Week 10 Notes
Popular in Fundamentals of Biology II: Ecology and E
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This 3 page Class Notes was uploaded by Chasia Notetaker on Sunday April 17, 2016. The Class Notes belongs to BIOL 12000 at Ithaca College taught by Nancy L Jacobson in Fall 2016. Since its upload, it has received 12 views. For similar materials see Fundamentals of Biology II: Ecology and E in Biology at Ithaca College.
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Date Created: 04/17/16
Week of April 4, 2015 Population Ecology Growth Population a group of animals of a single species that occupy the same general area rely on the same resources are influenced by the same environmental influences are likely to interact and breed with one another Population Growth Additions through births and immigration Losses through deaths and emigration Zero growth when births + immigration = deaths and emigration Exponential Growth Model G= how many individuals are added to the population in a certain amount of time (net gain) N= how many individuals are in the population at the beginning of the time period G increases by a constant that is related to N G= rN r=per capita growth rate (r= per capita birth rate per capita death rate) (r=bd) Logistic Growth Model is exponential when the population is very small slows as resources become less available, fewer and fewer individuals can be added zero growth when reaches K K= carrying capacity max population size that can live in a population “indefinitely” G= rN [(KN)/K] refers to the proportion of resources still available for growth when N is very small, there are lots of resources (KN)/ K ~ 1 and population increases exponentially when N = K, there are no extra resources (KN)/ K = 0 and population doesn’t increase Does population always show logistic growth as it reaches K? no, the population may overshoot K population gets so large it degrades the habitat then population crashes Which factors control population size? density dependent factors have greater effect as density increase limited essential resources = bottom up control ex. Food and breeding sites predators, parasites, and pathogens = top down control ex. Bubonic plague in Europe in 14th Century density independent factors have equal effect (same % die) regardless of density ex. Harsh weather (if no refuge), toxic pollution may be seasonal reduces the population in the winter than in spring and summer the population grows exponentially ex. Many insects in the Northeast demographic transition model: b and d change as a country becomes more economically developed d decreases first, which causes r to increase later b decreases based on Europe and United States, starting in the 1800’s in England death rates decreased due to more stable food supply ( mechanized agriculture, plant and animal breeding) decreases in infectious diseases food safety ( ex. pasteurization) sanitation (ex. realized cholera was spread through contamination of water by feces; addition of chlorine to the water) vaccinations (first was against smallpox) antibiotics (first was penicillin) birth rates decrease due to the usual measure of per capita birth rate is TFR TFR= total fertility rate = fertility rate average number of children born to each woman during her reproductive age 2 children per woman will replace her (and her husband) actually 2.1 ( on average because some daughters will die before reaching reproductive age) TFR=2.1 children per woman, leads to a population staying the same size world’s population’s TFR is 2.5 more women delay reproduction to early 30s greater access to contraceptives, including through government family planning programs better health care: infant mortality has been cut in half since 1990 from 8.9 million infant deaths in 1990 to 4.5 million in 2015 parents are more confident that children will survive to take care of them in their old age birth rates decrease Life History Patterns chances of survival and of reproduction often vary by age shown in a Life Table patterns of survivorship can also be depicted in survivorship curves follows a cohort as they age
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