Understanding Population Ecology and Demographic Changes Over Time

1. Chapter 53 Population Ecology Demography- study of the vital statistics of a population and how they change over time

2. Fig. 53-3 Density- number of individuals per unit area or volume Births Deaths Births and immigration add individuals to a population. Deaths and emigration remove individuals from a population. Immigration Emigration

3. Fig. 53-4 influenced by resource availability and behavior Territoriality absence of strong attractions or repulsions Dispersion - pattern of spacing among individuals within the boundaries of the population (a) Clumped (b) Uniform (c) Random

4. Life table - age-specific summary of the survival pattern of a population Cohort - group of individuals of the same age

5. Survivorship curve - graphic way of representing life table data 1,000 100 Number of survivors (log scale) Females 10 Males 1 8 10 0 2 4 6 Age (years)

6. Fig. 53-6 1,000 I 100 II Number of survivors (log scale) 10 III 1 0 50 100 Percentage of maximum life span

7. Table 53-2 Reproductive table(fertility schedule) -age-specific summary of the reproductive rates

8. Concept 53.2: Life history traits are products of natural selection • Life history - traits that affect schedule of reproduction and survival: • age at which reproduction begins • How often the organism reproduces • How many offspring are produced during each reproductive cycle • Life history traits are evolutionary outcomes reflected in the development, physiology, and behavior of an organism

9. Fig. 53-7 • Semelparity (aka big-bang reproduction) - reproduce once and die • Highly variable or unpredictable environments • Iteroparity (aka repeated reproduction) produce offspring repeatedl) • dependable environments

10. “Trade-offs” and Life Histories • Organisms have finite resources, which may lead to trade-offs between survival and reproduction • Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce • Other types of plants produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established • In animals, parental care of smaller broods may facilitate survival of offspring

11. Fig. 53-9 (a) Dandelion (b) Coconut palm

12. Fig. 53-12 Exponential growth 2,000 dN 1.0N = dt 1,500 K = 1,500 Population size (N) Logistic growth 1,000 1,500 – N dN 1.0N = 1,500 dt 500 0 0 5 10 15 Number of generations

13. Fig. 53-13b 180 150 120 Number of Daphnia/50 mL 90 60 30 0 0 20 40 80 100 120 140 160 60 Time (days) (b) A Daphnia population in the lab

14. The Logistic Model and Life Histories • Life history traits favored by natural selection may vary with population density and environmental conditions • K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density • r-selection, or density-independent selection, selects for life history traits that maximize reproduction

15. Population Change and Population Density • In density-independent populations, birth rate and death rate do not change with population density • In density-dependent populations, birth rates fall and death rates rise with population density

16. Fig. 53-15 Density-dependent birth rate Density-dependent birth rate Density- independent death rate Density- dependent death rate Birth or death rate per capita Equilibrium density Equilibrium density Population density Population density (a) Both birth rate and death rate vary. (b) Birth rate varies; death rate is constant. Density-dependent death rate Density- independent birth rate Birth or death rate per capita Equilibrium density Population density (c) Death rate varies; birth rate is constant.

17. Density-Dependent Population Regulation • Density-dependent birth and death rates are an example of negative feedback that regulates population growth • They are affected by many factors, such as competition for resources, territoriality, disease, predation, toxic wastes, and intrinsic factors • In crowded populations, increasing population density intensifies competition for resources and results in a lower birth rate

18. Territoriality • In many vertebrates and some invertebrates, competition for territory may limit density • Cheetahs are highly territorial, using chemical communication to warn other cheetahs of their boundaries • Oceanic birds exhibit territoriality in nesting behavior

19. Fig. 53-17 (a) Cheetah marking its territory (b) Gannets

20. Disease and Predation • Population density can influence the health and survival of organisms • In dense populations, pathogens can spread more rapidly • As a prey population builds up, predators may feed preferentially on that species

21. Population Dynamics • The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size • Long-term population studies have challenged the hypothesis that populations of large mammals are relatively stable over time • Weather can affect population size over time

22. Fig. 53-20 • Changes in predation pressure can drive population fluctuations • Some populations undergo regular boom-and-bust cycles Snowshoe hare 160 120 9 Lynx Number of lynx (thousands) Number of hares (thousands) 80 6 40 3 0 0 1850 1875 1900 1925 Year

23. Fig. 53-21 Metapopulations- groups of populations linked by immigration and emigration ˚ Aland Islands EUROPE Occupied patch Unoccupied patch 5 km

24. One important demographic factor in present and future growth trends is a country’s age structure Rapid growth Slow growth No growth Afghanistan United States Italy Male Female Age Male Female Age Male Female 85+ 85+ 80–84 80–84 75–79 75–79 70–74 70–74 65–69 65–69 60–64 60–64 55–59 55–59 50–54 50–54 45–49 45–49 40–44 40–44 35–39 35–39 30–34 30–34 25–29 25–29 20–24 20–24 15–19 15–19 10–14 10–14 5–9 5–9 0–4 0–4 10  8 6 4 2 0 2 4 6 8 10  8 6 4 2 0 2 4 6 8 8 6 4 2 0 2 4 6 8 Percent of population Percent of population Percent of population

25. Fig. 53-26 60 80 50 60 40 Life expectancy (years) Infant mortality (deaths per 1,000 births) 30 40 20 20 10 0 0 Less indus- trialized countries Less indus- trialized countries Indus- trialized countries Indus- trialized countries

26. Fig. 53-27 http://www.myfootprint.org/ http://www.footprintnetwork.org/en/ index.php/GFN/page/personal_footprint/ Log (g carbon/year) 13.4 9.8 5.8 Not analyzed Ecological footprint - aggregate land and water area needed to sustain the people of a nation