Understanding Variation in Nature
This page delves into the causes of variation among organisms, focusing on genetic and environmental factors.
Genetic Variation
Genetic variation arises from the inheritance of genes from parents. This explains why individuals look different, with less variation between family members than in the general population.
Example: Eye color, nose shape, and sex are determined by genetic information inherited from parents.
Environmental Variation
Environmental factors also contribute to differences between individuals of the same species.
Example: Scars are a form of environmental variation.
Combined Causes of Variation
Many characteristics are influenced by both genetic and environmental factors.
Example: Height and weight are affected by both genes and environment, such as the genetic tendency to be overweight.
Investigating Variation
Scientists use various methods to study variation:
- Growing genetically identical plants in different conditions
- Studying groups of genetically similar animals
- Observing identical twins
Highlight: Studying identical twins separated by adoption provides insights into the relative influences of genetics and environment on human traits.
Evolution by Natural Selection
This section introduces the concept of natural selection:
- Organisms compete within their species
- Those with advantageous traits are more likely to survive and reproduce
Mutation and Genetic Variation
Mutations are changes in the DNA code that can introduce new variants into a species' gene pool.
Vocabulary: Phenotype - the observable characteristics of an organism resulting from the interaction of its genotype with the environment.
Highlight: While many mutations have no effect or are harmful, some can produce adaptations that make an organism better suited to its environment.
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