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The Classification of Living Things
The Earth is populated by enormous numbers of different plants and animals. W hen
these organisms are studied and described, it becomes apparent that they can be
divided into groups. In each group of plants or animals, the rnembers resemble each other
strongly. These similarities are not always obvious but become apparent when the
characteristics of the group are known. Bees and butterflies, for example, though
differing considerably in appearance, size and habits, belong to the same group,
insects, because they both have hard outer skeletons, six legs and two pairs of wings.
The first division of organisms is into plant and animal kingdoms. The next
division is into phyla (singular: phylum), for example, the first nine gr oups of animals
listed below. The smallest natural group of , animals or plants is the s p e c i e s . F o r e x a m p l e ,
b i r d s a r e n o t a s p e c i e s , b u t r o b i n s a r e . G e n e r a l l y , a l l members of a species are
alike in all important respects and can breed among themselves. Breeding between
members of different species does not happen frequently in Nature.
Placing an organism in a particular category is not always easy. Certain s i n g l e celled creatures are not definitely anim als or plants but possess
characteristics of both. Fung i and bacteria are sometimes placed in the plant
kingdom although they do not contain chlorophyll and differ considerably from the green
plants in their methods of obtaining food. The list of living organisms given below is not
complete and does not conform to any strict biological classification but offers a
simplified and convenient scheme.
Taxonomists, biologists who classify living things, give each . type of organism
a scientific name in Latin. The scientific name is binomial ( bi-two; nomen-name). For
example, the name for humans is Homo sapiens, and for , corn is Zea mays. The first
word is the genus name, and the second word is the specific name that tells which
species
in
a
genus
is
being
discussed.
Note
that
the genus name is capitalized, but the species name is not.
Taxonomists group species into larger and larger groups according to their
shared characteristics using the Linnean system of organization, created in the 18th
century by the Swedish botanist, Karl von Linne:
Categories
Human Being
Corn
Kingdom
Ph ylum
Class
Order
Family
Animalia
Chordata
Mammalia
Primates
Homimidae
Plantae
Anthophyta
Monocotyledonos
Cornmelinales
Poaceae
Genus
Homo
Zea
Species
Horno sapiens
Zea Mays
.
_
In between genus and kingdom, each classification catego ry contains more species
that have fewer specific characteristics in common, until finally the s pec ies that
are in th e s am e k ingdom have on l y gen eral c harac teris tic s in
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common. For example, all species in the genus Zea look pretty much the same, t h a t i s , l i k e c o r n
p l a n t s , w h i l e t h o s e s p e c i e s i n t h e p l a n t k i n g d o m a r e q u i t e different, as when we compare
grass to trees.
Taxonomists disagree about the number of kingdoms there are today, however, recognize the 5
kingdoms that are listed below.
The five kingdom system: This classification system organizes the diversity of life into the kingdom Monera,
which comprises all prokaryotes, and four kingdoms of eukaryotes: Protoctista, Plantae, Fungi, and Animalia.
Kingdoms of life:
Monera
Small,
simple
singlecell(sometimes
chains or mats)
Absorb food (some
photosynthetic)
Bacteria including
cyanobacteria
Protista
Large, complex
single cell
(sometimes chains
or colonies)
All types
Protozoans, algae
of various types
Fungi
Multicellular
filamentous form
with specialized
complex cells
Absorb food
Molds and
mushrooms
Plantae
Multicellular form
with specialized
complex cells
Photosynthesize
food
Mosses, ferns,
wood and nonwood flowering
plants
Animalia
Multicellular form
with specialized
complex cells
Ingest food
Sponges, worms,
insects, fish,
amphibians,
reptiles, birds, and
mammals
Look at the vocabulary exercises that follow:
Text 2 : The Classification of Living Things
Exercise 1:
Match the terms with their definition.
1.eucaryote
a)a free-living, nonphotosynthetic, single-celled, motile eukaryotic organism.
Most of them live by feeding on other organisms, as predators or as parasites.
2. procaryote
b) the grasses: chiefly herbaceous but some woody plants including cereals;
bamboo; reeds; sugar cane.
3.protozoan
c) living organism composed of one or more cells with a distinct nucleus and
cytoplasm. Includes plants, animals, fungi, and protozoa; excludes bacteria
4. poaceae
d) An order of monocotyledonous herbs
5.commelinales
e)the basic unit from which living organisms are made, consisting of an
aqueous solution of organic molecules enclosed by a membrane.
6.cell
f) type of living cell distinguished by the absence of a distinct nucleus.
Bacterium
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Exercise 2:
Read the theoretical part on Latin or Greek plurals and then find the plurals of the words in the list; use a
dictionary if needed.
Theory: There are a lot of nouns in English of Latin or Greek origin, which often end in –us, -a, um, -on. The plural
forms of these nouns can sometimes cause difficulty.
a)some especially scientific terms have kept their original singular and plural forms: e.g. bacillus/ -i
b) many, especially those in general use, now only have a regular English plural form: e.g. arena-arenas, circuscircuses, electron-electrons
c) some have alternative plural forms, which are both acceptable. The Latin form is more formal: e.g. focus-foci,
formula-formulas/formulae, spectrum-spectrums/spectra
d) there is uncertainty with some nouns as to whether they are singular or plural: e.g. This data is correct. or These
data are correct.; medium-media, media
Now, write the plurals of the words:
embryo
virus
maximum
vacuum
alumin(i)um
atom
quantum
silicon
focus
genus
fetus
fungus
phylum
nucleus
radius
memorandum
optimum
equilibrium
minimum
bacterium
Exercise 3:
Find the synonyms of the following words:
obtain
considerably
breed
convenient
obvious
nomenclature
Exercise 4:
Fill in the gaps with the provided words; one is redundant
Bacteria, optimum, cytoplasm, rod-shaped, wall, reproduce, essentials, encloses, evolve, matrix, cervix
Among present-day cells,1)……… have the simplest structure and come closest to showing us life stripped down to its
2)……...... . They are typically spherical, 3)………., or spiral cells, a few micrometers long. They often have a tough
protective coat, called a cell 4) ……., beneath which a plasma membrane 5) ………. a single compartment containing
the 6) …………, including DNA. In the electron microscope this cell interior typically appears as a 7) ………. of varying
texture without any obvious organised internal structure. Bacteria typically are small and 8) ………… quickly by dividing
in two. Under 9) ………….. conditions, when food is plentiful, a bacterium can duplicate itself in this way in as little as 20
minutes. Because of their large numbers and rapid growth rates, populations of bacteria can 10)…………. fast, rapidly
acquiring the ability to use a new food source or to resist by being killed by a new antibiotic.
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