LESSON 1.
THE ROLE OF HUMANS IN THE ECOSYSTEMS
Humans are now the most important organisms in the
biosphere.
In the world today humans have a great direct
and indirect effects in all the ecosystems.
Let us discuss now the different roles/functions of
humans in the ecosystems and why humans are so important in
the ecosystem. But before doing so, we need to understand
the meaning of ecological dominance.
The Concept of Ecological Dominance
Dominant species can compete more successfully than
other organisms for the essentials of life in the same
habitat or physical environment and can exert a greater
influence on the habitat in which they live and on other
living components thriving in it (Tivy & O’Hare, 1981,
Smith, 1990).
Therefore, we can say that humans are very
important in all the ecosystems on earth because they are
considered as the ecologically dominant species.
On the other hand, plants can also be considered as
dominant species in a forest ecosystem because of their
number or size.
They comprise the greatest proportion of
the plant biomass. For example in a tropical rain forest,
the evergreen trees form the bulk of the biomass and so
they can compete more successfully for light, water, and
nutrients than smaller plants.
Likewise, the trees could
modify the physical factors such as light, temperature,
and humidity as well as the physical and chemical nature of
the soil. In contrast, other animals can attain ecological
dominance
due
to
their
size
or
number,
mobility,
aggressiveness, lack of predators and intelligence (Tivy &
O’Hare, 1981; Smith, 1990).
1.
Humans as the Ecological Dominants
Why are humans considered the most dominant
species? Why do they exert a great influence on other
organisms, and in the environment to which they live?
The answers to these questions are dependent on
the combination of characteristics of human beings.
These are the mental and emotional characteristics to
which they are allowed to compete more successfully for
what they want.
Humans are a distinct species of animal. They can
interbreed but cannot cross breed with any other
species. They share many anatomical and physiological
features in common with all other animals particularly
with the other primate animals but possess certain
ecologically significant features which distinguish
them from other primates. These are the following:
a)
b)
c)
d)
2.
Humans have a completely upright posture
combined with a bipedal locomotion.
Humans have hands with large, particularly
well-developed thumbs which can be brought
into easy contact with any of the few
fingers. Therefore, they are much more
prehensile,
i.e.
capable
of
grasping,
clinging, and holding.
Humans are both predatory and herbivorous.
They can be called omnivore organisms
because they are capable of eating plants
and animals
Human’s brain is exceptionally large in
proportion
to
the
size
of
the
body.
Therefore, they are considered the most
intelligent among the living organisms on
earth.
Humans as Tool Making Animals
Humans are the only animals that use tools to
make tools.
They evolved together with their tools.
This distinctive trait of humans as tool making animals
is closely related to their upright position, which
leaves their hands free to work; to their good vision
combined with their manipulative dexterity; to their
reasoning power and the high degree of inventiveness.
These are the result of a superior brain compared to
that of any other animal. The development of tools is
designed by human for the basic processes of:
a)
b)
killing animals for food;
digging the ground and cultivating plants;
c)
d)
making clothing and shelter; and
moving from one place to another.
The three most important initial technical advances
were discovery and use of fire, us of digging
implements, and the reinvention of the wheel (Tivy and
O’Hare, 1981)
3.
Humans as Robber Animals
Humans are characterized as the most exploitive
of all animals.
They have been called the “Robber
Animals”.
They make greater use of both terrestrial
and aquatic ecosystems than any other organisms.
The
main reason is that their needs or demands are more
diverse than other animals.
Moreover, humans tend to overcrop and overgraze,
too. When they harvest a particular crop such as rice
and corn, they remove most of the above ground and
sometimes all the above and below the ground biomass of
the
ecosystem.
This
practice
makes
nutrients
incorporated in the crop get lost. Similarly, humans
increase the number of a particular type of domestic
herbivore and initiate overgrazing. Selective and
intensive grazing deplete the more nutritive plant
species at the expense of the poorer and less nutritive.
So the feeding value of the pasture decreases. In like
manner, the grazing animals may crop the forage plants
at a rate greater than these plants can grow.
Then
they can be overgrazed as to be eaten out completely
(Tivy and O’Hare, 1981).
Humans exploit the ecosystem for non-consumptive
uses, i.e. for uses other than for nutrition and purely
domestic
purposes.
These
uses
can
be
cultural,
particularly when associated with peoples’ beliefs in
the supernatural power or significance of plants and
animals.
Likewise, humans use plants and animals for
their pleasure, satisfaction, and for aesthetic values.
Plants have been used for purely decorative and
ornamental purposes, and for cultivating of gardens.
In like manner, animals have been domesticated by
humans as pets, friends, and companions for their
pleasure and happiness, and as foods for their growth
and development.
4.
Humans as Agent of Evolution
Humans have emerged as the most powerful agent in
the process of organic evolution due to the increasing
technical skills and knowledge. The rate of organic
evolution has been accelerated as a result of the
accidental and deliberate disturbance of the ecosystem,
Many species of both plants and animals have their
population reduced to a critical level or have become
extinct as a result of their activities. On the other
hand, other organisms have increased in number while
many new varieties, subspecies or species have emerged
as
a
consequence
of
direct
or
indirect
human
intervention (Tivy and O’Hare, 1981).
Humans have exerted a powerful influence on the
course of evolution. This is a result of the following:
a)
b)
c)
d)
the domestication of plants and animals
the creation of new habitat
the worldwide dispersal of plants and animals
biotechnology/genetic engineering.
Hey, are you still there?
Do you understand
now why we are considered as the most ecologically
dominant among all the other living organisms?
Want to know more about what human dominance can do
to humanity and ecology?
Read the supplemental readings in Box 1 and Box 2
Box 1
THE BIOTECHNOLOGY
CENTURY
By Walter Isaaacson
ING FAREWELL TO THE CENTURY OF PHYSICS. THE ONE
IN WHICH WE SPLIT THE ATOM
and turned silicon into computing power. It’s time to ring
in the century of biotechnology. Just as the discovery of
the electron in 1987 was a
seminal event for the 20th century, the seeds for the 21st
century were spawned in 1953,
when James Watson blurted out
to Francis Crick how four nucleic acids could pair to form
the self-copying code of a DNA
molecule. Now were just few
years away from one of the most
important breakthrough of all
time: deciphering the human genome, the 100,000 genes encoded by 3 billion chemicals
pairs in our DNA.
R
Before this century, medicine consisted mainly of amputations
saws,
morphine
and
crude remedies that were about
as effective as blood-letting.
The flu epidemic of 1918 killed
as many people (more than 20
million) in just a few months
as perish in four years of
World War I. Since then, antibiotic and vaccines have allowed us to vanquish entire
classes of disease. As a result, life expectancy in the
U.S. jumped from about 47 years
at the beginning of the century
to 76 now.
But 20th century medicine did
little to increase the natural
lifespan of healthy humans. The
next
medical
revolution
will
change that, because genetic engineering has to potential to
conquer cancer, grow new blood
vessels in the heart, block the
growth of blood vessels in tumors, create new organs from
stem cells and perhaps even
reset
the
primeval
genetic
coding that causes cells to age.
Our children may be able (I
hope, I fear) to choose their
kids’ traits: to select their
gender and eye color; perhaps to
tinker with their IQs, personalities and athletic abilities.
They could clone themselves, or
one
of
their
kids,
or
a
celebrity they admire or may be
even us after we’ve died.
In the 5 million years
since we hominids separated from
apes, DNA has evolved less than
2%. But in the next century
we’ll be able to alter our DNA
radically, en-coding our visions
and vanities while concocting
new
life-forms.
When
Dr.
Frankenstein made his monster,
her wrestled with the moral
issue of whether he should allow
it to reproduce: “Had I the
right, for my own benefit, to
inflict the curse upon everlasting
generation?”
Will such
question require us to
new moral philosophies?
develop
Probably not. Instead, we’ll
reach again for time tested moral
notion, one sometimes called the
Golden Rule and which Immanuel
Kant, the millennium’s most meticulous moralist, gussied up into
a categorical imperative: do unto
others as you would have them do
unto you; threat each person as
an individual rather as a means
to some end.
Under this moral precept we
should recoil at human cloning,
because
it
inevitably
entails
using humans as means to other
humans’ ends – valuing them as
copies of others we loved or as
collections of body parts, not as
individuals in their own right.
We should also draw a line however fuzzy, that would permit
using genetic engineering to cure
diseases and disabilities (cystic
fibrosis, muscular dystrophy) but
not to change the personal attributes that make someone an individual (IQ, physical appearance,
gender and sexuality).
The biotech age will also
give us more reason to guard our
personal privacy. Aldous Huxley,
in Brave New World, got it wrong;
rather than centralizing power in
the hands of the state, DNA technology has empowered individuals
and families. But the state will
have an important role, making
sure that no one, including insurance companies, can look at our
genetic data without our permission or use it to discriminate
against us.
Then we can get ready
for the break through that
could come at the end of next
century and is comparable to
mapping our genes; plotting
the 10 billion or more neurons of our brain. With that
information we might someday
be able to create artificial
intelligence that think and
experience consciousness in
ways
that
are
indistinguishable
from
a
human
brain. Eventually we might be
able to replicate our own
minds in a machine, so that
we could live on without the
“wet-ware” of a biological
brain
and
body.
The
20th
century’s revolution in infotechnology will thereby merge
with
the
21st
century’s
revolution in biotechnology.
But this is science fiction. Let’s turn the page now
and get back to real science.
From: TIME MAGAZINE
March 22, 1999
Box 2
WHO OWNS OUR
GENES?
By Jefferey Kluger
I
T’S NOT FOR NOTHING THAT
SCIENTISTS ARE IN SUCH A
footrace to get the human
genome
mapped.
There’s
more
than just knowledge at stake,
after all – there’s money. Who
walks away with most of the
booty won’t be decided in labs
or universities, however, but
in courts and patent office.
researches trying to map genes
get no further than marking off
fragments stretches of DNA that
may be thousand of bases in
length.
These
so-called
expressed sequence tags may have
genetic information embedded in
them,
but
determining
where
those nuggets are and what their
structure is takes more digging.
Though deciphering the entire human genetic blueprint is
still a few years away, scientists have begun laying claim
to the stretches of DNA whose
codes they have succeeded in
cracking. In recent years researches have flooded the U.S.
Patent
and
Trademark
Office
with applications for thousands
of genes and gene fragments and
they have stirred a lot of
controversy in the process.
Geneticists
have
lately
been filing patent applications
for these ESTS anyway, figuring
that it’s best to protect their
turf
now
and
go
spelunking
around in it later. In a science
that prizes precision above all
else, this can be an odd way to
do business. “I would guess that
in many cases the scientists
didn’t even examine all the
material,” says Bruce Lehman,
commissioner of the U.S. Patent
and Trademark Office.
The biggest problem with
patenting genes is that while
scientists have at least a general idea of what specific
strands of genetic coding do,
often it’s just that - general.
Investigators do sometimes
succeed in isolating a single,
crisp genes with a single known
function.
Often,
however,
Not only can such filings
be sloppy genetics, they can
also
be
bad
business.
EST
applications may lead to socalled
sub-marine
patents,
claims that are made today and
then vanish, only to reappear
when
some
unsuspecting
scientists
finds
something
useful to do with genes hidden
in
the
patent.
To
prevent
this, Lehman requires that EST
applications include no more
than
more
than
10
genetic
sequence. Each group of 10
after that requires a separate
application – and a separate
filing fee. “Companies will now
have an incentive to file more
selective applications,” says
Lehman.
More troubling than determination how to patent the
genome is the larger question
of whether anyone ought to be
laying claim to human DNA at
all. This is partly an economic
issue. If the entire genetic
schematic is preemptively owned
by the research teams studying
at now, where is the incentive
for independent scientists –
often
sources
of
great
innovation – to work on it
later? Licensing costs, warns
Jefferey Kahn, Director of the
University
of
Minnesota’s
Center
for
Bioethics,
could
hold medical progress hostage.
Patenting
proponents
insists
that
an
equally
persuasive
argument could be made that the
large genome – mapping groups
need patent protection to make
their work worthwhile to them.
Sticker than the economic
question is the ethical one.
Most of us reflexively shrink
from
the
idea
of
anyone’s
owning the rights to any part
of the human form. Besides, if
the first anatomist to spot say
the pancreas was not granted
title to it, why should modern
genome-mapping
scientists
be
able to claim even a single
gene? As Kahn points out, “You
could
patent
a
system
for
mining gold from ore. We don’t
let people patent the gold.”
That
kind
of
argument
is
grounded not in law but in the
very idea of what it means to
be human – an issue that even
the highest federal court is
not likely to settle.
From: TIME MAGAZINE
March 22, 1999
5.
Humans as Dirty Animals
In contrast to other animals, humans are the only
animals that “foul their own nests” and pollute their
environment. Humans create additional organic waste, as
well as other substances normally present in the
environment. These add to the feces produced by all
animals. These human wastes are in significantly in
greater amounts, and distributed and concentrated
across a wide variety of habitats.
In addition, they
also produce synthetic waste materials that are nonbiodegradable or which are slow in decomposing. Lastly,
they produce toxic waste materials in greater and more
concentrated amounts than natural plant or animal
toxins (Tivy and O’Hare, 1981).
Note:
This topic will be further explained in the module on
pollution.
How about checking your understanding of the texts you
have read by doing Activity 1.
If you doubt your answer,
please do not hesitate to read again.
However, I suggest
you do the activity without referring to the text first,
then you may read again to check your answers.
ACTIVITY 1
1.
Enumerate the role/functions of human in the ecosystem.
_______________________________________________________
_______________________________________________________
2.
Fill the table below to describe the different ways by
which humans are different from plants and animals.
1.
Attributes
Locomotion
2.
Structural
Features
3.
Size of Brain
4.
Intelligence
5.
Means of
Acquiring Food
Human
Plants
Animals
3.
Make a reaction paper on the two supplemental readings
on “The Biotechnology Century” and “Who Owns Our
Genes?”
4.
Collect newspaper clippings from 1999 Newspapers on
human impacts on the ecosystem. Paste them on clean
sheets of blank white paper. Write one Reaction Paper
for all these clippings.
Note: Submit the reaction papers (for 3 and 4) when
you report to your professor.