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Lecture 2

PSYC 3420 Lecture 2: Lecture #2

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PSYC 3420
Krista A Phillips

Lecture 2 Pre Darwin • The idea of evolution was in the air • The Earth is old; the principles of geology- the Earth is older than previously thought • Charles Lyell was the first to propose that geological changes are very slow processes • Also proposed that geological changes were not the result of a higher power • Organic structures change over time; they are not part of a static hierarchy • Dominant idea for a long time was that things did not change; stasis • 19th century naturalists and biologists took note of shared features in the anatomy among species; adult structures have similar developmental patterns, similar embryonic precursors • Structures of organisms have purpose/function; this is true in architecture, design, organic life; a difference between the image of an organism and the function • What was missing was a mechanism to put the pieces together! This was Darwin’s challenge! History of Darwin-> H.M.S Beagle (1831-1836) • As a youngster, he was fascinated with the natural world • He started as a medical student, but did not have the stomach for it • He then went to divinity school where he was a failure • He rekindles his passion for natural history; began to gain a reputation for having a notable collection of specimens • He embarked on a voyage to the Galapagos Islands to survey the waters; critical experience for him • He was struck by the huge variety of species; he saw things that he had never seen before nor anywhere else on the planet • Off the coast of Argentina, he found fossils of huge mammals (mammoths, round sloths) • He pondered their relation to the sloths that were still alive • He realized that the fossils in the ground were the very ancestors of the animals alive on the islands • He was able to pair these ideas with that of Charles Lyell; these were very new principles of reasoning in geology, which had a huge influence over Charles Darwin • He noticed on the islands that there variations in the tortoises; he was told by the locals that by looking at the shells, you could determine which island they were from • He also noticed that the birds of similar species had unique traits (Finch Beaks) based on their geographical location • He regretted not doing a systematic study before he left; he was shocked that the finches he collected were 13 different species and they were island specific! • He created an idea that competed against the dominant view that species remain in their fixed form; the finches had a common ancestor, but they had diversified, and the same happened to the tortoise • From this insight emerged a bold idea; all organisms are related through descent from a common ancestor that lived in the remote past….he called this descent modification or adaptations • Organisms share many characteristics; the wing of a bird vs the flipper of a fish • Over evolutionary time, the descendents of the common ancestor have accumulated diverse modifications or adaptations that allow them to survive…but why? • Then came the idea of natural selection Why do species change? • Animals that survive are the ones best for suited for the environment; anatomically and structurally suited to deal with the traits of the environment ; a selection in nature for adaptive traits Key Influences: • He was well acquainted with human’s artificial selection: breeding of traits- an exploitation of variation(breeding of dogs to look a certain way, and to have a particular temperament )…Darwin believes that this variation must be inheritable; variation must be the ‘starting point’ in nature’ • He was very interested in the work of Thomas Malthus: Essay on the Principle of Populations- competition for resources…the fear that populations would exceed the resources the world could produce • Darwin observes that there must be a ‘struggle for existence’- not all organisms born within a population survive; the ones that do survive, reproduce. • It took him 20 years to publish ‘Origin of Species’ because it conflicted with the religious views of the time • Natural Selection was the process by which the form and behavior or organisms in a population
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