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 classifications? How have you classified your musicians similarly/differently to others in the class? What is helpful about your classifications?

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.

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 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 relationships between organisms

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.

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