ENVIR ST 260 1st Edition Lecture 2 Outline of Last Lecture I Populations A Why Study Population B Definition of Population C Population Ecology and Growth II E Writing Assignment Outline of Current Lecture I Populations A What Controls Size and Growth B Impact of Competition and Density C What We Learn from Studying Populations II Evolution A Definition B Observation of Genetic Changes Current Lecture Populations What controls population size and growth Biotic Factors Things in environment that are living Competition Predation Parasites Mates Abiotic Factors Nonliving things Light Topography Nutrients Water Climate Competition and Population Density Competition only occurs when something is limited two types These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Same species can compete over resources Intraspecific competition Many species can compete over resources Interspecific competition Example Different plants can compete Trees shade grasses There s competition for water There s competition for space because once a plant is set no one else can take up their space Which type of competition has the greatest impact on a population If a single species has a limited resource Example of Single Species The Koala bear Diet is primarily eucalyptus leaves single resource everyone is dependent on Same need for all individuals When you limit this resource you re then lowering the number of individuals that you can support and because they all have the same exact requirements it s more likely to have a negative impact on that population Example of Multiple Species The Lion Vultures and Hyenas Different species may have overlap but they do not have the SAME requirements There isn t the same nutritional needs or behaviors By not having the same requirements different species can shift where they re getting resources from Population Density is important How tightly packed together a population is Factors are density dependent or density independent Example Disease and Drought Disease It moves through a tightly packed population a lot faster than one that s more spread out It is density dependent Drought It impacts a dense population more initially But if you have an extensive drought eventually it s going to catch up the population regardless of how packed the individuals are It s density independent Large scale disturbances are typically density independent What can we learn from studying populations Changes in climate Example A lot of bird s and mammal s range is expanding due to climate change Changes in resources When you see populations that are either increasing or decreasing it might be because food sources change or there s an invasive species Changes in traits over time evolution Evolution works on a population level Individuals can change over time they might mutate but changes in one single individual don t mean much When an entire population is changing something more interesting is going on Evolution 3 Part Definition Change in genetic makeup Genetic makeup is key component Populations change in a lot of ways but when the focus is genetics we re getting into evolution Of a population Individuals don t tell us much Over time This is important This is generational time Example Ecoli has a generation time of just hours However animals like elephants and whales have a long gestational and generational time The time component isn t tied into what we think of as time It s a species dependent time scale Observation of Genetic Changes We can observe the proportion of a population expressing a given trait Example Flowers Population 50 50 split with purple flowers and orange flowers Traits are linked to underlying genes One locus two allele trait controlling flower color Mendelian genetics AA homozygous dominant Aa heterozygous aa homozygous recessive In a simplified system any flower with the dominant gene is going to express that trait In this example the dominant color is purple and the recessive is orange What if one trait has an advantage If there s a pollinator partial to one color the population can change over time For example if bees like purple flowers the purple flowers will be more abundant Relative fitness values Values of 0 1 AA homozygous dominant 1 Aa heterozygous 1 aa homozygous recessive 9 because the bees aren t as attracted to it If we know the frequency of A We can calculate the frequency of a since there are only TWO options two alleles control this trait p A q a p q 1 9 q 1 q 1 We can also calculate the frequency of the genotypes p2 2pq q2 1 Hardy Weinberg Equation P squared is frequency of individuals who are AA 2PQ is frequency of individuals who are heterozygous or Aa Q squared is frequency of individuals who are aa With the information as A 9 and a 1 calculate the ffrequency of AA Aa and aa individuals in this population