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Fall 2010 IB Workshop Series sponsored by IB academic advisors

Fall 2010 IB Workshop Series sponsored by IB academic advisors. Winning Resumes for IB Students Wednesday, Sept. 22 4:00-5:00pm 161 Noyes Lab

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Fall 2010 IB Workshop Series sponsored by IB academic advisors

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  1. Fall 2010 IB Workshop Seriessponsored by IB academic advisors Winning Resumes for IB Students Wednesday, Sept. 22 4:00-5:00pm 161 Noyes Lab Career Center staff will discuss the basics of writing a resume including format and objectives. Cover letters and special situations are also addressed.

  2. ASSIGNMENT FOR THURSDAY 1) Complete Problem Set 3: 223-226 in lab manual 2) Go to: Course website for Sept. 24 Read article BEFORE class ‘Human Population Explosion’ 3) No LO or PPT for Thursday; only ICA.

  3. This lecture Ch 10 + 12:Population Dynamics and Structure Read LO Major Concepts

  4. Objectives • Temporal dynamics: fluctuations through time • Density-dependent vs. independent regulation • Types and causes of fluctuations • Models with time delays • Population abundance • How to estimate? • Age and sex structure • Spatial structures • Distribution (range) • Density • Dispersion

  5. What determines the abundance and distribution of populations?Read LO I + II

  6. What controls population size? density-dependent Chance?? K change in environment N density-independent time time time

  7. Logistic equation assumes: • Instantaneous (d-d) feedback of K onto N • If time lags in response --> fluctuation of N around K • Longer lags---> more fluctuation; may crash. N K time

  8. How well do populations fit the logistic growth model?

  9. Density-dependent factors drive populations toward equilibrium(stable population size), • BUT • they also fluctuate around equilibrium due to: 1) changes in environmental conditions 2) chance 3) intrinsic dynamics of population responses

  10. Fluctuation is the rule for natural populations. • Less fluctuation for large animals with • long life span because of: • greater homeostasis • many overlapping generations--> high intrinsic stability

  11. Fluctuations greater if small/short lifespan • little homeostasis • populations turn over rapidly--> • low intrinsic stability

  12. Population cycles synchronized among species in a region. Periodic cycles with peaks separated by same number of years.

  13. Other species may vary in their response to changes in the environment --> asynchronized cycles.

  14. Environmental fluctuations (extrinsic factors) (and organism responses) tend to be irregular, not periodic. But many populations change with periodic, non-random frequency. *** Is an extrinsic or intrinsic factor likely to be responsible? Explain.

  15. Some populations exhibit regularfluctuations (cycles) in size.

  16. What density-dependent factor causes grouse populations to cycle? Consider abiotic and biotic interactions…

  17. What factor causes grouse populations to cycle? ICA 1 • Hypothesis: Density-dependent infections by a parasitic roundworm cause the cycles. • Prediction: Populations treated with anti-roundworm drugs will not crash following treatments, but control populations will. • Graph the prediction. Label axes.

  18. Control:no drugs Control: No drugs

  19. Results Experimental # Drug Drug Control # What is conclusion? Is hypothesis proven? Time

  20. An intrinsicmechanism for population cycles? • ‘Momentum’ by high birth rate at low density --> overshoot K. • Low survival at high density--> overcompensate and decrease below K. • Population cycles result from time delays in the birth and death rates of populations in response to their own densities.

  21. Discrete-time models with density-dependence: • Built-in time delay ---> can’t continually adjust • Patterns of oscillations depend on value of R • (per capita growth rate) >>2 chaos

  22. Population dynamics reflect a complex interaction of biotic and abiotic influences, and are rarely stable.

  23. Population: all individuals of a species in an area Subpopulations: in different habitat patches *** What are structures (traits) of populations? • Size (abundance) • Age structure • Sex ratio • Distribution (range) • Density (#/unit area) • Dispersion (spacing) • Genetic structure

  24. Population size may be estimated by several methods, e.g. mark-recapture

  25. Aerial censuses

  26. Censusing a population • Number of individuals • Sex ratio • Age structure • complex if: • can’t age • size does not = age (plants) • Long-term vs. short-term

  27. Size classes of individuals of same age.***What’s the ‘take-home message’ = main conclusion?

  28. Temporal variation in recruitment of new individuals affects age structure ---> long-term implications on population growth.

  29. Species distributions (ranges): are they really continuous? Read LO II

  30. What must happen for species to extend range at periphery?What prevents it from doing so?

  31. ***What factors limit the (geographic) distribution (+ range) of organisms? • Phenology • Dispersal • Behavior (habitat selection) • Biotic factors (other species) • Abiotic factors (chemical / physical) • Human introductions • Chance • History

  32. Geographic distributions are discontinuous. Within itsrange, only suitable habitatsare occupied.What factor determines this distribution?

  33. ICA 2 • Transplant 2 species to • range of elevations --> • measure fitness components. • What is the main result : • for lowland species on L? • for highland species on R? • What is the main conclusion? LOW HIGH

  34. Geographic range includes all areas occupied during entire life history; must include migration.

  35. Geographic ranges with migration - know no political boundaries…adds complexity to protection.

  36. Are ranges stable through time? Introduced starlings

  37. Population density declines as body size increases.

  38. ICA 3 Summarize the major result in Fig. 1. Fig. 1

  39. Summarize major result in Fig. 2 Range

  40. Summarize major result in Fig. 3

  41. Within its range, population density (#/area) varies with differences in habitat quality.

  42. ICA 4 What accounts for this owl’s distribution? Owl location ‘Old growth’ forest

  43. Density and reproduction success are dependent on amount of suitablehabitat for prey. Number per km2 Older forest (%)

  44. Contrasting patterns of dispersion

  45. Dispersion = spacing of individuals with respect to others in a population (Even) • Which is most common in plants? animals?

  46. ***What factors influence dispersion of individuals within populations? • habitat heterogeneity • dispersal limitation • reproductive mode • social interactions

  47. Dispersal mode of plants affects their spatial dispersion.

  48. ICA 5What type of dispersion is shown here? Hypothesize what causes the pattern. A B

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