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Part 1: The ‘whys’ and ‘hows’ of classification

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1 Part 1: The ‘whys’ and ‘hows’ of classification
Of Living Things Part 1: The ‘whys’ and ‘hows’ of classification

2 Why Classify Things? Imagine going to the supermarket or the library where the items have not been placed in particular categories, that is, not classified. Even the items in our kitchen are classified one way or another in different drawers and cupboards. How are items classified in the supermarket and library? Could you think of any ways to improve these classification systems? Would it be very different using the library or supermarket without a classification system? Why? Justify the changes you would or wouldn’t make

3 Why Classify Living Things?
Biologist have found over 1.5 million different species currently living on our planet It is estimated that there could actually be about 12 million different species (and some believe up to 50 million) living amongst us but as yet undiscovered – many of them microscopic Some of these may never be discovered as they will become extinct before scientists find them About 2/3 of the 1.5 million species currently described are insects It is also estimated that up to 99% of organisms that have once lived on the planet, are now extinct – some show up in the fossil record This is a large amount of living things (present and past) that need to be classified…

4 What Advantages are there to Classifying Living Things?
Classifying living things helps… …identification of new species when they are discovered – not only ones currently living, but those found in the fossil record as well …scientists communicate more precisely (especially on an international level) …understand the relationship between organisms so that we can help with things like conservation …describe living things quickly and more accurately.

5 Who First Classified Living Things?
Carolus Linnaeus   One of the most important 18th century naturalists was a Swedish botanist and medical doctor named Karl von Linné.  He wrote 180 books mainly describing plant species in extreme detail.  Around 1740, Linnaeus published Systema Naturae in which he outlined his scheme for classifying all organisms according to their similarities. This Linnaean system of classification was widely accepted by the early 19th century and is still the basic framework for all taxonomy in the biological sciences today. Taxonomy is the science concerned with classification of living things. Since his published writings were mostly in Latin, he is known to the scientific world today as Carl Linnaeus, which is the Latinized form he chose for his name.

6 Development of Systems of Classification
Initially, according to Linnaeus, organisms were divided up into two main groups – plantae and animalia. These two groups were called ‘kingdoms’. By the middle of the 19th century German biologist, Ernest Haeckel created a third kingdom for all the single celled organisms he found by using a microscope. He called this kingdom protista. When the electron microscope was discovered in the 1950s, prokaryotic cells were discovered. A fourth kingdom, monera was created to accommodate them. In 1967 it was decided that fungi were neither plants or animals, protista or monera, so a fifth kingdom was created for them. Today the five kingdom system is still in use.

7 Difficulties with Classifying Living Things?
Scientists needed to agree Not all organisms look the same at birth as they do as adults ie insects Classifying extinct organisms is difficult as there is not always enough information about the characteristics of the organisms Organisms live in remote places that humans find hard to access, such as the bottom of the ocean or in icy arctic caves, so even getting at them was difficult Which qualities were used to classify the organisms … let’s have a closer look at this…

8 Qualities used to Classify Living Things
Q. Which characteristics are the most useful when classifying an organism? A. Structural characteristics No, that would not work as organisms can change size as they grow – you need to be able to classify it correctly at any age. How about colour? No, colour wouldn’t work either. That would mean green frogs, alligators and spinach would all be in the same category. What a about structure? The structural characteristics of the organism would work well. ie. Do they have flowers, wings, scales, a backbone, a pouch or radial symmetry. What about the size of an organism?

9 5 Kingdom Classification System
All Living Things Animals Plants Fungi Protista Monera Animals can come in all shapes or forms; from humans to corals to snails to sharks to sea anemones. Don’t have a cell wall and are mostly mobile We recognise plants because they are usually green in colour. This is because they contain chlorophyll to photosynthesise and therefore make their own food. They are autotrophic and have a cell wall. Monera are prokaryotic bacteria, some make us sick, but many more help us. They don’t have a true nucleus. Protists are usually small single celled organisms that can contain qualities of both plants and animals together. Fungi are not plants or animals as many like to think. They are mushrooms, toadstools and molds that grow on bread. They have a cell wall made of chitin.

10 This small model shows only one set of branching on three levels
This small model shows only one set of branching on three levels. Imagine each branch with anything from 2 – 10 more branches. This will give you some idea of how extensive this system is. The next slide give the names of these categories… Level 1 Level 2 Level 3 The organisms within each of the 5 kingdoms are divided up into numerous other categories, again depending on their structural characteristics. In fact each of those next groups then branches again into numerous categories. They are divided four more times to make a total of 7 hierarchical categories. Each organism has a different name for each of the 7 hierarchical categories it is in. That makes for a large number of categories in the final stage!! Let’s have a look…

11 Hierarchical Levels of Classification
A mneumonic to help you remember A human example Kingdom King Animal Largest number in group Least characteristics in common Phylum Philip Vertebrate Class Can’t Mammal Order Order Primate Family Five Hominidae Genus Most characteristics in common Gin Homo Smallest number in group Species Slings sapiens

12 Binomial System of Nomenclature
You may have noticed on the previous slide that the last two names an organism has (the genus and species name) were in italics, and that the species name did not start with a capital letter This is because these last two names are the Latin or Scientific names the organism has. ‘Human’ is the common name and Homo sapien is the scientific name It is called a binomial system as ‘bi’ = ‘two’ and ‘nomial’ = ‘naming’ Carl Linnaeus developed this system of naming when he first developed classification. It has remained in use all this time What are the common names for these organisms on the next slide…?

13 Binomial System of Nomenclature
Canis familiaris Viola odorata Macropus giganteus Baccillus thuringiensis Agaricus bisporus

14 Definition of ‘Species’
The species name is the last hierarchical level of classification and the second part of the latin ‘binomial’ name Organisms belong in the same species if they are able to breed AND produce a fertile offspring (an offspring that is not sterile and can also breed) Liger – although born from the mating of a tiger and lion it is sterile

15 Dicotymous Keys When scientists want to identify and unknown specimen, they use a dicotymous key A dicotymous key asks a series of questions about the specimen and allows the user to place the specimen in one of two categories Dicotymous key can be used to place organisms within any of the hierarchical classification categories Here is an examples of a dicotymous key used to place all living things in a kingdom – the first level of classification…

16 Dicotymous Keys All living things Monera Prokaryotic Eukarytoic
Unicellular Multicellular Protista Autotrophic Heterotrophic Plants Non-Motile Motile Fungi Animals

17 Okay, that is the end of part one
Okay, that is the end of part one. If you have time to stick around, the second part of this PowerPoint takes you through some of the phylum in the 5 different kingdoms. This way you can really see how the classification of living things works.

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