I.    Community Habitat

Definition:

1.    A community can be defined as several interacting populations
that inhabit a common environment and are interdependent with each other. Each
population has characteristics like natality, mor­tality, age structure, growth
dynamics, and so on, but when several populations share a common habitat and
its resources, they interact among themselves and develop into a biotic
community or simply, a community.

2.    A habitat is the place where plants and animals
normally live. It is, simply, the place where you can find communities.

 

Differences
of community and habitat:

The
kind of community you find is mostly defined by the type of habitat it is
located at, and communities are often named after their habitats. A habitat
however, can hold different types of communities. Example is the rainforest.
The rainforest is the habitat where the rain forest community, a population of
different plants and animals, live. But a rainforest can also contain an insect
community composed of different interacting insect populations, or a stream
community, located in a stream in a rainforest where different insects and
amphibian population interact with each other within the stream and forming a
community.

 

II.   Biodiversity

              Biodiversity is the variety of living
organisms, their number, and their variability or the simply diversity of life
on earth. This includes all the species, the diversity between species and within
species, and the diversity of different environments present in the biosphere. The
concept also covers how this changes from one location to another and over time.

Importance
of Biodiversity:

              Biodiversity is very important in
the maintenance and improvement of the ecosystem. Each specie, no matter how
big or small has a role to play in the ecosystem, and the interactions that
takes place within and between ecosystems make up the life on Earth. Although
the ecosystem is governed by cycles like the water cycle or the nutrient cycle,
there is a constant change happening, especially in organisms. As each
organisms reproduce, they make offspring that although identical to the
parents, are still unique in their own way. The environment changes too, and
the organisms have to adapt to survive. These organisms depend on each other to
survive, and the more diverse a place is the more services an organism can give
to support others as well as more sources to support itself.

              One example of the importance of biodiversity
is when a species is diverse, it also means it contains a wide range or a
variety of genetic material. It is known that in-breeding usually results in
genetic defects in animals, including humans. When a specie is few in number,
there is a lack of variety of genetic material as well, leading to offspring
that are born without the means to survive and this could eventually lead to
extinction. An extinction of a specie could lead to imbalance in an ecosystem
that would take years to recover from.

              The same principle can be applied
to crops. Crops that are asexually propagated or are cloned from a single mother
plant usually have shorter life-spans and are more susceptible to disease. The
lack of diversity removes an organism’s ability to adjust to change and adapt
to its environment.

              If taken in the context of human
benefits alone, biodiversity means a wide range of resources to use. A diverse
plant populations, for example, could potentially contain medicinal value that
humans could use. If rice, for example, is a diverse plant species. If rice only
comes in one variety, then it could only be grown in a particular strict set of
conditions and would only contain a single set of properties. It would have
been very difficult to grow and it wouldn’t have been the staple food for most
of Asia.

 

 

Living
Planet Index

              The
living planet index is the indicator of the state of the world’s biodiversity,
measuring the trends in population of vertebrates in marine, freshwater, and
terrestrial species. The trend shows that since 1970-200, there is a decline in
the biodiversity. This is largely caused by human intervention in the
ecosystem. We disturb it in a way that doesn’t give it time to recover. The
decline is because of pollution, climate change, the destruction of habitats, excessive
tree logging, etc.

 

III.  Trophic Function

 

          Trophic Function, or Functional Response,
represents the consumption of prey assuming a given number of predators. Functional
responses describe the relationship between an individual’s rate of consumption
and food density. They have generally been divided into three types: Type I,
Type II, and Type III

 

          Simply put, Functional Response is how
a prey or predator behave when one or the other is abundant or scarce.

 

Type I

         

          Type I is the increased consumption of
food by an organism. It is the constant intake of food modelled as
predator-prey relationship where the consumption of food does not interfere
with searching for food. This means the prey and the predator increases linearly.
The predator does not need to find food because it is always present, and the
prey is abundant enough that there is no threat to its decline by predator
consumption. The amount of prey is proportional to the amount of predator, and
there is no hunting involved.

          The type I functional response can be
described by a linear equation of the form y = ax + b, where a is the slope of the
line and b is the intercept, as seen in Figure 3.

 

Type
II

 

          In the type II functional response,
the rate of prey consumption by a predator rises as prey density increases, but
eventually levels off at a plateau (or asymptote) at which the rate of
consumption remains constant regardless of increases in prey density.

          It is the decrease of feeding activity
of a predator because there is a constant supply of prey and the predator does
not have to spend time hunting for prey. This could mean that the number of
prey is higher than the number of predator, making it easier for the predator
to hunt for it’s prey and is thus satiated. Figure 4 illustrates Type II functional
response when plotted into a graph.

 

Type
III

 

          Type III functional response is
similar to type II in that at high levels of prey density, saturation occurs.

          In type III, there is a prey switching
of predators. The population of a certain prey is low and to survive they would
hide, making them harder to find. The predator will then have look for
alternative prey. This could mean that the number of predator is more than the
prey population, and they find it harder to find prey because of competition. In
type III the predator takes a considerable amount of time hunting, either for
their main prey or for other prey. When plotted in a graph, type III would
appear like the example in Figure 5.

 

 

IV. Competitive Interactions within Communities

              Competition is occurs when a
limited resource is needed by two or more species. When two or more niches overlap,
chances are a certain resource becomes difficult to obtain. That’s when
competition happens. The more niches that overlap, the more chances that a
competition happens.

              Competitions are necessary because
in a way, it is the nature’s way to balance itself out. It is also a good way
to weed out the weaker or the inferior specie, making way to stronger and more
adaptable species.

Types
of Competition:

1.    Interspecific Competition – a form of competition in
which individuals of different species compete for the same resources in an
ecosystem

Examples: 2 predators with the same prey; weeds and crops
competing for soil, water and sunlight;

2.    Intraspecific Competition – a form of competition between
organisms of the same species

Examples: A pack of wolves eating the same carcass; wild
range chickens compete for food

3.    Exploitative Competition – a form of competition when all
individuals have the equal access to the resource, but differ in how fast or
how efficiently they can exploit it

Example: Birds on the forest competing on fruit available
in trees;

4.    Interference Competition – a form of competition when
certain individuals are able to restrict or prevent access of others to the
resources and so control the use of it.

Example:
animals marking their territory and attacking anyone who enters it; two male
animals fight for a mate

 

V.  Interaction Among Biotic Communities

 

          Organisms interact with each other in
order to benefit and survive. Different interactions are as follows:

1.    Predator-Prey – Interaction can benefit both species. Prey
obtains food and the reduced numbers in prey means more resources for those individuals
(prey) that are left

2.    Consumer-Producer – the consumer benefits

3.    Commensalism – an interaction of two species where in one
species benefits while the other is not affected

4.    Mutualism – an
interaction of two species wherein both benefits from each other

5.    Parasitism – an
interaction between two species wherein one species benefits and the other is
harmed

 

VI.  Conclusion

 

          In a community and/or ecosystem,
different interactions takes place and different factors affect these
interactions that ultimately affect the balance in an ecosystem. A habitat
holds and is composed of communities that interact with one another. The different
interactions in the community depend on one another and is centered in the
survival of the organisms. The more diverse a community is, more interactions
takes place and the more resources can be found, both for the organisms and the
humans. Lastly, humans create a huge difference in the interactions of these
communities as a human can manipulate its surroundings and would cause a lot of
damage if left unchecked. By understanding how the interactions in a community
work, we could use it for our benefit with, hopefully, minimal damage to the
community.