1. © 2012 John Wiley & Sons, Inc. All rights reserved. Population Ecology A population is a group of individuals of a single species living in the same general area Population Ecology = study of how population size of a species changes over time and space – Due to biotic and abiotic interactions

2. © 2012 John Wiley & Sons, Inc. All rights reserved. Population Density v. Size Population size = number of individuals Population density = number of individuals in a given unit of space (area or volume). – Ex: minnows per Liter of pond water A B

3. © 2012 John Wiley & Sons, Inc. All rights reserved. Calculating Population Change r = (b – d) + (i – e)

4. © 2012 John Wiley & Sons, Inc. All rights reserved. r = intrinsic rate of increase = the rate at which a population increases in size if there are no limitations on population growth r = per capita rate of increase = increase in population size (number of offspring that survive to reproduce) “Biotic potential”

5. © 2012 John Wiley & Sons, Inc. All rights reserved. Exponential Growth Intrinsic Rate of Growth (Biotic Potential) – Growth rate under ideal conditions—no limits Expansion into new habitat, re-colonization post-disturbance, rebound after population decline Limited time span – J- Shaped Curve (exponential growth)

6. © 2012 John Wiley & Sons, Inc. All rights reserved.

7. Environmental Resistance Environmental limits (resistance) – Prevent indefinite reproduction – Density dependent factors Carrying Capacity (K) – Maximum # of individuals an environment can support Can change over time – Causes S- shaped curve (logistic population growth) resistance

8. © 2012 John Wiley & Sons, Inc. All rights reserved. Carrying capacity (K) is the maximum population size the environment can support Carrying capacity varies with the abundance of limiting resources which can change over time

9. © 2012 John Wiley & Sons, Inc. All rights reserved. Environmental Resistance Environmental limits (resistance) – Prevent indefinite reproduction – Unfavorable food, water, shelter, predation, etc. Carrying Capacity (K) – Maximum # of individuals an environment can support – Causes leveling off of exponential growth – S- shaped curve of logistic population growth

10. © 2012 John Wiley & Sons, Inc. All rights reserved.

11. Factors That Affect Population Size  Density Dependent Factor  Factor whose effect on population changes as population density changes  Examples: Predation Disease/parasitism Competition (for limited resources) Waste accumulation Intrinsic physiologic factors

12. © 2012 John Wiley & Sons, Inc. All rights reserved. Figure 53.18 Competition for resources Territoriality Intrinsic factors Disease Predation Toxic wastes 5 µm

13. © 2012 John Wiley & Sons, Inc. All rights reserved. Figure 53.11 1,000 800 600 400 200 0 051015 Time (days) (a) A Paramecium population in the lab (b) A Daphnia population in the lab 020406080100120140160 180 150 120 90 60 30 0 Time (days) Number of Daphnia/50 mL Number of Paramecium/mL

14. © 2012 John Wiley & Sons, Inc. All rights reserved. Boom-Or-Bust Population Cycles

15. © 2012 John Wiley & Sons, Inc. All rights reserved. Factors That Affect Population Size Density Independent Factors – Factors that affects population size, but is not influenced by changes in population density – Examples: Killing frost Severe blizzard Fire Landslide/avalanch flooding

16. © 2012 John Wiley & Sons, Inc. All rights reserved. Evolution and Life History Diversity A life history entails three main variables – The age at which reproduction begins – How often the organism reproduces – How many offspring are produced per reproductive episode

17. © 2012 John Wiley & Sons, Inc. All rights reserved. Semelparity--big-bang reproduction--reproduce once and die – Unpredictable environments – Probability of adult survival, low – Relatively low parental investment in offspring Iteroparity--repeat reproduction--produce offspring repeatedly – Predictable environments – Probability of adult survival high – Relatively high parental investment in offspring.

18. © 2012 John Wiley & Sons, Inc. All rights reserved. Life History Strategies are trade-offs Resources are finite: – Adult survival v. reproductive output – High output; low investment v. low output; high investment r v. K

19. © 2012 John Wiley & Sons, Inc. All rights reserved. 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

20. © 2012 John Wiley & Sons, Inc. All rights reserved. Reproductive Strategies r-selected speciesK-selected species - Smaller body size - Early maturity - Short life span - Large broods (# of offspring each reproductive event) - Little or no parental care - Probability of long term survival is low - e.g., Mosquitoes, Dandelions, - Larger body size - Slow development - Late reproduction - Long life span - Small broods (# of offspring each reproductive event) - Significant often prolonged parental care - Low reproductive rate - e.g., Redwood trees, elephants, human beings

21. © 2012 John Wiley & Sons, Inc. All rights reserved. Figure 53.6 I Percentage of maximum life span Number of survivors (log scale) 050100 1,000 100 10 1 II III

22. © 2012 John Wiley & Sons, Inc. All rights reserved. Survivorship curves can be classified into three general types – Type I: Low death rates during early and middle life and an increase in death rates among older age groups – Type II: A constant death rate over the organism’s life span – Type III: High death rates for the young and a lower death rate for survivors Many species are intermediate to these curves

23. © 2012 John Wiley & Sons, Inc. All rights reserved. Survivorship