1 / 101

Chapter 52

Chapter 52. pop Ecology. Overview: Earth’s Fluctuating pop's. To understand human pop growth, we must consider general principles of pop ecology. pop ecology- study of pop’s in relation to environ, including density & distribution, age structure, & pop size

louvain
Download Presentation

Chapter 52

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 52 pop Ecology

  2. Overview: Earth’s Fluctuating pop's • To understand human pop growth, we must consider general principles of pop ecology

  3. pop ecology- study of pop’s in relation to environ, including density & distribution, age structure, & pop size • The fur seal pop of St. Paul Island, off the coast of Alaska, has experienced dramatic fluctuations in size

  4. Concept 52.1: Dynamic biological processes influence pop density, dispersion, & demography • pop-grp of indiv's of 1 spp living in the same general area

  5. Density & Dispersion • Density- # of indiv's per unit area or volume • Dispersion- pattern of spacing among indiv's w/in the boundaries of the pop

  6. Density: A Dynamic Perspective • Determining the density of natural pop's is difficult • In most cases, it is impractical or impossible to count all indiv's in a pop • Density is the result of an interplay b/w processes that add indiv's to a pop & those that remove indiv's

  7. LE 52-2 Immigration Births pop size Emigration Deaths

  8. Patterns of Dispersion • Environmental & social factors influence spacing of indiv's in a pop

  9. clumped dispersion- indiv's aggregate in patches • A clumped dispersion may be influenced by resource availability & behavior Video: Flapping Geese (clumped)

  10. LE 52-3a Clumped. For many animals, such as these wolves, living in groups ↑'s the effectiveness of hunting, spreads the work of protecting & caring for young, & helps exclude other indiv's from their territory.

  11. uniform dispersion- indiv's are evenly distributed • It may be influenced by social interactions such as territoriality Video: Albatross Courtship (uniform)

  12. LE 52-3b Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions b/w neighbors.

  13. random dispersion- position of each indiv is independent of other indiv's Video: Prokaryotic Flagella (Salmonella typhimurium) (random)

  14. LE 52-3c Random. Dandelions grow from windblown seeds that land at random & later germinate.

  15. Demography • Demography- study of the vital statistics of a pop & how they change over time • Death rates & birth rates are of particular interest to demographers

  16. Life Tables • A life table is an age-specific summary of the survival pattern of a pop • It is best made by following the fate of a cohort • The life table of Belding’s ground squirrels reveals many things about this pop

  17. Survivorship Curves • A survivorship curve is a graphic way of representing the data in a life table • The survivorship curve for Belding’s ground squirrels shows a relatively constant death rate

  18. LE 52-4 1,000 100 # of survivors (log scale) Females 10 Males 1 2 0 10 6 8 4 Age (years)

  19. Survivorship curves can be classified into 3 general types: Type I, Type II, & Type III

  20. LE 52-5 1,000 I 100 II # of survivors (log scale) 10 III 1 100 50 0 Percentage of maximum life span

  21. Reproductive Rates • A reproductive table, or fertility schedule, is an age-specific summary of the reproductive rates in a pop • It describes reproductive patterns of a pop

  22. Concept 52.2: Life history traits are products of natural selection • Life history traits are evolutionary outcomes reflected in the development, physiology, & behavior of an organism

  23. Life History Diversity • Life histories are very diverse • Semelparity- “big-bang” reproduction, reproduce once & die • Iteroparity- repeated reproduction, produce offspring repeatedly

  24. “Trade-offs” & Life Histories • Organisms have finite resources, which may lead to trade-offs b/w survival & reproduction

  25. LE 52-7 100 Male Female 80 60 Parents surviving the following winter (%) 40 20 0 Normal brood size Reduced brood size Enlarged brood size

  26. Some plants produce a lg # of small seeds, ensuring that at least some of them will grow & eventually reproduce

  27. LE 52-8a Most weedy plants, such as this dandelion, grow quickly & produce a large # of seeds, ensuring that at least some will grow into plants & eventually produce seeds themselves.

  28. Other types of plants produce a moderate # of lg seeds that provide a lg store of energy that will help seedlings become established

  29. LE 52-8b Some plants, such as this coconut palm, produce a moderate # of very large seeds. The large endosperm provides nutrients for the embryo, an adaptation that helps ensure the success of a relatively large fraction of offspring.

  30. In animals, parental care of smaller broods may facilitate survival of offspring

  31. Concept 52.3: The exponential model describes pop growth in an idealized, unlimited environ • It is useful to study pop growth in an idealized situation • Idealized situations help us understand the capacity of spp to ↑ & the cond’s that may facilitate this growth

  32. Per Capita Rate of ↑ • If immigration & emigration are ignored, a population’s growth rate (per capita ↑ ) equals birth rate minus death rate

  33. dN  rN dt • Zero pop growth occurs when the birth rate equals the death rate • Most ecologists use differential calculus to express pop growth as growth rate at a particular instant in time:

  34. Exponential Growth • Exponential pop growth- pop ↑ under idealized cond’s; J-shaped curve • Under these cond’s, the rate of reproduction is at its maximum, called the intrinsic rate of ↑

  35. dN  rmaxN dt • Equation of exponential pop growth:

  36. LE 52-9 2,000 dN = 1.0N dt 1,500 dN = 0.5N dt pop size (N) 1,000 500 0 15 10 5 0 # of generations

  37. The J-shaped curve of exponential growth characterizes some rebounding pop's

  38. LE 52-10 8,000 6,000 Elephant pop 4,000 2,000 0 1920 1900 1980 1960 1940 Year

  39. Concept 52.4: The logistic growth model includes the concept of carrying capacity • Exponential growth cannot be sustained for long in any pop • A more realistic pop model limits growth by incorporating carrying capacity

  40. Carrying capacity (K)- max pop size the environ can support

  41. The Logistic Growth Model • logistic pop growth model- per capita rate of ↑ declines as carrying capacity is reached; sigmoid (S-shaped) curve • We construct the logistic model by starting w/ the exponential model & adding an expression that reduces per capita rate of ↑ as N ↑'s

  42. LE 52-11 Maximum Per capita rate of ↑ (r) Positive N = K 0 Negative pop size (N)

  43. (K  N) dN  rmax N dt K • The logistic growth equation includes K, the carrying capacity

  44. LE 52-12 2,000 dN = 1.0N Exponential growth dt 1,500 K = 1,500 Logistic growth pop size (N) 1,000 dN 1,500 – N = 1.0N dt 1,500 500 0 0 15 10 5 # of generations

  45. The Logistic Model & Real pop's • The growth of laboratory pop's of paramecia fits an S-shaped curve

More Related