GCSE Biology Revision "Variation"

Summary

This video explains the concept of variation in biology, describing the differences in characteristics within a population. It covers three main causes of variation: genetic factors (such as inherited alleles affecting traits like eye and hair color), environmental influences (such as the effect of soil pH on flower color), and a combination of genes and environment (like human height). The video also discusses mutations as a key driver of genetic variation, illustrating how some mutations can lead to new, sometimes beneficial, phenotypes that may spread within a population.

Takeaways

• 🧬 **Variation Defined**: Variation refers to the differences in characteristics among individuals within a population.
• 🧬 **Genetic Causes**: The first cause of variation is genetic, such as inherited alleles which can affect traits like hair and eye color.
• 🌱 **Environmental Causes**: The environment can also cause variation, like the pH level of soil affecting flower color or language acquisition in humans.
• 🤝 **Combined Causes**: Some variations are a mix of genetic and environmental factors, like height in humans which is influenced by both genetics and diet.
• 🧬 **Genetic Variation**: There is a vast amount of genetic variation in any species population, primarily due to mutations.
• 🧬 **Mutations**: Mutations are random changes to DNA that occur frequently, with most having no effect, but some can influence phenotype.
• 👁️ **Eye Color Example**: Eye color is an example where a small number of mutations can significantly determine phenotype.
• 🌟 **Beneficial Mutations**: Occasionally, mutations can lead to new, beneficial phenotypes that may rapidly change a species in response to environmental changes.
• 🐇 **Rabbit Resistance Example**: In the 1950s, a mutation made some UK rabbits resistant to a virus, showing how beneficial mutations can spread in a population.
• 📚 **Further Study**: The video suggests using a revision workbook for more questions on variation, accessible via a provided link.

Q & A

What is meant by 'variation' in biology?

Variation refers to the differences in the characteristics of individuals within a population.

What are the three main causes of variation in a population?

The three main causes of variation are genetic inheritance (alleles), environmental factors, and a combination of both genes and the environment.

Can you give an example of genetic variation?

Yes, hair color and eye color are examples of genetic variation. For instance, red, blond, and dark hair, as well as blue or brown eyes, are determined by inherited alleles.

How can the environment cause variation? Provide an example.

Environmental factors can cause variation, such as the color of flowers being influenced by the pH of the soil. Another example is human language, which is shaped by the environment in which a person grows up.

What is an example of variation caused by both genetics and the environment?

Human height is influenced by both genetics and the environment. While certain alleles may make a person more likely to grow taller, proper nutrition, including enough calcium, is necessary for bones to fully develop.

What causes genetic variation within a species?

Genetic variation is caused by mutations, which are random changes in DNA. These mutations happen constantly, but most have no effect on the phenotype.

Can mutations affect the phenotype? If so, how?

Yes, some mutations can influence the phenotype. For example, alleles for tallness may result in a taller height if the person's diet is suitable.

What role do mutations play in creating new phenotypes?

Mutations can sometimes create new phenotypes, and in rare cases, these new phenotypes can be beneficial, especially if the environment changes.

What is an example of a mutation leading to a new beneficial phenotype?

A good example is the UK rabbit population in the 1950s. A virus killed 99% of wild rabbits, but a mutation made some rabbits resistant to the virus. This new phenotype became widespread in the population.

How can a beneficial mutation affect the species in the long term?

A beneficial mutation can lead to rapid changes in a species, especially if the environment favors the new phenotype. Over time, this can lead to the spread of the beneficial trait throughout the population.