Heritable Variation as the Basis of Evolution

Heritable Variation as the Basis of Evolution

  1. Heritable Variation refers to differences among individuals that are passed on from parents to offspring through genes.

  2. Variation can be genetic or environmental. Genetic variation results from differences in the DNA sequence, while environmental variation arises from external factors like diet and climate.

  3. Mutations are the original source of new genes and, therefore, genetic variation. These can be random changes in DNA, brought about by errors during replication, or in response to environmental factors such as UV radiation.

  4. Sexual reproduction is another source of heritable variation. During meiosis, the process that creates sex cells, homologous chromosomes (pairs of chromosomes, one inherited from each parent) undergo crossing over. This exchange of genetic material leads to offspring with combinations of traits different from either parent.

  5. Genes, the fundamental units of heredity, are sections of DNA within each chromosome. Each gene controls/supervises certain characteristics or group of features in an organism.

  6. An allele is one variant form of a gene. Individuals inherit two alleles for each gene, one from each parent. These pairs of alleles could be identical (homozygous) or different (heterozygous).

  7. Genotype refers to the specific set of alleles that an individual possesses, while phenotype refers to the observable traits or characteristics. While genotype can influence phenotype, environmental factors can also impact how genes get expressed.

  8. Natural selection is the process where organisms that are better adapted to their environment tend to survive and produce more offspring. This mechanism of evolution relies on heritable variation within species.

  9. Over time, populations can evolve. Evolution refers to changes in the genetic composition of a population over generations. The source of this change is the genetic variation among individuals leading to variation in traits.

  10. Speciation, the formation of new and distinct species in the course of evolution, can occur when a species is split into two or more isolated groups that do not interbreed. Over time, the genetic differences between these groups may become so great that they can no longer interbreed, resulting in the formation of new species.

Understanding the principles of heritable variation and the mechanisms of evolution provides insights into the diversity of life on Earth and helps elucidate how organisms adapt to changes in their environment.