History and meaning of the word Ecology A. Definition 1. Oikos, ology - the study of the house - the place we live B. Etymology study of the origin and development of a word 1. Earliest - Haeckel (1869) - comprehensive science of relationship of organism and environment 2. Elton (1927) - scientific natural history 3. Andrewartha (1961) - Scientific study of the distribution and abundance of organisms 4. rebs (1985) - scientific study of the interactions that determine the distribution and abundance of organisms C. Note that all talk about scientific Why??? Separation of induction (natural history) and deduction (scientific method) Definitions (levels of ecological organization) A. Individual (can be difficult to define! Generally, a biological organism that ) 1. Lives, reproduces, dies 2. Has a unique genotype 3. Is the unit of selection 4. Is autonomous of other organisms B. (a collection of individuals in an area, of the same species, that ) 1. Interact with one another 2. Interbreed C. Species (characterized by ) 1. Individuals, naturally capable of interbreeding and producing fertile offspring D. Community 1. A group of populations (species) in a given place - usually implies that populations (species) interact E. Ecosystem 1. A biotic community and its abiotic (physical) environment 1
Basic Biology - losses may matter Basic Biology 1 8 6 4 2 2 4 6 8 1 Basic Biology- Unlimited Growth = Malthusian Growth or exponential growth Logic: at time t = N t at time t + 1= N t +birthrate (b) + immigration (i) + emigration (e)+ death rate (d) Where t= time t and t+1= sometime after that 2
Exponential Growth Basic Biology - losses may matter Assumptions: 1) Emigration = immigration, then N t+1 = N t +births (b) - deaths (d) where b and d are instantaneous estimates 2) Generations overlap 3) Resources are unlimited Now let the instantaneous per capita rate of growth (r) equal the birth death rate: r = b-d Basic Biology - losses may matter Exponential Growth - calculation N t = N e rt N = population at time r= per capita rate of growth (b d) t= time e= base of the natural log (~2.72) 1 8 6 Births > Deaths r > Essentially same formula as compounded interest 4 2 2 4 6 8 1 3
Basic Biology - losses may matter Exponential Growth - calculation N t = N e rt Births < Deaths r < N = population at time r= per capita rate of growth (b d) t= time e= base of the natural log (~2.72) 1 8 6 4 2 2 4 6 8 1 Basic Biology - losses may matter Exponential Growth an Understanding of Rates Let r =.2.5.1 Rate of growth = of population Using calculus we can derive a function for the instantaneous rate of growth of populations. The rate of change of the population is equal to growth rate x the population dn / dt = rn N t 1 8 6 4 2 High Low population size (N), population growth rate is high low because rn = large small value t N 2 4 6 8 1 4
Basic Biology - losses may matter Exponential Growth - why is growth unlimited? The assumption is that the per capita growth rate (r) is unrelated to population size (N). This means: 1) Birth rates are unaffected by population size, and Per capita growth rate (r) Does this make sense? remember r = b - d 2) Death rates are unaffected by population size Death rate (d) Birth rate (b) (N) (N) Basic Biology - losses may matter Assumptions: Limited Growth 1) Resources become limited as populations increase 2) Thus, per capita rate of growth must decrease with increasing population Resources Per capita growth rate (r) (N) (N) 5
Basic Biology - losses may matter Limited Growth caused by changes to birth and death rates that are density dependent Per capita growth rate (r) (N) Birth rate Death rate Rate (N) Basic Biology - losses may matter Limited Growth density dependence Exponential rate of population growth dn / dt = rn Logistic (limited) rate of population growth 1 8 6 4 dn / dt = rn (-N) = carrying capacity 2 2 4 6 8 1 6
ey consequence of density dependence: regulation: when population fluctuations are bounded so as not to increase indefinitely or decrease to extinction 1 8 6 4?? 2 2 4 6 8 1 Basic Biology - losses may matter Logistic (limited) growth implications for conservation I 1 8 6 4 2 2 4 6 8 1 Excess Adults Growth Rate / 2 Maximum Excess Adult 7
Basic Biology - losses may matter Logistic (limited) growth implications for conservation II Excess Juveniles - Compensation 1 8 6 4 2 Adult Excess 2 4 6 8 1 Juveniles Basic Biology - losses may matter Excess or Resource should the buffers be given away? Growth Rate / 2 Maximum Excess Adult Adult Juveniles Excess 8
Basic Biology - losses may matter Excess or Resource should the buffers be given away? 1) Provides buffer for cumulative effects 2) Provides buffer for natural and anthropogenic impacts Growth Rate / 2 Maximum Buffer Adult Adult Juveniles Buffer Basic questions are: 1) Do density-dependent processes produce excess individuals (that are essentially wasted) or population buffers that provide a safety mechanism against I) Natural variability II) Natural disturbances III) Additional anthropogenic impacts 2) Are population (demographic) buffers the property of the general public or industry? 3) Example: fish losses due to fishing (adults) and power plant entrainment (larvae) 9
Structure: Contrary to assumptions of Logistic Growth, not all individuals in a population are the same! Structure: relative abundance of individual traits among individuals in a population: i) size ii) age iii) stage (e.g., larvae, juveniles, adults) iv) sex v) genetic (distribution of genotypes throughout population) vi) spatial (distribution and interaction of individuals within and among populations) All of these influence per-capita rate of mortality (D) and reproduction (B) Size Matters: Bigger Fish Produce Far More Larvae Approx. 7-fold increase Approx. 11-fold increase 1
Number of fish Fished population 1 8 6 4 2 5 1 15 2 Non-fished population 1 8 6 4 2 5 1 15 2 Number of Larvae (millions) 7 6 5 4 3 2 1 5 1 15 2 7 6 5 4 3 2 1 5 1 15 2 Number of Larvae (millions) 7 6 5 4 3 2 1 5 1 15 2 Size Class Age matters: older females produce higher quality larvae with a higher likelihood to survive black rockfish (Sebastes melanops). Larval growth in length (mm/day) (d) to 5% larval mortality Berkeley et al. 24. Fisheries 29: 23-32. Berkeley et al. 24. Ecology 85:1258-1264. Maternal age (yr) Moreover: Different aged fish spawn at different times Bobko, S. J. and S. A. Berkeley. 24. Fishery Bulletin 12:418-429. 11
ey consequence of density dependence: regulation: when population fluctuations are bounded so as not to increase indefinitely or decrease to extinction 1 8 6 4?? 2 2 4 6 8 1 Bipartite life cycle of benthic marine organisms with pelagic larvae Larvae survive, grow, develop, disperse reproduce Pelagic Environment Benthic Environment settlement Adult Juvenile survive, grow, mature 12
Bipartite life cycle of benthic marine fishes with pelagic larvae Closed s Open s Production Supply Production Supply Little or no exchange among populations Significant exchange among populations Production Supply Supply Production 13
Spatial structure of populations implications for gene flow, genetic diversity and population persistence Closed populations: self-replenishing Limited dispersal: stepping-stone Single source: mainland - island Multiple sources: larval pool LARVAL POOL Spatial structure creates metapopulations Collection of isolated selfreplenishing sub-populations Collection of highly connected sub-populations Mostly self replenishing Separate dynamics No rescue effect from other sub populations Persistence based only on local sub population size and processes, densitydependence, independent of other sub populations Little self replenishment Sub populations with very similar dynamics Highly influenced by rescue effect from other sub populations Persistence based largely by system wide dynamics and processes, especially the number of connected sub populations 14
Spatial structure creates metapopulations Metapopulation: collection of partially-connected sub-populations Some self replenishment, some external replenishment Variation in sub population dynamics (asynchronous) Influenced by rescue effect from other populations Persistence based on both local and system wide dynamics and processes, especially the size and number of sub populations, and density dependence Life History Traits (individual, heritable, species-wide) longevity, fecundity reproductive modes life cycle Attributes distribution structure (size, age, genetic, spatial) dynamics Community Attributes structure (composition, abundance) diversity biogeography dynamics 15
16