Variation in Biology PDF

VARIATION What is Variation in Biology? Variation is defined as differences between individuals of the same species Types of Variation Continuous Variation: Traits that can take any value within a range (e.g., height, weight). Discontinuous Variation: Traits that fall into distinct categories (e.g...

VARIATION What is Variation in Biology? Variation is defined as differences between individuals of the same species Types of Variation Continuous Variation: Traits that can take any value within a range (e.g., height, weight). Discontinuous Variation: Traits that fall into distinct categories (e.g., blood type, flower color). Continuous Variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale Examples include height, mass, finger length etc. where there can be many ‘inbetween’ groups Discontinuous Variation is when there are distinct differences for a characteristic For example, people are either blood group A, B, AB or O; are either male or female; can either roll their tongue or not - there are no When graphs of these data are plotted, continuous variation gives smooth bell curves (a result of all the small degrees of difference), whereas discontinuous gives a ‘step – like’ shape Blood group is an example of discontinuous variation which gives rise to a step-shaped graph Causes of Variation Genetic Variation: Differences in genes due to mutations, sexual reproduction, and gene flow. Environmental Variation: Differences caused by environmental factors (e.g., temperature, nutrition). Genetic Variation Mutations: Changes in DNA that can introduce new traits. Sexual Reproduction: Mixing of parental genes through meiosis and fertilization. Gene Flow: Transfer of genes between populations. Environmental Variation Examples: Effect of sunlight on plant growth. Influence of diet on animal size. Impact on Phenotype: How environmental factors can affect the expression of traits. Phenotypic Variation Phenotypic variation can be caused in two main ways: It can be genetic - controlled entirely by genes Or it can be environmental - caused entirely by the environment in which the organism lives Genetic Variation Examples of genetic variation in humans include: 1. blood group 2. eye colour 3. gender 4. ability to roll tongue 5. whether ear lobes are free or fixed Natural Selection In any environment, the individuals that have the best adaptive features are the ones most likely to survive and reproduce This results in natural selection: Individuals in a species show a range of variation caused by differences in genes When organisms reproduce, they produce more offspring than the environment is able to support This leads to competition for food and other resources which results in a ‘struggle for survival’ Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce Therefore the alleles resulting in these characteristics are passed to their offspring at a higher rate than those with characteristics less suited to survival This means that in the next generation, there will be a greater number of individuals with the better adapted variations in characteristics This theory of natural selection was put forward by Charles Darwin and became known as ‘survival of the fittest’ Introduction to Natural Selection Definition: Natural selection is the process where organisms better adapted to their environment tend to survive and reproduce. Key Concept: "Survival of the fittest" – fitness refers to reproductive success. Key Components of Natural Selection Variation: Differences among individuals in a population. Competition: Limited resources lead to competition among individuals. Survival and Reproduction: Individuals with advantageous traits are more likely to survive and reproduce. The Role of Variation in Natural Selection Adaptation: Variations can lead to adaptations that enhance survival. Example: Camouflage in prey species helps avoid predators. Slide 6: Example of Natural Selection Peppered Moth: Background: Light and dark forms of the moth. Observation: In industrial areas, dark moths became more common due to pollution. Conclusion: Natural selection favored the dark form.