Unit 1.2 – Classification of organisms
Classification – meaning and significance
Classification means putting things into groups.
The main reason for classifying living things is to make it easier to study them.
Earlier, scientists used to classify organisms on the basis of their morphological and anatomical features.
We still use these methods of classification today. But we now have new tools like DNA analysis for more
accuracy in the procedure.
1. Explain how DNA analysis is helpful in classification?
a. DNA is the chemical from which our chromosomes are made.
b. It is the genetic material, passed on from one generation to the next.
c. Each DNA molecule is made up of strings of smaller molecules, containing four different bases.
d. These bases, called A, C, G and T, can be arranged in any order.
e. Biologists can compare the sequences of bases in the DNA of organisms from two different species.
f. The more similar the base sequences, the more closely related the species are to one another.
g. They have a more recent common ancestor than species that have DNA base sequences that are less
similar.
The classification system of Carl Linnaeus
The first person to try to classify organisms in a scientific way was a Swedish naturalist called Linnaeus.
He introduced his system of classification in 1735.
He divided all the different kinds of living things into groups called species.
He recognised 12000 different species.
Linnaeus's species were groups of organisms that shared the same appearance and behaviour.
2. Define the term species:-
a. Organisms belong to the same species if they can breed together successfully, and the offspring that
they produce can also breed.
(Species is a group of organisms that can reproduce and produce fertile offspring)
Classification levels - from species to Kingdom
Species
Species are grouped into larger groups called genera (singular: genus).
Genus
(Each genus contains several species with similar characteristics)
Several genera are then grouped into a family Families
Families into orders
Orders
Orders into classes
Classes into phyla and Classes
Finally phyla into kingdoms.
Phyla
Kingdoms
,The binomial naming system
Binomial system is an internationally agreed system in which the scientific name of an organism is made up of
two parts showing the genus and species.
Linnaeus gave every species of living organism two names, written in Latin. This is called the binomial system.
The first name is the name of the genus the organism belongs to, & always has a capital letter (first letter only).
The second name is the name of its species, and always has a small letter (all small letters).
For example, a wolf belongs to the genus Canis and the species lupus.
Its binomial is Canis lupus.
These names are printed in italics. When you write a Latin name, you cannot write in italics, so you should
underline it instead.
The genus name can be abbreviated like this: C. lupus.
More examples-
o Dog - Canis familiaris
o Wolf - Canis lupus
o Jackal - Canis mesomelas
o Pony - Equus caballus
o Zebra - Equus burchelli
, 3. The table shows how two organisms a monarch butterfly and a giant pangolin are classified.
a. Use the information in the table to suggest whether these two organisms are not related at all, distantly
related or closely related. Explain how you made your decision.
Monarch butterfly Giant pangolin
b. Write down the genus of the giant pangolin.
o Manis
c. Use the Internet to find out how a human is classified. Write it down in a table.
Kingdom Animals
Phylum Vertebrate
Class Mammals
Order Primates
Family Hominids
Genus Homo
Species sapiens
Classification – meaning and significance
Classification means putting things into groups.
The main reason for classifying living things is to make it easier to study them.
Earlier, scientists used to classify organisms on the basis of their morphological and anatomical features.
We still use these methods of classification today. But we now have new tools like DNA analysis for more
accuracy in the procedure.
1. Explain how DNA analysis is helpful in classification?
a. DNA is the chemical from which our chromosomes are made.
b. It is the genetic material, passed on from one generation to the next.
c. Each DNA molecule is made up of strings of smaller molecules, containing four different bases.
d. These bases, called A, C, G and T, can be arranged in any order.
e. Biologists can compare the sequences of bases in the DNA of organisms from two different species.
f. The more similar the base sequences, the more closely related the species are to one another.
g. They have a more recent common ancestor than species that have DNA base sequences that are less
similar.
The classification system of Carl Linnaeus
The first person to try to classify organisms in a scientific way was a Swedish naturalist called Linnaeus.
He introduced his system of classification in 1735.
He divided all the different kinds of living things into groups called species.
He recognised 12000 different species.
Linnaeus's species were groups of organisms that shared the same appearance and behaviour.
2. Define the term species:-
a. Organisms belong to the same species if they can breed together successfully, and the offspring that
they produce can also breed.
(Species is a group of organisms that can reproduce and produce fertile offspring)
Classification levels - from species to Kingdom
Species
Species are grouped into larger groups called genera (singular: genus).
Genus
(Each genus contains several species with similar characteristics)
Several genera are then grouped into a family Families
Families into orders
Orders
Orders into classes
Classes into phyla and Classes
Finally phyla into kingdoms.
Phyla
Kingdoms
,The binomial naming system
Binomial system is an internationally agreed system in which the scientific name of an organism is made up of
two parts showing the genus and species.
Linnaeus gave every species of living organism two names, written in Latin. This is called the binomial system.
The first name is the name of the genus the organism belongs to, & always has a capital letter (first letter only).
The second name is the name of its species, and always has a small letter (all small letters).
For example, a wolf belongs to the genus Canis and the species lupus.
Its binomial is Canis lupus.
These names are printed in italics. When you write a Latin name, you cannot write in italics, so you should
underline it instead.
The genus name can be abbreviated like this: C. lupus.
More examples-
o Dog - Canis familiaris
o Wolf - Canis lupus
o Jackal - Canis mesomelas
o Pony - Equus caballus
o Zebra - Equus burchelli
, 3. The table shows how two organisms a monarch butterfly and a giant pangolin are classified.
a. Use the information in the table to suggest whether these two organisms are not related at all, distantly
related or closely related. Explain how you made your decision.
Monarch butterfly Giant pangolin
b. Write down the genus of the giant pangolin.
o Manis
c. Use the Internet to find out how a human is classified. Write it down in a table.
Kingdom Animals
Phylum Vertebrate
Class Mammals
Order Primates
Family Hominids
Genus Homo
Species sapiens
