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Chapter 4

Chapter 4 Summary.docx

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University of Guelph
PSYC 2410
Elena Choleris

Chapter 4 Summary Evolution:  Change that occurs across generations  Evidence: fossil records, similarities yet differences (divergent [same origin in body, different function] and convergent evolution), artificial selection (human manipulation), peppered moth biston (before – white, after industrial revolution – black), Darwin’s finches (drought – those with bigger beaks survived because they could eat larger seeds)  Variability in structure, physiology and behaviour are associated with higher survival rates and reproduction of genes into next generation (natural selection leads to evolution) Leclerc: environment acts directly on genes through organic particles Erasmus Darwin: proposed sexual selection and competition Lamark: conscious will, use and disuse leads to change; characteristics are inheritable, preordained to perfection, environment has effects on organ development Darwin: species have large capacity to overproduce yet populations remain relatively stable therefore there must be competition for survival, conspecifics differ in their characteristics and these characteristics are carried over to their offspring, individuals that have the characteristics that are adaptive reproduce more and more successfully and over time those characteristics become more frequent in population Alfred Russell Wallace had similar ideas to Darwin – co-wrote paper year before Origin of Species Neodarwinism: natural selection + genetics, fitness (ability to contribute genes to next generation either directly or indirectly) Spandrels: evolutionary byproducts, used to have function in survival (belly buttons) Exaptations: things that have a different function than what they were originally evolved for (feathers – warmth  flight) Noise: 2 parts that have same function, both evolutionarily functional therefore both continue to exist in population Human Evolution:  Big brain, great variability, cerebrum and brain stem are common among most animals  Increased in size over evolution (mostly in cerebrum), more convolutions Evolution of Behaviour:  Dominance hierarchies (dominant males copulate more)  Mating bonds (dividing parental responsibilities)  Courtship displays (when one of 2 sexes is picker than the other, other sex competes for attention, can cause speciation)  Altruistic behaviour: broken wing display in killdeer birds, squirrel alarm call, alliances in male baboons, vampire bats and feeding (best if there is individual recognition, long lived individuals, stable communities and developed memory) Genetics:  Behaviour is part of phenotype but is mediated by genotype Dichromatic traits – gene has 2 versions (dominant and recessive)  DNA is packaged by histones – chromatin = DNA + histones  Meiosis  2 gametes (haploid)  1 zygote (diploid)  mitosis  male XY, female XX Chapter 4 Summary Variability in genes: crossing over (segments of DNA are “swapped” and uniquely spliced together, gene linkage tells us genes that are closer together are normally swapped together, allows us to map genome), mutations (Down Syndrome – extra chromosome 21) DNA :  Phosphate + deoxyribose + 4 bases (A—T, G—C)  Not 1 gene = 1 protein (undergo chemical modifications that affect how active they are, when they are active and what role they serve) Structural genes: code for proteins, DNA uncoiled  complementary mRNA strand made (single stranded, process of transcription)  in cytoplasm bind to ribosome and tRNA  3 bases called codon and 1 codon codes for an amino acid (translation)  sequence of amino acid  protein Operator Genes: control one or more structural genes, a.k.a. enhancers Non-Active DNA: does not participate in synthesis of protein – control structural expression Alternative Splicing: after transcription, splice out chunks of DNA that do not code for protein (introns) and put back together those that do (exons) and can do this in multiple ways MicroRNAs: bind to mRNAs and affect translation, mostly inhibitory effects (selective silencing), 60% of genes can be reg
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