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Chapter 5: Modern Evolutionary Theory (Mendelian Genetics (Mendel's…
Chapter 5: Modern Evolutionary Theory
Mendelian Genetics
Identified mechanism of heritability(how traits are passed to offspring)
Peas as test subjects
Mendel's Law of Segregation
1) Genes= unit of heredity, Alleles = alternative versions of genes
2) Two alleles per gene, homozygous = same two alleles, heterozygous = two different alleles
3) Dominant vs. Recessive alleles
4) One allele from each parent
Phenotype: Observable physical trait
Genotype: genetic composition of a trait
Chromosomes: contain most of cells DNA
DNA: genetic code of organisms. 4 bases A T G C
Mitosis: making copies of the cells
Meiosis: halves chromosome number so offspring have correct number of chromosomes
Discrete traits: phenotypical expression controlled by a single gene
Sources of Biological Variation
Genetic Recombination:Chromosomes segregate independently and randomly during meiosis. Crossing over.
Mutation: Change in DNA sequence, errors in translation/transcription.
Genetic Drift: Fluctuations in allele frequency by chance, usually in small populations.
Creates genetic divergence between populations
Gene Flow:Movement of genes between populations(through mating).
Cline
: Variation in gene frequency across a region
Hybridization: creation of viable offspring between two species
Epigenetics: interaction of genes during development that influences the phenotype
Modern Synthesis of Evolution
Evolution is gradual, though small genetic changes acted on by natural selection
Origin of species(macroevolution) depends on natural selection on individual phenotypes(microevolution)
Natural Selection behavioural traits
Human behaviour=phenotype, behaviour = heritable, e.g. childrens behaviour
Various perspectives to study cultural transmission, e.g. sociobiology: "cultural" gene = meme
All organisms are the product of interactions between biology, environment, society, culture, & history