Download Niche, Habitat, and Competition

Niche, Habitat, and Competition
Niche, refers to the role that a species plays within its ecosystem. In balanced
ecosystems, each species occupies its own niche. The niche is like the organism's
profession - what it does to survive.
Habitat refers to the place were an organism lives. The habitat of a species is different
than its niche, it is the particular part of the environment in which it lives. The habitat of
an organism is part of its niche. The organism's habitat is its address - where it lives.
Every organism has its own habitat. The organism's habitat is where the organism is best
adapted to survive.
Plants and animals live where they can gather or find the necessary resources to satisfy
their needs. Every habitat includes factors that limit the kinds and numbers of organisms
that live there. Goldfish and pond plants require fresh water. On the other hand, the
barnacles that cling to the ship must live in salt water. In some cases, creatures can adapt
themselves to a changing habitat.
A single area may satisfy the needs of many kinds of plants and animals. These
organisms that associate together in a common habitat form communities.
Competition
Competition between organisms exists in every ecosystem. Organisms are forced to
compete against their own species and also different species in order to survive. The
stronger and fit organisms have an advantage over those who are weaker, and they have a
better chance of surviving.
Competition arises when organisms have requirements in common and they must
compete to meet their own needs. The more needs organisms have in common, the more
intense the competition. When the resources that are being competed for become scarce
the competition becomes more intense, and eventually one of the species becomes
eliminated.
Competition between the same species is called intraspecific competition. Many birds
of the same species compete for the best nesting grounds. In cases when food or water is
scarce, members of the same species will compete for food in order to survive.
Competition between different species is called interspecific competition. Different
species often compete for space, food, or water. For example the lion and the hyena both
compete for zebra. The majority of feeding relationships in an ecosystem are based on
competition, food chains and food webs. Each species has it's own niche, that species has
a particular habitat and has a particular way of obtaining its own food. But when two
different species overlap or interfere with one another, competition occurs. When worst
comes to worst, those with the most helpful adaptations will survive and the less-well
adapted will not.
Pests and Pesticides
What are pests?
Pests are living organisms that are not wanted around us. Examples of pests include
unwanted dandelions growing in the lawn; rodents or insects that eat fruits, vegetables or
other crop species; micro-organisms that cause disease in forest, fish, or crop resources,
etc. A pest is any organism that man believes is undesirable, has a negative impact on the
human environment, or is in competition with human use of a resource, either natural, or
cultivated.
Early Pesticide Use:
Early pesticides included the use of toxic inorganic metallic salts such as copper sulfate,
lead salts, arsenic, or mercury. These substances were generally effective against the
intended pest, but also created some environmental problems because they also killed
other beneficial organisms, and polluted water and soil resources used by man. Most
early pesticides were non-biodegradable (meaning that they were not broken down within
the ecosystem). As a result, these early pesticides began to accumulate in the
environment, contaminating water and soil resources, eventually poisoning humans.
Modern Pesticides:
By the twentieth century, chemists began to develop organic pesticides that were
designed to be less toxic to man and more specific toward the intended pests. Although
this was initially believed to be a step in the right direction, man soon discovered that the
organic pesticides also caused unexpected environmental effects. Some of these
pesticides were fat-soluble. This characteristic leads to a problem known as
bioaccumulation.
As each organism feeds on one lower in the food chain, the fat-soluble pesticide began to
be concentrated in ever higher amounts as one moved toward the top of the food pyramid.
Since every organism eats far more than its own body mass in food, the tiny amounts
found in each organism in the lower levels of the food web began to accumulate in
greater concentrations in species located at higher trophic levels.
One example of this problem is illustrated by the damage done to predatory birds as a
result of bioaccumulation of DDT. As a result of this problem DDT has been banned
from use in North America.
Biogeochemical Cycles
Biochemists are scientists who study the type of chemical compounds that are found in
living things. They study the interaction of these compounds in an attempt to understand
how life works at the chemical level. The work of biochemists has lead to the realization
that living organisms are composed of some of the same elements that are found in the
air, water and soil. Following many years of analysis on many different organisms,
biochemists have been able to describe the types of elements found in plant and animal
tissues.
Although each organism is different in terms of the relative amounts of each type of
element, the types of elements present are the same. Although there are 92 elements
know to occur naturally on Earth, fewer than 20 elements are presently known to occur in
the tissues of living things. Only 6 elements make up 99.2% (rounded to 3 significant
digits) of human or pumpkin tissues. The table below compares the relative abundance
(percentage by weight) of a few selected elements found in the Earth's crust, human, and
pumpkin.
Element Name
Earth
Human
Pumpkin
(Symbol)
% weight
% weight
% weight
Oxygen (O)
46.6
65
85
Carbon (C)
0.19
18
3.3
Hydrogen (H)
trace
10
10.7
Nitrogen (N)
trace
3
0.16
Calcium (Ca)
3.6
2.0
0.02
Phosphorus (P)
trace
1.2
0.05
Potassium (K)
2.6
0.20
0.34
trace
0.25
<0.05
Sodium (Na)
2.8
0.1
0.001
Magnesium (Mg)
2.1
0.05
0.01
trace
0.15
<0.05
5.0
trace
0.008
Copper (Cu)
trace
trace
0.0001
Iodine (I)
trace
trace
<0.05
Silicon (Si)
27.7
trace
trace
Zinc (Zn)
trace
trace
0.0002
8.1
trace
trace
trace
trace
trace
Sulfur (S)
Chlorine (Cl)
Iron (Fe)
Aluminum (Al)
others
As you can see from the table, oxygen, carbon, hydrogen and nitrogen make up the vast
majority of living tissue. These four elements are recycled between living organisms and
the soil, water and atmosphere of the Earth.
These elements are first taken up by plants, some oxygen is released to the atmosphere as
a product of photosynthesis, but the rest is converted into food, passed through the food
web as they pass through plants, consumers, and finally decomposers such as fungi and
bacteria, and then returned to the environment in a continuous recycling of materials. If
recycling of these materials did not occur, life could not exist.
The continuation of life depends on the continued recycling of the materials that make up
the food that passed through the ecosystem. Some of these elements (carbon, oxygen,
sulfur, nitrogen) are found in gaseous forms and their cycles involve the atmosphere. As a
result they have a global nature. One should also be aware that some of the elements may
have a short term cycle such as when carbon is transferred from animals to plants in the
form of carbon dioxide and a long term cycle such as the transfer of carbon from a fossil
fuel to a plant following combustion.
The elements are cycled between the living organisms and the environment (both long
and short term). It is a combination of biological and geological processes that drives
chemical recycling.
Biological processes include:





respiration,
decomposition,
excretion,
photosynthesis,
and assimilation.
Geological processes involve fossilization, erosion, combustion of fossil fuels (peat, oil,
coal), weathering, and formation of sedimentary rock.
Carbon Cycle
Plants extract carbon dioxide and water from their environment. They use the energy they
capture from the sun to carry on a process known as photosynthesis which converts the
atoms in the carbon dioxide and water into sugar and oxygen.
6CO2 + 6H2O + energy → C6H12O6 + 6O2
The oxygen, released as a byproduct of photosynthesis, generally passes into the
atmosphere. The sugar (known as glucose) serves a food for all consumers in the
ecosystem. The consumers carry on a metabolic process known as cellular respiration.
During cellular respiration, oxygen is taken in from the atmosphere and used to break
down the sugar resulting in a release of energy and the molecular products, carbon
dioxide and water.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
What do you notice about these two reactions?
As you can see from the equations, photosynthesis and cellular respiration are
complementary processes. Provided these processes occur in balance, the amount of
carbon dioxide (about 0.023% of the air) and oxygen (about 21% of the air) are
maintained in equilibrium. This balance is called the carbon-hydrogen-oxygen cycle (or
simply carbon cycle for short).
In modern times (past 200 years) people have discovered these fossil fuel deposits and
have used them to supply our energy needs. Humans have also affected the carbon cycle
by cutting down forests. As a result of human activity, the amount of carbon dioxide is
being produced at a faster rate than nature can recycle it. As a result of this imbalance,
the amount of carbon dioxide in the atmosphere is increasing. As a result the earth is
presently undergoing an enhanced greenhouse effect in which the atmosphere is
gradually heating up. The gradual rise in temperature is predicted to have a disastrous
effect on world biomes. If the rise in temperature occurs too fast for organisms to adapt,
widespread extinction of plants and animals may be the result. Extinction events have
occurred in past history, but never the result of human influence. We are the only species
that can do something about the problems we have created.