Variation+&+Classification

Variation & Classification

Introduction
Living things have been organised by scientists into different categories which are based on their common characteristics. This is known as the ‘classification system’ and has many levels of groupings. On this page, we will be looking at:


 * Species – one of the categories within the classification system
 * Variation within a species – continuous & discontinuous, inherited or environmental.
 * Natural & artificial selection within species
 * Genetic engineering
 * The modern classification system & the five kingdoms


 * Species **

A species is a way of grouping and classifying a living organism. A species is a group of organisms that have similar characteristics and are able to breed together to produce fertile offspring. So, living things that are similar are grouped together as a species. Some examples of species are; Cats, Dogs and Humans:

 Different species can not usually interbreed; they can only reproduce with an individual of the same species. There are exceptions to this such as the Liger. A Liger is produced when a Lion and a Tiger reproduce. However, due to the fact that Lions and Tigers are different species, a Liger is infertile and therefore unable to reproduce. Similar species are grouped together to form a genus, for example there are many different types of cat within the cat species. Evolution, which is responsible for creating new species, is continuous – it is always changing. This means the lines between species can often be blurred. Variation can be seen between species and within species. Variation is the presence of differences between organisms. An example of this can be seen in humans. We are all part of the same species; however we can see differences in eye colour, height and hair colour. These are known as variations. Variation between different species is always greater than those within species.

There are two different types of variation. These are continuous and discontinuous.

**Continuous **

Continuous variation is characteristic that changes gradually over a range of values. An example of this is weight. This can very within a species between the lightest and heaviest person within a species. As this is changing we refer to it as continuous. Here is another example using height, also a continuous variation:

 **<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">Discontinuous **

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Discontinuous variation is a characteristic of any species with a limited number of variations. An example of this would be eye colour. There a limited number of eye colours therefore it is a discontinuous variation. Here is a graph highlighting this using blood types:

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<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 18.6667px;">Variation within a species

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">The variation within a species is incredible. Humans for example are all the species however we vary in race, weight, height, intelligence etc. Again this is slight in comparison to the variation we see in other species such as dogs and horses. <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">There are two different forms variety within a species takes place, via Natural Selection and Artificial Selection. Natural Selection occurs when those within a species with inherited variations suited to their environment survive better than those who do not. More of these survive to reproduce and thus these variations are then passed onto the next generation of that particular species. Darwin provides a great example of this with finches. Different finches have different beaks in accordance to what they eat; they have evolved over time.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">In opposition to this we have artificial selection. Artificial selection occurs when people partake in selective breeding. The best way to exemplify this is dog breeding: dog breeders select a characteristic they want from one variety of dog and breed it with another that has another characteristic that they want.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Our genetic make up is the cause of inherited variation. In the reproductive process we get half of our genetic information from the egg and half of the information from the sperm: thus we inherit genetic information from both our biological mother and biological father. The characteristics we inherit depend upon the combination of the dominant and recessive genes. For example the gene that allows a person to roll their tongue is dominant. So if you cannot roll your tongue you are homozygous for this gene – in other words you have two recessive genes.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Other examples of inherited variation in humans are: eye colour, hair colour, skin colour, lobed ears.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 18.6667px;">Environmental Causes of Variation

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Environmental variation is defined as variation that is caused by our surroundings. (bbc ks3 bitesize). An example of environmental variation is weight: if you eat too much you will put on weight. Both plants and animals can be affected by environmental factors such as climate, lifestyle, our diets etc. A human’s religion is dependent upon their beliefs and culture, we do not have a gene that determines this for us and this is therefore an example of environmental variation. A plant for example will grow in the direction of sunlight, something that also isn’t affected by genetics.



<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Genetic engineering
<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">We have seen that variation within a species is natural, and can be as a result of both inherited and environmental factors. We have also learned that individual species can include distinctive varieties within them, for example dogs, of which there are many different varieties, or ‘breeds’.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Variation within a species can also be created artificially, by means of a process called genetic engineering, or genetic modification (also known as ‘GM’). This is an artificial type of variation, since it is engineered scientifically in laboratories.

//<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">How does it work? // <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Scientists can produce variation through genetic engineering by altering the genetic material present in the DNA of an animal or plant (or any other living organism). This could include using the DNA of another species entirely.

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//<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">Why use genetic engineering? // <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Genetic engineering has some strong scientific advantages. It can allow scientists to eliminate some of the inherited genetic information that can cause problems in species, for example health problems and genetic disease. This can result in the creation of a stronger and healthier organism as a result. It can be used to create medicines - a good example of this is insulin, which is produced after scientists alter the DNA of bacteria.

//<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">What might be the problems? // <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> Genetic engineering has produced moral arguments, with many people opposed to it. This is because it is seen to ‘play God’ or alter DNA in a way which is unnatural. It could also be dangerous. Genetic engineering is a relatively new area of science, and many people are worried that it could produce long-term, irreversible damage, including producing new species that could dangerously alter the natural balance of the environment.



<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 20px;">**Modern Classification System**

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 16px;">There are a huge number of different species on the planet, well into the millions, and due to this it would be very difficult to provide a description for every single one. However, many of the different species do possess similar characteristics. This allows us to implement a classification system where we are able to group a lot of these species together.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 16px;">The first modern classification system was introduced by Carl Linnaeus in the 18th century. This system involved putting species of organisms into certain group and giving that group a scientific name. All the names used in this system are Latin words, meaning that the same name can be used all over the country, avoiding any unnecessary confusion.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 16px;">One example of the scientific names which can be assigned to different groups is:
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 16px;">Homo sapiens (Latin word for “wise man”).

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 16px;">This process of grouping species due to their similarities is called **CLASSIFICATION.**

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 16px;">The first stage of the classification system is to separate all of the species into five different kingdoms. The species is assigned to a kingdom depending on how the organism’s cells are arranged.

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 20px; text-align: center;">The Five Kingdoms.

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">__ Protoctists __



Examples include:

<span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 120%; text-align: center;">Amoeba <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Paramecium

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">__ Prokaryotes __

Examples include:

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Bacteria <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Blue-green algae

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">__ Fungi __

Examples include :

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Mushrooms <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Yeast <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Moulds

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">__ Plants __

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">This kingdom includes all green plants including:

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Algae <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Ferns and mosses (these don’t produce seeds) <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Conifers and flowering plants (these do produce seeds)

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">__ Animals __

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">This kingdom includes all multicellular animals including:

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Jellyfish <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Worms <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Arthropods <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Molluscs <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Echinoderms <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Fish <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Amphibia <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Reptiles <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Birds <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: 16px; text-align: center;">Mammals

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Conclusion
<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">The following are the key points about variation and classification which we have learned on this page:


 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">The classification system groups all living things and involves many different categories, such as species and kingdoms.
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Species are groups of organisms of the same type, and can breed with each other to produce offspring which can, in turn, breed with each other.
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Variation occurs between species and within them, but is always less within species. The variation within species can be continuous and discontinuous. Some variation is inherited, and some is caused by the environment in which we live. It can also be a mixture of both.
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Natural selection describes the ways in which species develop over time, due to offspring inheriting positive features from their parents. Artificial selection can be achieved by the selective breeding of different varieties within a species. This is popular with breeders of dogs and cows.
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Genetic engineering, or genetic modification, occurs when scientists alter the genetic material contained within the DNA of a living organism. This can involve adding genetic material from one species to the DNA of an organism belonging to another species.
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Different species can be put into groups according to similar features. The modern classification system was developed in the 18th century and uses Latin names for species.
 * <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 120%;">The first division in the modern classification system is the 5 kingdoms, into which all living things are places. These are based upon the types of cells the organisms contain, and are: animals; plants; fungi; prokaryotes; and protoctists.

**<span style="font-family: Arial,Helvetica,sans-serif;">Links **

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">**Recap the basics with this fun KS2 game - could be a good one to use with your pupils:** media type="custom" key="10740324" align="left"

**<span style="font-family: Arial,Helvetica,sans-serif;">BBC KS3 Bitesize Video to help explain all of the areas we've just looked at: ** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">:[] <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">**And why not test yourself too?!**: []

**<span style="font-family: Arial,Helvetica,sans-serif;">If you fancy a challenge, have a look at BBC GCSE Bitesize (especially ‘Evolution’ - for natural selection - and ‘Reproduction & cloning’ – for more on genetic information & genetic engineering) **

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