Overview
This lecture explains the sources and types of variation among individuals, focusing on continuous and discontinuous variation, and the difference between interspecific and intraspecific variation.
Sources and Nature of Variation
- All organisms within a population display some variation, making each individual unique.
- Variation can be due to genetics (inherited DNA) or environmental factors (like sunlight exposure).
- Traits can be influenced by genetics, environment, or a combination of both (gene-environment interaction).
Types of Variation: Interspecific and Intraspecific
- Interspecific variation is the difference between members of different species (e.g., palm trees vs. ash trees).
- Intraspecific variation is the difference among individuals within the same species (e.g., different breeds of dogs).
- Populations with greater genetic diversity have higher intraspecific variation.
Continuous Variation
- Continuous variation shows a full range of values between two extremes (e.g., height, weight).
- Most individuals cluster around the mean value, forming a normal distribution.
- Continuous traits are usually controlled by multiple genes and influenced by environmental factors.
Discontinuous Variation
- Discontinuous variation has distinct, separate categories with no intermediates (e.g., eye color: blue, brown, green).
- Individuals are distributed among specific categories.
- Discontinuous traits are generally controlled by a single gene and not affected by the environment.
Key Terms & Definitions
- Variation — Differences among individuals within or between populations.
- Interspecific Variation — Variation between different species.
- Intraspecific Variation — Variation within members of the same species.
- Continuous Variation — Traits with a full range of possible values between two extremes.
- Discontinuous Variation — Traits with distinct categories and no intermediate states.
- Genetic Diversity — The total number of genetic characteristics in the genetic makeup of a population.
Action Items / Next Steps
- Review definitions and examples of continuous and discontinuous variation.
- Practice distinguishing between interspecific and intraspecific variation in sample questions.