Variation

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Lesson notes

What is Variation?

**Variation** is the diversity of shapes, sizes and colours seen in living things.
Variation can be seen **between different species** and **within the same species**.
Different species have **different sets of genes**, leading to distinct characteristics (e.g., birds have feathers, fish have scales).
Individuals of the same species share many genes but have **unique combinations** causing differences like eye colour or height.

Continuous Variation

**Continuous variation** shows a range of differences that **gradually change** with no clear divisions.
Example: **human height** – people can be any height within a range, no fixed categories.
Often represented using a **histogram** (e.g., distribution of heights of 155 year 9 students).
Controlled by **many genes** (polygenic inheritance).

Discontinuous Variation

**Discontinuous variation** has **distinct categories** with no intermediate forms.
Example: **blood type** (A, B, AB, O) – you are one type, no in-between.
Represented using a **bar chart**.
Usually controlled by a **small number of genes**.

Examples of Variation

Between species: birds vs fish – different genes produce feathers vs scales.
Within species: human eye colour, height, hair type – each person is unique.
Continuous: height, weight, skin colour.
Discontinuous: blood type, ability to roll tongue, attached earlobes.

Illustration of continuous variation (height in rabbits) and discontinuous variation (blood types).

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Practice questions

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1.Which of the following best defines variation in biology?
Easy
- ADifferences between individuals of the same species only
- BDifferences between different species only
- CDifferences between individuals of different species and within the same species
- DDifferences that are always caused by the environment
2.Which of the following is an example of discontinuous variation?
Easy
- AHeight
- BWeight
- CBlood type
- DSkin colour
3.Continuous variation is usually represented using which type of graph?
Easy
- ABar chart
- BPie chart
- CLine graph
- DHistogram
4.Which of the following statements about variation is true?
Easy
- AIndividuals of the same species have identical genes.
- BDifferent species have the same sets of genes.
- CVariation within a species is what makes each individual unique.
- DVariation only occurs due to environmental factors.
5.A scientist measures the height of 200 students and finds a range from 140 cm to 190 cm with no clear categories. This is an example of:
Medium
- ADiscontinuous variation
- BContinuous variation
- CGenetic variation only
- DEnvironmental variation only
6.Which of the following is NOT a characteristic of discontinuous variation?
Medium
- AControlled by a small number of genes
- BShows distinct categories
- CCan be represented using a bar chart
- DShows a range of differences that gradually change
7.The table shows the distribution of heights of 150 year 8 students. Which height category has the highest number of students?
Medium
- A140-149 cm
- B150-159 cm
- C130-139 cm
- D160-169 cm
8.Which type of graph is most appropriate for representing discontinuous variation?
Hard
- AHistogram
- BBar chart
- CLine graph
- DScatter plot

More questions

9.A student plots a histogram of human height and observes a bell-shaped curve. This suggests that height is:
Hard
- ADiscontinuous variation
- BControlled by a single gene
- CContinuous variation
- DNot affected by genes
10.Which of the following best explains why different species have different characteristics?
Medium
- AThey live in the same environment.
- BThey have different sets of genes.
- CThey have identical genes but express them differently.
- DVariation only occurs within species.
11.Variation within a species is caused by:
Easy
- AGenes only
- BEnvironment only
- CBoth genes and environment
- DNeither genes nor environment
12.A bar chart showing the number of students with each blood type (A, B, AB, O) would have:
Hard
- ABars that touch each other
- BGaps between the bars
- CA continuous curve
- DNo bars, only points
13.A scientist measures the beak depth of 100 finches on an island and records the following measurements (in mm): 8.2, 8.5, 8.3, 8.6, 8.4, 8.7, 8.5, 8.6, 8.8, 8.9, and so on, with values ranging continuously from 8.0 to 9.5 mm. This is an example of:
Medium
- Acontinuous variation
- Bdiscontinuous variation
- Cgenetic mutation
- Dselective breeding
14.The table shows the distribution of heights of 150 year 8 students. How many students are less than 150 cm tall?
Medium
- A79
- B67
- C46
- D58
15.The table shows the distribution of heights of 150 year 8 students. What is the mode (most common) height category?
Medium
- A140-149 cm
- B150-159 cm
- C130-139 cm
- D160-169 cm
16.The table shows the distribution of heights of 150 year 8 students. What percentage of students are 170 cm or taller?
Hard
- A12%
- B8.7%
- C5%
- D13%
17.A student plots a bar chart showing the number of students with each blood type (A, B, AB, O). This type of variation is called:
Easy
- Adiscontinuous variation
- Bcontinuous variation
- Cenvironmental variation
- Dgenetic variation
18.Which of the following is most likely to show continuous variation?
Medium
- Ashoe size
- Bhand span length
- Ceye colour
- Dability to roll tongue
19.In a population of 200 plants, flower colour is controlled by a single gene with two alleles: R (red) and r (white). The number of plants with each genotype is: RR = 50, Rr = 100, rr = 50. Which type of variation does flower colour show?
Hard
- Adiscontinuous variation
- Bcontinuous variation
- Cboth continuous and discontinuous
- Dneither
20.The histogram below (not shown) shows the distribution of a trait with a bell-shaped curve. Which of the following traits would most likely produce this pattern?
Hard
- Ahuman height
- Bhuman blood type
- Cgender in humans
- Dability to taste PTC
21.A scientist measures the mass of 50 eggs from a chicken farm and records values from 45 g to 70 g. The data is grouped into 5 g intervals. Which type of graph is most appropriate to display this data?
Medium
- Ahistogram
- Bbar chart
- Cline graph
- Dpie chart
22.Which of the following statements about variation is correct?
Medium
- AVariation only occurs between different species.
- BContinuous variation is usually controlled by many genes.
- CDiscontinuous variation is usually represented by a histogram.
- DEnvironmental factors do not affect variation.
23.The table shows the distribution of heights of 150 year 8 students. What is the median height category?
Hard
- A140-149 cm
- B150-159 cm
- C130-139 cm
- D160-169 cm
24.A student measures the height of 150 year 8 students and records the data in the table below. Which type of graph is most appropriate to display this data? | Height category (cm) | Number of students | |----------------------|--------------------| | Less than 130 | 12 | | 130–139 | 21 | | 140–149 | 46 | | 150–159 | 35 | | 160–169 | 17 | | 170–179 | 13 | | 180–189 | 5 | | More than 180 | 0 |
Medium
- ABar chart
- BHistogram
- CLine graph
- DPie chart
25.A scientist investigates variation in the number of petals on flowers of the same species. She counts the petals on 200 flowers and records the following frequencies: 3 petals (5 flowers), 4 petals (20 flowers), 5 petals (150 flowers), 6 petals (20 flowers), 7 petals (5 flowers). Which term best describes this type of variation?
Hard
- AContinuous variation
- BDiscontinuous variation
- CEnvironmental variation
- DGenetic variation
26.In an experiment to investigate variation in leaf length, a student measures 50 leaves from a single oak tree. Which of the following is the most likely shape of the distribution?
Medium
- AUniform distribution
- BBell-shaped curve (normal distribution)
- CTwo distinct peaks (bimodal)
- DSkewed to the right
27.A student plots a histogram of the heights of 155 year 9 students. The histogram shows a peak in the 150–160 cm category and fewer students in the shorter and taller categories. Which of the following statements is correct?
Medium
- AHeight is an example of discontinuous variation.
- BThe distribution shows two distinct groups of students.
- CMost students are of average height, with fewer very short or very tall students.
- DThe data should be displayed as a bar chart instead.
28.A biologist measures the mass of 100 adult frogs from a pond. The masses range from 20 g to 50 g, with most frogs around 35 g. The biologist then removes the five heaviest frogs from the pond and measures the masses of the remaining frogs again after one year. What is the most likely change in the distribution of masses?
Hard
- AThe mean mass will increase.
- BThe mean mass will decrease.
- CThe range will increase.
- DThe distribution will become bimodal.
29.A student investigates variation in the length of bean seedlings grown from the same batch of seeds. She plants 50 seeds in identical soil and gives them the same amount of water and light. After two weeks, she measures the shoot length of each seedling and finds a range from 5 cm to 15 cm. What is the most likely cause of this variation?
Hard
- ADifferences in the genes of the seeds
- BDifferences in the amount of water each seedling received
- CDifferences in the amount of light each seedling received
- DMeasurement error
30.The table shows the distribution of heights of 150 year 8 students. How many students are 150 cm or taller? | Height category (cm) | Number of students | |----------------------|--------------------| | Less than 130 | 12 | | 130–139 | 21 | | 140–149 | 46 | | 150–159 | 35 | | 160–169 | 17 | | 170–179 | 13 | | 180–189 | 5 | | More than 180 | 0 |
Medium
- A70
- B65
- C75
- D80
31.A scientist measures the length of 100 leaves from a tree and records the following data: 5 leaves are 4 cm, 15 leaves are 5 cm, 40 leaves are 6 cm, 30 leaves are 7 cm, 10 leaves are 8 cm. Which type of graph should be used to display this data?
Medium
- ABar chart
- BHistogram
- CLine graph
- DScatter graph
32.In a study of variation, a scientist measures the wingspan of 200 birds of the same species. She finds a range from 20 cm to 30 cm, with a mean of 25 cm. She then measures the wingspan of the offspring of these birds and finds the same range but a mean of 24.5 cm. Which of the following is the most likely explanation?
Hard
- AThe offspring had a different diet.
- BThe offspring inherited different genes from their parents.
- CThe scientist made a measurement error.
- DThe offspring were all female.
33.The table shows the distribution of heights of 150 year 8 students. Which height category has the highest number of students? | Height category (cm) | Number of students | |----------------------|-------------------| | Less than 130 | 12 | | 130-139 | 21 | | 140-149 | 46 | | 150-159 | 35 | | 160-169 | 17 | | 170-179 | 13 | | 180-189 | 5 |
Medium
- A130-139
- B140-149
- C150-159
- D170-179
34.What type of graph is most appropriate for representing continuous variation?
Easy
- ABar chart
- BPie chart
- CHistogram
- DLine graph
35.A scientist measures the height of 200 students and records values from 140 cm to 190 cm with no clear categories. This is an example of:
Medium
- ADiscontinuous variation
- BContinuous variation
- CGenetic variation
- DEnvironmental variation
36.A scientist measures the mass of 50 eggs from a chicken farm and records values from 45 g to 70 g. The data is grouped into 5 g intervals. Which type of graph is most appropriate?
Hard
- ABar chart
- BHistogram
- CPie chart
- DScatter graph
37.A student plots a histogram of the heights of 155 year 9 students. The histogram shows a peak in the 150–160 cm category and fewer students in the shorter and taller categories. This distribution is typical of:
Medium
- ADiscontinuous variation
- BContinuous variation
- CGenetic mutation
- DArtificial selection
38.A student measures the height of 150 year 8 students and records the data in the table below. Which type of graph is most appropriate to display this data? | Height category (cm) | Number of students | |----------------------|-------------------| | Less than 130 | 12 | | 130-139 | 21 | | 140-149 | 46 | | 150-159 | 35 | | 160-169 | 17 | | 170-179 | 13 | | 180-189 | 5 | | More than 180 | 0 |
Medium
- AHistogram
- BBar chart
- CPie chart
- DLine graph
39.A scientist investigates variation in leaf length of a plant species. She measures 100 leaves and records the following data: 5 leaves are 4 cm, 15 leaves are 5 cm, 40 leaves are 6 cm, 30 leaves are 7 cm, and 10 leaves are 8 cm. What is the mean leaf length?
Hard
- A6.0 cm
- B6.2 cm
- C6.5 cm
- D6.8 cm
40.A student plots a histogram of the heights of 155 year 9 students. The histogram shows a peak in the 150–160 cm category and fewer students in the shorter and taller categories. This distribution is best described as:
Medium
- AUniform distribution
- BBell-shaped distribution
- CSkewed distribution
- DBimodal distribution

Revision notes

## Variation Variation is the diversity in shapes, sizes, and colours among living things. It can be between different species or within the same species. - **Between species**: Different species have different sets of genes, leading to distinct characteristics (e.g., birds have feathers and can fly; fish have scales and can swim). - **Within a species**: Individuals of the same species share many genes but have unique combinations, causing differences like eye colour, height, and hair type. ### Types of Variation 1. **Continuous variation**: Shows a range of differences that gradually change, with no clear divisions. Example: human height. Often shown with a histogram. 2. **Discontinuous variation**: Has distinct categories with no intermediate forms. Example: blood type (A, B, AB, O). Usually controlled by a small number of genes. Shown with a bar chart. **Key point**: Continuous variation = gradual range (e.g., height); discontinuous variation = separate categories (e.g., blood type).

Variation: The diversity in shapes, sizes, and colours among living things, seen between different species and within the same species.
Continuous variation: A type of variation that shows a range of differences that gradually change, with no clear divisions between them (e.g., human height).
Discontinuous variation: A type of variation characterised by distinct categories with no intermediate forms (e.g., blood type).

Flashcards

What is variation?

Variation is the diversity in shapes, sizes, and colours among living things, seen both between different species and within the same species.

Why do different species have different characteristics?

Different species have different sets of genes, leading to different characteristics, e.g., birds have genes for feathers and flight, fish for scales and swimming.

Does variation exist within a species?

Yes, individuals of the same species share many genes but have unique combinations, causing differences like eye colour, height, and hair type.

What is continuous variation?

Continuous variation shows a range of differences that gradually change with no clear divisions, e.g., human height.

What is discontinuous variation?

Discontinuous variation has distinct categories with no intermediate forms, e.g., blood type (A, B, AB, O).

How is continuous variation usually represented?

Continuous variation is often represented using a histogram.

How is discontinuous variation usually represented?

Discontinuous variation is represented using a bar chart.

Give an example of continuous variation in humans.

Human height is an example of continuous variation; people can be any height within a range.

Give an example of discontinuous variation in humans.

Blood type is an example of discontinuous variation; types are A, B, AB, or O with no in-between.

What type of variation is controlled by a small number of genes?

Discontinuous variation is usually controlled by a small number of genes.

True or False: Variation refers only to differences between different species.

False. Variation includes differences both between species and within the same species.

True or False: Continuous variation shows a range of differences that gradually change.

True.

True or False: Blood type is an example of continuous variation.

False. Blood type is an example of discontinuous variation.

Is height an example of continuous or discontinuous variation?

Height is an example of continuous variation.

What type of graph is used to represent continuous variation data?

A histogram is used to represent continuous variation data.

What type of graph is used to represent discontinuous variation data?

A bar chart is used to represent discontinuous variation data.

How many categories does discontinuous variation typically have?

Discontinuous variation has distinct categories with no intermediate forms.

What causes variation between different species?

Different species have different sets of genes.

What causes variation within a species?

Individuals have unique combinations of the same basic set of genes.

What is the difference between continuous and discontinuous variation?

Continuous variation has a range with no clear divisions; discontinuous variation has distinct categories.

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