Read-to-Learn Study Guide - Classification of Organisms
Learning Objectives:
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Analyze the historical development of classification
Analyze the similarities and differences between prokaryotes and eukaryotes
Analyze the similarities between and differences among kingdoms: Eubacteria, Archaebacteria, Protists, Fungi, Plants, and Animals.
Classify organisms using dichotomous keys.
Read to Learn
In biology, an organism is any complete living system (such as an animal, fungus, micro-organism, or plant). In at least some form, all
organisms are capable of metabolizing nutrients for energy, responding to stimuli, and maintaining homeostasis. Living things also
grow and develop over time and reproduce by passing on genes to their offspring which is referred to as heredity. All living things
are made of a basic building block called a cell but an organism may either be unicellular (made of a single cell) or, as in the case of
humans, comprised of trillions of cells grouped into specialized tissues and organs. The term multicellular (many cells) describes any
organism made up of more than one cell.
There are over 10 million different forms or species of life on Planet Earth! This tremendous degree of diversity makes necessary the
development of a system for classifying and grouping organisms. Based on cell type, organisms may be divided into prokaryotic and
eukaryotic groups. The prokaryotes are now represented in two kingdoms Eubacteria and Archaebacteria. The organisms in both
kingdoms are prokaryotic (having no nucleus), and are unicellular. Under Whittaker’s initial schema all prokaryotes were in one
group called Moneran. Eukaryotic organisms are constructed of complex cells with a membrane-bound nucleus and other
organelles like mitochondria and chloroplasts (in plants). Protista, fungi, animals and plants are examples of species that are
eukaryotes.
Most members of the kingdom Protista are unicellular, some are autotrophs (can photosynthesize their own food) and some are
heterotrophs. Most members of the kingdom Fungi are multicellular, all are heterotrophs and have cell walls made of chitin. All
members of the kingdom Plantae are multicellular autotrophs. Most plants cannot move about, and the cells have cell walls made of
cellulose. All members of the kingdom Animalia are multicellular heterotrophs. Most animals can move about and their cells lack cell
walls.
Classification: Taxonomy is a branch of biology dealing with the identification and naming of
organisms. The ancient Greek philosopher Aristotle apparently began the discussion on
taxonomy. British naturalist John Ray is credited with revising the concept of naming and
describing organisms. During the 1700s, Swedish botanist Carolus Linneus classified all thenknown organisms into two large groups: the kingdoms Plantae and Animalia. Robert Whittaker in
1969 proposed five kingdoms: Plantae, Animalia, Fungi, Protista, and Monera. Other schemes
involving an even greater number of kingdoms have lately been proposed, however many
biologists still employ Whittaker's five kingdoms.
Linnaeus was the first to use a two name system called binomial nomenclature (which literally
means two names) to help classify and name organisms. In this system all organisms are classified
into levels called taxons or taxa. Linneaus’ system has seven levels, which run from the largest,
most diverse and inclusive taxon called kingdoms to the smallest, most specific and exclusive
taxon called species. This system of classification is shown in the figure at left.
For example, Homo sapiens is the Latin scientific name for modern humans. All members of the
species sapiens are, at least in theory, genetically able to interbreed. Several species may belong
to a genus, but the members of different species within a genus are unable to interbreed to
produce fertile offspring. Homo, however, only has one surviving species, sapiens, which are
modern humans. Prehistoric humans species like Homo erectus, Homo neanderthalensis, etc.
became extinct thousands of years ago. Several genera belong to the same family and so on up the hierarchy, eventually reaching the
kingdom (Animalia, in the case of humans).
All living organisms known to science are given classification by this system which can be used to confirm which groups of organisms
are most closely related. The rule of thumb to follow is: The more taxa organism share, the more closely related they must be.
Key Vocabulary – match the vocabulary word with its definition
_____ 1. Multicellular
_____ 2. Binomial
_____3. Taxonomy
_____4. Linnaeus
_____5. Genus
_____6. Eukaryotic
_____7. Eubacteria
_____8. Prokaryotic
_____9. Species
_____10. Heterotrophic
_____11. Autotrophic
_____12. Kingdom
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
Naming system that gives each organism a two-word name
Developed the first system of classification
Branch of biology that groups and names organisms
Consists of a group of similar species
Kingdom that bacteria belong to
Describes organisms that must eat other organisms for nutrients
The most exclusive taxon; identifies the second part of an organism’s scientific name.
Largest, most inclusive taxon; all living things fall into 1 of these 5 categories
Describes organisms that can produce nutrients using energy from light
Describes one of two groups of organisms that lack a cell nucleus
Describes organisms constructed of many cells that work in groups to form tissues.
Describes organisms whose cells contain complex membrane-bound organelles and nucleus
Putting Vocabulary to Use!
Linnaeus, binomial, taxonomy ________________________________________________________________________
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eukaryotic, protists, bacteria, unicellular _______________________________________________________________
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Show What You Know!
1.
2.
3.
4.
5.
6.
Which taxon includes the most specific characteristics? _____________________________________________
Which taxon includes the broadest characteristics? ________________________________________________
Which taxon includes more species, an order or a family? ___________________________________________
Which taxon includes only organisms that can successfully interbreed? ________________________________
If two organisms belong to the same family, what other taxonomic groups must they share? _______________
Which two organisms on the chart above are most closely related? Explain how you know. ________________
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7. To which taxa (more than one taxon) do all four organisms belong? ____________________________________
8. What is the order, family, and genus of a human? ___________________________________________________
9. Using the information in the chart, what can you conclude about the classification taxa of an organism with the
scientific name Rana temporaria? In other words, which kingdom, phylum, class, order, and genus, must this
species belong to? __________________________________________________________________________
10. Explain how the shape of the diagram to the left and the diagram
below could be helpful to students trying to understand how the
science of taxonomy works. _________________________________
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11. True or False: Organisms belonging to the same Phylum will
always belong to the same Kingdom? __________
12. True or False: Organisms belonging to the same Family will
belong to the same Genus? ________
13. True or False: Classes are less diverse than Families? _______
14. True or False: Orders are more inclusive than species? ______
BE CAREFUL!! DON’T BE TRICKED!!
Organisms can be further broken into groups beyond the species level. For example, dogs, while they all belong to the
same genus and species, Canis familiaris, can be divided into breeds. In the plant world, plants of same genus and
species can be further organized by varieties.
Check out this example below:
All live oaks belong to the genus, Quercus. All live oaks belong to the species, virginiana. Therefore, they all
share the same scientific name, Quercus virginiana. However, there are different varieties of live oaks like Bay
live oak (Quercus virginiana var. maritima.), Texas live oak (Quercus virginiana var. fusiformus), and Sand
live oak (Quercus. virginiana var. geminata). Now carefully answer this question.
15. Which tree is most closely related to Bay live oaks (Quercus virginiana var. maritima)?
A. Batis maritima
B. Carpinus caroliniana var. maritima
C. Quercus Falcata var. pagodaefolia
D. Clematis virginiana
16. Directions: Compare and contrast these six kingdoms by filling the columns with check marks beside the
characteristics that define each kingdom. Then use your chart to complete the Venn diagrams that follow.
KINGDOMS
CHARACTERISTICS
EUBACTEIA
ARCHAEBACTERIA
PROTISTA
FUNGI
PLANTAE
ANIMALIA
PROKARYOTIC
EUKARYOTIC
UNICELLULAR
MULTICELLULAR
AUTOTROPHIC
HETEROTROPHIC
HAS A CELL WALL
HAS A NUCLEUS
ALL MEMBERS
REPRODUCE
ASEXUALLY
PHOTOSYNTHETIC
FEED ON OTHER
ORGANISMS
17. Plants vs Fungi vs Animals
18. Protists vs Plants vs Animals
19. Dichotomous Keys: Can you name these fish? Use the key below to write their name in each box.
20. Describe in detail what a Glass-eye snapper looks like according to the dichotomous key above: _____________
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