BIO 101 1nd Edition Lecture 20 Outline of Last Lecture II Gene expression III Inactivation of chromosomes IV Translation V Cell to cell communication VI Mutations VII Cancer VIII Telomeres Outline of Current Lecture IX What is ecology X Density Dependent factors XI Poverty in India XII Variation Current Lecture What is Ecology Ecology is the study of interactions between organisms and their environments It can be studied at many levels including o Individuals Individual organisms o Populations Groups of individual organism that interbreed with each other o Communities Populations of different species that interact with each other within a locale o Ecosystems All living organisms as well as non living elements that interact in a particular area In your own neighborhood which list below defines a biological community The animals including humans as well as the plants living in your neighborhood Population ecology is the study of how populations interact with their environments Take home message Mot ecological processes cannot be observed or studied within an individual Rather when studying them it is necessary to consider the entire group of individuals that regularly exchange genes in a particular locale 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 Population ecology examines features that cannot be studied on an individual organism such as population size Exponential Growth Occurs when each individual produces more than single offspring necessary to replace itself According to realistic and moderate estimates of birth and birth rates a population of just 500 elk would grow to more than billion individuals within 80 years and eventually would cover the earth Big Idea Exponential growth is not really possible for long since a populations growth is limited by the environment page 323 Density dependent factors The limitations on a populations growth that are a consequence of population density This ceiling on growth is the carrying capacity of the environment page 322 Density dependent factors limit population size Food supply Habitat for living and breeding Parasite and disease risk Predation risk Realistically biotic and abiotic factors in the environment limit the growth of a population These limiting factors include o Temperature o Water o Energy nutrient availability Human Population How high can it go Very difficult to assess just how many resources each person needs Ecological footprints o Evaluating how much land how much food and water and how much fuel among other things are necessary Poverty in India Too many people habitat overuse unequal distribution of resources Result Environmental destruction and irreversible changes to ecosystems Take home message The world population is currently growing at a very high rate but limited resources will eventually limit it most likely at a population size between 7 and 11 billion How many people can earth support Why does the answer keep increasing o Development of agricultural technologies is one example of how carrying capacity can be increased o As we increase the carrying capacity of humans we are decreasing the carrying capacity of other organisms Focus questions How has the earth s changing environments climate impacted the human species o Genographic project and human migrations How has human population impacted the ecology of the earth Population size is also influenced by the way in which each type of organism lives called Life History The vital statistics o the species this includes the rate of population increase Includes age at first reproduction probabilities of survival and reproduction at each age litter size and frequency and longevity Variations in life histories Big Bang reproduction o Reaches sexual maturity at one year o Mates intensely over a three week period o Males die shortly after mating period Fast intensive reproductive investment o Reaches sexual maturity at one month o Produces litters of six to ten offspring every month Slow Gradual reproductive investment o Reaches sexual maturity at one year o Produces about one offspring per year Why all the variation Is one strategy better than others for the survival of a species There are many possible responses to the challenge of o When to reproduce o o How often to reproduce How much to reproduce Life history tradeoffs Reproduction and survival o Big bang reproducers such as salmon make a single exceptionally high investment in reproduction then die shortly after Survivorship curves Graphs of the proportion of individuals of a particular age that are alive in a population o Type 1 Giant tortoise high survivorship until old age then rapidly decreasing survivorship o Type 2 cedar waxwing survivorship decreases at a steady regular pace o Type 3 mackerel high morality early in life but those that survive the early years live long lives Age at time of reproduction A key factor determining longevity Early reproduction will also favor early aging Later reproduction will also favor later aging Environmental risks and aging High hazard factors o Individuals tend to reproduce earlier o Earlier aging o Shorter life spans Low hazard factor o Individuals tend to reproduce later o Later aging o Longer life spans In environmental characterized by low morality risk populations of slow aging individuals with long life spans evolve In environments characterized by high morality risk the opposite occurs Hazard factors High risk worlds o Death from external sources o Reproduce early Low risk worlds o Death from external sources low Take home message The rate of aging and pattern of morality in a species is determined by the hazard factor of that organisms environment In environments characterized by low morality risk populations of slowly aging individuals with long life spans evolve In environments characterize by high morality risk the opposite occurs