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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Components of the ecosystem involve
interacting abiotic factors and biotic
factors.
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The abiotic environment includes physical and
chemical factors which affect the ability of
organisms to live and reproduce.
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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
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what species can exist in those regions.
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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A population is all the
members of a species
inhabiting a given
location
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All the interacting populations in a
given area represent
a community
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An ecosystem is the living community
and the physical environment functioning
together as an interdependent and relatively
stable system.
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The biosphere is the portion of the earth in
which life exists. It is composed of
numerous complex ecosystems.
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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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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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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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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
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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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Characteristics: heavy rainfall;
constant warmth
Climax Flora: many species of
broad-leafed plants
Climax Fauna: snake, monkey,
leopard
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Characteristics: considerable variability in
rainfall and temperature;
strong prevailing winds
Climax Flora: grasses
Climax Fauna: pronghorn antelope, prairie
dog & bison
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Characteristics: sparse
rainfall;extreme daily temperature
fluctuations
Climax Flora: drought-resistant
shrubs and succulent plants
Climax Fauna: kangaroo rat & lizard
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Climatic conditions change with
latitude and altitude.
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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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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. 24
Marine Aquatic Biomes are found in the Earth’s
oceans, covering nearly 75% of the Earth’s surface.
Most of the planet’s rainfall is from the evaporation
of the Earth’s oceans, and the temperatures of the
oceans strongly effect the world’s 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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The ecosystem is the structural and
functional unit studied in ecology.
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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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Nutritional Relationships involve the
transfer of nutrients from
one organism to another within an ecosystem.
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These organisms can synthesize
their own food from
inorganic compounds
and an unable energy source.
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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,
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herbivores, carnivores, or omnivores.
- include those heterotrophic
plants, fungi, and
bacteria which live
on dead matter.
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- are those animals which consume plants
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- 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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- are those animals which
consume both plants and
animals.
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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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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
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dogs.
If an ecosystem is to be self-sustaining it must contain
a flow of energy
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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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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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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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coyotes
Rats
spiders
rabbits
snakes
hawks
Grasses
shrubs
frogs
lice
Seed-eating
birds
insects
Deer
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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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Organisms that feed directly upon green plants are primary consumers or
herbivores. Secondary consumers, or carnivores, feed upon other consumers.
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Omnivores may be either primary or secondary consumers.
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
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organisms.
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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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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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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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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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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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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Succession may be defined as a continuous
unidirectional, sequential change in species
composition of natural communities.
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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 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
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the organisms is termed allegoric.
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
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on the bare rock.
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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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, with64 the
greatest diversity populating the climax community.
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. 65
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. 66
Humans, in exercising a unique and powerful
influence on the physical and living world, have
modified their environment.
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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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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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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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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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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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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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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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Major water
pollutants include:
heat, sewage,
and chemicals such
as phosphates,
heavy metals,
and PCB’s.
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PCB’s or Polychlorinated Biphenyl’s 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, PCB’s 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. PCB’s usually enter our aquatic
ecosystems via precipitation, industrial discharges and agricultural runoff.
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For many years PCB’s 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 PCB’s 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
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and dermal contact PCB’s can be easily absorbed by most animals.
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 PCB’s
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.
PCB’s 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 1970’s the production of PCB’s 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 PCB’s. 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
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waste.
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" 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, coalfired 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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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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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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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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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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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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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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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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The
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