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KS3 Biology
7D Variation and Classification
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7D Variation and Classification
Contents
Spotting variation
What causes variation?
Summary activities
The classification system
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What are the differences between these organisms?
Spot the differences
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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 from different species.
Spot the differences
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There are also differences between organisms of the same species.
For example, these people are all from the same species but how many differences between them can you spot?
Spot the differences – same species
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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 called variation.
What is variation?
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Contents
Spotting variation
What causes variation?
Summary activities
The classification system
7D Variation and Classification
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Variation is caused by two factors:
1. Some features are cause by inherited factors.
These are features that are passed on from parents. For example, natural hair colour is an inherited feature.
2. Some features are caused by environmental 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.
What causes variation?
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Environmental or inherited?
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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?
Environmental or inherited?
1. natural eye colour2. natural hair colour3. blood group4. some inherited diseases
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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.
How can the environment affect skin colour?
What about other features?
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.
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Contents
Spotting variation
What causes variation?
Summary activities
The classification system
7D Variation and Classification
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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?
Common features
Compare a cow and a dolphin, you might think they do not have many things in common but you will be surprised.
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Common features
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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 called classification.
What is classification?
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Sort these organisms into four groups based on their similarities.
Classification – grouping organisms
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One way that a scientist might have grouped theseorganisms is to put them into the following four groups:
These groups come from the scientific system for classifying organisms.
Classification – grouping organisms
1. Plants
2. Birds
3. Mammals
4. Reptiles
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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 the kingdoms.
All living things are classified into five different kingdoms.
The classification system
plants protoctistaanimals monerafungi
living things
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The five kingdoms
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Which kingdom?
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Classifying animals
How can different types of animals be classified?
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Animal classification
invertebratesvertebrates
animals
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 animal kingdom is divided into two groups:
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Animal classification
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Animal classification – activity
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Features of vertebrates
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Which type of vertebrate?
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Which classification group?
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whaletuna
perch
shark
sprat
sturgeon
trout
flounder
salmon
seahorse
In terms of classification, which of these organisms is the odd one out and why?
The odd one out
The whale is the odd one out. All of the rest are fish, a whale is a mammal.
whale
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ravenpenguin
platypus
duck
kiwi
swanrobin
eaglepigeon
owl
In terms of classification which of these organisms is the odd one out and why?
The odd one out
The platypus is the odd one out. All of the rest are birds, a platypus is a mammal.
platypus
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In terms of classification which of these organisms is the odd one out and why?
caterpillar
ladybird
ant
moth
horse fly
silverfish
scorpion
cockroach
lice
cicada
The odd one out
The scorpion is the odd one out. All of the rest are insects, a scorpion is an arachnid.
scorpion
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Contents
Spotting variation
What causes variation?
Summary activities
The classification system
7D Variation and Classification
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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.
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Anagrams
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Multiple-choice quiz