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Anthro 1026F/G Lecture 2: Evolution Notes

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Anthropology 1026F/G
Alexis Dolphin

Anthropology Lecture 2: Evolution Western Worldviews on Nature: - Paradigm: a conceptual framework • how theories are developed Middle Ages in Europe: - Antiquity of Earth – earth was not thought to be very old - Fixity of Species – species did not change into anything else - Great Chain of Being – hierarchy of species (some low, some higher, noble and close to heaven) - James Ussher – famous for attempting to calculate the age of the earth by going through the Old Testament and looking at sons and going back through generations (eg. roughly 25 years per generation and going back) • 4004 BC - One creation event – when all plants and animals were created by God – have not changed since that time Enlightenment: - 17 to 19 century - Social, political, economic, scientific revolutions - Thoughts: where have we been, where are we going, where are we now - Colonial expansions – seeing new people, animals, plants, environmental contexts  seeing diversity - Note: not just western societies that thought of these ideas  other people that discovered natural selection (before Darwin)  but it is about development in Western society) - *non-western ideas about evolution (paper) Carolus Linnaeus (1707 – 1778): - Binomial nomenclature – genus and species name • Genus may include multiple species – physically have something in common, but the different species would not reproduce with each other • Homo (genus) sapiens (species) – were the last species surviving of the genus Homo - Dsteloped hierarchical order: every species has a place - 1 taxonomy: a system for classifying plants and animals • Classify all species from local species to species being found on travels - Not looking to develop evolutionary theory; however, got people thinking about connections between organisms  related to each other? Why are some similar to each other? Geroges Cuvier (1769 – 1832) - In the mindset of the time - Established the fact of extinction – found fossils in the ground and wondered why these animals were not found alive anymore • If species can go extinct, might some other species arise? - Catastrophism: changes in the landscape due to periodic catastrophies • Applied to organisms • Multiple creation events  there are some organisms alive now that we don’t see fossils for – so: explanation later on in his career = multiple creation events Jean-Baptiste Lamarck (1774 – 1829) - Linked environmental change to biological change - Inheritance of Acquired Characteristics – now known to be false - New environment = new activities / uses = physical changes - Traits acquire during the lifetime depending on how the body is used – these acquired characteristics can then be passed on to offspring • Eg. giraffes - Did not explain mechanism behind this – just vital forces in animal that were stimulated to produce changes in the body • Could not logically explain what the mechanism was  thus, open to critique Charles Lyell (1797 – 1875) - Uniformitarianism: geological processes observed in the present are the same as those that occurred in the past - Thus: great antiquity of the earth  takes a long time for these processes to occur • So, breaking down of common ideas Thomas Malthus (1766 – 1834) - Populations grow exponentially while resources do not (grow faster than resources can support them) • Influential for Darwin and Wallace • More animals are born than can survive long-term  notion of competition for survival Charles Darwin (1809 – 1882) - Grandfather = famous naturalist who developed some ideas about change and organisms and what might have caused it - From wealthy family and exposed to many ideas early in life - Went on Beagle for 5 years (approx.) • Not looking for a solution to a problem • Went on as a naturalist and aligned with fixity of species and great chain of being, etc. • However: came to perspective that there is a lot of diversity, came into contact with some fossils  Noticed some organisms are similar to one another  why? - Wallace came up with idea about natural selection at the same time - 7 major postulates / ideas of natural selection: 1) More offspring are produced than can survive  competition 2) Individuals within a species vary biologically 3) Individuals with the most beneficial variations (traits) are more likely to survive and reproduce (*passing on to next generation = key) 4) The environment determines whether a trait is beneficial (sometimes smaller is better, sometimes bigger is better, etc. note also: environment is susceptible to change, so a perfectly adapted organism might not be perfectly adapted within a period of time) 5) Individuals with beneficial traits have greater reproductive success 6) Over geological time, beneficial traits accumulate in a population, and a new species may appear 7) Selective pressures may lead to selection Mechanisms of Evolutionary Change by Natural Selection - A trait must be inherited in order to have importance in natural selection • Importance: what is being passed on to next generation – will this lead to development of new species - Natural selection cannot occur without variation in inherited characteristics • Must already have variation in population  might not be helpful to individuals, but as long as a few member of species that have a trait that will help them survive if some catastrophe happens, then the population will not be eliminated - Fitness is a relative measure that will change as the environment changes • Might not work the same if the environment changes - No mechanism for natural selection  could only get so far How Does Inheritance Work? - Pre 1800s  • blending (identical to father, but as it grows in mother’s womb it blends mother’s traits with father) • homunculus (baby curled up in sperm = basic template of the person – once it comes into contact with female body it can fully develop) - Early 1900s  • Gregor Mendel’s particulate inheritance  pea plants – knew he had pure bread tall and short pea plants  what happens when you put these together?  Done in systematic way – had never been done before - 1953  • Watson, Crick, Franklin discover structure of DNA Bodies and Cells - Bodies are made up of cells (1000 billion) - Cells are made of proteins - Cells have a nucleus (containing genetic code – DNA) - DNA provides instructions for the development and function of organisms DNA (deoxyribonucleic acid): - Strands of DNA = chromosomes - Humans have 46 chromosomes (23 from male and 23 from female)  *exam question • chimpanzees have 48 chromosomes (look this up) - Double helix molecule - Matching base pairs from the “rungs” • One ½ of rung = one nucleotide • 4 nucleotides:  Adenine binds with Thymine  Cytosine binds with Guanine • A specific sequence of bases codes for a gene Function of DNA: 1) Protein synthesis: (no detailed questions – maybe location) - Codon: sequence of 3 bases - Each codes for an amino acid - Amino acids strung together = protein - Occurs in the nucleus (where DNA is located) • DNA splits to expose a particular sequence of bases (gene) • Active strand attracts free-floating bases to form mRNA (A-U, G-C) • mRNA will leave nucleus and travels to ribosome • Each mRNA codon attracts a free-floating tRNA anticodon • Amino acids are strung together to make a protein • Errors = can lead to severe results, sometimes it doesn’t hurt individual at all 2) Replication - DNA strand ‘unzips’ - Bases become exposed (old bases) - Complementary free-floating bases attach to the ‘old’ bases (A-T, G-C) - Result is 2 DNA molecules with the same code  2 identical daughter strands - When cell divides, a copy goes to each daughter cell Replication of Somatic Cells (Mitosis) - Replication of body cells (somatic cells) 1) Starts with
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