Evolution

EVOLUTION Origin of Life –> Evidence of evolution - homology –> Theory of Evolution - microevolution - mechanism of evolution –> reproduction genetics Theory explains facts – a framework to ask questions to explain phenomenon – leads to predictions – explains laws and facts - evolution explains biodiversity - It is the process that results in heritable changes in a population spread over many generations - inferences: - common ancestor - change over time - heritable change (not physical, environmental change) - change in the properties of populations of organisms that transcend the lifetime of a single individual - refers to populations and not to individuals - changes must be passed on to the next generation - heritable - any change in the frequency of alleles (subset of genes, particular genes for particular trait - within characteristic there are variations) within a gene pool from one generation to the next - development of change of characteristics of a line of organisms over time - change over time in the characteristics of population or of a species - Wallace: geography with biology, malay archipelago, found 700 species of beetles in Singapore

- Darwin: all organisms are modified descendents of previously existing forms of life - mechanism - darwin noticed 13 species of finches within the different islands of Galapagos –> a single ancestral group could give rise to several different varieties or species - Stanford's 10 lectures on evolution - Darwin's deductions from his observations: 1. populations have the potential to increase exponentially (becoming more and more rapid) 2. Populations are fairly constant in size 3. Natural resources are limited 4. There is variation within a species, and variation is inherited 1, 2, 3: deduction: only some organisms survive. There is a struggle for existence among individuals in a population. deduction 1, observation 4: deduction 2: individuals with favourable variations are more likely to survive and reproduce –> accumulation of variation over many generations is evolution. - gene pool is the total number of genes of organisms in a population - organisms with useful characteristics are more likely to survive and pass them on to the next generation - populations change in accordance with environmental factors. changes are driven by environmental pressures. - **natural selection**: mechanism to explain origin of species - **overpopulation of species**: organisms produce more offsprings than can survive - **struggle for survival**: for food, space, mate etc. within the species, with other species... - **differential survival and reproduction**: favours individual with advantageous (not best, just not the last) traits. will determine the composition of the gene pool: frequency of gene (advantageous) will increase in gene pool –> inherited by more offsprings in the next generation; disadvantageous genes may eventually be wiped out from gene pool. - evolutionary history shaped by natural selection. - small change – time –> large change - overpopulation: more species than can survive, only some survive. excess production results in struggle, competition for food, space and mates. - traits determined by DNA inherited from parents - natural selection as central force in evolution - assumptions made: - the traits seen must be found in the genes and hence be able to be passed on to the next generation - traits arose from random events like meiosis and mutation and not by intent (traits must already be in the genotype) - darwin didn't know about genes and DNA at his time - variation + differential reproduction + heredity = natural selection - natural selection: 3 categories: 1. stabilising selection - normal distribution curve: the majority is the average (in centre range) 2. directional selection - factors make one extreme of the phenotypic range more favoured 3. disruptive or diversifying selection - ends up with two - Larmarck: thought giraffes stretched their necks longer to reach higher leaves –> acquired characteristics can be passed down. acquired: genes not in gene pool. he had false thinking - current findings refute these reasons of selection. - larmarck's hypothesis - evolution mechanism: features needed for survival are developed in each individual –> characteristics developed/acquired by individuals are somehow passed on to their offspring, who can continue that development –> eventually, over many generations, enough differences have arose to give rise to species - differences between: environment changes thus creating a 'need' to change VS variations of inheritable features which already normall exist - development of new features "in order to survive" or "so that one can survive" VS environment "screens out" features contributing to survival and tends to eliminate others - newly acquired traits somehow get passed down to offspring VS
 * - genetic variation**: is heritable –> not base on "needs" or "intent". traits are different from siblings. those with more favourable phenotype survive.

__Adaptation and fitness__ - **adaptation**, any **heritable** trait that suits an organism to its function in its niche - may be structural, physiological or behavioural - physiology - the way in which a living organism or bodily part functions. physiological adaptations permit the organism to perform special functions (for instance, making venom, secreting slime); but also more general functions such as growth and development, temperature regulation, ionic balance and other aspects of homeostasis. - genetive adaptation has to be **functional** in the organism's natural habitat - it is not **acclimatisation:** an organism's ability to adapt during its lifetime to changing environmental conditions - **fitness** is a measure of how well suited an organism is to survive in its habitat and its ability to maximise numbers of offspring to reproductive age - survival + fecundity (reproductive success) + mating success –> fitness of the organism

- antibiotic resistance as evidence for micro evolution - tuberculosis: some strains resistant to drugs - multi-drug resistant tb