Biology and ecology

Juan Diego Castellanos1 Andrés Sánchez 2, Karenn Rubio 1

1
Electrical Engineering Program University of La Salle, Bogotá Colombia.
2
Chemical engineering program University of La Salle, Bogotá Colombia.

1. Species
In taxonomy, the basic unit of biological classification is called species (from Latin species).
A species is a set of organisms or natural populations capable of interbreeding and
producing fertile offspring, although -in principle- not with members of populations belonging
to other species. In many cases individuals who separate from the original population and
isolate themselves from the rest can reach a sufficient differentiation to become a new
species, therefore, reproductive isolation from other populations is crucial. In short, a
species is a group of organisms reproductively homogeneous, although very changeable
over time and space.
While in many cases this definition is adequate, it is often difficult to demonstrate whether
two populations can cross and give fertile offspring (for example, many organisms can not
be kept in the laboratory long enough). Besides that it is impossible to apply it to organisms
that do not reproduce sexually (like the bacteria or extinct organisms known only by their
fossils). Currently, molecular techniques are used, such as those based on DNA similarity.
• Population
In its most common use, the word refers to the group formed by people who live in a certain
place or even on the planet in general. It also allows referring to the spaces and buildings of
a locality or another political division, and to the action and consequences of population.
For the ecology, a population is formed by a grouping of specimens of a certain species that
share a habitat. Sociology, on the other hand, considers populations as groups of people or
things that can be analyzed based on statistics thanks to the elaboration of samplings.
It should be noted that the study of populations, in general, is developed according to
probabilistic laws, so that the conclusions of such investigations may not be applicable to
certain individuals. The discipline that studies human populations is called demography.
• Community
A community is a group of human beings that have certain elements in common, such as
language, customs, values, tasks, world view, age, geographic location (a neighborhood,
for example), social status or roles. In general, in a community a common identity is created,
by differentiating other groups or communities (usually by signs or actions), which is shared
and elaborated by its members through socialization. Generally, a community is united
under the need or improvement of a common goal, such as the common good; Although this
is not necessary, a common identity is sufficient to form a community without the need for a
specific objective. It is also called community to any set of living beings that share certain
elements.
• Ecosystem
An ecosystem is a biological system constituted by a community of living organisms
(biocenosis) and the physical environment where they are related (biotope). It is a unit
composed of interdependent organisms that share the same habitat.Ecosystems usually
form a series of chains that show the interdependence of organisms within the system.It can
also be defined as follows: «An ecosystem consists of the biological community of a place
and of the physical and chemical factors that constitute the abiotic environment ".4 It is
considered that the abiotic and biotic factors are linked by the trophic chains that is the flow
of energy and nutrients in the ecosystems.
This concept, which was introduced in 1935 by the English ecologist AG Tansley, takes into
account the complex interactions between organisms (eg plants, animals, bacteria, protists
and fungi) that form the community (biocenosis) and energy flows and materials that go
through it.
2. Ecology
Ecology is the branch of biology that studies the relationships of different living beings with
each other and with their environment: "the biology of ecosystems" (Margalef, 1998, p.2).
Study how these interactions between organisms and their environment affect properties
such as distribution or abundance. The physical and chemical properties that can be
described as the sum of local abiotic factors, such as climate and geology, and the other
organisms that share that habitat (biotic factors) are included in the environment.
Ecosystems are composed of parts that interact dynamically with each other along with the
organisms, the communities they integrate, and also the non-living components of their
environment. Ecosystem processes, such as primary production, pedogenesis, the nutrient
cycle, and the various habitat construction activities, regulate the flow of energy and matter
through an environment. These processes are based on organisms with specific historical
features of life, and the variety of organisms that are called biodiversity. The integrating
vision of ecology raises the scientific study of the processes that influence the distribution
and abundance of organisms, as well as the interactions between organisms and the
transformation of energy flows. Ecology is an interdisciplinary field that includes biology and
Earth science.
3. Biotic and abiotic factors in an ecosystem
• Abiotic Factors: The abiotic factors are the physical and chemical among which is:
 Light: Level of illumination essential for photosynthesis
 Water: factors that affect the availability of water are humidity, precipitation and
evaporation time.
 Wind: has an impact on the transfer of nutrients.
 Soil: physical and chemical characteristics of the substrate.
 Salinity: amount of salts.
• Biotic Factors: Biotic factors are all those that have life. Due to their trophic level, they
are classified as:
  Producers U, organisms capable of manufacturing or synthesizing their own food
from inorganic substances such as carbon dioxide, water and mineral salts. The
plants are beings.
 Consumers or, organisms unable to produce their food, therefore they ingest it
already synthesized. The animals are consuming beings.
 organisms that feed on decaying organic matter. Among them are yeasts, fungi,
bacteria and multicellular and cellular.
4. Biodiversity:
Biodiversity refers to the variety and variability of life on Earth. Biodiversity is typically a
measure of variation at the genetic, species, and ecosystem level. Terrestrial biodiversity
is usually greater near the equator, which is the result of the warm climate and high
primary productivity. Biodiversity is not distributed evenly on Earth, and is richest in the
tropics. These tropical forest ecosystems cover less than percent of earth's surface, and
contain about percent of the world's species. Marine biodiversity is usually highest along
coasts in the Western Pacific, where sea surface temperature is highest, and in the mid-
latitudinal band in all oceans. There are latitudinal gradients in species diversity.
Biodiversity generally tends to cluster in hotspots, and has been increasing through time,
but will be likely to slow in the future.
Genetic diversity is the variety of genes within a species. Each species is made up of
individuals that have their own particular genetic composition. This means a species may
have different populations, each having different genetic compositions. To conserve
genetic diversity, different populations of a species must be conserved. Genes are the
basic units of all life on Earth. They are responsible for both the similarities and the
differences between organisms. Not all groups of animals have the same degree of
genetic diversity. Kangaroos, for example, come from recent evolutionary lines and are
genetically very similar. Carnivorous marsupials, called dasyurids, come from more
ancient lines and are genetically far more diverse. Some scientists believe that we should
concentrate on saving more genetically diverse groups, such as dasyurids, which include
the Tasmanian Devil, the Numbat and quolls. If we lose one species of dasyurid, we lose a
substantial genetic resource. Several species of dasyurids are endangered and at least
one, the Tasmanian Tiger, has disappeared forever since Europeans arrived in Australia.

5. Food chain:
A food chain is a linear network of links in a food web starting from producer organisms
(such as grass or trees which use radiation from the Sun to make their food) and ending at
apex predator species (like grizzly bears or killer whales), detritivores (like earthworms or
woodlice), or decomposer species (such as fungi or bacteria). A food chain also shows
how the organisms are related with each other by the food they eat. Each level of a food
chain represents a different trophic level. A food chain differs from a food web, because
the complex network of different animals' feeding relations are aggregated and the chain
only follows a direct, linear pathway of one animal at a time. Natural interconnections
between food chains make it a food web. A common metric used to the quantify food web
trophic structure is food chain length. In its simplest form, the length of a chain is the
number of links between a trophic consumer and the base of the web and the mean chain
length of an entire web is the arithmetic average of the lengths of all chains in a food web.
Food chains were first introduced by the Arab scientist and philosopher Al-Jahiz in the 9th
century and later popularized in a book published in 1927 by Charles Elton, which also
introduced the food web concept.

Food chain in a Terrestrial Ecosystem:

The sun is the source of energy, which is the initial energy source. This is used by the
producers or plants to create their own food, through photosynthesis and grow. Next up, in
this chain is another organism, which is the consumer that eats this food, taking in the
energy.
The primary consumers are the organisms that consume the primary producers. In a
terrestrial ecosystem, it could be a herbivore like a cow or a goat or it could even be a
man. When a goat is consumed by man, he becomes the secondary consumer. As the
energy goes one level up, the food chain also moves up. Each level in the food chain is
called a trophic level. The different trophic levels are Primary producers, primary
consumers, secondary consumers, tertiary consumers and quaternary consumers.
6. The following relationships to define the living organisms are:
 Parasitism: In evolutionary biology, parasitism is a relationship between species,
where one organism, the parasite, lives on or in another organism, the host,
causing it some harm, and is adapted structurally to this way of life.[1] The
entomologist E. O. Wilson has characterised parasites as "predators that eat prey
in units of less than one".[2] Parasites include protozoans such as the agents of
malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms,
lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of
ringworm; and plants such as mistletoe, dodder, and the broomrapes. There are six
major parasitic strategies of exploitation of animal hosts, namely parasitic
castration, directly transmitted parasitism (by contact), trophically transmitted
parasitism (by being eaten), vector-transmitted parasitism, parasitoidism, and
micropredation.
 Comensalism: commensalism is a relationship between two organisms in which
one organism benefits, and one is unaffected. This can be contrasted with other
types of symbiosis, such as mutualism and parasitism. The supposed difference
between commensalism and other types of symbiosis is that in commensalism, the
second party or host remains unaffected. Some scientist argue that this is likely
 improbable, and that most commensalism will be found to be mutualism or
parasitism once the effects on the host can be appropriately studied. Other
scientists argue that commensalism does exist when the effect on the host is
imperceptible.
 Symbiosis: Symbiosis, any of several living arrangements between members of
two different species, including mutualism, commensalism, and parasitism (qq.v.).
Both positive (beneficial) and negative (unfavourable to harmful) associations are
therefore included, and the members are called symbionts. Any association
between two species populations that live together is symbiotic, whether the
species benefit, harm, or have no effect on one another.