Ecology a branch of biology (from Greek: "house" and “study of") is the

study of the relationships between living organisms, including humans,

and their physical environment. Ecology considers organisms at the
individual, population, community, ecosystems, and biosphere level.
Ecology overlaps with the closely related sciences of biogeography,
evolutionary biology, genetics, ethology and natural history.

It is also the study of the interactions of living organisms with their

environment. Within the discipline of ecology, researchers work at four
specific levels, sometimes discretely and sometimes with overlap. These
levels are organism, population, community, and ecosystem. In ecology,
ecosystems are composed of dynamically-interacting parts, which include
organisms, the communities they comprise, and the non-living (abiotic)
components of their environment. Ecosystem processes, such as primary
production, pedogenesis (the formation of soil), nutrient cycling, and
various niche construction activities, regulate the flux of energy and
matter through an environment. These processes are sustained by
organisms with specific life-history traits. The variety of organisms, called
biodiversity, which refer to the differing species, genes, and ecosystems,
enhances certain ecosystem services.

1. Global Ecology is the study of the Earth's ecosystems among the

land, oceans, and atmosphere. With four major environmental issues
occurring on the global scale, habitat destruction, invasive species,
decline of population densities and pollution, global ecology is needed
to understand what is happening and why. Explore the definition and
overview of global ecology, the scale of ecology, influence of
globalization, and major problems surrounding ecology on a global
scale.
Global ecology is very important because it is used to understand large
scale interactions and how they influence the behavior of the entire
planet, including the earth's responses to future changes.

An example is Tropical rainforest - found near the Equator. The

climate is hot and humid and many different species can be found
here.
2. Population Ecology is the study of the interactions of a single
species with other members of its species and the species'
environment. Population ecology deals with problems that are on a
smaller scale and influence a single species within the environment.
 It deals with factors that alter and impact the genetic composition and
the size of the population of organisms. Ecologists are interested in
fluctuations in the size of a population, the growth of a population and
any other interactions with the population.

In biology, a population can be defined as a set of individuals of the

same species living in a given place at a given time. Births and
immigration are the main factors that increase the population and
death and emigration are the main factors that decrease the
population.

Population ecology examines the population distribution and density.

Population density is the number of individuals in a given volume or
area. This helps in determining whether a particular species is in
endanger or its number is to be controlled and resources to be
replenished.

An example of population ecology would be a study on the distribution

of herds of deer.

3. Organismal Ecology is the study of an individual organism’s

behaviour, morphology, physiology, etc. in response to environmental
challenges. It looks at how individual organisms interact with biotic
and abiotic components. Ecologists research how organisms are
adapted to these non-living and living components of their
surroundings.

Individual species are related to various adaptations like physiological

adaptation, morphological adaptation, and behavioural adaptation.

4. Ecosystem Ecology: It deals with the entire ecosystem, including

the study of living and non-living components and their relationship
with the environment. This science researches how ecosystems work,
their interactions, etc.
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).
Ecosystems are complex adaptive systems where the interaction of life
processes form self-organizing patterns across different scales of time
and space. Ecosystems are broadly categorized as terrestrial,
freshwater, atmospheric, or marine. Differences stem from the nature
 of the unique physical environments that shapes the biodiversity
within each. A more recent addition to ecosystem ecology are techno
ecosystems, which are affected by or primarily the result of human
activity.

Ecosystem biologists ask questions about how nutrients and energy

are stored, along with how they move among organisms and the
surrounding atmosphere, soil, and water.

For example the Karner blue butterflies and the wild lupine live in an
oak-pine barren habitat. This habitat is characterized by natural
disturbance and nutrient-poor soils that are low in nitrogen. The
availability of nutrients is an important factor in the distribution of the
plants that live in this habitat. Researchers interested in ecosystem
ecology could ask questions about the importance of limited resources
and the movement of resources, such as nutrients, though the biotic
and abiotic portions of the ecosystem.
5. Molecular Ecology: this study of ecology focuses on the production
of proteins and how these proteins affect the organisms and their
environment. This happens at the molecular level. DNA forms the
proteins that interact with each other and the environment. These
interactions give rise to some complex organisms.
The important relationship between ecology and genetic inheritance
predates modern techniques for molecular analysis. It uses various
analytical techniques to study genes in an evolutionary and ecological
context. Molecular investigations revealed previously obscured details
in the tiny intricacies of nature and improved resolution into probing
questions about behavioural and biogeographical ecology. For
example, molecular ecology revealed promiscuous sexual behaviour
and multiple male partners in tree swallows previously thought to be
socially monogamous.[153] In a biogeographical context, the marriage
between genetics, ecology, and evolution resulted in a new sub-
discipline called phylogeography.

6. Landscape Ecology: It deals with the exchange of energy, materials,

organisms and other products of ecosystems. Landscape ecology
throws light on the role of human impacts on the landscape structures
and functions.
It provides an important framework for Critical Zone Research
through:
 · Integrating 3D dimensionality in the analysis of landscape
system.
· Contextualizing the Critical Zone processes both temporally and
spatially
· Investigating problems related with scaling

Landscape ecology describes and explains the landscapes'

characteristic patterns of ecosystems and investigates the flux of
energy, mineral nutrients, and species among their component
ecosystems, providing important knowledge for addressing land-use
issues.

7. Community ecology is the study of the interactions among a

collection 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.
Community ecology examines how interactions among species and
their environment affect the abundance, distribution and diversity of
species within communities.

It deals with how community structure is modified by interactions

among living organisms. Ecology community is made up of two or
more populations of different species living in a particular geographic
area.

For example, the larvae of the Karner blue butterfly form mutualistic
relationships with ants. Mutualism is a form of a long-term
relationship that has coevolved between two species and from which
each species benefits. For mutualism to exist between individual
organisms, each species must receive some benefit from the other as a
consequence of the relationship. Researchers have shown that there is
an increase in the probability of survival when Karner blue butterfly
larvae (caterpillars) are tended by ants. This might be because the
larvae spend less time in each life stage when tended by ants, which
provides an advantage for the larvae. Meanwhile, the Karner blue
butterfly larvae secrete a carbohydrate-rich substance that is an
important energy source for the ants. Both the Karner blue larvae and
the ants benefit from their interaction.