CONCEPTS OF ECOSYSTEMS
ARIZONA STATE UNIVERSITY
ABS 370 - ECOLOGY
SPRING 2024
Introduction:
In short, ecosystem means a system that takes place in an environment. In the
environment, there are components, both physical components (living / biotic objects and
inanimate /abiotic objects) and non-physical components in the form of the relationship
between the benefits of one object to another (trophic). In the environment there is also a
dynamic phenomenon concerning the interaction between physical groups, or it can be said
that in the environment there is a dynamic system. From the description above, the broad
definition of ecosystems is the relationship between living things and their environment
(biotic and abiotic), each of which is mutually influencing and is needed to maintain a
balanced, harmonious and harmonious life. In this case, the functions in the ecosystem are
emphasized on mandatory relationships, interdependence and reciprocal and cause-and-effect
relationships of all components that make up the ecosystem. According to their location,
ecosystems can be divided into terrestrial ecosystems, freshwater ecosystems and
marine/coastal ecosystems. Each ecosystem differs only in terms of the type, structure,
characteristics and quality of the components involved.
Ecosystems are classified into larger categories of biomes that are generally identified
by the vegetation that characterizes them. Tropical forests, deserts, grasslands, are examples
of biomes. Biomes are the largest ecological units in the biosphere. The biosphere is the
entire living environment of the planet. Each ecosystem differs in size and complexity, as
well as in carrying capacity and resistance to disturbance. Ecosystems that are initially large
and stable become compartmentalized and highly vulnerable to new disturbances. In fact,
there are hardly any ecosystems that are not significantly affected by human activities. For
example, under normal circumstances, wet tropical forests do not burn even during long
droughts, but after being degraded by excessive logging, they do, as was experienced two
years ago.
A.
ECOSYSTEM CONCEPT
An ecosystem is the unity of all the components that make it up. Within an ecosystem
there is a unity of interrelated and influencing processes between all components. In an
ecosystem there are living components (biotic) and non-living components (abiotic).
Ecosystems are also defined as a functional basis in ecology, given that they include
organisms and abiotic environments that influence each other. Ecosystems are also real
objects that have various sizes according to their level of organization.
According to the Law on the Environment (UULH, 1982), an ecosystem is an order of
unity as a whole between all elements of the environment that affect each other. In
Ecosystems contain living things (biotic) and non-living environments (abiotic). An
ecosystem is a higher level of organism than a community, or is the unity of a community and
its environment in which interrelationships occur. It includes not only a range of plant and
animal species, but also all forms of matter that cycle through the system and the energy that
powers it. All communities depend on the abiotic environment to obtain the energy and
matter necessary for life. Producing organisms require energy, light, oxygen, water, and salts,
all of which are taken from the abiotic environment. Energy and matter from first-order
consumers are passed on to second-order consumers and so on to other consumers through
food webs.
Material and energy from the abiotic environment will return to the abiotic
environment. In this case, the community in its abiotic environment is a system called an
ecosystem. So the concept of an ecosystem concerns all relationships within a community
and in addition all relationships between the community and its abiotic environment.
Dynamic relationships in ecosystems involve several components. These components can be
seen from two different aspects, namely from the aspect of the feeding level (trophic level /
food chain level) and the aspect of life.
From the aspect of the feeding tier, the ecosystem consists of autotrophic components
and heterotrophic components, emphasizing the level of energy transfer.
The word Autotrophic comes from the word Auto = own and trophikos = provide food.
Autotrophs are organisms that are able to provide / synthesize their own food in the form of
organic matter from inorganic materials with the help of energy such as sun and chemistry.
Autotroph components function as producers, for example green plants.
Autotrophic components (self-feeding), here the binding of sunlight energy occurs using
simple inorganic compounds and building complex compounds. Example: Green plants.
1.
Heterotropic Component
The word Heterotrophic comes from the word Heteros = different and trophikos = food.
Heterotrophs are organisms that utilizes organic materials as food and these materials are
provided by other organisms. Heterotrophs include humans, animals, fungi, and microbes.
The heterotrophic component (eating others), here the use, re-organization and
breakdown of complex materials occurs.
According to Wiegert Van Owens (1970), Heterotropic components:
1.
Biophag: organisms that eat living organisms.
2.
Saprophages: organisms that eat dead organisms.
From the aspect of life, ecosystems consist of biotic components and abiotic components
that are closely related and have a reciprocal relationship with each other.
1.
Biotic Component
Humans, animals and plants include biotic components found in an ecosystem. Biotic
components are divided into 3 groups, namely producers, consumers and decomposers.
a.
Manufacturer
All producers can produce their own food so called autotrophic organisms. As
producers, green plants produce food (carbohydrates) through the process of photosynthesis.
Food is utilized by the plant itself and other living things. Thus producers are the main source
of energy for other organisms, namely consumers.
b.
Consumer
All consumers cannot make their own food in their bodies, so they are called
heterotrophs. They get organic substances that have been formed by producers, or from other
consumers who become their prey.
Based on the type of food, consumers are grouped as follows:
•
Plant-eaters (herbivores), such as goats, buffaloes, rabbits and cows.
•
Carnivores, such as tigers, birds, eagles and wolves.
•
Plant and meat eaters (omnivores), such as chickens, ducks and jungle people.
c.
Decomposer
This group plays an important role in the ecosystem. If this group didn't exist, we
would see garbage piling up and dead living things remaining intact forever. Decomposers
act as decomposers, breaking down organic matter (from carrion) into its constituent organic
substances.
2.
Abiotic Component
The abiotic component is the second component in the ecosystem in terms of life. This
component consists of non-living materials in the form of physical elements (environment)
and chemical elements (organic compounds and inorganic compounds), such as soil, water,
air, sunlight and so on, which are in the environment in the form of a medium or substrate to
sustain life. For example, in lake ecosystems, abiotic components are found consisting of
inorganic compounds such as H2O, CO2, O2, K, Na, and P, and organic compounds such as
amino acid compounds and carbon compounds (humus).
Part of the abiotic component is :
•
Land
The physical properties of soil that play a role in the ecosystem include texture, maturity,
and water holding capacity.
•
Water
Important things in water that affect the lives of living things are water temperature,
water mineral content, salinity, water currents, evaporation, and water depth.
•
Air
Air is an abiotic environment in the form of gas. The gas is in the form of an atmosphere
that surrounds living things. Oxygen, carbon dioxide and nitrogen are the most important
gases for living things.
•
Sunlight
Sunlight is the main source of energy for life on earth. However, the distribution of light
on earth is uneven. Therefore, organisms must adapt to environments with different light
intensity and quality.
•
Temperature.
Every living thing requires an optimum temperature for its metabolic activities and
reproduction.
Ecosystems and the environment are two things that are inseparable. In the discussion
of ecosystems, the environment will also be the object of discussion. Physically, the
environment means the container or place where an organism's life system or a community
takes place. Environmental conditions will change if there are changes in the ecosystem or
vice versa, each influencing the other in a dynamic balance and is a functional unit. Thus, the
ecosystem includes all living things and the physical environment that surrounds them, and is
a unit that includes all living things in an area that allows interactions with their environment,
both abiotic and biotic. All forms of interaction between ecosystem components constitute a
principle, namely the principle of diversity, the principle of cooperation, the principle of
competition, the principle of interaction and the principle of diversity. These principles
function as a means to maintain the existence of continuity in the reciprocal relationship
between ecosystem components and between these components and their environment. If
each component works together in accordance with its function, the balance and harmony in
the environment will be maintained and run well.
Humans are the determinants of environmental quality, so in utilizing environmental
resources, humans can carry out activities that have a positive or negative impact on the
environment. Humans also have the strongest influence in changing ecosystems, both directly
and indirectly human activities can often change the volume, composition and structure of the
components of the ecosystem organic environment by converting existing organic matter.
The relationship between organisms and their physical environment is very close and
cannot be separated from one another. Changing the relationship between organisms and their
physical environment means making changes to the biotic and abiotic composition and
structure, or changing the environment, which leads to various impacts and risks for humans
themselves. Humans interact with the environment, are influenced and affect the
environment. The relationship between humans and their environment is circular. Various
human activities, from breathing to damming rivers, will more or less change the
environment and the changes in the environment will in turn affect humans again. The
influence on one element will propagate to other elements that move subtly, often the
influence on humans cannot be seen and felt, but at some point the influence will accumulate
and have a real impact.
The quality of life depends on the degree of fulfillment of basic needs obtained from
an environment, and environmental quality can be a measure of the degree of fulfillment of
these basic needs. The higher the degree of quality of life in an environment means the higher
the degree of fulfillment of basic needs, or vice versa. Thus, good environmental quality will
produce a good degree of quality of fulfillment of basic needs, and subsequently produce
good environmental quality. If the quality of the environment has decreased, then the decline
in quality will result in several things, among others:
a)
Health, infectious disease
•
Toxic substances in air, food and water
•
The effect of uncontrolled physical energy on health
b)
Comfort, efficiency and aesthetics
•
Unpleasant appearance, pungent odor and bad taste
•
Heat, noise and light
•
Structure features: convenience and efficiency
c)
Influence on ecosystem development and natural resources
From a functional point of view, ecosystems can be analyzed according to :
1.
Energy Circle
In accordance with the first principle of the basic principles of environmental science,
all energy entering a living organism or population or ecosystem can be considered as stored
or released energy. Energy can be converted from one form to another but cannot be lost,
destroyed, or created. Food Chain
A food chain is the transfer of food energy from plant resources through a series of
organisms or through feeding stages (plant-herbivore-carnivore). At each stage of energy
transfer, 80 - 90% of the potential energy is lost as heat, therefore the steps in the food chain
are limited to 4-5 steps only. In other words, the shorter the food chain, the more energy is
available.
There are two basic types of food chains:
•
Grazing food chain E.g. plant-herbivore-carnivore.
•
Detritus food chain
Dead material of microorganisms (detrivores = waste-eating organisms) predators.
2.
Patterns of diversity in time and space
It is the third principle of the basic principles of environmental science, namely
matter, energy, space, time and diversity, all of which are categorized as natural resources.
3.
Development and evolution
It can be approached with the thirteenth principle of the basic principles of
environmental science, namely that a physically stable environment allows for the
accumulation of biological diversity in a stable ecosystem, which can then further promote
population stability.
4.
Control (Cybernetics)
Organisms adapt to the physical environment, but organisms can also make their
environment adapt to their biological needs, for example, plants can affect the soil where they
grow. In this case there has been a control function.
The relationship between ecosystem components is a relationship that is fixed and
regular and is a unity that influences each other, so that the ecosystem is the central or core
concept of ecology. The relationship is also neutral, mutualistic and adaptive, but some are
controlling other components. In the end, nature determines the harmony and balance in the
interaction between the components of the ecosystem. However, ecosystems will tend to
resist change to maintain their balance, some succeed and some fail. Ecosystems that have a
tendency to resist changes due to relationships between components and continuously
maintain balance are called ecosystems that are in a homeostatic state. Ecosystems are a
functional basis in ecology, given that they include organisms and abiotic environments that
influence each other. Ecosystems are also real objects that vary in size according to their level
of organization.
B.
ECOSYSTEM CHANGE AND ENVIRONMENTAL IMPACTS
Human activities and natural disasters can cause changes to an ecosystem. Natural
disasters, such as volcanic eruptions and earthquakes, are beyond human control. However,
human activities, such as pollution and over-exploitation of natural resources, will directly or
indirectly lead to ecosystem change. Destruction of a community's habitat will directly
change the ecosystem in that habitat. For example, the exploitation of fish in lakes or rivers
using explosives, electric current or toxic materials results in the destruction of the habitat of
the community in the lake/river and further causes ecosystem changes and a decrease in
biodiversity.
Figure 4.5. Disturbance to the forest ecosystem
Figure 4.6. Disturbance to the river ecosystem
In freshwater ecosystems, there are limiting factors that allow the mechanisms that
take place in the ecosystem to run steadily. These limiting factors are related to the condition
of the freshwater habitat (aquatic environment), namely:
a.
Temperature
b.
Transpiration
c.
Turbidity
d.
Current
e.
Mainstream gas in water
f.
Dissolved Oxygen (DO)
g.
Dissolved carbon dioxide
h.
Biogenic salts in water
i.
Na and K
j.
Calcium and Magnesium
k.
Phosphorus
l.
Water convection
The disruption of the above limiting factors, such as an increase or decrease in the
concentration and magnitude of these factors, will undoubtedly affect the community and
abiotic environment of the lake/river ecosystem. An example of a case due to water pollution
from the effluent of a paper factory that has a negative impact on the environment and
disturbance to the ecosystem is as follows:
1.
Disturbance to vegetation
Rice plants in paddy fields in polluted areas are often attacked by wilting disease with
symptoms of leaf tops drying and rotting and ending with the death of the plant.
2.
Disturbance to fauna
Animals and poultry that drink the polluted river water die or produce deformed
offspring.
3.
Human disturbance
In cultivating rice fields, farmers have to change the way they plant rice, especially in
the dry season, because during the growing season there are many layers of paper that settle
and cover the surface of the soil; farmers have to provide extra labor to pick up the layers of
paper that settle on the surface of the soil, which means increasing production costs. From the
above example, it is clear that disturbance or pollution to the environment will result in
changes to the ecosystem.
C.
BIOLOGICAL CONTROL OF THE ENVIRONMENT CHEMICAL
Organisms adapt to the physical environment (xerophyt, halophyt, and hydrophyt), but
they can also make the geochemical environment adapt to their biological needs. In other
words, organisms can influence their environment. For example, plants can affect the soil in
which they grow, Coelenterata can form coral reefs that affect the environment, and humans
can change the environment for their own benefit.
D.
PRODUCTION AND DECOMPOSITION IN NATURE
In nature, there is always a production process as a result of photosynthesis from
producer organisms. As an illustration, it can be mentioned that the results of photosynthesis
per year can reach 1017 grams. Besides the production process in nature, there is also always a
process of decomposition. There are three stages of the decomposition process, namely:
1.
Formation of small granular debris by biological action.
2.
Humus production and release of soluble organic matter by saprotrophs
3.
Humus mineralization.
In this process, bacteria are important in the destruction of meat, while fungi are
important in the process of wood if large organisms die (including plants) will become a
special habitat for microorganisms and broken down by detrivores (eg insects) into detritus.
Although insects do not eat cellulose, they help in its decomposition because:
1.
Breaking the wood into small pieces for easy eating.
2.
Produces growth factors.
By feeding, the bacteria maintain the natural bacterial population in the log phase state, where
bacterial development is very rapid. Some detrivores are Coprophagus, which eat dung
pellets after the pellets have been enriched by microbes, e.g. popilus (a type of beetle) that
lives on decaying wood using its home channel as an outhouse where dung pellets and wood
chews enriched by fungi are eaten again thus accelerating wood decay. Coprophagus in this
case involves the cooperation of insects and fungi and allows beetles to utilize
wood energy and accelerate wood decay.
Organic substances resulting from decay have a special influence on the growth of other
organisms in the ecosystem. This substance by Julian Huxley (1935) is called external
diffusion hormone, while Lucas mentions ectorine or environmetal hormone or exocrine.
These substances can inhibit the growth of other organisms such as antiboitics or stimulate
growth such as vitamins (thiamin, biotin, B12), uracil, and histidine.
Saprotrophs play a role in exocrine production. An important phenomenon is the
production of volatile secretions called pheromones, which can control the behavior of
insects and other organisms. According to Winogradsky, organisms that decompose humus
are called zymogenius, while those that decompose humus are called autochathonous.
Detritus, humus, and other compounds that undergo decay play an important role in soil
fertilization. Complex organic compounds together with minerals can be absorbed by plants
and the complex formation of organic substances together with minerals is called chalation.
Organic matter degredation controls a number of functions in ecosystems, for example:
1.
Nutrient recirculation through mineralization.
2.
Food formation in the detritus food chain.
3.
Formation of extorins that are regulatory in nature.
Modify virgin materials from the soil. Humans can accelerate decomposition by:
1.
Changes in organic matter (fossil fuels) that add CO2 to the air. CO2 can be penetrated
by sunlight, causing the greenhouse effect, and causing a rise in temperature and if this
happens, the polar ice caps will melt, raising sea levels.
2.
Agricultural efforts will accelerate humus decomposition.
E.
ECOSYSTEM HOMEOSTATIS
Ecosystems are as self-maintaining and self-regulating as the components that
compose them, namely organisms and populations. cybernetics (the science of control)
therefore has an important role in ecology because humans tend to disrupt natural control
systems.
Homoestatic is a term for the tendency of biological systems to resist change and
always remain in equilibrium.
•
That ecosystems are able to maintain and regulate themselves like the components that
compose them (organisms and populations).
•
Cybernetics (the science of control) therefore has a role to play important in ecology because
humans tend to disrupt natural control systems.
•
Homeostatis: the tendency of biological systems to resist change and always remain in
balance.
CONCEPT OF ENERGY IN ECOSYSTEMS:
Each individual needs a certain physical environment as a biotic community must
interact with the abiotic community. In the habitat there are very complex and very
complicated interactions between components, between communities and habitats, even so
the interactions continue to run normally so that between biotic communities and habitats
form an ecological system or called an ecosystem. Systems are interactions that unite existing
components into a single unit and make a certain function.
From another point of view, the system is a group of components that are interrelated,
and influence each other so that they form a whole. The requirements of a good system are
that the interactions between components must be harmonious and balanced, the balance in
the ecosystem is called a dynamic balance (steady state), which is a balance that can change
at any time which will be followed by various processes so that it will end with a new
balance.
Energy is the power used to carry out the activity of the main energy source: Sunlight.
The sun is utilized directly by green plants in the form of electromagnetic energy for the
photosynthesis process. Energy that enters the ecosystem in the form of solar radiation energy
or light energy but not all of it can be utilized. Energy stored in the form of plant matter can
be channeled through food chains and food webs from producers to consumers to
decomposers. If the material is not consumed, the energy will be stored in the system and
then passed on to decomposers. Each level of traffic in the food chain uses energy to live and
some is released as heat. Possible export of energy to other ecosystems in the form of organic
matter.
A.
DEFINITION AND ENVIRONMENT ENERGY
Energy is anything that can do work (heat energy, potential energy, chemical energy).
Law of Thermodynamics I: energy cannot be created and eliminated but can change form.
Second Law of Thermodynamics: the entropy of a system always increases, or a system
always goes into disorder unless energy is added (dead organisms always decompose but
living organisms do not, due to the addition of energy).
From this explanation, it can be understood that no process involving energy transfer can
occur spontaneously unless there is energy degradation (hot objects always become cold and
here there are energy degradation). Light energy during photosynthesis is converted into
chemical energy, but there is also energy degradation. All organisms get their energy from
the sun through the food chain where at every step of the energy transfer some energy is lost.
Ecosystems are fundamentally concerned with the transfer of energy from solar energy
through the food chain.
Solar energy green plants herbivores 100% 5%1 %
Organisms on earth receive radiation from the environment, namely from the sun and
reflected light from the earth, but only a small part of the light energy can be utilized in the
photosynthesis process, which results in a source of energy for the biotic components of the
ecosystem.
B.
CONCEPT PRODUCTIVITY
The primary productivity of an ecosystem/community is the rate at which energy is
PPB - the use of heterotrophs during time
stored in the process of carbohydrate synthesis (photosynthesis) by producers, especially
green plants, in the form of organic compounds that can be used as food.
The four steps in the production process are:
1.
Gross primary production (=PK)/Gross Primary Productivity is the entire photosynthetic
output (including that used for respiration).
2.
Net primary productivity (= PPB)/Net Primary Prod. Is the net result of photosynthesis
which can be described by the speed of the accumulation of organic compounds in plants and
can be written as :
3.
Clean community productivity
It is the rate of storage of organic matter that is not used by heterotrophs in units of time or
can be written with the formula:
4.
Secondary productivity is the speed
This is the rate of energy storage at the consumer level. Since consumers only take the
food produced by producers (after respiration) and convert it into tissues, secondary
productivity is not divided into gross and net.
Biological productivity is generally not the same as the productivity of the chemical
industry because in the chemical industry production is the result of the last reaction but in
biological processes the process continues so that a time must be included.
Rainforest production will be higher than agricultural areas. However, humans can
increase production by using superior seeds and fertilizers. In other words, additional
production occurs due to additional energy.
Primary productivity-energy input relationship
Table 5.1 Energy Transfer (%)
Step
1
2
3
4
Total
solar
radiation
energy
Which is
sucked in by
the
autotrophic
stratum
Gross
primary
production
Net primary
production
(usable
heterotrophs)
Maximum
average
100
50
5
4
Good condition
average
100
50
1
0,5
Biosphere
100
<50
0,2
0,1
Table 5.2 Time efficiency (%)
Step
Maximum
Average state
both
Average across the
biosphere
1-2
50
50
<50
1-3
5
1
0,2
1-4
4
0,5
0,1
2-3
10
2
0,4
3-4
80
50
50
The relationship between gross and net production can be explained by the graphical
model of leaft area index (LAI). LAI plotted on the X-axis can be considered as a measure of
biomass photosynthesis. Maximum productivity is obtained at an LAI of about 4 (i.e. leaf
surface area exposed to light is 4X the surface area of the soil). However, gross production
(GPP) is achieved when the LAI is 8-10 in old-growth forests.
Net primary productivity (NPP) decreases at high levels due to losses caused by
respiration to produce large leaves and supporting tissues. In conclusion, it can be said that
nature will maximize GPP while humans will maximize NPP.
1.
Human Use of Primary Production
In developing countries the GNP is more than $600/year and 30% of the world's
population is in this state. In developing countries, the rate of population increase is less than
1%/year.
In less developed countries GNP is less than $300/year and 65% of the world's
population is in this situation. The rate of population increase in less developed countries is
2%/year. In less developed countries, people lack protein and even carbohydrates. Due to the
large increase in population, the increase in agricultural production cannot catch up. This is
because the increase in agricultural production is small due to no increase in energy (either in
the form of fertilizer or good irrigation).
2.
Primary Productivity Measurement
In reality, productivity measurement can be done by measuring indirect quantities, such
as by measuring.
•
Number of compounds produced
•
Raw materials produced
•
By-products produced
3.
Some Methods of Productivity Measurement
a)
Harvest Method
Measures net community production. Used if a steady state is never reached. This
method is generally used for cultivated crops. The method is done by weighing the
harvest. This method is less precise if some of the yield is eaten by herbivores.
b)
Oxygen Measurement
Oxygen production can be used as a basis for measuring productivity. Production
of aquatic ecosystems can be measured using the diurnal curve method. This method
measures gross primary production because the oxygen produced during the day plus the
oxygen produced at night is the oxygen produced by the entire community.
In lakes there is an upper layer that is penetrated by light and hot temperatures
called the epilimnion layer, while the layer below is called the hypolimnion.
The so-called hypolimetic method measures the amount of oxygen that disappears
from the ecosystem, which represents the amount of oxygen used for decomposition. In
other words, the greater the productivity of the epilimonion, the more organic
compounds will descend to the hypominion, and thus the more oxygen will be required
for decomposition. So the hypolimony method will measure net productivity.
c)
Carbon Dioxide Method
This method is practical for land plants/organisms. During the day, photosynthesis
and respiration occur while at night there is only respiration.
d)
PH Method
In aquatic ecosystems, water pH is a function of dissolved carbon dioxide levels.
Productivity measurements using this method must prepare a calibration curve of water
pH in advance.
e)
Productivity Measurement Method with Raw Material Cessation
The reduction in available raw materials reflects the level of productivity. Good for
aquatic ecosystems. This method measures the net production of the community.
f)
Determination of Productivity with Radioactive Materials
This method measures net productivity. Radioactivity can be used to measure net
productivity.
g)
Chlorophyll Method
This method is based on chlorophyll content per area in a community. Plants in the
shade have more chlorophyll than plants growing in the light. Because of this, plants in
the shade can capture more light energy so their efficiency is high. Whereas plants in
bright areas have lower efficiency. This method measures gross productivity.
C.
FOOD CHAINS, FOOD WEBS AND TROPHIC LEVELS
A food chain is the transfer of food energy from plant resources through a series of
organisms or through a feeding pathway (plant - herbivore - carnivore).
At each stage of transfer 80-90% of the potential energy is lost as heat, therefore the
steps in food are limited to 4-5 steps only. In other words, it can be stated that the shorter the
food chain, the more energy is available.
There are two basic types of food chains:
a.
Grazing food chain
Plant - herbivore - carnivore
b.
Detritus food chain
Dead material → microorganisms (detrivores = waste-eating organisms) predators Food
chains will be interconnected to form a food web. Simple food chains occur in polar regions
in winter. This is because in winter there is little light, so there are few plant producers, as a
result there are also few herbivores and carnivores.
Organisms whose food sources are obtained from plants with the same number of steps
are said to have the same trophic level (trophic level). Trophic level 1 is producers, level II is
herbivores and trophic level III is carnivores (consumers II). The classification of organisms
by trophic level (food level) is based on the function of organisms in the food chain and not
based on species. Therefore, one species in a population can occupy more than one food
level.
Of the 100% of sunlight that can be utilized for photosynthesis, only 1%, while 80-90%
of the potential energy of food will be lost in the transfer of energy in food. Therefore only a
small human population can be supported in a society (population) whose main diet is meat,
because to produce meat requires a long food chain.
Sunlight----> Producer > Consumer 1
In the elimination of insects by spraying with DDT, it will be absorbed by detritus →
microbes → invertebrates (worms, insects) → fish, crabs → birds.
In this case, there will be an accumulation of DDT residues at the end of the food chain.
This is called food chain concentration or biological magnification. DDT or other chlorine-
containing compounds can affect eggshell formation in large enough quantities to cause eggs
to break before chicks hatch and this can lead to the extinction of certain birds. So
concentrations of substances that are not lethal to individuals can be lethal to populations.
Therefore, pest eradication should be done by biological means, namely with natural
enemies.
1. Ecological Efficiency
Ecological efficiency is the ratio of energy flows at various points along the food chain
in percent. In calculating efficiency, the dimensions must be the same, meaning that the
numerator and denominator are expressed in the same unit, for example measuring the
efficiency of chicken food, then meat and food must be measured in dry state (hours / kg). It
is best if the measurement is in
% of calories.
For example, a chicken farmer says the efficiency of converting chicken meal into meat
is 40% (Pt/It). In this case, please remember that the weight of meat in wet state is equivalent
to 2 Kcal/gram, while chicken meal is weighed in dry state and equivalent to 4 Kcal/gram. So
the efficiency is actually less than 20%.
In the transfer of energy between trophic levels, PG/L = 1 - 5%: PG/LA = 2 - 10 %,
while production efficiency between food levels = 10 - 50 % or greater. If the organism is fed
a good diet, consisting of calories and protein, the efficiency approaches 100% and some
energy is assimilated for growth.
It is not appropriate to compare the efficiency of long-lived ecosystems with short-lived
machines because some of the ecosystem's energy is used for repair and growth in addition to
being lost as heat, while machines cannot repair themselves. In addition, rapid ecosystem
growth per unit time has a greater survival value than high efficiency. In fuel use, the analogy
is that it is more important to reach the destination at high speed but less efficient than to
drive slowly and long, but efficiently.
D.
METABOLISM AND SIZE OF ORGANISMS
Standing Crop Biomass (expressed as dry weight or total caloric content of organisms at
any one time) can be supported by a constant flow of energy in the food chain and is to some
extent influenced by the size of the organism. The smaller the organism, the smaller the
biomass that can be supported at a certain food level of the ecosystem. Conversely, the larger
the organism, the larger the standing crop biomass.
Example:
Phytoplankton algae in a lake that weighs only a few kg can have a metaboilism that matches
that of a large tree, and the metabolism of a few kg of zooplankton is equivalent to the
metabolism of a cow.
The speed of metabolism can be measured by measuring the amount of O2 for
respiration or O2 produced by photosynthesis. The speed of metaboilism of organisms is
influenced by the surface area of the organism's body. This is because the more extensive the
body surface will be the greater the heat radiation, also homoitherm organisms metabolize
higher than poikiotherm organisms. In plants the wider the leaves the higher the metabolism.
A large tree can be considered one organism but can also be considered each leaf one
organism.
E.
FOOD LADDER STRUCTURE AND FOOD PYRAMID
The phenomenon of interactions in food chains where energy is lost during transfer from
one food level to another and the relationship between size and metabolic rate that results in
communities having a certain trophic structure that is often characteristic of an ecosystem
(lake, forest, reef, etc.).
Trophic structure can be described and measured by calculating the standing crop per
unit area, measuring the energy bound per unit area for a time at a trophic level.
Ecosystems can be said to be communities of their physical environment, each of which
can be applied to small and large entities interactions between organisms and their
environment. There are two known laws of thermodynamics, namely 1) that energy can
change form, cannot be destroyed and created, 2) that there is no efficient change in the form
of energy. The flow of energy in nature or ecosystems is subject to these laws of
thermodynamics. With the process of photosynthesis, sunlight energy is captured by plants,
and converted into chemical energy or food stored in the plant body. Plants are eaten by
herbivores, thus food energy from plants flows into the body of herbivores. Herbivores are
eaten by carnivores, so the food energy from herbivores enters the body of carnivores. In
nature, the food chain is not simple, but there are many interrelated or interconnected to form
a food web. Organisms that obtain food energy from plants with the same number of steps are
included in the same trophic level. The higher the trophic level, the higher the efficiency.
its ecology.
A living organism will always need other organisms and their environment. The
relationship that occurs between individuals and their environment is very complex, mutually
influencing or reciprocal. The reciprocal relationship between biological and non-biological
elements forms an ecological system called an ecosystem. Within the ecosystem, food chains,
energy flows, and biogeochemical cycles occur.
A food chain is the transfer of energy from its source in a plant through a series of
organisms that eat and are eaten. Ecologists recognize three main types of chains: predator
chains, parasite chains, and saprophytic chains.
1.
Predatory Chain
The predatory chain is based primarily on green plants as producers. The chain of prey
starts with herbivorous animals as the first consumer, followed by carnivorous animals that
prey on herbivores as the second consumer and ends with carnivorous and herbivorous prey
animals as the third consumer.
2.
Parasite Chain
The parasitic chain starts from large organisms to organisms that live as parasites.
Examples of parasitic organisms include worms, bacteria, and parasites.
3.
Saprophytic Chain
The saprophytic chain starts from the dead organism to the decomposer. For example,
fungi and bacteria. The above chains do not stand alone but are interconnected with each
other to form food webs.
4.
Food Chain and Trophic Levels
One of the ways communities interact is through eating and being eaten, resulting in the
transfer of energy, chemical elements and other components from one form to another along
the food chain.
Organisms in ecological groups involved in food chains are classified into trophic levels.
A trophic level is composed of all organisms in the food chain that are numbered at the same
level of eating.
The original source of energy is the sun. Plants that produce sugar through photosynthesis
use only solar energy and C02 from the air. Therefore, these plants are classified in the first
trophic level. Herbivorous animals or organisms that eat plants are members of the second
trophic level. Carnivores that directly eat herbivores belong to the third trophic level, while
carnivores that eat carnivores in the third trophic level belong to the fourth trophic level.
5.
Ecological Pyramid
Trophic structure in ecosystems can be presented in the form of ecological pyramids.
There are 3 types of ecological pyramids, namely the number pyramid, biomass pyramid, and
energy pyramid.
Trophic structure and trophic function can be described by ecological pyramids. There are
three ecological pyramids, namely:
a.
Number pyramid
Organisms with their respective trophic levels can be presented in a pyramid of numbers, as
we organisms in the first trophic level are usually the most abundant, while organisms in the
second, third, and subsequent trophic levels are decreasing. It can be said that in most normal
communities, plants are always more abundant than organisms herbivores. Similarly, the
number of herbivores is always more than the number of level 1 carnivores. Level 1
carnivores are also always more than level 2 carnivores. This pyramid of numbers is based on
the number of organisms at each trophic level.
b.
Biomass pyramid based on total dry weight or caloric value
Often a simple pyramid of numbers is not helpful in demonstrating the flow of energy in an
ecosystem. A more realistic depiction can be presented with a biomass pyramid. Biomass is a
measure of the weight of living matter at any given time. To measure biomass at each trophic
level, the average weight of organisms at each level must be measured and then the number
of organisms at each level estimated. Biomass pyramids represent the combined mass of all
organisms in a particular habitat, and are measured in grams. To avoid habitat destruction, a
small sample is usually taken and measured, then the total biomass is calculated.
Measurements like this give more accurate information about what is happening in the
ecosystem.
c.
An energy pyramid based on the speed of energy flow or productivity at the trophic
level.
Often, biomass pyramids do not always provide the information we need about a particular
ecosystem. The energy pyramid, on the other hand, is based on the observations made in the
long time. Energy pyramids are able to provide the most accurate picture of energy flow in
ecosystems.
In the energy pyramid, there is a consecutive decrease in the amount of energy available at
each trophic level. The reduction in energy that occurs at each trophic level occurs due to the
following:
a.
Only a certain amount of food is captured and eaten by the next trophic level.
b.
Some of the food eaten cannot be digested and is excreted as waste.
c.
Only part of the food is digested to become part of the organism's body, while the rest is used
as an energy source.
