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| Ecology addresses
the full scale of life, from tiny bacteria to
processes that span the entire planet.
Ecologists study many diverse and complex
relations among species, such as predation and
pollination. The diversity of life is organized
into different habitats, from terrestrial
(middle) to aquatic ecosystems. |
Ecology
Ecology is the science which studies the biota, the
environment, and their interactions. It comes from the
Greek oikos = house; logos = study.
Ecology is the study of ecosystems. Ecosystems describe
the web or network of relations among organisms at
different scales of organization. Since ecology refers
to any form of biodiversity, ecologists research
everything from tiny bacteria in nutrient recycling to
the effects of tropical rain forests on the Earth's
atmosphere. Scientists who study these interactions are
called ecologists.
Terrestrial ecoregion and climate change research are
two areas where ecologists now focus.
There are many practical applications of ecology in
conservation biology, wetland management, natural
resource management (agriculture, forestry, fisheries),
city planning (urban ecology), community health,
economics, and applied science. It provides a framework
for understanding and researching human social
interaction.
Levels, scope, and scale of
organization
The scope of ecology contains a wide array of
interacting levels of organization spanning micro-level
(e.g., cells) to a planetary scale (e.g., biosphere)
phenomena.
Biodiversity
Biodiversity (an abbreviation of "biological diversity")
describes the diversity of life from genes to ecosystems
and spans every level of biological organization. The
term has several interpretations, and there are many
ways to index, measure, characterize, and represent its
complex organization. Biodiversity includes species
diversity, ecosystem diversity, and genetic diversity
and scientists are interested in the way that this
diversity affects the complex ecological processes
operating at and among these respective levels.
Biodiversity plays an important role in ecosystem
services which by definition maintain and improve human
quality of life. Preventing species extinctions is one
way to preserve biodiversity and that goal rests on
techniques that preserve genetic diversity, habitat and
the ability for species to migrate. Conservation
priorities and management techniques require different
approaches and considerations to address the full
ecological scope of biodiversity. Natural capital that
supports populations is critical for maintaining
ecosystem services and species migration (e.g., riverine
fish runs and avian insect control) has been implicated
as one mechanism by which those service losses are
experienced. An understanding of biodiversity has
practical applications for species and ecosystem-level
conservation planners as they make management
recommendations to consulting firms, governments, and
industry. |
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| Termite mounds with
varied heights of chimneys regulate gas
exchange, temperature and other environmental
parameters that are needed to sustain the
internal physiology of the entire colony. |
Biome
Biomes are larger units of organization that categorize
regions of the Earth's ecosystems, mainly according to
the structure and composition of vegetation. There are
different methods to define the continental boundaries
of biomes dominated by different functional types of
vegetative communities that are limited in distribution
by climate, precipitation, weather and other
environmental variables. Biomes include tropical
rainforest, temperate broadleaf and mixed forest,
temperate deciduous forest, taiga, tundra, hot desert,
and polar desert. Other researchers have recently
categorized other biomes, such as the human and oceanic
microbiomes. To a microbe, the human body is a habitat
and a landscape. Microbiomes were discovered largely
through advances in molecular genetics, which have
revealed a hidden richness of microbial diversity on the
planet. The oceanic microbiome plays a significant role
in the ecological biogeochemistry of the planet's
oceans.
Biosphere
The largest scale of ecological organization is the
biosphere: the total sum of ecosystems on the planet.
Ecological relationships regulate the flux of energy,
nutrients, and climate all the way up to the planetary
scale. For example, the dynamic history of the planetary
atmosphere's CO2 and O2 composition has been affected by
the biogenic flux of gases coming from respiration and
photosynthesis, with levels fluctuating over time in
relation to the ecology and evolution of plants and
animals. Ecological theory has also been used to explain
self-emergent regulatory phenomena at the planetary
scale: for example, the Gaia hypothesis is an example of
holism applied in ecological theory. The Gaia hypothesis
states that there is an emergent feedback loop generated
by the metabolism of living organisms that maintains the
core temperature of the Earth and atmospheric conditions
within a narrow self-regulating range of tolerance.
Individual ecology
Understanding traits of individual organisms helps
explain patterns and processes at other levels of
organization including populations, communities, and
ecosystems. Examples of such traits include features of
an organisms life cycle such as age to maturity, life
span, or metabolic costs of reproduction. Other traits
may be related to structure, such as the spines of a
cactus or dorsal spines of a bluegill sunfish, or
behaviors such as courtship displays or pair bonding.
Other traits include emergent properties that are the
result at least in part of interactions with the
surrounding environment such as growth rate, resource
uptake rate, winter, and deciduous vs. drought deciduous
trees and shrubs.
The traits of organisms are subject to change through
acclimation, development, and evolution. For this
reason, individuals form a shared focus for ecology and
for evolutionary ecology. |
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| Interspecific
interactions such as predation are a key aspect
of community ecology. |
Population ecology
Population ecology studies the dynamics of species
populations and how these populations interact with the
wider environment. A population consists of individuals
of the same species that live, interact, and migrate
through the same niche and habitat.
Metapopulations and
migration
In metapopulation terminology, migrating individuals are
classed as emigrants (when they leave a region) or
immigrants (when they enter a region), and sites are
classed either as sources or sinks. A site is a generic
term that refers to places where ecologists sample
populations, such as ponds or defined sampling areas in
a forest. Source patches are productive sites that
generate a seasonal supply of juveniles that migrate to
other patch locations. Sink patches are unproductive
sites that only receive migrants; the population at the
site will disappear unless rescued by an adjacent source
patch or environmental conditions become more favourable.
Metapopulation models examine patch dynamics over time
to answer potential questions about spatial and
demographic ecology. The ecology of metapopulations is a
dynamic process of extinction and colonization. Small
patches of lower quality (i.e., sinks) are maintained or
rescued by a seasonal influx of new immigrants. A
dynamic metapopulation structure evolves from year to
year, where some patches are sinks in dry years and are
sources when conditions are more favourable. Ecologists
use a mixture of computer models and field studies to
explain metapopulation structure.
Community ecology
Community ecology is the study of the interactions among
a collections of species that inhabit the same
geographic area. Community ecologists study the
determinants of patterns and processes for two or more
interacting species. Research in community ecology might
measure species diversity in grasslands in relation to
soil fertility. It might also include the analysis of
predator-prey dynamics, competition among similar plant
species, or mutualistic interactions between crabs and
corals.
Ecosystems may be habitats within biomes that form an
integrated whole and a dynamically responsive system
having both physical and biological complexes. Ecosystem
ecology is the science of determining the fluxes of
materials (e.g. carbon, phosphorus) between different
pools (e.g., tree biomass, soil organic material).
Ecosystem ecologist attempt to determine the underlying
causes of these fluxes. |
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| A trophic pyramid
(a) and a food-web (b) illustrating ecological
relationships among creatures that are typical
of a northern boreal terrestrial ecosystem. The
trophic pyramid roughly represents the biomass
(usually measured as total dry-weight) at each
level. Plants generally have the greatest
biomass. Names of trophic categories are shown
to the right of the pyramid. Some ecosystems,
such as many wetlands, do not organize as a
strict pyramid, because aquatic plants are not
as productive as long-lived terrestrial plants
such as trees. Ecological trophic pyramids are
typically one of three kinds: 1) pyramid of
numbers, 2) pyramid of biomass, or 3) pyramid of
energy. |
Food webs
A food web is the archetypal ecological network. Plants
capture solar energy and use it to synthesize simple
sugars during photosynthesis. As plants grow, they
accumulate nutrients and are eaten by grazing
herbivores, and the energy is transferred through a
chain of organisms by consumption. The simplified linear
feeding pathways that move from a basal trophic species
to a top consumer is called the food chain. The larger
interlocking pattern of food chains in an ecological
community creates a complex food web. Food webs are a
type of concept map or a heuristic device that is used
to illustrate and study pathways of energy and material
flows.
Food webs are often limited relative to the real world.
Complete empirical measurements are generally restricted
to a specific habitat, such as a cave or a pond, and
principles gleaned from food web microcosm studies are
extrapolated to larger systems. Feeding relations
require extensive investigations into the gut contents
of organisms, which can be difficult to decipher, or
stable isotopes can be used to trace the flow of
nutrient diets and energy through a food web. Despite
these limitations, food webs remain a valuable tool in
understanding community ecosystems.
Food webs exhibit principles of ecological emergence
through the nature of trophic relationships: some
species have many weak feeding links (e.g., omnivores)
while some are more specialized with fewer stronger
feeding links (e.g., primary predators). Theoretical and
empirical studies identify non-random emergent patterns
of few strong and many weak linkages that explain how
ecological communities remain stable over time. Food
webs are composed of subgroups where members in a
community are linked by strong interactions, and the
weak interactions occur between these subgroups. This
increases food web stability. Step by step lines or
relations are drawn until a web of life is illustrated.
Trophic levels
A trophic level is "a group of organisms acquiring a
considerable majority of its energy from the adjacent
level nearer the abiotic source." Links in food webs
primarily connect feeding relations or trophism among
species. Biodiversity within ecosystems can be organized
into trophic pyramids, in which the vertical dimension
represents feeding relations that become further removed
from the base of the food chain up toward top predators,
and the horizontal dimension represents the abundance or
biomass at each level. When the relative abundance or
biomass of each species is sorted into its respective
trophic level, they naturally sort into a 'pyramid of
numbers'.
Species are broadly categorized as autotrophs (or
primary producers), heterotrophs (or consumers), and
Detritivores (or decomposers). Autotrophs are organisms
that produce their own food (production is greater than
respiration) by photosynthesis or chemosynthesis.
Heterotrophs are organisms that must feed on others for
nourishment and energy (respiration exceeds production).
Heterotrophs can be further sub-divided into different
functional groups, including primary consumers (strict
herbivores), secondary consumers (carnivorous predators
that feed exclusively on herbivores), and tertiary
consumers (predators that feed on a mix of herbivores
and predators). Omnivores do not fit neatly into a
functional category because they eat both plant and
animal tissues. It has been suggested that omnivores
have a greater functional influence as predators,
because compared to herbivores, they are relatively
inefficient at grazing.
Trophic levels are part of the holistic or complex
systems view of ecosystems. |
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| Sea otters, an
example of a keystone species. |
Keystone species
A keystone species is a species that is connected to a
disproportionately large number of other species in the
food-web.
Sea otters (Enhydra lutris) are commonly cited as an
example of a keystone species; because, they limit the
density of sea urchins that feed on kelp. If sea otters
are removed from the system, the urchins graze until the
kelp beds disappear, and this has a dramatic effect on
community structure. Hunting of sea otters, for example,
is thought to have led indirectly to the extinction of
the Steller's sea cow (Hydrodamalis gigas). While the
keystone species concept has been used extensively as a
conservation tool, it has been criticized for being
poorly defined from an operational stance. It is
difficult to experimentally determine what species may
hold a keystone role in each ecosystem. Furthermore,
food web theory suggests that keystone species may not
be common, so it is unclear how generally the keystone
species model can be applied. |
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| Mutualism:
Leafhoppers (Eurymela fenestrata) are protected
by ants (Iridomyrmex purpureus) in a mutualistic
relationship. The ants protect the leafhoppers
from predators and stimulate feeding in the
leafhoppers, and in return the leafhoppers
feeding on plants exude honeydew from their anus
that provides energy and nutrients to tending
ants. |
Behavioural ecology
Chameleons change their skin colour to match their
background as a behavioural defence mechanism and also
use colour to communicate with other members of their
species, such as dominant versus submissive patterns..
All organisms can exhibit behaviours. Even plants
express complex behaviour, including memory and
communication. Behavioural ecology is the study of an
organism's behaviour in its environment and its
ecological and evolutionary implications. Ethology is
the study of observable movement or behaviour in
animals.
Adaptation is the central unifying concept in
behavioural ecology. Behaviours can be recorded as
traits and inherited in much the same way that eye and
hair colour can. Behaviours can evolve by means of
natural selection as adaptive traits conferring
functional utilities that increases reproductive
fitness.
Predator-prey interactions are an introductory concept
into food-web studies as well as behavioural ecology.
Prey species can exhibit different kinds of behavioural
adaptations to predators, such as avoid, flee, or
defend. Many prey species are faced with multiple
predators that differ in the degree of danger posed. To
be adapted to their environment and face predatory
threats, organisms must balance their energy budgets as
they invest in different aspects of their life history,
such as growth, feeding, mating, socializing, or
modifying their habitat.
(Iridomyrmex purpureus) in a symbiotic relationship. The
ants protect the leafhoppers from predators and in
return the leafhoppers feeding on plants exude honeydew
from their anus that provides energy and nutrients to
tending ants. |
|
 Kiddle: Ecology
Wikipedia: Ecology |
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