Darwin’s theory of evolution posits that living things are constantly evolving in response to selection pressure. As the environment changes, the native species adapt to their habitat conditions by evolving new inheritable physical/behavioral traits. This lab report focuses on an experiment that demonstrates an evolution in action in finches. Darwin finches comprise of over 13 passerine bird species native to the Galapagos Islands, South America (Grant and Grant 135). Darwin’s finches show remarkable evolutionary changes that allow them to occupy different niches in similar habitats. The finches evolved distinct beak types to adapt to different diets in response to selection pressure. The beak type determines each bird’s access to a particular food source available in its natural habitat i.e., the Galapagos Islands. While some evolved long, slender beaks suitable for eating insects, others developed shorter, thicker beaks for feeding on seeds of different sizes. The evolution of different beak sizes/types ensured that up to 15 different species of finches could coexist in the islands.
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The theory of natural selection dictates that organisms must adapt to their habitats to survive (Grant and Grant 135). It produces heritable biological variations that could be favorable, deleterious, or neutral. The accumulation of advantageous traits makes a species fit to compete and survive in changing habitats. The underlying assumptions of this theory include a natural variation that produces desirable, unfavorable, or neutral traits, inheritance, and survival for the fittest (Podos and Nowicki 509). Therefore, Darwin’s finches evolved different beaks to feed on different food sources as an adaptive strategy.
For this experiment, the aim was to demonstrate how different beak types/sizes, represented by normal pliers, curved pliers, large forceps, and small forceps, determine each bird’s access to seeds of variable sizes. We hypothesized that the small pliers would pick small-sized seeds (millet) more quickly than tongs, which would be suited for picking larger seeds (thistle). The underlying rationale is that each beak size (tool) is suited for picking a particular seed size, which would explain the variation in total seed collections at the end of the experiment. The experiment helped mimic how selection pressure drives evolutionary changes in organisms.
In the experiment, we simulated natural selection in finches, where the ‘beak’ type determined the ability to compete for different forms of food sources, i.e., sunflower, millet, and thistle. The differently shaped beaks would be successful in picking different types of seeds. The experiment involved four types of ‘beaks’ represented by normal pliers, curved pliers, large forceps/tongs, and small forceps. The simulation involved using the beaks to pick or ‘eat’ different types of seeds, which included sunflower, millet, and thistle.
Seven groups of four students were assigned different ‘beaks’ to mimic beak adaptations in the Darwin finches. Each student was required to use the same ‘beak’ throughout the experiment. The seeds (about 50) of each type were tossed on a desk. Using the assigned beak, each student ‘ate’ as many seeds of a particular type as possible within one minute. The seeds ‘eaten’ were placed in a collection cup for each trial. Each experiment was repeated four times (trials) for each seed type. The experiment involved two treatment arms, i.e., normal and drought conditions. An average of the seeds collected in each cup represented the number of seeds ‘eaten’ by individual beaks within one minute. The results were recorded in an Excel spreadsheet.
Grant, Peter and Rosemary Grant. “Adaptive Radiation of Darwin’s Finches.” American Scientist, vol. 90, no. 1, 2002, pp. 130–139.
Podos, Jeffrey and Stephen Nowicki. “Beaks, Adaptation, and Vocal Evolution in Darwin’s Finches.” Bioscience, vol. 54, no. 6, 2004, pp. 501-511.