Biology 213 Chapter 53

1. Biology 213 Chapter 53 Introduction to Ecology: Population Ecology Part 1

2. You will be able to… • List various fields of study in Ecology • Explain what factors change populations • Calculate population rate changes • Compare and contrast density-dependent to density-independent factors

3. Ecology: Oikos = home Ology = study of Integrates all biological fields Organismal ecology: physiology, behavior, interactions with environment Population ecology: factors affecting groups of individuals in an area. Community ecology: interactions between species in an area

4. Ecosystem ecology: biotic and abiotic interactions; E flow & chem. Cycles • Landscape ecology: exchange of E & materials across multiple ecosystems • 6. Global ecology: biosphere: regional exchange of E & materials affecting entire functioning & distribution of organisms wotldwide.

5. Ecology & evolution: changes in environment impacting populations’ alleles over time. Ecology & environmental issues Complexity of Nature: Why are some species present in an area? Dispersal difficulties (accessibility?) Behaviour limits distribution (habitat preference)? Biotic factors: competition/parasitism/predation/etc Abiotic factors: Chem: H2O, O2, pH, salinity, nutrients Phys: Macro & micro climate: Temp, light, fire, soil composition, moisture

6. Estimate: one million years to get from 2.5 million to human population of ~ 5 million people in 6000 B.C. (2x) • population did not reach 500 million until almost 8,000 years later -about 1650 A.D (100x) • doubled roughly once every thousand years or so • reached a billion ~ 1850, doubling in 200 years • reached two billion around 1930 – doubling in 80 years • 1970’s it reached 4 billion ~ 40 year doubling time • Today’s population ~ 7 billion

7. What factors have allowed human population to increase so rapidly?

8. Ecologists study population trends rather than individual organisms. Properties of populations include • Population size • Population density • Patterns of dispersion • Demographics • Population growth • Limits on population growth

9. Population density • # individuals of a species per unit at a given time • Population dispersion (spacing) • How are individuals distributed in a habitat? • Why would this be important to know if you were studying a population? • What does a dispersion pattern tell you?

10. Individual members distributed in a # of different ways: • Clumped - • Uniform - • Random -

11. Why would a clumped population pattern form? individuals _____________ to each other, or __________________________________.

12. What factors encourage a uniform population pattern? individual organisms actively _____ each other or all _________________________________

13. What abiotic or biotic features would encourage a random population pattern? Rare in nature - occurs in absence of strong attractions or repulsions among individuals.

14. Dispersion patterns and density may change over time Habitat changes: food, nutrients, water, sunlight (plants) Age / size / developmental stages change:

15. Four factors that produce changes in population size

16. Natality: birth rate

17. Mortality rates

18. Mortality rate of cheetahs Increased Infant Mortality • Is the cheetah dangerously inbred? • Majority of deaths in wild due to predation. • Future for cheetah population?

19. How a population changes: D in # ofindividuals in a certain period of time N = r =

20. How a population changes: D in # individuals /time N = # individuals r = * Per 1,000 individuals Growth rate =

21. Example: N = 300,000 humans: 3,000 births + 1,500 deaths in one year r = (birth rate) – (death rate)

22. Example: N = 300,000 humans: r = (birth rate) – (death rate) r = r =

23. Example: N = 300,000 humans: r = 0.005 x 100 = 0.5% increase rN = 0.5 x 300,000 rN =

24. If r is positive, increase in pop. If r is negative, pop. is decreasing If r = 0, population is stable

25. Are there other factors besides birth and death and size of a population that can change a population?

26. Immigration • What causes immigration biologically? • Favorable factors

27. Factors encouraging immigration: New environment made available • Natural disasters large and small • Competitive or predatory species goes extinct / moves away • Climate change or new resources • Hitch-hiking (“alien” species) Less competition in new area

28. Succession after a disaster Immigrants have an opportunity to invade: Reduced competition

29. Factors that encourage successful immigration: Distribution methods: • dispersal is at or near ground level vs. aerial dispersal • dispersers actively engage in searching, or not • dispersers able to orient toward preferred habitat from some distance, or not

30. Wind dispersing Golden Orb spiders

31. Emigration Unfavorable Factors: *Excessive competition: mates or food *Lack of resources *Disease *Avoidance of in-breeding

32. Population change includes immigration and emigration: r = (birth rate) – (death rate) plus (immigration – emigration) e.g. Example: N = 300,000 humans: 3000 births + 1500 deaths in one year 3,000 immigrated into the area 9,000 emigrated out of the area

33. r = (b – d) + (i – e) b – d = (10/1000) – (5/1000) = 0.005 i – e = 1/1000 – 3/1000 = 0.001 – 0.003 = -0.002 r = (b – d) + (i – e) = (0.005) + (-0.002) = 0.003 x 100 = 0.3% Growth rate: rN = (0.3%)(300,000) = 900 more people in the population

34. Intrinsic rate of increase (rmax) Maximum rate at which species or population can increase under ideal conditions • Exponential population growth

35. Exponential population growth

36. According to Malthus: • Population, when unchecked, increases in a geometrical ratio. • Subsistence increases arithmetically.

37. Carrying capacity • Carrying capacity (K) = largest population maintained without degrading environment they live in • Changes as environment changes • Logistic population curve (S-shaped curve)

38. Carrying capacity and logistic population growth Limiting Factors

39. Density-dependent factors • Regulate population growth by affecting large proportion of population as population rises:

40. Density-dependent factors • What do you think would impact a population as it got bigger? • Predation • Disease • Competition • Toxic wastes

41. Density-dependent factors and negative feedback

42. Density-independent factors • Limit population growth but are not influenced by changes in population density: usually ABIOTIC • Examples include natural disasters: • Hurricanes • Blizzards • Forest fires • Mudslides • Volcanoes, tsunamis, and earthquakes

43. Limiting Factors Biotic and abiotic, Density dependent or independent factors that limit a population’s growth: What would be a limiting factor?

44. What can you think of that would be a limiting factor? Which are biotic and which are abiotic? • increase death rate • decrease birth rate • limits immigration • encourages emigration • Any factors that slows population growth.

45. How are up & down cycles explained? Can be very complex relationships and factors.

46. Biology 213 Chapter 53 Introduction to Ecology: Population Ecology Part 2

47. You will be able to… • Explain what factors change populations • Calculate population rate changes • Compare and contrast density-dependent to density-independent factors • Analyze human population patterns and make predictions about future trends

48. Semelparous reproduction • Expend their energy in a • Iteroparous reproduction • Exhibit ________________________ throughout their lifetimes

49. Semelparity: Expend energy to reproduce in one big effort Most insects, invertebrates, many annual plants, and some fish What’s the advantage?

50. Iteroparous reproduction • Expend energy to reproduce in cycles • Most vertebrates, perennial plants. • What’s the advantage?