permaculture

[Lawrence London <lfljvenaura@gmail.com>]

ecology.PDF - ecology.pdf
http://csmbio.csm.jmu.edu/biology/renfromh/gbio/ho/ecology.pdf

ECOLOGY

Derived from Greek oikos = house, logos = study, literally = study of our
home
Ecology = study of organisms and their interactions with each other and
with their environment.
Population - group of individuals of the same species that interact and
interbreed with each other.
Habitat -place where an organism lives.
Niche -what an organism does, its role in the environment.
(habitat = address, niche = job)
Community -group of associated species sharing a common habitat.
Ecosystem - a large group of interacting organisms together with the
non-living environmental factors

with which they interact.

Biome -large terrestrial complex of communities of living organisms that
are characterized by distinctive
vegetation and climate.
A given habitat may support a number of populations, each with their own
niche. Usually partition the

habitat to reduce competition for scarce resources.
Communities may alter their habitat in such a way that it can support new
populations, and may become
less suitable for some of the established populations. This may lead to
changes in communities over
time.

ECOLOGICAL SUCCESSION

Succession -progressive changes in the composition of communities over
time.

Primary succession - occurs where no life is present. Pioneering organisms
move in and occupy an
area such as rocky outcropping, newly deposited soil (landslide), lava
flows, etc. Lichens and mosses
tend to be pioneer species.

Secondary succession - changes in communities following disturbance of an
ecosystem. May involve
new species, or re-introductions of previous species.


Climax community - stable and self-maintaining. Here, climax community is
the oak-hickory forest.
Part of temperate deciduous forest biome.

FOOD CHAINS AND FOOD WEBS

Life depends on flow of energy through communities. Energy is captured by
producers who use the
energy to produce food compounds. Photosynthetic autotrophs -plants.

Primary consumers -eat the producers
Secondary consumers -eat the primary consumers, and so on.
Forms a chain of trophic levels. (trophos = food/feeding)

Food chain is formed.
Food chain -sequential linkage from plants (primary producers) to consumers
(herbivores, then
carnivores) to decomposers.
It is the inter-related, associated trophic levels of producers and
consumers.
In nature, one is more likely to see food webs.
Food web - system of associated and inter-related food chains.
The greater is the extent of inter-relationships, the greater is the
stability of the ecosystem. The greater
is the diversity seen in the food web, the greater is the ecological
stability!

Remember: DIVERSITY IS STABILITY!!!

POPULATION ECOLOGY

population -group of individuals of a single species that interact and
interbreed with each other.

Population density -number of individuals per unit area or per unit volume.

Biotic potential -reproductive capacity of a population, when unrestricted.
It is a potential of the intrinsic rate of growth, and when plotted, forms
a J-shaped curve.

Environmental resistance -all physical and biological limiting factors that
prevent a species from
reproducing at its maximum rate.

Environmental resistance prevents populations from growing at their biotic
potential, instead populations
usually grow according to a logistic (S-shaped) curve.

The population usually levels off at its carrying capacity. The carrying
capacity is the maximum
number of individuals that can be supported by a given habitat without loss
of quality to that habitat.


POPULATION REGULATION

Control may be through reproduction.

Large parental investment may help survival of offspring, but parents
cannot afford to produce
as many offspring. Organisms that do not invest in parental care often
produce many offspring so that
some may survive.

Control through mortality.

Mortality may be the result of density-dependent controls such as
competition, predation,
prasitism and disease. Density-dependent controls are often biotic in
nature.

Mortality may be the result of density-independent controls, such as
weather (drought, cold), or
natural catastrophes (flood, volcanoes, hurricanes, etc.).
Density-independent controls are often abiotic
in nature.

Populations may overshoot their carrying capacity, in which case
environmental resistance will bring the
population back toward equilibrium around the carrying capacity. The
population may overcorrect and
fall below the carrying capacity for a period of time.

If a population overshoots the carrying capacity by too much, the quality
of the environment will be
degraded and the carrying capacity of the habitat will be reduced.

HUMAN POPULATION

Human population has increased dramatically over last several hundred years
compared to last 8,000
years. Several factors may account for this increase.

1. We have developed the capacity to expand into new habitats and new
climatic zones.
2. We have increased the carrying capacity of occupied environments.
3. We have removed some limiting factors (immunizations against some
diseases).
In the 1970s the rate of increase of the human population slowed. Possible
factors that may account for
this decrease in rate of increase include:

1. Changing role of women in society.
2. Changes in attitudes toward family size.
3. Advances in birth control.
4. Liberalized abortion laws.

BIOMES: THE VALUE OF BIODIVERSITY

On the planet earth, there is incredible biological diversity. Perhaps 30
million species of organisms live
on this planet. Because habitats are so diverse, the genetic diversity
among those organisms is also very
large.

That genetic diversity represents a vast warehouse of potential resources
as well as offering a
kaleidoscope of beauty and a sense of man's place in the world. Humans have
expanded into every
habitat in the world and may shepherd the planet or may ruin the planet.
What we do in the next 30
years may well decide what will be left for your children and their
children.

If we want this genetic diversity to persist, we must maintain the habitats
that foster that diversity. Is
habitat diversity and genetic diversity important to us, or should we have
nothing but apartments,
shopping centers, and corporate farms? If we overexploit a single part of a
biome so that the structure
of the biome is disturbed, because of the interconnections between
organisms, we stand to lose the
entire biome and many additional resources.

Yet there are economic and political pressures to drain and develop the
wetlands, to open the remaining
old-growth forests to logging, to mine the tundra for oil, coal and
minerals, to use the oceans and
deserts as dumping grounds. As one example, consider what has happened to
watersheds and natural
waterways. What is the result of channelization of natural waterways, the
removal of forests from
watersheds, and the covering of acres of land with pavement and buildings?
Why do we see recurring
flooding in developed areas? Why are so-called 100 year floods and 500 year
floods occurring so
regularly?

You don't have to make a choice between jobs and the environment. It is
possible to have economic
development while preserving the environment. Many would claim that it is a
necessity that
development occur in balance with environmental protection if we are to
survive as a species. Today's
biomes house all of tomorrow's natural products.

There is still another side to this we have not examined much. All of our
discussion has been very
anthropocentric. It is extremely egotistical and arrogant to think of the
earth's life forms as being nothing
more than potential products for human use. We should at least consider
that these life-forms have an
intrinsic right to life just as much as humans. With our ability to
dominate events on this planet, we have
a responsibility to shepherd and nurture the planet, not exploit and ruin.

These organisms add to the natural beauty of the world. They have been an
inspiration to mankind for
centuries. Artists, poets, architects, have all found inspiration in
nature. We can find fulfillment in
ourselves by helping to maintain the beauty of the natural world and in
studying and trying to understand
our part in a scheme that is far greater than ourselves. Humans have been
developing their sense of the
aesthetic ever since they stopped being hunter-gatherers. It is part of
human culture and human nature.
Are we losing that quality of our humanity?


You cannot save isolated parts of a system and save the system. Everything
is interconnected
ecologically. Biological diversity = ecological stability.

Aquatic Ecosystems

In addition to their importance as sources of food, as breeding grounds and
homes for countless
organisms, below are listed some of the unique attributes of these
ecosystems which may be beneficial in
terms of commercial development for human use.

Freshwater Ecosystems -Often subject to freezing, these ecosystems may hold
important information
about unique physiological adaptations. Animals that can survive freezing
may provide answers as to
how we may freeze organs and tissues. Cryogenic organ banks may reduce the
pressure to find organ
donors when people are in critical need of transplants.

Estuaries -Here is where freshwater runs into seawater. Here we find
organisms that can tolerate salt,
but can live in freshwater. We may find unique mechanisms for regulation of
salt balance and
maintenance of metabolism. Salt tolerance mechanisms may be transferable to
crops.

Salt water marshes -We find lots of nitrogen-fixing bacteria that may be
important as future food
sources. There are other unique bacteria and fungi whose properties we are
just beginning to examine.

Ocean – This extensive ecosystem is the home to fish, sponges, corals and
algae, all of which are
proving to be important sources of medicines. Also we are finding pigments,
neuroactive agents for
medicinal uses and potential cancer cures.

These are just a few examples of the resources that we can develop if, and
only if, we protect the
habitats that foster their survival.

Terrestrial Ecosystems

In Table 1 you will find listed the various terrestrial biomes with
descriptions of their characteristics and
a brief sampling of some of the unique qualities found there.


Table 1. Characteristics of biomes and examples of one or more unique
features found in each biome.

BIOME CLIMATE VEGETATION UNIQUE FEATURES
Temperate deciduous
forest
Temperate, seasonal
changes, 30-50 inches
annual rainfall
Hardwood trees: oak,
hickory, maple, beech,
poplar
Polyzonia millipede
produces a chemical that
is a strong insect
repellent
Grassland Tropical or temperate,
10-40 inches annual
rainfall
Grasses, small shrubs World's most abundant
food sources; world's
most efficient
photosynthetic systems
Desert Temperature extremes,
hot days, cold nights,
less than 10 inches
annual rainfall
Cacti, succulents, short
life cycle annuals
genes for drought
tolerance; physiological
adaptations for stress
metabolism; potentially
useful for kidney
problems and trauma
patients
Tropical rain forest Hot, rainy season, 80160
inches annual
rainfall
Broad-leaved
evergreens, air plants
(epiphytes), multilayers
Biotically most diverse
regions of earth; many
predator-prey
interactions; many host-
pathogen interactions;
many potential cancer
cures, anti-viral agents,
and anti-parasitic
compounds
Tundra Snowbound most of
year,
Less than 10 inches
annual rainfall
Lichens, mosses, small
herbs, small and
prostrate shrubs
Moss that can survive
desiccation;
genes for drought
tolerance
Taiga Short summers; long,
cold, wet winters; most
precipitation is frozen
Conifers: pine, spruce,
fir, hemlock, sparse
understory
Tree communication by
chemical signaling;
inducible insect
resistance

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