2. Population Dynamics & Carrying Capacity IV.

4. Colonized by Polynesians 2,500 years ago Used palm trees for: Shelter Tools Fishing Boats Fuel Food Clothing Population grew (about 10,000)

5. Unsustainable use of trees led to: Reduced fishing (no boats) No fuel wood Runoff & erosion = crop decline Famine …cannibalism? Easter Day, 1722: Dutch explorers find a mostly barren island with only 2,000 inhabitants

6. Characteristics of a population include: 2. Geographic Distribution  The area inhabited by a population Ex: population of 75 deer in 1000 acres 3. Population Density  The number of individuals per unit area Ex:75 deer in 1,000 acres 75 deer 1000 acres =.075 deer/acre A. Demographics (the study of population dynamics) 1. Size

7. 4. Population Growth = a. When does Zero Population Growth (ZPG) occur? (Births + Immigration) = (Death + Emigration) (Births + Immigration) – (Death + Emigration) Gain Loss * All population dynamics respond to changes in the environment

8. B. Types of Population Growth 1. Exponential Growth  Occurs when a population reproduces at a constant rate Starts slowly, then size increases rapidly Must h ave ideal conditions: unlimited resources (space, food…) protected from predators free from diseases EX: Bacteria doubling time – 1  2  4  8  16  32  64 etc

9. 2. Logistical Growth  Occurs after a period of exponential growth when the population reaches natural limits

10. C. Carrying Capacity: The # of individuals (of a single species) that can be sustained by an ecosystem Population Growth Environmental Resistance

11. Population Growth Environmental Resistance C. Carrying Capacity: The # of individuals (of a single species) that can be sustained by an ecosystem limited resources competition predators Carrying Capacity disease Dynamic Equilibrium } * Determined by limiting factors:

13. D. Limiting Factors: Physical or chemical factors that regulate a population more than any other 1. Density-Independent Limiting Factors Can limit a population regardless of its density Floods Droughts a. b. c. d. e. f. Hurricanes Fires Unseasonable Weather Human Interference (habitat destruction, pesticides, etc.)

14. a. Competition for Resources  Between individuals or species that share the same Niche (role in the ecosystem) Ex: Owls and snakes compete for mice: Interspecies competition Ex: Finches compete for seeds: Intraspecies competition 2. Density-Dependent Population Limiting Factors Have a stronger affect as population’s density increases

15. b. Parasitism and Disease  May spread easily when the population is dense

17. Parasitism (+/-) Barnacles on Whales

18. c. Predation  PREDATOR / PREY RELATIONSHIPS: Cyclic rise and fall of both populations Predators are more successful when their prey population is dense.

23. http://animal.discovery.com/videos/natures-perfect-predators-mountain- lion.html

24. 3. Primary Productivity & Nutrient Limitation: a) Gross Primary Productivity (GPP) In other words… the rate of food production. c) Plants need various nutrients in order to produce biomass The rate at which producers carry out photosynthesis to convert solar energy into chemical energy stored in biomass b) Net Primary Productivity (NPP) The amount of energy stored in producer biomass that is available to consumers (after producer metabolism) Approximately 10% of GPP Limits the size of consumer populations

26. d) Limiting Nutrient:a nutrient that slows down primary productivity because it cycles slowly or it is scarce. * Limits the entire ecosystem * Human solution =fertilizers potential problem:Algal bloom leading to Eutrophication & Hypoxia * Major LNs: Nitrogen & Phosphorus

35. The DEC re-certified shellfish harvesting in parts of Hempstead Harbor It had been closed to shell fishing since the 1970s!