Variation

Define *variation*

The presence of differences between individuals

Define *interspecific variation*

differences between species

Define *intraspecific variation*

Differences between members of the same species

What is continuous variation?

Gradual changes over a range

eg height, root length

Which characteristic shows continuous variation?

Polygenic (determined by many gene loci which have additive effects on eachother)

What can influence polygenic characteristics?

The environment

What is discontinuous variation?

Variation that exists in distinct categories

eg blood type

Which characteristics show discontinuous variation?

Monogenic (determined by a singular gene loci)

Nymphae thermarum is the world’s smallest and most endangered water lily. Individual N. thermarum plants measure 10-20cm across.

Explain why the size of the N. thermarum is an example of continuous variation. \[3\]

A range of values that are influenced by polygenic characteristics and the environment

Complete the following passage by using the most appropriate terms. \[5\]

Variation can be described as the differences in characteristics between (1). The type of variation that is caused by differences in DNA is known as (2) variation. Variation can also be caused by the (3). Variation between members of the same species is known as (4) variation. Evolution depends on variation and (5) of the best adapted individuals.

1. individuals
2. genetic
3. environment
4. intraspecific
5. survival/ selection

What 2 factors cause variation?

Genetic and environment

What is the main source of genetic variation, what does it produce?

Mutations can produce different alleles of genes

What are other sources of genetic variation?

* Independent assortment in meiosis
* Crossing over in meiosis
* Random fertilisation in gametes during sexual reproduction

How does the environment affect gene expression?

Biological factors like predators

Non-biological factors like sunlight availability