KS4 Biology
B1a / Side 1
Classification
All living organisms are classified into groups. Classification involves putting
organisms with similar characteristics into large groups and then dividing these
groups into smaller groups based on further features that they may share.
The largest classification group is called a Kingdom. A kingdom is then broken down
into smaller and smaller groups:
Kingdom
-
made up of lots of phyla (plural of phylum)
Phylum
-
made up of different classes
Class
-
made up of different orders
Order
-
made up of lots of families
Family
-
made of lots of different genera (plural of genus)
Genus
-
Usually made up of many different species
Species
-
the basic single unit of classification
An example is given below for
the classification of the brown
rat, Rattus noregicus.
Level
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Classified as: Why?
Animalia
Has animal cells, in common with all other
Animalia
Chordate
Has a spinal cord, in common with all other
Chordates
Mammalia
Has sweat glands, hair and mammary
glands in common with all other Mammalia
Rodentia
Gnaws at its food, in common with all other
Rodentia
Muridae
All members of this family are either rats
or mice
Rattus
A groups of rats that share many features
in common above those already mentioned
Novegicus
An organism which has characteristics
that are unique to this organism
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KS4 Biology
B1a / Side 2
Why bother classifying organisms?
In a library books are classified and placed into groups based on characteristics that
they share in common. Imagine if we did not do this, it would be very difficult to
find a book or use.
On a computer we classify our different types of information by placing them into
labelled folders so that we can find our information quickly.
For these same reasons biologists classify organisms.
Classification:
 Acts like a ‘filing system’ allowing organisms to be found and referred to easily.
 Allows newly discovered organisms to easily placed into a group, ‘filed’.
 Allows a scientist to easily find closely related organisms.
e.g. a plant may have been found that produces an anti-cancer drug. A
scientist could easily find closely related plants and test to see if they
produce anti-cancer drugs.
 Allows evolutionary relationships between organisms to be easily studied.
 Allows precise international scientific communication because the classification
system is based in Latin and therefore is the same across all countries.
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KS4 Biology
B1a / Side 3
Binomial system of Nomenclature
Every single organism is given a name that consists of two words. The first name is
the genus. The genus is a large group of closely related species. The second name is
the species name that is descriptive of a single species.
 The genus is always spelt with a capital whereas the species name is in lower
case.
 Both names are either written underlined or written in italics.
The species is the lowest level of classification it is defined as organisms that show
many features in common and are capable of interbreeding to produce fertile
offspring.
Things to do:
1. The classification of the brown rat has been shown on page one. Use the
Internet of books to make a similar table for the classification of man.
2. Imagine you are talking to a gardener who is getting frustrated with the use
of Latin names on packets of seeds or in gardening books. Write down what
you would say to the gardener so that he understands why it is important that
Latin names are used.
3. Using the Internet or books find out the Latin names for 10 different
organisms. Choose the two simplest ones to revise and remember for your
IGCSE examination.
Common Name
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Latin Name
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KS4 Biology
B1b / Side 1
Vertebrate Classification
The animal kingdom is divided into lots of different phyla (plural for phylum). One
phylum is known as the vertebrates. All vertebrates share the common feature of
having a spinal cord.
This phylum is then further divided into classes.
amphibians, mammals and reptiles.
These classes are birds, fish,
Things to do:
 Look at the information below about each of the five classes of vertebrates
and use this to fill in the table accompanying this sheet. You may need to use
your textbook to fill in the information about reproduction.
Glossary
Ectotherm has the same meaning as cold-blooded. This describes animals whose body
temperature reflects that of their environmental surroundings.
Endotherm has the same meaning as warm blooded. This describes animals whose
body temperature can be kept at a constant level despite changes in their
environmental temperature.
Learn three visible features for each class of vertebrates.
Class Fish
 Skeleton of
cartilage or bone
 All aquatic
 Marine or
freshwater
Class Amphibia
 Lungs in adults
 Gas exchange
also through skin
 Aquatic and
terrestrial
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KS4 Biology
B1b / Side 2
Class Reptilia
 Ectotherms
 Eggs with soft
leathery shells
 Mostly terrestrial
Class Aves (Birds)
 Terrestrial
endotherms
 Eggs with hard
shells (calcareous)
 Gas exchange
assisted by air sacs
Class Mammalia
(mammals)
 Endotherms
 Hair or fur
 Give birth to live
young
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Examples
Special features
Warm or cold
blooded
Breathing
Reproduction
Skin covering
FEATURE
FISH
AMPHIBIANS
REPTILES
There are five groups (classes) of vertebrates and they show differences:
All vertebrates have a
Vertebrates
BIRDS
MAMMALS
KS4 Biology
B1b / Side 3
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KS4 Biology
B1c / Side 1
Arthropod Classification
The animal kingdom is divided into lots of different phyla (plural for phylum).
One phylum is known as the arthropods. This phylum is then further divided into
classes. Three of those classes are Arachnida (spiders), Crustacea and Insecta
(insects).
Things to do:
 Look at the information below and from it select three features that are
shown by all classes of arthropods. Fill in these features on the reverse of
the sheet.

Study the information and look closely at the diagrams of the three classes of
arthropods shown. Complete the table of the reverse of the sheet for each of
the three classes.
Learn three visible features for each class (wings absent would not be a visible
feature, we could be classed as a crustacean because we have no wings!!!).
Arthropods
Exoskeleton made of chitin; Jointed; Segmented
bodies; Grow in stages after moulting.
Class Crustacea
 Mainly marine
 Exoskeleton
with mineral
salts
 Gills often
Class Arachnida
 Mainly
terrestrial
 2 body parts
Class Insecta
 Mostly
terrestrial
 Most can fly
 3 body parts
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Examples
Special features
Number of main body
Wings present
Number of antennae
Number of legs
FEATURE
INSECTS
CRUSTACEANS
ARACHNIDS
There are several types of arthropod including the three in the table below and they show some differences:
3.
2.
1.
All arthropods have:
Arthropods do not have a backbone. Such animals are called invertebrates.
Arthropods
KS4 Biology
B1c / Side 2
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KS4 Biology
B1d / Side 1
Using Dichotomous Keys
In biology keys are used to identify organisms based on the presence or absence of a
characteristic. They are called dichotomous keys because a choice always has to be
made between two options. They may either be in the form of a diagram or written.
Questions
Using the key below to identify each of the leaf types.
1.
Leaf is shaped like a needle …………………………………………….
Leaf is not shaped like a needle ……………………………………..
Pine
Go to 2
2.
Leaf has five main veins which spread out from the base ……………….
Leaf does not have five main veins which spread our from the base
Sycamore
Go to 3
3.
Leaf has several sharp points …………………………………………………….
Leaf does not have several sharp points ………………………………….
Holly
Go to 4
4.
Leaf is narrow in shape …………………………………………………………………
Leaf shape is not narrow ………………………………………………………………
Willow
Beech
Leaf
A
Name
B
C
D
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KS4 Biology
B1d / Side 2
Using the key below to identify the shells below:
Shells
Coiled
Not coiled
Short, Pointed
Long, Pointed
Long, narrow
Rounded
Periwinkle
Tower shell
Razor shell
Clam
Shell
A
Name
B
C
D
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KS4 Biology
B1e / Side 1
Bugs to be identified using the ‘Bug Identification Key’
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
Name =
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KS4 Biology
B1e / Side 2
Bug Identificatoin Key
Wings
No
Yes
Plain Body
Striped Body
Yes
No
Yes
No
Legs
Legs
Legs
Legs
4
6
4
6
4
6
4
6
Antennae
Antennae
Antennae
Antennae
Antennae
Antennae
Antennae
Antennae
Yes
No
Yes
No
Yes
No
Yes
No
Selina
Jeanne
Jeffrey
Jyoti
Hayley
Queenie
Mike
Ada
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Yes
No
Yes
No
Yes
No
Yes
No
Lawton
Dicky
Armilyn
Jan
Lisa
Jim
Thomas
Joe
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KS4 Biology
B1f / Side 1
How to Make a Dichotomous Key
Use the following guidelines when making a key:





First examine the groups of objects closely looking for any differences in
their characteristics.
Try to divide your group of organisms into roughly two equal halves using one
characteristic.
Each statement of the couple should be the opposite of each other
Write all the descriptive coupled statements for the first half and then start
on the second half.
Use measurements or clearly visible characteristics and try not to use
descriptors like large or small as these are based on personal judgment.
Look at the group of organisms below:
Orca (Killer whale)
Swordfish
Jellyfish
Sea cucumber
Great white shark
Squid
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KS4 Biology
B1f / Side 2
Roughly half the organisms have a tail and the other half do not so the first coupled
statement could read:
1.
Tail is present
Tail is not present
Go to 2
(Leave this blank until
you have identified all
the organisms in the
first half)
2.
Gill are visible on the side of the body
Gill are not visible on the side of the body
Go to 3
Killer Whale
3.
Nose is about half the length of the body
Nose is not about half the length of the body
Swordfish
Great white shark
(Now you can go back to question 1 and after tail is not present insert Go to 4)
4.
Body is hemispherical in shape
Body is not hemispherical in shape
Jellyfish
Go to 5
5.
Tentacles are longer than the body
Tentacles are not longer than the body
Squid
Sea cucumber
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KS4 Biology
B1g / Side 1
Constructing your own dichotomous key
1. When a scientist visited a desert island she discovered some insects. She
made some drawings and brought them back to the laboratory.
Here are her sketches:
a. Make a name up for each of the insects.
b. Construct a dichotomous key that can be used to identify each of them.
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KS4 Biology
B1g / Side 2
2. Construct a dichotomous key that can be used to identify the plants that
these leaves have come from.
a. Sycamore
b. Privet
d. Horse Chestnut
e. Mountain Ash
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C. Oak
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KS4 Biology
B1h / Side 1
Kingdom Pasta
You have in front of you a group of organisms found within Kingdom Pasta.

Look closely at the organisms and arrange them so that those most closely
related are near each other.

You have to firstly give each organism a scientific name, genus and species
descriptor e.g. Shellus minuteus.
You may decide that some organisms are very closely related and decide to
place them in the same genus but with different species names.

Remember to write each species name correctly, the genus name should start
with a capital and the species lower case and the whole name should be
underlined.

Make separate name labels for each of your species.

Construct a dichotomous key that can be used to identify each species.

Give another group your dichotomous key and labels and see if they can
correctly name all the species using your key.
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