week 4: how does nature play a role in bhv?

evolution of bhv

  • evolution depends on survival

    • most organisms born die before reproducing

  • every organism’s claims of their ancestors are:

    • none died in infancy

    • had good genes

    • survived until sexual maturity

    • found a mate

natural selection = traits that turn out to provide gppd solutions to/protections from recurrent pressures become increasingly prevalent across a species populations

survival of the fittest = traits spread across local phenptypes as a function pf their contribution towards a hpst fitness - better competing for rescources/mates eg peppered moths

  • all living species are nmodified descendants of their ancestors

  • characteristic traits (phenotypes) are inherited by succeeding members of a population

  • combining genes via mating patterns leads to change across subsequent generations

genes vs success - chicken and egg

  • do good genes lead to success or vice versa

  • genes pass unchanged except for random modifications/errors

  • good genes increase likelihood of successful ancestry

three core principles of darwin observable in all sexually reproductive populations

  • trait variance - individual members of a species vary in phenotypes

  • differential fitness - different phenotypes will predict differential rates of survival/reproduction in different environments

  • biological heritability - significant relationship between parents and offspring in contributions t future generations

intersexual selection = signalling of phenotypic ornaments which communicate mate quality to influence potemtial for individuals to be selected - between sexes

intrasexual selection = traits allowing members within a sex to succeed in mating eg antler size

  • asexual reproduction = rapid/requires less energy/continuous without mate

    • however minimises intergenerational variation - mutations reducing fitness are also passed on

  • sexual reproduction reduces population growth in comparison/some offspring still inherit bad genotypes

    • however guarantees most offspring still get healthy and useful genes

    • modification adaptive in uncertain environments

spandrel = non adaptive trait linked to something else adaptive - byproducts preserved because they link with something adaptive

exaptation = shifts in the functions of a trait across evolutionary development

  • trait can evolve because it served one particular function but can come to serve qnother eg feathers

functionality

  • adaptations can lose value - high calorie food can now cause more health issues due to change in lifestyle

  • adaptations can foster others - eg reading and writing are very advantageous but are too recent to be independently evolved, likely related to other established capacities

mendelian genetics

  • phenotype = physical expression of organism’s genetic makeup

  • genotype = set of genes organism carries

mendel and his pea plants

  • law of dominance = when parents are pure for contrasting traits only one factor appears in the next generation

    • some alleles dominate others

    • punnett squares

  • law of segregation = crossing offspring of two previous crosses (heterozygous) results in a 75/25 split

    • factors for a trait separate before conception otherwise recessive factors cannot be expressed

    • when parents have the same phenptype for a trait but offspring look different, parents must be heterozygous

  • law of independent assortment = factors for different traits are distributed to gametes and offspring independently of each other

  • 9:3:3:1 see slides

units of heredity - i’m not writing this down i learnt it at 9am two years ago

genetic engineering = strategic modification of an organism’s genes via artificial means

  • selective breeding = selectively picking parents showing specific characteristics ti breed

    • select best offspring to breed again

  • cloning

  • transgenic technology = manipulating genotypes

    • creation of chimeric species

    • knock in - genes added and expressed in subsequent generations

    • knock out - inactive genes so they fail to express in offspring

twin/adoption studies - see slides i’m not writing all this down

calculating variance

  • heritability/additive genetic effects

    • genetic factors

  • common shared environment

    • environmental influences shared by twins contributing to similarities between them

  • non shared environment

    • environmental factors not shared by twins making twins differ from each other