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Lecture 5

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York University
Environmental Studies
ENVS 1500
Gail Fraser

Lecture Five ENVS 1500 10/7/2013 6:25:00 AM Video Sheet: 1) what did the narrator say wrong at the start?  Finches held the secrete of the origin of species of diversity, not for the origin of life. It is a model that helps us understand the spices diversity  He should of said it was a hypothesis not theory 2) what did the grants do when they went ashore?  Rinsed everything with seawater to prevent non-native organisms from establishing themselves on the island 3) primary cause of death or finches?  Lack of food driven from weather. Weather is the main driver 4) 2 species of Finches  Medium ground finch and cactus finch. Focused on medium ground finch, and could identify every piece of food they eat 5) Major biological process they observed  Evolution by natural selection. They believed these processes were much slower. 6) 3 primary question trying to answer?  Trying to understanding species co-op., why populations are variable, how species are formed  What they found was natural selection was operating under stressful conditions. Galapagos Islands are isolated from other land masses. Darwin never kept track of which finch’s came from which islands. Finches diversified form one pair that arrives form South America. Adaptive radiation is the term used to describe the diversification into 13 types. A. Introduction:  Evolution by natural selection: all species have arose form a common ancestor from 3.5 billion years ago. Not a model for how life began – model for why we have so many species  Science needed a model to account for diversity + for their inter- relatedness.  Methodological materialism: must be observable and detectable. Science is inherently limited by ability to make reliable observation. Dependence on evidence is not a problem of science it is the essence of science.  1) special creation – cannot be tested (based on faith not observation) and therefore outside the realm of science. (not for science to say, needs to be observable and measurable)  2) spontaneous generation – an early hypothesis used to explain how species arose. (tested and rejected).  A. Lamarck: Inheritance of acquired characteristics of individuals – hypothesis subject to many tests and failed. (this is largely abandoned by most ppl). B. Darwin & Wallace: evolution by natural section – Model repeatedly tested and refined – supported by the scientific community  Populations were descendants form common ancestors whose descendants changed – through differential survivals and reproduction of individuals over time hence evolution of natural section. 1) Variation – must have variability to have nat. selection  variation exists, some variation has a genetic basis & is therefore inheritable, all genetic variation arises by change (mutations and meiosis) o Ex. Turtles: eggs in moist soil result in longer wider shells compared to eggs in drier soil. DNA – basis of information that is passed. Different forms of genes (alleles)  Heterozygous (differ
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