The study of the interactions

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Ecology is
The study of the interactions among organisms
and their interrelationships with the
physical environment. No organism exists as an
entity, separate and distinct from its
environment
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1. Components
Components of the ecosystem involve interacting
abiotic factors and biotic factors.
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a. Abiotic Factors
The abiotic environment includes physical and
chemical factors which affect the ability of
organisms to live and reproduce.
Light Intensity
Temperature
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The Abiotic Factors include
- Intensity of light - Range of temperatures
- Amount of moisture - Type of substratum -
Availability of inorganic substances such as
minerals - Supply of gases such as O2, CO2,
N2. - pH
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Each of these factors varies in the environment
and, as such, may act as a limiting
factor, determining the types of organisms which
may exist in that environment.
Examples include - A low annual temperature
common to the northern latitudes determines
determines in part what species of plants can
exist in that area. - The amount of oxygen
dissolved in a body of water will help determine
which species of fish will exist there. - The
salt-laden air and water of coastal areas
limit what species can exist in those regions.
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B. Biotic Factors
Biotic Factors are all the living things that
directly, or indirectly affect the environment.
Thus, the organisms, their presence, parts,
interaction, and wastes, all act as biotic
factors. Biotic Factors interact in many ways
such as in nutritional relationships and symbolic
relationships.
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Part I
Ecological
Organization
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A. Population
A population is all the members of a
species inhabiting a given location
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B. Community
All the interacting populations in a given area
represent a community
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C. Ecosystem
An ecosystem is the living community and the
physical environment functioning together as an
interdependent and relatively stable system.
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D. Biosphere
The biosphere is the portion of the earth in
which life exists. It is composed of numerous
complex ecosystems.
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Biomes
A major regional or global biotic community, such
as a grassland or desert, characterized chiefly
by the dominant forms of plant life and the
prevailing climate. Biomes may be terrestrial or
aquatic. The temperate deciduous forest of the
northeastern United States is a terrestrial
biome. The ocean is an aquatic biome.
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a. Terrestrial Biomes
The major plant and animal associations on land
are determined by the major climate zones of the
world, modified by local land and water
conditions. Climates will vary as to
temperature, solar radiation, and precipitation.
The presence or absence of water is a major
limiting factor for terrestrial biomes.
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1) Characteristics
Land biomes are characterized and sometimes named
by the climax vegetation in the region. The
major land biomes, and their characteristics,
flora, and fauna are listed on the next pages.
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Tundra
Characteristics permanently frozen
subsoil Climax Flora Lichens, mosses,
grasses Climax Fauns Caribou, Snowy Owl
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Characteristics long, severe winters summers
with thawing subsoil. Climax Flora
conifers Climax Fauna moose black bear
Taiga
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Temperate-Deciduous Forest
Characteristics moderate precipitation cold
winters, warm summers Climax Flora trees that
shed leaves (deciduous trees) Climax Fauna gray
squirrel, fox deer
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Tropical Forest
Characteristics heavy rainfall constant
warmth Climax Flora many species of
broad-leafed plants Climax Fauna
snake, monkey, leopard
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Grassland
Characteristics considerable variability in
rainfall and temperature
strong prevailing
winds Climax Flora grasses Climax Fauna
pronghorn antelope, prairie dog
bison
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Desert
Characteristics sparse rainfallextreme daily
temperature fluctuations Climax Flora
drought-resistant shrubs and succulent
plants Climax Fauna kangaroo rat lizard
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2) Geographic Factors
Climatic conditions change with latitude and
altitude.
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Altitude Latitude
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b. Aquatic Biomes
The largest part of the biosphere (the earth) is
made up of aquatic biomes. It was here that life
first arose, and here it evolved for almost three
billion years, before plants and animals moved
onto land. There are two main types of Aquatic
Biomes Freshwater and Marine. Freshwater biomes
usually have a salt concentration of less than
1, whereas Marine biomes have a salt
concentration that averages 3.
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b2. Freshwater Biome
Freshwater Aquatic Biomes have close ties to
their surrounding terrestrial biomes. Runoff of
water from land creates streams and rivers, and
where runoff in trapped, ponds and lakes are
formed. Also, the characteristics of a
freshwater biome are influenced by the pattern
and speed of water flow, as well as the climate
to which the biome is exposed.
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b3) Marine Aquatic Biomes
Marine Aquatic Biomes are found in the Earths
oceans, covering nearly 75 of the Earths
surface. Most of the planets rainfall is from
the evaporation of the Earths oceans, and the
temperatures of the oceans strongly effect the
worlds climate and wind patterns. Marine Algae
are a major source of oxygen for the world, as
well as consuming huge amounts of carbon dioxide
from the atmosphere.
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Part II Ecosystems
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Ecosystems are
The ecosystem is the structural and functional
unit studied in ecology.
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A. Ecosystem Structure and Function
An ecosystem involves interactions between
abiotic and biotic factors. An ecosystem is a
self-sustaining unit if the following
requirements are met - A constant source of
energy and a living system capable of
incorporating this energy into organic
compounds. - A cycling of materials between
organisms and their environment.
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1) Nutritional Relationships
Nutritional Relationships involve the transfer
of nutrients from one organism to another within
an ecosystem.
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a) Autotrophs
These organisms can synthesize their own food
from inorganic compounds and an unable energy
source.
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b) Heterotrophs
These organisms cannot synthesize their own food
and are dependent upon other organisms for food.
On the basis of this dependency, organisms are
classified as either saprophytes, herbivores,
carnivores, or omnivores.
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(1) Saprophytes
- include those heterotrophic plants, fungi, and
bacteria which live on dead matter.
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(2) Herbivores
- are those animals which consume plants
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(3) Carnivores
- are those animals which consume other animals.
These include - PREDATORS ---- animals which
kill and consume their prey. - SCAVENGERS ----
animals which feed on other animals which they
did not kill.
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(4) Omnivores
- are those animals which consume both plants
and animals.
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2) Symbiotic Relationships
Different organisms may live together in a
close association. This living together in a
close association is known as symbiosis.
Symbiosis relationships may or may not be
beneficial to the organisms involved. Symbiotic
Relationships may include Nutritional.
Reproductive, and protective relationships.
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These types of Symbiosis include
a) Commensalism -
In this relationship one organism is benefited
and the other is not adversely affected.
Example Barnacles Whales In this relationship
both organisms benefit from this
association. Example Nitrogen-fixing bacteria
within the nodules of legumes certain protozoa
within termites. In this relationship, the
parasite benefits at the expense of the
host. Example Tapeworm and heart worm in dogs.
b) Mutualism -
c) Parasitism -
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2) Energy Flow Relationships
If an ecosystem is to be self-sustaining it must
contain a flow of energy
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a. Energy Flow
Those life activities which are characteristics
of living organisms require the expenditure of
energy The pathways of energy through living
components of an ecosystem are represented by
food chains and food webs.
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b. Food Chain
Green plants convert radiant energy from the sun
into chemical energy (food). A food chain
involves the transfer of energy from green plants
through a series of organisms with repeated
stages of eating and being eaten.
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C. Food Web
In a natural community, the flow of energy and
materials is much more complicated than is
illustrated by any one food chain. Since
practically all organisms may be consumed by more
than one species, many interactions occur among
the food chains of any community. These
interactions are described as a food
web. Interactions in a food web involve 1)
Producers 2) Consumers 3) Decomposers
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A Simple Food Web
coyotes
Rats
spiders
rabbits
snakes
hawks
Grasses shrubs
lice
frogs
Seed-eating birds
insects
Deer
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Producers
The energy from a community is derived from the
organic compounds synthesized by green plants.
Autotrophs are therefore considered the
producers.
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Consumers
Organisms that feed directly upon green plants
are primary consumers or herbivores. Secondary
consumers, or carnivores, feed upon other
consumers. Omnivores may be either primary or
secondary consumers.
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Decomposers
Organic wastes and dead organisms are eventually
broken down to simpler substances by
decomposers, such as the bacteria of decay.
Through this action, chemical substances are
returned to the environment where they can be
used by other living organisms.
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D. Pyramid of Energy
Energy flows through ecosystems from producers to
various levels of consumers. Each time an
organism eats one another, not all of the energy
is transferred. Only about 10 of energy of a
producer is transferred to the consumer who eats
it. Therefore, there is a progressive loss of
energy at each level of the food chain. We can
represent each amount of energy at each level as
a part of a pyramid.
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d.Pyramid of Energy
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E. Biomass Pyramid
It is possible to estimate the mass of all the
organisms living in a given area or ecosystem.
The estimation is known as the bio mass. If the
mass of the producers and each type of consumer
is recorded, a pyramid can be constructed showing
the bio mass of the producers is far greater then
the bio mass of the consumers.
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e. Biomass Pyramid
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3. Material Cycles
In a self-sustaining ecosystem, material must be
cycled among the organisms and the abiotic
environment. Therefore, the same materials can
be reused.
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Carbon-Hydrogen-Oxygen Cycle
involves the processes of photosynthesis and
respiration.
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Water Cycle
The Water Cycle involves the processes of
photosynthesis, transpiration, evaporation and
condensation, respiration, and excretion.
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EVAPORATION - The first stage of the water cycle
is evaporation. As water is heated by the sun,
its surface molecules become energized to break
free of the attractive force binding them
together. They then rise as an invisible vapor
into the atmosphere.
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CONDENSATION As water vapor rises, it cools and
eventually condenses, usually as tiny particles
of dust in the air. When it condenses, it becomes
a liquid again or turn directly into solid ( ice,
hail or snow). These water particles
then collect and form clouds.
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When the clouds are too heavy, they fall as rain.
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Nitrogen Cycle
Is the the continuous flow of nitrogen
through the biosphere by the processes of
nitrogen fixation, ammonification (decay)
nitrification, and denitrification. Nitrogen is
vital to all living matter, both plant and
animal it is an essential constituent of amino
acids, which form proteins of nucleic acids, and
of many other organic materials.
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Nitrogen Cycle
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B. Ecosystem Formation
Ecosystems tend to change over time until a
stable system is formed. The type of ecosystem
that is formed depends on the climatic
limitations of a particular geographical area.
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1. Succession
Succession may be defined as a continuous
unidirectional, sequential change in species
composition of natural communities.
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Succession - 1
The sequence from grass to shrub to forest that
terminates in a relatively stable community
historically has been called a sere and each of
the changes a seral stage. Although seral stage
is a point on a continuum of vegetation through
time, it is recognizable as a distinct community.
Each has its characteristic structure and species
composition. A seral stage may last only one or
two years or may last for decades. Eventually,
succession slows and the plant community achieves
some degree of equilibrium or steady state with
the environment. This mature, relatively
self-sustaining seral stage traditionally been
called the climax.
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Succession - 2
Succession that begins on areas unoccupied or
unchanged by organisms is called primary
succession. Succession that proceeds on areas
where other organisms were present is called
secondary succession. Barren areas, whether they
are natural primary sites, such as rock outcrops,
sand dunes, and alluvial deposits, such as
abandoned cultivated fields or road banks, are a
natural vacuum eventually filled by living
organisms. Organisms that colonize such sites
comprise the pioneer species. Succession that is
self-driven or autogenic when changes in the
environment are brought about by organisms
themselves. In other cases changes in the
environment are caused by some external factor
unaffected by the organisms is termed allegoric.
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a. Pioneer Organisms
Succession may be said to begin with pioneer
organisms, since these are the first plants to
populate a given location. Some examples are
Lichens, they are the pioneer organisms on bare
rock. Pioneer organisms modify their
environment. Seasonal die back and erosion, for
example, would create pockets of soil in the
crevices and hollows on the bare rock.
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b. Changes
Each community modifies the environment, often
making it more unfavorable for itself and,
apparently, more favorable for the following
community which infiltrates the first community
over a period of years. A typical successional
sequence in New York State might be pioneer,
grass, shrub, conifer, and deciduous
woodland. Plant species (flora) dominate in the
sense that they are most abundant food sources.
Plant succession is a major limiting factor for
animal (fauna) succession. Communities are
composed of populations able to exist under the
prevailing conditions and are identified by their
dominant plant species-- the one that exerts the
most influence over the other species present.
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c. Climax Community - 1
A climax community is one that has reached the
stable stage. When extensive and well defined,
the climax community is called a biome. Examples
are tundra, grassland, desert, and the deciduous,
coniferous, and tropical rain forests. Stability
is attained through a process known as
succession, whereby relatively simple communities
are replaced by those more complex. Thus, on a
lakefront, grass may invade a build-up of sand.
Humus formed by the grass then gives root to oaks
and pines and lesser vegetation, which displaces
the grass and forms a further altered humus.
That soil eventually nourishes maple and beech
trees, which gradually crowd out the pines and
oaks and form a climax community. In addition to
trees, each successive community harbors many
other life forms, with the greatest diversity
populating the climax community.
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c. Climax Community - 2
Similar ecological zonings occur among marine
flora and fauna, dependent on such environmental
factors as bottom composition, availability of
light, and degree of salinity. In other respects,
the capture by aquatic plants of solar energy and
inorganic materials, as well as their transfer
through food chains and cycling by means of
microorganisms, parallels those processes on
land. The early 20th-century belief that the
climax community could endure indefinitely is now
rejected because climatic stability cannot be
assumed over long periods of time. In addition
nonclimatic factors, such as soil limitation, can
influence the rate of development. It is clear
that stable climax communities in most areas can
coexist with human pressures on the ecosystem,
such as deforestation, grazing, and urbanization.
Polyclimax theories stress that plant development
does not follow predictable outlines and that the
evolution of ecosystems is subject to many
variables.
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2. Competition
Competition occurs when different species or
organisms living in the same environment
(habitat) utilize the same limited resources,
such as food, space, water, light, oxygen, and
minerals. The more similar the requirements of
the organisms involved, the more intense the
competition. If two different species compete
for the same food or reproductive sites, one
species may be eliminated. This usually
establishes one species per niche in a community.
The niche is the organisms role in the community.
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A. Past Present
Humans, in exercising a unique and powerful
influence on the physical and living world, have
modified their environment.
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1. Negative Aspects
Natural systems have been upset because humans
have not realized that they not only influence
other individuals, other species, and their
nonliving world, but are, in turn, influenced by
them. Although most ecosystems are capable of
recovering from impact of minor disruptions,
human activities have sometimes increased the
magnitude of such disruptions so as to bring
about a more lasting and less desirable change in
the environment upon which all life depends. Such
disruptions will directly affect at least one of
the components of an ecosystem and this, in
turn, may affect the remaining.
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Human Population Growth
Many of us have seen linear graphs of human
population showing the enormous growth in the
last two centuries. However, significant changes
in population dynamics are lost in the
exponential growth and long time scales. If the
data are replotted on a log-population by
log-time scale, significant population dynamics
emerge. First, it is apparent that population
growth has occurred in three surges and second,
that the time between surges has dramatically
shortened.
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Human Population Chart
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b. Human Activities
Some human activities have led to led to the
extinction or endangerment of numerous species of
plants and animals as well as producing less
favorable living conditions for many species,
including humans. Such activities include
1) Over hunting 2) Importation of
Organisms 3) Exploitation 4) Poor Land Use
Management 5) Technological Oversight a)
water pollution b) Air pollution c)
Biocide Use d) Disposal Problems
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1) Over Hunting
Uncontrolled hunting, trapping, and fishing still
occur in many parts of the world. The extinction
of the Dodo Bird and the Passenger Pigeon
resulted from such activities. Endangered
species include the blue whale.
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2) Importation of Organisms
Humans have accidentally and/or intentionally
imported organisms to areas where they have no
natural enemies leading to the disruption of
existing ecosystems. Examples include the
Japanese beetle, Gypsy Moth and disease-causing
organisms such as those that cause Dutch Elm
Disease.
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3) Exploitation
The exploitation of wildlife, both flora and
fauna, for their products and their pet trade has
to led threatened populations and ecosystem
disruptions. Examples include the African
Elephant and the Pacific Walrus -- ivory the
Colombian parrot -- pet trade Tropical
Rainforest -- plywood.
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4) Poor Land Use Management
Increased urbanization /sub-urbanization claims
increasing amounts of agricultural lands
modifies watersheds, disrupts natural habitats
(including wetlands), and threatens the existence
of the wildlife species. Poor Land use
management practices have led to to over
cropping, overgrazing and failure to use cover
crops. This has resulted in the loss of valuable
soil nutrients.
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5) Technological Oversight
Technological oversights have led up to
unplanned consequences which have contributed to
the pollution of water, air, and land.
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a) Water Pollution
Major water pollutants include heat, sewage,
and chemicals such as phosphates, heavy metals,
and PCBs.
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PCB page 1
PCBs or Polychlorinated Biphenyls are a class
of chlorinated compounds. They are a group of
chlorinate hydrocarbons that are manufactured by
the controlled chlorine substitution of the
biphenyl molecule. They mainly exist in two
states the form of a solid and in a liquid. In
a solid state at 15 degrees Celsius it is a white
powder and in a liquid state it is an oily liquid
with a pale yellow coloring. The structure
consists of two atomic rings that are 6 membered
and have varying degrees of chlorinating on each
ring. Generally, PCBs are non reactive, very
stable compounds that exist in our environment.
They were first used in industrial applications
in 1929 due to their unique chemical stability,
thermal stability, high dielectric constant, non
flammability and their low cost. They are used in
paints, printing inks, carbonless copy paper,
sealants, and adhesives. They are also used to
insulate fluids in electrical transformers and
capacitors in the power industry, heat transfer
substances, cutting oils, hydraulic fluids,
lubricating oils and plasticizers for making
brittle plastic pliable. PCBs usually enter our
aquatic ecosystems via precipitation, industrial
discharges and agricultural runoff.
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PCB page 2
For many years PCBs have been used for
industrial purposes. Concern about the impact on
the environment and human health did not arise to
a noticeable height until 1966. Due to their
unique chemical stability and their resistance to
chemical oxidation, photodegradation, thermal
changes, most chemical agents, acid-base
reactions and hydrolysis they are very poorly
metabolized by biological systems. Also they are
extremely soluble in oils and fat and yet in
water their solubility is very poor and varies
inversely to the degree of chlorinating. More
heavily chlorinated congeners have a higher
likelihood of undergoing absorption to the
surface of a soil particle. This is then followed
by a slower diffusion into the soil. The lower
the organic content the faster this absorption
takes place. With this activity of absorption
into the soil PCBs are barely detectable in
surface waters with low particulate loads.
However, they may exist in high concentrations in
the bottom sediments. They partition out of the
aquatic ecosystem and into biologic tissue. As a
result of their persistence and poor rate of
metabolization this substance accumulates in the
food chain and increases in concentration at each
level of consumption and can build up from 10
million times. Through inhalation, ingestion and
dermal contact PCBs can be easily absorbed by
most animals.
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PCB page 3
Affects due to exposure can range from acute to
chronic. Slight exposure to the vapor may
irritate eyes, nose and throat, high exposure
could result in damage to the liver. Chronic
(long term heath affects) can occur some time
after exposure and may last for months or years.
In animals they have been shown to be teratogens.
So it is likely that they may be teratogens in
humans thus being hazardous to reproduction. They
may be passed from mother to child and can affect
adult reproductive systems. Another concern is
that PCBs are probable carcinogens in humans.
There is possible evidence that they cause skin
cancer in humans and liver cancer in animals.
Other possible affects are a severe rash similar
to acne that lasts for many years. High exposure
may also result in damage to the nervous system
causing "pins and needles" in the arms and legs.
PCBs can however be partially dechlorinated in
anaerobic environments. With the addition of
hydrogen peroxide to the aqueous system
bioremediation processes can be accelerated and
expedite PCB removal. In the 1970s the
production of PCBs was stopped, however, many
still exist and continue to pose a threat to our
environment despite strict regulations and
efforts to make the public aware of the hazards
of PCBs. Further development through research to
discover effective techniques to remove these
compounds from our environment and remove the
hazards to ourselves and our wildlife are vital.
Hopefully, one day we will finally be able to
generate lasting solutions and to put an end to
the problem of hazardous waste.
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b) Air Pollution
Major air pollutants include carbon monoxide,
hydrocarbons, and particulates. Nitrogen oxides
and sulfur dioxide combine with water vapor
creating acid rain problems. On the next page
you will find information on acid rain.
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Acid rain
"Acid rain" is a general name for many phenomena
including acid fog, acid sleet, and acid snow.
Although we associate the acid threat with rainy
days, acid deposition occurs all the time, even
on sunny days. Something is acidic if it has a
low pH. The pH of a liquid is measured on a scale
which ranges from 0 to 14 with 7.0 being neutral.
Anything with a pH value lower than 7.0 is
acidic, and anything higher than 7.0 is basic.
(For more information see the chart on pH.)
Particles of sulfur and nitrogen emitted by cars,
coal-fired generators, and non-ferrous smelters
can be carried great distances and deposited
anywhere from a few hundred to a few thousand
kilometers from their source area. Even when
sulfur and nitrogen particles fall to the surface
as dry deposition they combine with water at the
earth's surface or in the ground to produce the
same effects as wet deposition.
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c) Biocide Use
The use of some biocides (such as pesticides and
herbicides) without a complete assessment of
their environmental impact has contaminated the
soil, atmosphere, water supply, and has disrupted
food webs. Examples include DDT effects on the
Bald Eagle and Peregrine Falcon.
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d) Disposal Problems
The affluent lifestyle of humans currently
requires increasing supplies of products and
energy, the production of which produces
considerable wastes solid, chemical, and
nuclear
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2. Positive Aspects
Through increased awareness of ecological
interactions humans have attempted to prevent
continued disruption of the environment and to
counteract the results of many of our past
negative practices. A. POPULATION CONTROL
methods of controlling the human reproductive
rate has been, and will continue to be,
developed. B. CONSERVATION OF RESOURCES Soil
cover plantings (reforestation and cover
cropping) serve as erosion occurs. Water and
energy conserving measures are currently being
implemented. The economic significance of
recycling is now being realized.
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2. Positive Aspects - 2
C. Pollution Control - Attempts are being made to
control air and water pollution by laws and by
the development of new techniques of
sanitation. D. Species Preservation - Some
efforts to sustain endangered species have
included habitat protection (wildlife refuges and
natural parks) and wildlife management (game laws
and fisheries). Animals which were once
endangered but are presently successfully
reproducing and increasing their numbers are
bison and egrets. Endangered animals which are
currently responding to conservation efforts and
beginning to make a comeback are the whooping
crane, bald eagle, and peregrine falcon. The
future of some species are still in doubt.
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2. Positive Aspects - 3
E. Biological Control - Biological control of
insect pests continues to be encouraged. This
method is less likely to 1. Affect those
species which are beneficial to humans 2.
Disrupt food webs 3. Contaminate the land The
use of sex hormones and natural parasites are an
example.
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F. Laws
There are laws which regulate and guide the use
of natural habitats. SEQR -- A New York State
Law designed to provide the opportunity for
citizen review and comment of the environment
impact of any proposed development that has been
determined to have significant effect on the
environment. FRESHWATER WETLANDS ACT -- A New
York State Law designed to regulate the use of
large or unique freshwater wetlands both publicly
and privately owned so as to prevent their
destruction and thus maintain valuable wetlands
for all life forms.
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B. The Future
While human technological advances have led to a
higher standard of living for many, the
environment has often suffered. Through a
greater awareness of ecological principles, wise
use of our energy resources, and concern for
future generations not only of humans, but also
of all species, each individual can help to
assure that there will be suitable environments
for succeeding generation.
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By Kerri Dunnege