Variation in Biology

This section explores the concept of variation within species, a fundamental aspect of Inheritance, variation and evolution GCSE Biology.

Variation refers to the differences observed among organisms of the same species. There are two main types of variation:

1. Genetic Variation:

   • Determined by inherited genes passed on through gametes
   • Examples include eye color, blood group, and inherited disorders

2. Environmental Variation:

   • Caused by the conditions in which organisms live and grow
   • Examples include suntans or physical injuries

Highlight: Most characteristics result from a combination of both genetic and environmental factors, such as body weight, height, and skin color.

Mutations play a crucial role in introducing new variations:

• They change the sequence of bases in DNA
• While most have no effect, some can create new phenotypes
• Beneficial mutations may become common in a species through natural selection

Vocabulary: Phenotype - The observable characteristics of an organism resulting from the interaction of its genotype with the environment.

This understanding of variation is essential for tackling AQA GCSE Biology Inheritance, variation and evolution exam questions.

Selective Breeding in Biology

This page focuses on selective breeding, an important application of genetic principles covered in Topic 6 Biology AQA a level and GCSE curricula.

Selective breeding is the process by which humans artificially select plants or animals to breed for particular characteristics:

1. Purpose:

   • Develop useful or attractive features in organisms
   • Examples include high-yield crops, disease-resistant plants, and animals that produce more meat or milk

2. Process:

   • Select organisms with desired traits from existing stock
   • Breed selected organisms
   • Choose best offspring and continue breeding over several generations
   • Eventually, all offspring will possess the desired trait

Example: The development of various dog breeds with specific temperaments or physical features is a result of selective breeding.

3. Historical Context:

   • Humans have been practicing selective breeding for thousands of years
   • It has led to the development of edible crops and domesticated animals

4. Drawbacks:

   • Reduces genetic diversity within a population
   • Can lead to inbreeding, potentially causing health defects

Vocabulary: Gene pool - The total genetic diversity found within a population or species.

Understanding selective breeding is crucial for answering AQA GCSE Biology Topic 6 questions and comprehending human influence on evolution.