Knowledge and Skills Statement
Science concepts--biological evolution. The student knows evolutionary theory is a scientific explanation for the unity and diversity of life that has multiple mechanisms.
Further Explanation
One common early misconception about adaptation was that it was intentional and guided by need or desire. For example, a theory proposed by Jean-Baptiste Lamarck suggested that a giraffe wanted to reach leaves higher up on the tree, so it stretched its neck and legs longer and longer each generation until it became the current animal.
Another misconception is that environmental conditions are responsible for changes in traits, causing adaptations to occur. On the contrary, changes to DNA are caused by random mutations or new combinations of existing genes, which will only affect the population if they occur in germ cells.
For example, a population of insects was exposed to a pesticide, and 98% of them died. The 2% that survived were somewhat resistant to the pesticide and they reproduced, making the population more resistant to it. Over multiple generations, this pattern continued until the pesticide only killed 10% of the insects.
Evolutionary fitness results from the interplay between adaptations and the environment. An organism that is a good fit for its environment can readily secure resources, survive, and reproduce.
Supporting Information
Research
Karlsson, Elinor K., Dominic P Kwiatkowski, and Pardis C Sabeti. "Natural Selection and Infectious Disease in Human Populations." Nature Reviews Genetics 15, no. 6 (June 2014): 379–393. https://www.nature.com/articles/nrg3734
Summary: The ancient biological 'arms race' between microbial pathogens and humans has shaped genetic variation in modern populations, and this has important implications for the growing field of medical genomics. As humans migrated throughout the world, populations encountered distinct pathogens, and natural selection increased the prevalence of alleles that are advantageous in the new ecosystems in both host and pathogens. This ancient history now influences human infectious disease susceptibility and microbiome homeostasis, and contributes to common diseases that show geographical disparities, such as autoimmune and metabolic disorders.
Research
Williams, Larissa M., and Marjorie F. Oleksiak. "Signatures of Selection in Natural Populations Adapted to Chronic Pollution." BMC Evolutionary Biology 8, no. 10 (October 2008): 282. doi: 10.1186/1471-2148-8-282
Summary: Much of the research on the genetic basis of adaptation has been focused on the classic model systems of Drosophila and Arabidopsis. Recently, insight into adaptation in non-model species has become possible due to advances in molecular biology and statistics. This recent expansion into studies of non-model systems allows further development of evolutionary inferences, such as the role that selection, mutation, gene flow, and drift play in adaptation. A powerful approach to understand genome-wide adaptation is to investigate independent natural populations that inhabit environments with strong selective pressures.