HUMAN ECOLOOOOOOOOOOOOOOOOOOOOOOOGY.pptx

SCIENCE

1. HUMAN ECOLOGY and SUCCESSION Eugene Jay M. Aquino Instructor I, Natural Sciences Department Gordon College

2. Introduction “ Population ecology has its deepest historic roots, and its richest development, in the study of population growth, regulation, and dynamics, or demography. Human population growth serves as an important model for population ecologists, and is one of the most important environmental issues of the 21 st century.” – Nature Education, 2014

3. POPULATION ECOLOGY Concerned with changes in population size and the factors that regulate populations over time .

4. POPULATION Groups of individual of a single species that occupy the same general area that live together and influence each other’s survival.

5. POPULATION These individuals rely on the same resources , are influenced by the same environmental factors , and have a high likelihood of interacting and breeding with one another.

6. POPULATION Although we humans picture ourselves as different from populations of animals living in the wild, factors that affect wild populations, such as: Population densities ; Dispersion ; Growth ; Competition ; Sharing of resources - affects human populations in similar ways.

7. POPULATION In simple terms -- a researcher must define a population by geographic boundaries appropriate to the questions being asked. For example, a population biologist studying the effects of hunting on deer might define a population as all the deer within a particular state.

8. POPULATION Another example is that another studying the effects of the AIDS epidemic on researcher the human population , might focus on the HIV infection rate in one nation or throughout the world.

9. POPULATION Regardless of the scale, two important characteristics of any population are its: DENSITY and DISPERSION patterns.

10. POPULATION GROWTH : Properties of Population

11. POPULATION SIZE Number of individuals in the population. SOMETHING TO PONDER: If an entire species consists only of one or few small populations, is that specie most likely will become extinct? Why or why not?

12. POPULATION DENSITY Number of individuals of a species per unit area or volume. Number of oak trees per square kilometer (km2) in a forest Number of earthworms per cubic meter (m3) in forest soil.

13. POPULATION DENSITY The density of a population, how closely individuals associate with each other, is an indication of how they live. Animals that live in large groups, such as herds of wildebeests or zebras, may find safety in numbers.

14. HOW DO WE MEASURE POPULATION DENSITY? In most cases, it is impractical or impossible to count all individuals in a population. Instead, ecologists use a variety of sampling techniques to estimate population densities. They might base an estimate of the density of alligators in the Florida Everglades on a count of individuals in a few sample plots of 1km2. The larger the number and size of sample plots, the more accurate the estimates.

15. HOW DO WE MEASURE POPULATION DENSITY? In some cases, population densities are estimated not by counts of organisms but by indirect indicators, such as: Number of bird nests or rodent burrows or even animal dropping or tracks.

16. POPULATION DISPERSION Scatter of individuals within the population’s range . Individuals may be spaced : randomly (less common in nature) c lumps (due to uneven distribution of resources or in response to social interactions) Uniformly (as a result of competition for resources)

17. POPULATION DISPERSION These patterns are important characteristics for an ecologist to study, since they provide insights into the environmental effects and social interactions in the population.

18. POPULATION DISPERSION CLUMPED PATTERNS – individuals are aggregated in patches, is the most common in nature. Clumping often results from an unequal distribution of resources in the environment.

19. POPULATION DISPERSION UNIFORM PATTERNS – often results from interactions between the individuals of a population. Some animals may exhibit uniform dispersion as a result of territorial behavior.

20. POPULATION DISPERSION RANDOM PATTERNS – individuals in a population are spaced in a pattern less, unpredictable way. Varying habitat conditions and social interactions make random dispersion rare.

21. POPULATION GROWTH Estimates of population density and dispersion patterns are both important in analyzing populations. They enable researchers to monitor changes in population and to compare and contrast the growth and stability of populations in different areas.

22. FACTORS INFLUENCING POPULATION GROWTH Exponential Growth Model Limiting Factors Logistic Growth Model Carrying Capacity

23. EXPONENTIAL GROWTH MODEL The rate of population increase under ideal conditions. Whole population multiplies by a constant factor during each time interval. This kind of model produces J-shaped curved – typical for exponential growth.

24. EXPONENTIAL GROWTH MODEL

25. EXPONENTIAL GROWTH MODEL G= rN G = growth rate of a population (No. of new individuals added per time interval) N = population size (No. of individuals in the population at a particular time) r = per capita rate of increase ( ave. contribution of each individual to population growth)

26. EXPONENTIAL GROWTH MODEL G= rN This model gives an idealized picture of unregulated population growth.

27. CARRYING CAPACITY No matter how rapidly populations grow, they eventually reach a limit imposed by shortages of important environmental factors such as space, light, water, or nutrients. A population ultimately stabilizes at a certain size called carrying capacity of the particular place where it lives. K = maximum number of individuals that an area can support, a dynamic rather than static measure as the characteristics of an area change.

28. LOGISTIC GROWTH MODEL As a population approaches its carrying capacity, its rate of growth slows greatly, because fewer resources remain for each new individual to use.

29. TWO MODELS OF POPULATION GROWTH

30. INFLUENCE OF POPULATION DENSITY Population density – regulates the growth of a population in nature. Some of these factors act independently of the size of the population, others do not.

31. DENSITY-INDEPENDENT EFFECTS Effects that are independent of the size of a population and act to regulate its growth.

32. DENSITY-DEPENDENT EFFECTS Effects that are dependent of the size of a population and act to regulate its growth.

33. MAXIMIZING POPULATION PRODUCTIVITY (SIGMOID CURVE) In natural systems that are exploited by humans, such as fisheries, the aim is to maximize productivity by exploiting the population early in the rising portion of its sigmoid growth curve.

34. MAXIMAL SUSTAINABLE YIELD

35. TWO MODES OF POPULATION GROWTH

36. POPULATION DEMOGRAPHY DEMOGRAPHY – statistical study of populations. DEMOS = the people ; GRAPOS = measurement DEMOGRAPHY = science that helps predict how population sizes will change in the future

37. POPULATION DEMOGRAPHY Population grow if births outnumber deaths and shrinks if deaths outnumber births. Because birth and death rates depend significantly on age and sex, the future size of a population depends on its present age structure and sex ratio.

38. AGE STRUCTURE COHORT – group of individuals of the same age. - Example – perennial plants FECUNDITY – birthrate MORTALITY – death rate The rate of population’s growth depends directly on the difference between these two rates.

39. SEX RATIO The proportion of males and females in a population. No. of births = No. of females, but not necessarily related to No. of males = mate with several females.

40. MORTALITY and SURVIVORSHIP CURVES Population increase depends on the ages and reproductive performance of individuals in the various age groups.

41. MORTALITY and SURVIVORSHIP CURVES When a population lives in a constant environment for a few generations, its age distribution – the proportion of individuals in different age categories – tend to stabilize.

42. MORTALITY and SURVIVORSHIP CURVES Depending on the mating system of the species, sex ratio and generation time can also have a significant effect on population growth.

43. MORTALITY and SURVIVORSHIP CURVES A population whose size remains fairly constant through time is called a “STABLE POPULATION” In such a population, BIRTH + IMMIGRATION must balance DEATHS EMIGRATION.

44. SURVIVORSHIP CURVES One way to express the age distribution and survivability of a cohort is through survivorship curves. Survivorship – percentage of an original population that survives a given age.

45. TYPES OF SURVIVORSHIP TYPE I – population exhibits high survivorship throughout their life cycle. TYPE II – have a constant proportion of individuals dying over time. TYPE III – survivorship have high mortality at young ages

46. TYPES OF SURVIVORSHIP

47. POPULATION DECLINE AND EXTINCTION EXTINCTION happens when a species is said to no longer lives anywhere on the planet. It happens when the last members of a species die because they cannot acquire the food, water, shelter, and/or space to survive.

48. ALTERING POPULATION GROWTH Increasing the extraction of resources from the environment. Increasing the burning of fossil fuels for energy to generate electricity Increase in freshwater use Increase ecological impacts on environments Increase fishing and hunting Increasing the transport of invasive species Transmission of diseases.