1. CHAPTER 52 - POPULATION ECOLOGY Themes: Heritable Information, Interaction with the Environment, Regulation, Evolution

2. Objectives: Two important characteristics of a population are density and the spacing of individuals Demography is the study of factors that affect the growth and decline of populations Life histories are diverse, but show patterns in their variability Limited resources mandate trade-offs between survival and reproduction Exponential model of population - idealized population in an unlimited environment Logistic model of population – incorporates the idea of carrying capacity Negative feedback Population boom and bust cycles What is the carrying capacity for humans?

3. Root Words Co – Demo – - graphy Itero – Semel – - parity

4. Population Dispersion: (I) Population Dispersion: 1. Most common is clumped (ex. Humans). Why? Because resources for us are usually in certain areas. 2. Know Other patterns – What organism would fit these patterns? Note: Make sure you know the definition of Population. Life History: (II) Life History: 1. R-selected populations (are opportunistic species) – usually fish and marine invertebrates. a. Usually small species that do not care for their young. b. Large # of offspring in one reproductive episode/lifetime. c. Survivorship is low. Populations fluctuate dramatically. d. Curve # 3 Fig. 52.3. (Next slide).

5. Fig. 52.3 Survivorship Curves

6. (III) Population Density - # of organisms per area. Formula : Organisms/area = 50 squirrels per 1 sq.mile. (IV) Density – Independent Factor- Any factor influencing population that acts to reduce population by the same %, regardless of the size of the population. Examples: earthquakes, tornadoes (V) Density-Dependent Factor – Any factor influencing population regulation that has a greater impact as population density increases. Examples – accumulation of toxic wastes; competition for nutrients; predation. (VI) K = Carrying capacity : maximum stable population size that the environment can support over a long period of time. Many times this is determined by energy limitations. K selected species – equilibrium species.

7. 1. Repeated production of smaller # of offspring – better endowed for survival. 2. Slow to mature, parental care. Usually large terrestrial vertebrates (like humans). Offspring have a good chance of survival. Often determined by the energy limitations of the organism 3. This is not the way most populations occur. 4. Fits the logistic equation. 5. Fits curve I in Fig. 52.3. Cohorts Cohorts – Group of individuals of the same age. 6. Differ among different species but not within a given species.

8. Mark-Recapture Method – 1 Question : Process of Science 1. Used to estimate fish and wildlife populations – populations that are very mobile. 2. Traps placed in area of study. Trapped animals are tagged then immediately released. 3. After a period of time traps are set again. (enough time to allow marked animals to randomly mix with the rest of the pop.). Formula (population sized N) = # marked in the first catch x total # in second catch # of recaptures in second catch

9. Big-bang Reproduction Big-bang Reproduction – A life history in which adults have but a single reproductive opportunity to produce large numbers of offspring. Also called semelparity ( Latin, semel – once & parito – to beget) Example: Typical of the pacific salmon. Certain things must occur: 1. Many gametes are produced by the parents at reproductive maturity. 2. Could be that reproduction is triggered by an “unpredictable” event. 3. A life span that could requires a number of years of maturing before reproduction.

10. Life Tables – deal with mortality rates, fate of cohorts newborns & organisms throughout their lifetime. Life Tables do not show Carrying capacity!!

11. Good Table to show (r) vs (K) selected populations.

12. Allele effect– Individuals may have a more difficult time surviving or reproducing if the population size is too small. 1.Example – an individual plant may have a difficult time surviving a strong wind but if there were more individuals the chance of this plant surviving would be increased. 2. Example -Predator might be more likely to be spotted if a large number of prey are together than it would be by a single prey animal. 4. Thus the allele effect is a density dependent factor Demography – study of vital statistics that affect population size.

13. Fig. 52.22 – Age Structure of Three Nations. 1. Which country will have the best chance of decreasing in the future? Why? 2. Which country will be the most stable over a long period of time? Why? 3. Which country will have the worst future unemployment? Why? 4.Which country will probably experience ZPG? (Zero Pop. Growth) Why? ZPG ZPG is when # of deaths = # of births in a given time.

14. Figure from the Test: (5 questions) HINTS: What is a Barnacle? Pg. 624. How would any tree fit into this survivorship curve? What is meant by molting? Pg. 615. What curve would be impossible?