6.4 Classification of living organisms

Question 1

Linnaeus classification

Answer 1

There are millions of species of organisms on Earth.
These species can be classified into groups by the features that they share.
Traditionally living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus.
Organisms were first classified by a Swedish naturalist called Linnaeus in a way that allows the subdivision of living organisms into smaller and more specialised groups.
The species in these groups have more and more features in common the more subdivided they get.
He named organisms in Latin using the binomial system where the scientific name of an organism is made up of two parts starting with the genus (always given a capital letter) and followed by the species (starting with a lower case letter).
When typed binomial names are always in italics (which indicates they are Latin) e.g. Homo sapiens.

Question 2

Sequence of classification

Answer 2

Kingdom - animalia
Phylum - Chordata
Class - mammalia
Order - primates
Family - hominidae
Genus - homo
Species - Homo sapiens

Question 3

Development of classification

Answer 3

Organisms share features because they originally descend from a common ancestor.
Originally, organisms were classified using morphology (the overall form and shape of the organism.
As evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed, new models of classification were proposed.
As technology advanced, DNA sequencing allowed us to classify organisms using a more scientific approach.
Studies of DNA sequences of different species show that the more similar the base sequences in the DNA of two species, the more closely related those two species are.

Question 4

Three domain system

Answer 4

Due to evidence available from chemical analysis, there is now a ‘three-domain system’ of classification.
This was developed by Carl Woese in 1990
In this system, organisms are divided into three large groups called domains.
These domains are:
Archaea (primitive bacteria usually living in extreme environments such as hot springs and salt lakes).
Bacteria (true bacteria such as coli and Staphylococcus).
Eukaryota (which includes protists, fungi, plants and animals).

Question 5

Evolution tree

Answer 5

Evolution trees are diagrams that show the relationship between species over evolutionary time.
A new branch in the tree shows where speciation has occurred (when a new species has evolved).