1. Population Dynamics, Carrying Capacity & Conservation Biology Miller Chapter 9

2. Characteristics of Populations 1. They change in size (# of individuals) 2. They change in density (# of individuals within a certain area) 3. They change in dispersion (spatial patterns) 4. They change in age distribution Section 9-1

3. Dispersion Patterns Figure 9-2 Miller p191

4. These changes are called population dynamics and occur in response to environmental changes & stress.

5. Limits to Population Growth 1.Births 2.Deaths 3.Immigration 4.Emigration All depend on resource availability

6. Population Change = (births + immigration) minus (deaths + emigration)

7. Intrinsic Rate of Increase (r) Definition - rate at which a population would grow if it had unlimited resources. –It is high if: Individuals reproduce early in life Have short generation times Can reproduce many times Produce many offspring each time

8. Environmental Resistance Definition - all the factors that act together to limit population growth

9. Carrying Capacity (K) Definition - the # of individuals of a given species that can be sustained indefinitely in a given space –If a population exceeds its carrying capacity, it will suffer a dieback or population crash.

10. Carrying Capacity con’t Carrying capacity is not a fixed amount and can be affected by: –Competition –Immigration & emigration –Catastrophic events –Fluctuations occurring seasonally

11. Logistic vs. Exponential Growth

12. Density-Independent Population Controls Affect a population’s size regardless of population density –EX. floods, fires, hurricanes, habitat destruction

13. Density-Dependent Population Controls Effects are more severe as the population density increases. –EX. competition for resources, predation, parasitism, disease

14. Population Fluctuations Figure 9-7 Miller p194

15. Population Size & Predation Species that exhibit predator-prey relationships undergo cyclic changes in population. –EX. Snowshoe hare & Canadian lynx Top-down control systems Bottom-up control systems Section 9-2

16. Top-Down vs. Bottom-Up Figure 9-8 Miller p195

17. Reproductive Patterns Asexual reproduction – all offspring are clones of the parent. Occurs in single-celled organisms Sexual reproduction – all offspring are a combination of traits from 2 parents. Occurs in 97% of organisms. Section 9-3

18. Sexual Reproduction con’t Disadvantages: –Females must reproduce twice as much as organisms that reproduce asexually –Greater chance for genetic errors –More time consuming Courtship Mating rituals –Disease transmission

19. Advantages: –Provides greater genetic diversity –Males can gather food for, protect, & train the female & young Sexual Reproduction con’t

20. Reproductive Patterns r-selected – species with a capacity for a high intrinsic rate of increase –These species reproduce early & devote most of their energy to reproduction –Tend to be opportunist species –Ex. algae, rodents, bacteria, insects

21. K-selected – species that produce a few, fairly large offspring, but invest large amounts of time & energy to ensure the offspring reach reproductive age. –These species develop/mature slowly inside their mother –Tend to do well in competitive situations when population size is near carrying capacity (K) –Tend to be competitor species –Ex. elephants, whales, humans, birds of prey, cactus, oak trees, redwoods Reproductive Patterns

22. r-selected vs. K-selected Figure 9-10 Miller p196

23. The "J-shaped" Growth Curve –High numbers of offspring –No care for the young –Low recruitment (high mortality for the young) Low numbers of offspring The "S-shaped" Growth Curve –Care of the young –High recruitment Two Reproductive Strategies

24. Sigmoid Growth Curve Phases (S-curve) In a typical Sigmoid curve, the value of a variable (say population) initially increases exponentially, but instead of continuing unchecked, the rate of growth reaches a maximum and then gradually decreases to zero. The point at which the rate of growth (expressed as the slope of the curve) changes from increasing to decreasing is called the "inflection point" Time Number of Individuals Inflection point Carrying capacity (K)

25. Survivorship Curves Organisms with different reproductive strategies have different life expectancies. This can be shown graphically. I II III

26. Type I Curves Typical of populations in which most mortality occurs among the elderly (e.g., humans in developed countries). (Late loss curves) –produce few young –provide care for young until they reach reproductive age –low juvenile mortality

27. Type II Curves Occur when mortality is not dependent on age (e.g., many species of large birds and songbirds). (Constant loss curves) –constant rate of mortality

28. Type III Curves Occur when juvenile mortality is extremely high (e.g., plant and animal species producing many offspring of which few survive). Life expectancy increases for individuals who survive their risky juvenile period. (Early loss curves) –produce many offspring –high juvenile mortality rate –high survivorship once surviving young reach a certain age & size

29. Conservation Biology Definition - a multidisciplinary science (just like Environmental Science) that uses the latest science to help preserve species & ecosystems.

30. Conservation Biology con’t Seeks to answer the following three questions: 1. What species are in danger of extinction?

31. Conservation Biology con’t 2. What is the status of the functioning of ecosystems, & what ecosystem services of value to humans & other species are we in danger of losing?

32. Conservation Biology con’t 3. What measures can we take to help sustain ecosystem functions & viable populations of wild species?

33. Conservation Biology con’t To do so, we must: 1. Measure the current population size 2. Project population size change with respect to time 3. Determine if existing populations are likely to be sustainable

34. Human Impacts on Ecosystems 1. Fragmenting & degrading habitat 2. Simplifying natural ecosystems 3. Using, wasting, or destroying an increasing percentage of the earth’s NPP that supports all consumer species (including humans)

35. Human Impacts con’t 4. Strengthening pest species populations & disease-causing bacteria by speeding up natural selection & causing genetic resistance through overuse of pesticides & antibiotics 5. Eliminating some predators; Example: Prairie dogs 6. Deliberate or accidental introduction of nonnative species 7. Overharvesting of renewable resources; Example: livestock overgrazing 8. Interfering with normal chemical cycling & energy flows in ecosystems

36. What We Need To Realize ―We need the earth, it does not need us ―We need to discover the strongest, most important connections in ecology to avoid disruption ―What we do to the earth snowballs ―We need to help heal some of the already existing ecological wounds ―We need to “handle with care”