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KS3 Biology. 7D Variation and Classification. Contents. 7D Variation and Classification. Spotting variation. What causes variation?. The classification system. Summary activities. Spot the differences. What are the differences between these organisms? . Spot the differences.
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KS3 Biology 7D Variation and Classification
Contents 7D Variation and Classification Spotting variation What causes variation? The classification system Summary activities
Spot thedifferences What are the differences between these organisms?
Spot the differences • There are lots of differences between these organisms. • For example: • some have leaves; • some lay eggs; • some eat plants. • These organisms are different because they are all fromdifferent species.
Spot the differences – same species There are also differences between organisms of thesame species. For example, these people are all from the same species but how many differences between them can you spot?
What is variation? Even though people are all from the same species, there are many ways in which they are different from each other. Some of them are male, some are female, some are tall, some are short. The differences that occur both between different species and within the same species are calledvariation.
Contents 7D Variation and Classification Spotting variation What causes variation? The classification system Summary activities
What causes variation? • Variation is caused by two factors: • Some features are cause byinherited factors. • These are features that are passed on from parents. • For example, natural hair colour is an inherited feature. 2. Some features are caused byenvironmental factors. These are features that are affected by the surroundings. For example, someone can be born with brown hair which then gets lighter in the Sun or might be dyed a different colour.
Environmental or inherited? Sometimes it is not easy to determine whether a feature is inherited or environmental. Scientists have now decided that only four characteristics are truly inherited and not affected by the environment at all. Can you guess what they are? • natural eye colour • natural hair colour • blood group • some inherited diseases
What about other features? Some features are caused by a mixture of inheritance and the environment, for example, nose shape. Someone might have a nose that looks just like their mum’s. But if they were in an accident, they might break their nose and put a kink in it. So their initial nose shape was probably inherited but over time it is likely to have been affected by the environment. How can the environment affect skin colour?
Contents 7D Variation and Classification Spotting variation What causes variation? The classification system Summary activities
Common features There is a lot of variation between organisms, but some organisms also have many features in common. How many features common to both cows and dolphins can you think of? Compare a cow and a dolphin, you might think they do not have many things in common but you will be surprised.
What is classification? Cows and dolphins have several features in common. Many other organisms also share common features. Scientists use common features to put organisms into groups. Grouping organisms based on their common features is calledclassification.
Classification – grouping organisms Sort these organisms into four groups based on their similarities.
Classification –grouping organisms • One way that a scientist might have grouped these • organisms is to put them into the following four groups: • These groups come from the scientific system for • classifying organisms. • Plants • Birds • Mammals • Reptiles
The classification system The classification system begins with very big groups that include a lot of organisms and then moves down to smaller groups made up of fewer organisms. The biggest groups are called thekingdoms. All living things are classified into five different kingdoms. living things plants animals fungi monera protoctista
Classifying animals How can different types of animals be classified?
Animal classification The animal kingdom is divided into two groups: animals vertebrates invertebrates Invertebrates are animals that do not have a backbone. They have soft inner bodies which are held in shape by a flexible covering of outer cells or by a hard covering called an exoskeleton. Vertebrates are animals that have a backbone. They have a firm body because of the muscles that connect to their skeleton.
The odd one out whale The whale is the odd one out. All of the rest are fish, a whale is a mammal. In terms of classification, which of these organisms is the odd one out and why? sprat seahorse tuna whale shark trout salmon perch flounder sturgeon
The odd one out platypus The platypus is the odd one out. All of the rest are birds, a platypus is a mammal. In terms of classification which of these organisms is the odd one out and why? kiwi raven penguin owl robin duck swan platypus eagle pigeon
The odd one out scorpion The scorpion is the odd one out. All of the rest are insects, a scorpion is an arachnid. In terms of classification which of these organisms is the odd one out and why? caterpillar lice ant horse fly moth scorpion cicada ladybird silverfish cockroach
Contents 7D Variation and Classification Spotting variation What causes variation? The classification system Summary activities
Glossary • classification –Sorting living things into groups. • environmental variation –Differences between organisms that are due to the environment. • inherited variation –Differences between organisms that are due to their parents. • invertebrate –An animal without a backbone. • kingdom –The largest groups that living things are sorted into. • species –A group of organisms that can reproduce with each other to produce viable offspring. • variation –The differences between living things. • vertebrate –An animal with a backbone.
