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Variation

In this worksheet, students will get an explanation of how and why individuals of the same species show variation in their characteristics.

'Variation' worksheet

Key stage:  KS 3

Curriculum topic:   Biology: Genetics and Evolution

Curriculum subtopic:   Inheritance, Chromosomes, DNA, Genes

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

Differences between organisms are known as variation. There is a lot of variation between different types of animals. Organisms that share common characteristics belong to the same species, but there is variation even between organisms of the same species. Organisms of the same species can reproduce with one another and produce offspring that can also reproduce. For example, horses and donkeys belong to different species. Nevertheless, they can reproduce with each other, because they belong to the same family, and they produce mules. Mules cannot reproduce, because horses and donkeys do not belong to the same species and mules are not a species themselves.

 

Variation can be inherited, when offspring take features from their parents. Half of the information we inherit comes from the mother and half from the father. So, children have features from both parents, but the mix is different in each child. Natural eye colour and ear shape are two examples.

 

However, environmental factors (rainfall, sunshine and chemicals) cause variation, too. This is environmental variation. Using hair dyes to change your hair colour is an example of environmental variation.

 

Variation can be continuous, when there is range of values, like height. Usually, in this type of variation, the values can take any number. In the example of height, the value can be any height between a few centimetres and just above two metres, which are the normal heights found amongst humans.

The graph shows a normal distribution curve for height. Continuous variation graphs should be line graphs.

Graph of continuous variation

When there is not a continuous range of values, for example, blood type or eye colour, the variation is discontinuous. Discontinuous variation values are plotted on a bar graph (see graph below).

Graph of discontinuous variation

What do we call the differences between organisms?

What do we call the group of organisms that share the same characteristics?

What do we call organisms that are produced by their parents?

Tick two species that can reproduce with each other.

horse

dog

lion

donkey

Pick an example of inherited variation.

accent

eye colour

weight

Pick an example of environmental variation.

blood type

scar

hair colour

Pick an example of continuous variation.

height

eye colour

hair colour

Pick an example of discontinuous variation.

height

eye colour

weight

So, we've been looking at different types of variation, continuous and discontinuous.  We believe that this variation between individuals of a species is one of the major factors that drives natural selection, one of the forces that causes species to evolve.

 

Complete this sentence:

height

eye colour

weight

Tick two environmental factors that may affect variation.

rainfall

genes

DNA

sunshine

  • Question 1

What do we call the differences between organisms?

CORRECT ANSWER
variation
EDDIE SAYS
As we outlined in the introduction, the differences seen within individuals of a species constitute variation between them.
  • Question 2

What do we call the group of organisms that share the same characteristics?

CORRECT ANSWER
species
EDDIE SAYS
Species are defined as a group of organisms which all display the same characteristics, although that is an area that's difficult to define. Sometimes it's fairly straightforward, like spotting an Ailuropoda melanoleuca (Giant panda) but other times it's tough - you try to tell Ranunculus repens from other types of buttercup!
  • Question 3

What do we call organisms that are produced by their parents?

CORRECT ANSWER
offspring
young
EDDIE SAYS
Organisms that are produced by their parents are generally known as offspring (or young) but a variety of terms are available.
  • Question 4

Tick two species that can reproduce with each other.

CORRECT ANSWER
horse
donkey
EDDIE SAYS
Horses and donkeys can reproduce with each other. The union produces a mule, which is sterile and cannot produce its own offspring.
  • Question 5

Pick an example of inherited variation.

CORRECT ANSWER
eye colour
EDDIE SAYS
Weight is largely caused by your diet, although there is a certain amount of inherited influence which affects it, whilst accent is entirely environmental. Eye colour is caused by the combination of genes a child receives from its parents (although you can get coloured contact lenses that make them look weird!).
  • Question 6

Pick an example of environmental variation.

CORRECT ANSWER
scar
EDDIE SAYS
A scar is an example of environmental variation whereas hair colour is affected by both inherited and environmental factors (like dyes or bleaching by the sun). Blood type is determined by your genes.
  • Question 7

Pick an example of continuous variation.

CORRECT ANSWER
height
EDDIE SAYS
Human eyes are generally colours like blue/brown/green/hazel and hair tends to be (naturally) shades of black/brown/blonde/red and this data tends to be placed on a block graph or a pie chart as it's chunks of data (i.e. discontinuous). Height, on the other hand, is a continuous variable - in a typical school class there will be a range of heights between the smallest and tallest student - that's continuous variation.
  • Question 8

Pick an example of discontinuous variation.

CORRECT ANSWER
eye colour
EDDIE SAYS
Characteristics like height and weight demonstrate a range of data (continuous) whereas eye colour is an example of variation that is one thing or the other: brown or blue, for example. For this reason it's called 'discontinuous' and is displayed differently, say on a pie chart.
  • Question 9

So, we've been looking at different types of variation, continuous and discontinuous.  We believe that this variation between individuals of a species is one of the major factors that drives natural selection, one of the forces that causes species to evolve.

 

Complete this sentence:

CORRECT ANSWER
EDDIE SAYS
If you put "suited", good effort, but in KS3 you need to start using the right words (or nomenclature!!). You will know from your previous work that organisms which are best ADAPTED to their environment are more likely to survive and thrive there. Variation amongst individuals of a species ensures that each has slightly different characteristics which may give certain individuals an increased chance of survival (and thus of passing on their variation) in a changing world.
  • Question 10

Tick two environmental factors that may affect variation.

CORRECT ANSWER
rainfall
sunshine
EDDIE SAYS
So, DNA (and the genes on it) are going to be inherited factors, by their very nature. On the other hand, rainfall and sunshine will have a profound effect on an individual's ability to survive and are, therefore, environmental factors that may, over time, cause variations within a species.
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