Variation

Define a species.
Differentiate between inherited and environmental variation, providing examples of characteristics for each type.
Differentiate between discontinuous and continuous variation, providing examples of characteristics for each type.
Select and justify the appropriate graphical method (bar chart or histogram) for presenting discontinuous and continuous variation data.

A species is a group of organisms that share similar characteristics and can interbreed to produce fertile offspring.
While individuals within a species may exhibit variations, they are fundamentally similar enough to be considered part of the same group.

Variation means the differences in characteristics observed among individuals of the same species.
These differences can be influenced by both inherited traits passed down from parents and environmental factors like diet, lifestyle, and surroundings.
Inherited variation:
- Traits that are passed down from parents to their offspring through genes are known as inherited variation.
- These traits are determined by the specific combination of genes inherited from both parents.
- Examples include eye colour, being able to curl your tongue, or the number of fingers on your hand.
Environmental variation:
- Environmental variation occurs when external factors influence an individual's characteristics.
- Examples include differences in height due to nutrition, changes in skin color caused by sun exposure, or variations in language skills resulting from different cultural environments
Humans exhibit a wide range of variations, including differences in physical appearance, personality traits, and abilities. These variations are influenced by a combination of inherited and environmental factors.

Discontinuous variation occurs when a characteristic can only have a limited number of fixed values. Examples include blood type (A, B, AB, or O), gender (male or female), and the presence or absence of certain traits (e.g., lobed or lobeless ears).
Continuous variation occurs when a characteristic can take any value within a range. Examples include height, weight, and arm span. These characteristics often follow a normal distribution, with most individuals having values near the average and fewer individuals having extreme values.
To visualise patterns in variation, scientists often plot data on graphs.
- Discontinuous Variation: Bar charts are typically used to represent discontinuous data.
- Continuous Variation: Histograms are used to represent continuous data. A line can be added to a histogram to show the overall shape of the distribution, often resembling a bell curve.

Example of a bar graph.

Example of a histogram.

Species: A group of organisms that share similar characteristics and can interbreed to produce fertile offspring.
Variation: The differences in characteristics observed among individuals of the same species.
Inherited variation: Differences in characteristics that are passed down from parents to their offspring through genes.
Environmental variation: Differences in characteristics that are influenced by external factors like diet, climate, or lifestyle.
Discontinuous variation: Characteristics that can only take a limited number of fixed values (e.g., blood type).
Continuous variation: Characteristics that can take any value within a wide range (e.g., height, weight).
Bar chart: A type of graph typically used to represent discontinuous variation data.
Histogram: A type of graph typically used to represent continuous variation data, where the bars touch.

Plan and carry out a simple investigation to collect data on a variable characteristic within a local population (e.g., measure the height or hand span of individuals, or the length of leaves on a plant) and present the data using an appropriate graph.
Research the importance of variation within a species for the process of evolution by natural selection.