EVOLUTION AND GENETICS Chapter 5

Evolution Transformation of a species from generation to generation Timeline to Evolution Genesis and Creationism Biological diversity at Creation Ussher and Lightfoot dated to 4004 B.C. Carolus Linnaeus ( ) Father of taxonomy Grouped life forms based on: Vertebrate vs Invertebrate Presence of mammary glands Creationist Fossil Discoveries 18 th and 19 th Centuries Showed that other species had existed Rise of Catastrophism

Agents of Evolution Charles Lyell Geologist Uniformitarianism – belief that forces at work today explain past events Building block for evolutionary theory Earth is older than 300 million years Charles Darwin HMS Beagle 1859 On the Origin of Species Published theory of evolution Congruent with Alfred Russell Wallace

Evolutionary Theory Natural Selection – the selection of certain biological traits through reproductive success Key mechanism to evolution Opposite to inheritance of acquired traits Continues to work in human populations today

Genetics Gregor Mendel Father of modern genetics Pea plants Opposed “paint pot” theory of inheritance Population genetics – scientific study of the biological variation of breeding populations Traits Dominant – an allele that masks another allele in a heterozygote Recessive – an allele that is masked (not destroyed) by the dominant trait Chromosomes – paired lengths of DNA composed of multiple genes Alleles/genes, are located on the chromosomes Alleles – a variant of a particular gene Genes- the position on a chromosome that determines a trait

AlleleGene Refers to A specific variant of a gene. Segment of DNA that operates a specific trait. Examples Blue eyes, green eyes, type A blood, black skin, white skin Eye color, blood type, skin color

Genetics (cont’d) Heterozygous and Homozygous Dissimilar vs Similar alleles of a gene Aa, aA or AA, aa Genotype and Phenotype Genotype – the genetic makeup of an organism Phenotype – the visible biological traits (outward and inward) Mendel's peas Two available phenotype Three available genotype Independent Assortment – chromosomes are inherited independent of one another Recombination - production of offspring with combinations of traits that differ from those found in either parent Important to biological evolution Creates new “types”

Biochemical (Molecular) Genetics Mutation – changes in the DNA molecules of which chromosomes are built Mutations produce the variety on which natural selection depends More important to variety than recombination Mutative variants can sometimes lead to advantages, especially after environmental changes Mutations can sometimes lead to speciation, the creation of a new species Species – populations of animals whose members can interbreed to produce viable offspring Cell Division Mitosis – ordinary cell division of chromosomes Meiosis – cell division that results in sex-cell production Crossing Over Intertwining of homologous chromosomes, exchanging DNA Partially contradicts Mendel’s law of independent assortment

Population Genetics and Mechanisms of Genetic Evolution Study of stable and changing breeding populations Gene pool – all the alleles, genes, chromosomes, and genotypes available to a breeding population Genetic evolution – change in a gene frequency in a breeding population Any factors that alter gene frequency are mechanisms Natural selection, mutation, genetic drift, gene flow Genetic drift – genetic change by chance Occurs more rapidly in smaller populations Gene flow – exchange of genetic material through interbreeding Works in conjunction with natural selection Maintained gene flow prevents speciation

Natural Selection Three types Directional – long-term selection of the same traits The most adaptive traits will be selected Adaptive traits – those favored by natural selection Will continue unless the environment changes Reduces variety Sexual – selection for traits based purely on reproductive success Males or females may prefer one trait over another Stabilizing – two or more forces favor different traits Favors balanced polymorphism – alleles maintain a constant frequency in a population over time Maintains variety

Modern Synthesis Accepted view of evolution Combination of Darwinian theory of evolution and Mendel’s genetic discoveries Microevolution – genetic changes in a population that do not lead to speciation Macroevolution – large-scale significant genetic change, over a longer period, that does result in speciation Contemporary creationist opposition Only support is the fossil record Macro and micro are the same process, not distinct Punctuated equilibrium – periods of genetic stability followed by periods of evolutionary advancement Darwin thought evolution was ordered and gradual Extinction, evolution or introduction of other species Sudden environmental changes Extinction or adaptation Hominin record support