohydrates, proteins, other carbon-containing substances produced by plants or animals, required by some organisms. 
Nutrient Cycling

Cycling of chemicals like carbon, oxygen, phosphorus, nitrogen and water w/in (intrasystem) or b/w (intersystem) ecosystems. 

-Assimilated and broken down over n over again by organisms

Pathways of Cycles
Directions taken by a set of operations that are repeated as unit. 
within or among a community
Species Diversity
A collection is said to have high degree of diversity if it contains many species of fairly equal abundance. Diversity is low when species are few or uneven abundance. 
similar environments support similar or equivalent communities or organisms even though the species and locations may be different. 
Ecotones/Edge effect
Area where two different communities (physical areas) come together, a favorable margin b/w two plant communities. The narrow part adjacent to boarder. 

Population Properties


It has characteristics above that of the individual, like age structure, sex ratios, etc. 

-Generally function of food, water, shelter. 

Relative Abundance

A rough estimate of population density of a given species. 

(Number of individuals in period of time/total species in community) = percentage

Rates of Increase
Increase of a population over time, function of age composition, sex composition, specific growth rates due to reproductive potential of components of age groups. 
Natality, Mortality, Age distribution
Differences in which mortality, natality, fecundity, age composition, and manner in which variability relates to the environment and permits survival. 
Growth Forms, Cycles
Characterize community structure by the fact that certain growth forms are dominant, or conspicuous in the community. Classification according to size, morphology, and length of vegetative body.
Carrying Capacity
the maximum population that a habitat will support indefinitely. Function of food, water, shelter. 
adjustments that a population makes to remain w/in carrying capacity of its environment. 
Population regulation
role of biotic factors in the determination of population density
Density Independent (regulation)
-Population species is not regulated by its size or factors that are not influenced by population size (weather extremes) 
Density Dependent
Factors increase intensely as population numbers approach the carrying capacity of the environment. 
branch of biology dealing with energy transformations in living organisms.
Population structure – lateral patterns
Lateral patterns expressed by communities are a function of elevation, soils, exposure, etc. Each species has its own pattern of population distribution related to the environment. No two are exactly the same.
Individuals or pairs defend an area against intruders of the same or different species.

Occurrence of organisms in isolation from others of their species

-desert shrubs

Struggle b/w organisms of the same or different species striving for a limited resource in the same area in a similar time frame. 
competition among same species
competition b/w different species that use the same resource
Living together, various lasting close associations b/w organisms of different species.
killing and eating of an individual of one species by an individual of another species
the organism is dependent on its host for essential nutrient factors. Doesn’t usually destroy the host.
specific part of a habitat occupied by an organism. No two species occupy the same niche. 
Ecological Equivalents

Different species that have similar roles (niches) in similar ecosystems located in different parts of the biosphere

-anteaters in South America, aardvarks in Africa

Different species or subspecies whose areas of distribution do not overlap
Different species or subspecies whose areas of distribution overlap or coincide.
Behavior Patterns
Like responses in which organisms respond to stimuli, including the accommodation of a population. Individual interactions w/in a pop, reproductive behavior.
Social Behavior
any behavior on the part of an organism stimulated by, or acting upon, another member of the same species. 
Ecosystem Development
process of change ecosystems go through to the biotic components that is capable of modifying and controlling the physical environment to varying degrees. High production-biomass ratio.
a community is in equilibrium with existing environmental conditions, and forms the final stage of natural succession. 
the study of interactions b/w and among organisms and the environmental factors which determines organism’s distributions, abundance, rates of productivity, and evolution