Lecture 02.pdf

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Department
Biological Sciences
Course
BIOB51H3
Professor
Maydianne Andrade
Semester
Fall

Description
BIOB51 Lecture 02 Before Darwin  3 big questions : o How did life rise o What accounts for the diversity of species o Why are organisms so well suited to their environments (how do we explain adaption)  ANSWER to these question = Special Creation o Which can be seen as the historical view that used to explain biodiversity and adaption before Darwin  Judeo-Christian-Muslim traditions,1800s - idea was that we can understand the natural world through this framework that all species are: o Created independently (separately from each other) o Do not change through time (way you saw them in 1800 were same as they must be in the past) o Created recently and at the same time (earth and life are young)  traditional view held this sort of idea for life  the mechanism is via supernatural force meaning something outside of natural laws that you could observe on a day to day  BUT – even before Darwin wrote Origin of species  3 observations began to suggest the frame work didn’t work: 1. Species change over time a. found fossils that species did change over time 2. Extinction a. there were things around in the past that were longer no presented now 3. Time-series of species appearance a. as they began to look at geological column (= strata of rocks that make the crest of earth), they found fossil that changed over time & the different species they found on earth appear at different points in the geological timeline 4. Environments had changed over time a. a point that is important but wasn’t recognize by everyone b. evidence of environmental change over time was found  geologist were showing areas that were currently mountain that were used to be under ocean , areas previously wet are dry and vice versa all indicating radical environmental change over time  Alfred Wallace - why the 4 point is important because it challenged the idea was that if all organisms were created at the one time but environment changed since then  thus, why are organism still adapted to their environments o can’t use special creation to explain adaption at present time by organism because environment had changed since time it was created) 5. Relatedness of species (similarity w/in diversity; tree of life) a. people were beginning to suspect that species were independent of each other  grouped similarity they were seeing was from some form of relatedness b/w organism b. had idea that maybe similarity was inherited from common ancestor (e.g. tree of life)  These observations were making people question the historical traditional as explanation for life and biodiversity  e.g. Classification of Beetle (similarity suggest organism are related) o classification came before Darwin  Linnaeus came up w/ Binomial nomenclature and began to categorize organism according to their similarity o (don’t memorize this) Eukaryotes  Metazoa  Arthropoda  insecta  Endopterygota  Coleoptera  Darwin and others insight was the these clusters of similarity – for e.g. eukaryotes have true nuclei  they are classes of similar traits that define organism  people were beginning to suspect these traits were inherited from common ancestors  the environment in which Darwin was coming up w/ his ideas was when special creation was still dominant view point , new ideas were developing in the scientific community based on the observations that suggest species change over time, species derive from common ancestor, and earth and life are old o these ideas were challenges to special creation  but these new ideas had nothing to say about adaption only about life and diversity  Early definition (before Darwin) of evolution was that you had the development of new types of living organism from pre-existing types (different from historical )  so evolution was proposed instead of special creation to better understand life and diversity of life o But evolution proposed until Darwin & Wallace could not explain adaption ( how well organism are fit to the changing environment)  Darwin’s key contribution to evolutionary biology was NOT the theory of evolution which proposed by others which some had ideas about adaption which mostly turn out to be wrong - e.g. Lamarck ) o Darwin proposed the MECHANISM of evolution that could also explain adaption  = theory of evolution by natural selection in On the Origin of Species by Means of Natural Selection,1859 Darwin is consider the parent of evolutionary theory because: 1. Provided evidence that evolution had occurred 2. Proposed natural selection a. mechanism of evolution which could explain adaption 3. Provided evidence that evolution would occur by natural selection a. wide variety of different fields  put it together as strong case Evolution as proposed by Charles Darwin:  all species descended from one or few original species  he called it Descent with modification (Darwin’s definition of evolution) o emphasising the relatedness  there is descent through some sort of family lineage and modification that organism can adapt over the process of generation to their environment  his idea was that there were small changes w/in the populations from generation to generation can accumulate over long periods of time (have large difference b/w groups of organism) and lead to the origin of new species  key mechanism – natural selection (not supernatural intervention) Evolution by Natural Selection  logic of Darwin’s theory of evolution by natural selection is based on 4 postulates  Darwin realized that evolution by natural selection was inevitable if these 4 postulates were true o postulates – assertion of something that is true  asserted there are 4 things true about this world ( can go out and test any one of them & demonstrate it true) 4 Postulates: ( didn’t know anything about genes) 1. Individuals w/in populations are variable a. variation exists in almost every measurable characteristic in every species 2. Some of these variation based on to offspring ( heritable) a. we now know how this heritability of traits work but at that time didn’t know genes  but could recognize that variation were passed down through generations 3. Many more offspring are produced than can survive and reproduce a. how do we know this? Can see it - by deduction & observation b. Deduction - female Aphids giving brith (live which is rare for insects)  dots in back are eyeballs that are going to be born - by age 7 female aphids w/out mating can produce 14 babies a day until they die around 20 days i. Have organism such as aphid , elephant , starfish which have reproductive potential of 524 biilion year , 19 bilion in 750 years, 10^79 in 16 years 0 if all offspring are born and survived we would surrounded w/ them  calculation – not all offspring survive c. Observation: biological factors 1. Competition & 2. Predation & parasitism i. result in the death of organism before they come reproductive
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