Environmental Science and Engineering
The Food Chain
Defined Environmental Science and Engineering and
the role it plays in maintaining and/or improving the
biodiversity in different ecosystems and preserving
the balance of nature where different species coexist
Ecology and the different terms related were also
Review of defined and its different levels were discussed with
examples illustrated
MO11
The locations of different Biomes (e.g. tropical
rainforest, tundra, taiga, etc.) were introduced,
including the different plants and animals that live in
these Biomes
Mediating MO12. Articulate flow of energy in
the food system; food pyramid
Outcome
• Discuss the flow of energy in
the food chain.
Intended • Show the relationship between
Learning species as depicted in the food
chain
Outcomes • Explain the practical benefits
predators and parasitoids.
• Definition and example of Food
MO11 Chain
Discussion • Energy Flow in the Food Chain
Outline • Relationships of species in the
food chain/web
• As discussed in the previous videos,
different species in a habitat and
consequently in an ecosystem are
interrelated.
• These organisms in a species interact in
myriad ways and these interactions is what
keeps the balance in an ecosystem.
• Perhaps one of the very common and what
Introduction people see very often is when one organism
eat another organism and so on.
• This relationship is an example of a Food
Chain and it does not stop there. There is
also what we call Food Web which is an
intersection of various food chain.
• These further exemplifies the complex
relationships which exist in an ecosystem.
THE FOOD CHAIN
• Producers or autotrophs are organisms are
those who can produce their own food also
known as self-feeders
• Autotrophs can be classified into two (2)
1. Photoautotrophs – such as plants, use
energy from sunlight to make organic
compounds—sugars—out of carbon
dioxide in photosynthesis. Other examples
Producers of photoautotrophs include algae and
cyanobacteria.
2. Chemoautotrophs – use energy from
chemicals to build organic compounds out
of carbon dioxide or similar molecules.
This is called chemosynthesis. For
instance, there are hydrogen sulfide-
oxidizing chemoautotrophic bacteria
found in undersea vent communities
where no light can reach
Green Plants
Algae
Cyanobacteria
Iron-oxidizing Bacteria Thiovulum maius, a sulfur-oxidizing bacteria
• Consumers or Heterotrophs are also
known as other-feeders
• These organisms, unlike autotrophs,
cannot capture light or chemical
energy as a fuel to start making their
Consumers own food
• Heterotrophs get organic molecules
by eating other organisms or their
byproducts
• Animals, fungi, and many bacteria are
heterotrophs
• A food chain is a linear relationships among
organisms in which different nutrients and
energy is passed from the consumed organism
to the organism that consumes
• A typical food chain can be composed of the
Food Chain – following parts:
a definition • Producers
• Primary Consumers
• Secondary Consumers
• Tertiary Consumers
• Quaternary Consumers/Apex Consumers
• Producers – At the base of the food chain lie the primary producers.
The primary producers are autotrophs and are most often
photosynthetic organisms such as plants, algae, or cyanobacteria.
• Primary Consumers – usually herbivores, plant-eaters, though they
may be algae eaters or bacteria eaters.
• Secondary Consumers – organisms that eat the primary consumers
and are generally meat-eaters—carnivores
• Tertiary Consumers – organisms that eat the secondary consumers
and are carnivore-eating carnivores, like eagles or big fish
• Quaternary Consumers/Apex Consumers – on some food chains,
this is an additional level. They are at the very of the food chain.
• Trophic levels describe an organism’s
position in a food chain. Some consumers
feed on all trophic levels.
The Trophic • If we consider organisms according to
trophic levels, they often form a pyramid,
Level or the with a broad base of primary producers and
only a few individuals in the highest trophic
Ecological levels.
Pyramid • While there is endless variation in the
organization of ecosystems, the pyramid
idea helps us describe generally how energy
and matter move through ecosystems
• Decomposers eat dead matter and waste
products that come from organisms; for
instance, decaying and animal matters
• Fungi and bacteria are key decomposer; they
use the chemical energy in dead matter and
wastes to fuel their metabolic processes.
• Other decomposers are known as detritivores—
detritus eaters or debris eater such as
Decomposers earthworms, crabs, slugs, or vultures.
• They not only feed on dead organic matter but
often fragment it as well, making it more
available for bacterial or fungal decomposers.
• Decomposers as a group play a critical role in
keeping ecosystems healthy. When they break
down dead material and wastes, they release
nutrients that can be recycled and used as
building blocks by primary producers.
• Food chains give us a clear-cut picture of
who eats whom. However, some problems
come up when we try and use them to
describe whole ecological communities.
• For instance, an organism can sometimes
eat multiple types of prey or be eaten by
multiple predators, including ones at
Food Web different trophic levels.
• This is what happens when you eat a
hamburger patty. The cow is a primary
consumer, and the lettuce leaf on the patty
is a primary producer.
• This is the reason why food webs exist. In
food webs, arrows point from an organism
that is eaten to the organism that eats it.
Each time an organism feeds, it becomes a link in a food chain. In an ecosystem, food chains become
interconnected when predators feed on more than one kind of prey, thus forming a food web. The
arrows in this diagram indicate the direction in which matter and energy are transferred through
feeding relationships.
ENERGY FLOW
IN THE FOOD CHAIN
Energy Flow in the Food Chain
• Energy is transferred between trophic levels when one organism eats another
and gets the energy-rich molecules from its prey's body.
• However, these transfers are inefficient, and this inefficiency limits the length of
food chains.
• When energy enters a trophic level, some of it is stored as biomass, as part of
organisms' bodies. This biomass is the only energy is available to the next trophic
level
• As a rule of thumb, only about 10% of the energy that's stored as biomass in one
trophic level—per unit time—ends up stored as biomass in the next trophic
level—per the same unit time
• The following are the reasons why only a small amount of energy is
transferred from one trophic level to the next:
• In each trophic level, a significant amount of energy is
dissipated as heat as organisms carry out cellular respiration
and go about their daily lives.
• Some of the organic molecules an organism eats cannot be
digested and leave the body as feces, poop, rather than being
used.
• Not all the individual organisms in a trophic level will get eaten
by organisms in the next level up. Some instead die without
being eaten
• The feces and uneaten, dead organisms become food for
decomposers, who metabolize them and convert their energy
to heat through cellular respiration. So, none of the energy
actually disappears—it all winds up as heat in the end
RELATIONSHIPS OF SPECIES IN
THE FOOD CHAIN/WEB
Relationships of Species in the Food
Chain/Web
• A relationship among species or organisms called predation is very
common within the food chain and the food web.
• Predation is an inter-organism or inter-species relationship in which one
is called the predator and the other one is the prey
• The predator is the organism or species that kills and consumes the
other organism. That other organism that is killed and consumed by the
predator is called the prey.
• In the food chain, organisms located in the much higher trophic level are
the predators
• Predation is not the only relationship among species/organisms
present in a food chain or in the ecosystem in general. The
following are some relationships that are also present in the
ecosystem:
• Parasitism – is a relationship between two species of plants
or animals in which one benefits (parasite) at the expense
of the other (host), sometimes without killing the host
organism.
• Commensalism – a type of relationship between two
species of a plant, animal, fungus, etc., in which one lives
with, on, or in another without damage to either.
• Mutualism – is an association between organisms of two
different species in which each benefits. Mutualistic
arrangements are most likely to develop between
organisms with widely different living requirements
• At what may be observed, some of the
organisms specifically predators and
Important parasites seems to be leeching of to
Role played other organisms
by Predators
and Parasites • However, predators and parasites has
important roles to play to maintain
balance within their ecosystem
• Predators plays a role in natural selection. Animal
predators, for example, tend to kill the sick, weak,
aged, and least fit members of a prey population
because they are the easiest to catch.
• Individuals with better defenses against predation
Benefits of thus tend to survive longer and leave more
Predators offspring with adaptations that can help them
avoid predation.
• Over time, as a prey species develops traits that
make it more difficult to catch, its predators face
selection pressures that favor traits increasing
their ability to catch their prey.
• Then the prey species must get better at eluding
the more effective predators
• This is called co-evolution
• An example of coevolution, which would highlight the
importance of predators is the relationship of moth and bats
• Bats hunt at night through echolocation by emitting impulses
of high-frequency sound in order to locate the location of the
moth
• Over time, a species of moth seemed to have adapted the
bats’ way of hunting. They have evolved ears that is able to
hear these high frequency sounds so that when bats emit it,
they can find ways to evade the bats
• The bats has also learned to counter this defense mechanism
by changing the impulses they emit into a other frequencies
• With this the cycle of adaptation continues in order for these
species to survive.
• This only goes to show the importance and benefits of
predators
• Parasites play an important role in regulating the
populations of their hosts and the balance of the overall
ecosystem
• An example of this is the infection of Red Grouse Birds
with the nematode Trichostrongylus tenuis. Because of
Benefits of the presence of the parasite, the Red Grouse Bird emits
Parasites a scent that makes it easier for the predator to hunt
the bird, thus controlling the bird’s population.
• Parasites can also have indirect effects
• For examples, Periwinkle snails infected with the
trematode species Cryptocotyle lingua, for instance,
eat significantly less algae along their Atlantic coast
homes, because the parasite weakens their digestive
tracts. Their small appetites make more algae available
for other species to consume.
Assessment
• An online task to assess your understanding
regarding the topic will be posted in the
Blackboard Learn.
• The assessment will be an essay type assessment
to further hone your knowledge regarding the food
chain and its components
• Instructions and deadline will also be indicated
there.
Synthesis of MO12 – The Food Chain
The lecture has further We have also discussed
For this particular lecture,
established the fact that the roles of the species
we discuss the
was discussed in the last that belonged to certain
relationship of organisms
lecture video. Everything trophic levels such as the
and species through the
in the biosphere is producers, consumers,
food chain
interrelated and decomposers
The cascading of energy We have acknowledged the Lastly, we can conclude
throughout of trophic fact that there are no that the food chain in
useless sectors in ecology.
levels were also discuss general is one of the key
Even predators and
and we were able to know parasites has important
reason why balance is
how and why energy is roles to play in maintaining maintained throughout
distributed that way the balance of nature. the whole biosphere.
~DAS ENDE~
