SCIENCE – TERM 4
BIOLOGY – ORGANISING ORGANISMS
Classification — Introducing the scientists and technologies
that have impacted classification systems
Classification — Exploring classification
systems
Lesson Goals:
• Introduce the system of classification
• Introduce the scientists and technologies that have
helped develop our understanding of classification
systems.
Success Criteria:
• Recognise that scientific knowledge changes as new
evidence becomes available, and some scientific
discoveries have significantly changed peoples
understanding of the world.
Classification — Exploring classification
systems
Classification WarmUp:
Each group has a number of
photographs of monsters. Classify the
monsters under 3 headings, write these
classifications on the large labels. Think
about how the monsters might be
related.
Further classify your monsters into 4
subheadings; write these classifications
on the smaller labels.
Be prepared to justify your
classifications.
• What were the main criterion for
classifying your monsters?
• Why did you begin with these
classifications?
• What were your next criterion for
classifying your monsters?
• Why did you select these levelled
Classification — Exploring classification
systems
The man of many names
Living things today are
classified using two names:
their genus and species.
Humans, for example, are
Homo sapiens. This ‘genus–
species’ name was based on
the work of a Swedish man
by the name of Carl
Linnaeus.
Genus and species are just
two categories – can you list
another five?
Classification — Exploring classification
systems
• If you had to guess, which pair would you pick as
being more closely related: the cauliflower and the
Brussels sprout or, the African elephant and the Asian
elephant?
Classification — Exploring classification
systems
• If you had to guess, which pair would you pick as
being more closely related: the cauliflower and the
Brussels sprout or, the African elephant and the Asian
elephant?
Despite their huge difference in looks, it
turns out that the cauliflower and the
Brussels sprout are more closely related
than the two species of elephant. Scientists
have classified both of these vegies in the
genus Brassica and the species oleracea,
giving them the two-part name of Brassica
oleracea.
Classification — Exploring classification
systems
• If you had to guess, which pair would you pick as
being more closely related: the cauliflower and the
Brussels sprout or, the African elephant and the Asian
elephant?
Even though African and Asian
elephants look similar, they are
three different species. Of the
African elephants, the African bush
elephant is classified as Loxodonta
africana and the African forest
elephant as Loxodonta cyclotis.
Asian elephants are Elephas
maximus.
Classification — Exploring classification
systems
So, how do we draw the line between species?
Often it comes down to whether the organisms can breed
and produce offspring that can do the same, but it’s not a
hard and fast rule. It’s a tricky business for scientists to work
out how living things are related and how to classify them.
The techniques scientists have used have also changed over
the years.
Eighteenth century professor of botany, Carl Linnaeus,
journeyed throughout Sweden to collect and observe
different plants and animals. He observed their similarities
and differences and put them into groups. These groups
were used to give the organisms a two-part name, now
known as binomial nomenclature. The basics of his naming
system are still used by scientists today.
Classification — Exploring classification
systems
Exploring the development of classification
Scientists have identified about 2 million different living things.
But they also estimate that about a further 85 per cent of living
things has yet to be identified. Most of these organisms are
very small and difficult to find.
After living things are discovered, they are classified by placing
them into groups with other living things that share the same
set of characteristics. Organisms are more closely related to
other organisms in the same group than to those in other
classification groups.
The way in which animals are grouped is called a classification
system. These systems have changed over time because our
understanding of living things has expanded. New
technologies, such as microscopes, and areas of science, such
as genetics, have led to large changes in thought. The current
system has been in use for almost 200 years.
• https://www.youtube.com/watch?v=Gb_IO-SzLgk
Classification — Exploring classification
systems
Read the worksheet on Carl Linneaus and work in pairs to complete the questions.
• Why do you think the system for plant classification kept being changed before
Linnaeus’s system was adopted by science?
People were creating classification systems only for their specific area of interest.
Linnaeus’s system worked for many purposes and was simple to understand, and so
was accepted by the scientific community. (At about this time there was a significant
amount of exploration across the globe, which brought back new types of living
things to Europe and resulted in additions to and a restructuring of the classification
systems.)
• When did Linnaeus devise his classification system for living things?
He devised his classification system in 1735.
• Explain what this sentence means: ‘Because of the groups to which the genus
belongs to, the name of an organism then indicates the relationship between that
organism and all other living things.’
Similar genera belong to the same family. A Phylum contains similar families. The
more specific the group is that two organisms share, the more alike the organisms
will be. Organisms that only share a very general group are less alike. This shows the
Classification — Exploring classification
systems
• Physical characteristics can be readily used to tell apart two
different birds (for example, a duck and an emu); however, this
can be difficult for very similar birds. For some closely related
organisms, the external features are almost identical, and it
requires careful study by an expert to notice small differences.
For very small organisms, such as some insects, the external
features used to tell them apart are extremely small and can
only be seen under a microscope. This is also true for some
larger organisms where the characteristic used to tell them
apart is very small.
• Micro-organisms (also called microbes) are microscopic
organisms, most of which are not visible to the naked eye. They
include a wide range of organisms such as bacteria, fungi and
algae, which belong to different classification groups. They are
very difficult to identify because of their size. Bacteria are some
of the smallest microbes and are difficult to see under a light
microscope.
Classification — Exploring classification
systems
As you have seen, the way in which animals are grouped is
called a classification system. These systems have changed
over time because our understanding of living things has
expanded. New technologies, such as microscopes, have
led to large changes in thought.
https://www.youtube.com/watch?v=XgW1HiV9SJs
https://www.youtube.com/watch?v=Ue-86MDmjns
Classification — Exploring classification
systems
Microscopes have permitted us to make significant advances
in the understanding and grouping of organisms.
Why do you think many micro-organisms that have existed
for billions of years were not known until the 1670s?
• The new technology of lenses and microscopes in the
1600s enabled microbes to be seen for the first time.
Only then could they be studied, identified and
classified.
Why did the number of identified types of microbes increase
greatly in the mid to later 1900s?
• Only after the invention of the electron microscope in
the 1930s have scientists been able to see the internal
structure of microorganisms. This advance in technology
has enabled scientists to identify many more different
types of microbes.
Classification — Exploring classification
systems
• https://www.youtube.com/watch?v=F38BmgPcZ_I