of the Water
When we think about fish, we
always imagine water too, their natural world. Fish
have inhabited water nearly since life began on Earth,
when the evolutionary process was initiated that has
led to an enormous family: 20,000 to 30,000 different
species of fish have been recorded.
Britannica defines fish as ''any of a variety
of cold-blooded vertebrate animals (phylum Chordata)
found in the fresh and salt waters of the world.''
Any journey through the Internet's
world of fish found quickly reveals the meaning of
''ichthyology'': the science dedicated to the study
of these cold-blooded aquatic vertebrates. The cyber-excursion
also allows the traveler to explore the worlds of
aquariums, and even mythology.
Fish constitute an essential
part of life on this planet, and they are key to the
aquatic ecosystems that cover more than three-quarters
of the Earth's surface. As far as their connection
to humans, fish provide an important source of protein,
though over-exploitation of this natural resource
has caused profound distortions in the environment.
Following is a guide for beginning
your navigation through the watery world of fish:
than 100 Aquariums on Yahoo!
Frequently Asked Questions
of Fish Species
Ecosystems are the arena in which
life flourishes on this planet. The relationships
between organisms of any kind and the physical elements
around them reach a state of equilibrium within these
systems, allowing life to sustain itself over time.
But this balance can be disrupted, and is occurring
increasingly often here on Earth.
As far as definitions
go, ecosystems are the connections that are established
between living entities and the physical medium in
a determined location. But an ecosystem can have a
broad scope: the largest of all is our planet, and
the smallest… it could be the tiny drop of water that
is home to microorganisms.
Within an ecosystem, living organisms
interact with the existing physical components: light,
temperature, water, soil, and with each other.
The forest is used most often
to represent an ecosystem, and the degradation that
occurs when trees are cut down provides a clear example
of the impacts of human tampering.
Late last year, the Washington-based
World Resources Institute (WRI) and the United Nations
Environment Program (UNEP) presented a disturbing
report on the health of the world's ecosystems,
showing that they are deteriorating at an alarming
''Every measure used by scientists
to assess the health of the world's ecosystems tells
us that we are drawing on them more than ever and
degrading them at an accelerating pace,'' stressed
Klaus Töpfer, UNEP executive director.
''We depend on ecosystems to
sustain us, and their continued good health depends,
in turn, on how we take care of them,'' he stated.
and Ecosystems - A Report by the World Resources Institute
What is an ecosystem?
is a Biome?
Eco-regions of the world - National Geographic
Agriculture is seen as the key
to understanding the beginning of human civilizations.
Everything started during that mysterious and immense
time we now call pre-history, when our very distant
ancestors domesticated certain plant species for the
first time. This
is believed to have taken place some 14,000 years
The emergence of agriculture
had a major impact on humanity: people could now control
- to a large extent - the availability of food. The
consequences of this "discovery" were astounding.
For one, the first human settlements appeared because
nomadic hunter-gatherers turned into sedentary farmers.
Agricultural activity dominated
economies for thousands of years - until the industrial
revolution. But the importance of farming did not
diminish as factories were built, or with the arrival
of the digital age. After all, it is a question of
producing food. And without food, life is impossible.
On the Internet, there is intense
traffic as far as information on agricultural issues,
which is reflected in the number of portals
engines dedicated to this topic.
The worldwide web provides an
arena for discussions about agriculture's new frontiers:
the impact of biotechnology, the pros and cons of
genetically modified crops, the problems created by
soil erosion, the promotion of urban agriculture,
and, of course, the need for more
ecologically-sound agricultural practices.
Ecological, sustainable, organic
farming has to do with the responsible use of soils.
It is an attempt to prevent the degradation of the
land in order to ensure that future generations can
continue to reap its rewards.
A good place to start your agriculture-related
Internet navigation is the United
Nations Food and Agriculture Organization (FAO),
which has created a mega-portal. The FAO's efforts
are based on a critical observation: despite the advances
made in agriculture, today there are at least 800
million people in the world who suffer from the lack
What is conservation agriculture?
of Farming in the USA