Bacteria
Bacteria are among the earliest forms of life that appeared
on Earth billions of years ago. There are thousands of species
of bacteria, but all of them are basically one of three different
shapes:
Bacteria
are the most abundant of all organisms. They exist in soil and
water, and as symbionts (two unlike organisms that live together
for their mutual benefit) of other organisms. Many pathogens
are bacteria. Most are minute, usually only 0.5-5.0 µm
in size, though one type may reach 0.3 mm in diameter. Many
move around using flagella, a whip-like organelle (one of several
structures with specialized functions) that many unicellular
organisms, and some multicellular ones, use to move about.
Fungi
Fungi have similar characteristics to plants
and are sometimes mistakenly put in the plant kingdom, but plants
have chlorophyll that helps them make their own food and makes
them green. Fungi have no chlorophyll. Fungi decay dead organic
matter or grow on other organisms to get food for growth. Molds,
rusts, mildews, smits, mushrooms and yeasts are all fungi.
Microorganism
A microorganism, or microbe, is an organism that is so small
that it is microscopic (invisible to the naked eye). The study
of microorganisms is called microbiology.
Microorganisms
are found everywhere in nature. Even in hostile environments,
like the poles, deserts, geysers, rocks and the deep sea, some
types of microorganisms have adapted to the extreme conditions
and maintained colonies; these organisms are known as extremophiles.
Microorganisms
are used in baking, biotechnology, recycling of other organisms’
remains and waste products and many other processes. They can
also be harmful as pathogens (causative agents of disease) when,
as parasites, they cause infections.
