BIO152H5 Chapter Notes - Chapter 24: Irish Elk, Geologic Time Scale, Allele Frequency
Document Summary
Populations and species evolve, meaning that their heritable characteristics change through time. More precisely, evolution is defined as changes in allele frequencies over time. Natural selection occurs when individuals with certain alleles produce the most surviving offspring in a population. An adaptation is a genetically based trait that increases an individual"s ability to produce offspring in a particular environment. Evolution by natural selection is not progressive, and it does not change the characteristics of the individuals that are selected- it changes only the characteristics of the population. Animals do not do things for the good of the species, and not all traits are adaptive. All adaptations are constrained by trade-offs and genetic and historical factors. Typological thinking: ideas that species are unchanging types. Lamarck was the first to propose the theory of evolution- idea that species change through time. Species change through time via the inheritance of acquired characteristics (giraffe necks).
