Lecture 19 1 Describe the relationships among population community and ecosystem ecology 2 Explain how energy flows through ecosystems and describe the carbon nitrogen and water cycles Justify why altering the carbon cycle may alter other aspects of ecosystems 3 4 Describe how ecological populations grow and change 5 Explain carrying capacity and factors that alter carrying capacity 6 Describe the relationship between tropic levels and energy in a community and contrast the ideas of a trophic cascade and a keystone species 7 Explain the goals of conversation biology and why it is an applied field of biology and lst the factors that are likely to influence extinction rates 8 Describe and apply approaches used to preserve biodiversity Organisms interact with each other and their environment Ecology The study of the organisms interactions with each other and their environment Includes the study of human interactions Can also look at energy flow and nutrient cycling Short term changes Typically what ecology looks at Populations are local groups of a single species Population dynamics Populations have characteristics which can change Have a range Have spacing within that range How clumped they are Can change in size over time Population density How many individuals are in a particular area Population density can be estimated by sampling Estimate count how many you ve caught Full census Count every organism Mark recapture Estimated population size N n1 X n2 n1 2 n1 is the first captured n2 is the number re captured n1 2 is the number tagged n sampling event Age structure can influence how fast a population grows Faster population growth when more organisms are in their reproductive years Populations can be spaced differently through their range Clumped Regular Random Individuals are grouping together Orcas stay in groups to increase their chance of survival Where there is even space between the individuals Nesting defending territories No real distribution pattern Occurs when there is little interaction Can be due to the environment itself Environmental conditions Can affect spacing Populations change in size in response to demography Look at life tables and survivorship curves Sex ratios Generation time Births Deaths Immigration Emigration Rate Of growth Fecundity The amount of organisms coming into the population The amount of organisms that are leaving the population The number of offspring produced in the population Change in population size can be estimated N1 N0 B D I E Life tables Allows to measure mortality rate and survivorship rate Demography Cohort A group of individuals born within the same time frame Life stages Survivorship curves graphs show the probability of survival Type 1 Physiological Humans have a type 1 curve Shows a very high overall survivorship through to adulthood Low fecundity production of children and high parental care Risk of death highest when old Type 2 Ecological Almost a straight line The risk of death is constant Birds have a type 2 curve Type 3 Maturational Low juvenile survivorship youngest tend to die Very little parental care and lots of offspring being produced Insects have a type 3 curve Risk of death highest when young Life history strategy varies among species and environmental conditions Intrinsic rate of increase r b d rate births deaths Rate greater than 0 population that is growing Rate lower than 0 population that is decreasing Survivorship Fecundity Number of offspring produced by female Number of offspring brood Age at first reproduction Number of broods female Populations without limits grow exponentially Exponential growth Rare in nature Most organisms reach a carrying capacity Biotic potential Births deaths Population size is limited by carrying capacity Carrying capacity Logistic growth Reaches some sort of limit Births deaths Population levels off when it reaches carrying capacity R strategist K strategist Very high rate of increase R exponential K logistic Slower rate of increase the hits plateau Density dependent Biotic factors Resources Predators Pathogens Density independent Abiotic factors Don t have to do with the of individuals living there Earthquakes storms Human population is growing exponentially Resource exploitation Ecological footprint Populations are not supposed to be able to grow exponentially Communities are groups of species that coexist and interact Species richness The amount of species present in a community Includes plants Primary productivity Plants are the primary producers And other organisms that do photosynthesis Most important in community Determine the number of species that can thrive in a community Energy can alter community composition Primary producers Convert things into usable energy products Gross primary productivity The rate at which all of the primary producers are working Net primary productivity Gross primary productivity the amount of energy lost Biomass Energy loss The actual amount of a producer that is available for consumption Substantial energy loss as you move up each level Primary producers primary consumers secondary consumers tertiary consumers Trophic levels represent how an organism obtains energy Food web vs chain Food chains don t account for all of the relationships Consumers Ignores the connections that can be seen among organisms Eating the primary consumers Secondary Primary Typically herbivores Consumers are heterotrophs The number of individuals decrease as you move up trophic levels There is a relationship between productivity and species richness Habitat differences Affects the relationships Temperature affects productivity A medium level of productivity produces the community with the highest species richness Interactions of a single consumer can cause a trophic cascade Trophic cascade Removing one organism can change an entire ecosystem A keystone species will disproportionately alter and entire community Keystone species An organism that can exert an influence that is disproportionate to its abundance Can affect species richness and trophic levels in a community If removed can cause community to crash An ecosystem is all biotic and abiotic factors interacting in an area Energy nutrients Included in ecosystem Energy flows and nutrients cycle through compartments Atmosphere Oceans Freshwater Land Energy flows through ecosystems Source sun Net primary productivity The amount of solar energy that is captured and passed on through the chain Solar energy primary