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Studying Human Population

Studying Human Population. Demography. Def: Study of human populations. Properties of Populations. Density : The number of individuals per unit area or volume. Properties of Populations. Dispersion : Is the relative distribution or arrangement of individuals within a given amount of space.

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Studying Human Population

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  1. Studying Human Population

  2. Demography • Def: Study of human populations

  3. Properties of Populations • Density: The number of individuals per unit area or volume

  4. Properties of Populations • Dispersion: Is the relative distribution or arrangement of individuals within a given amount of space

  5. Dispersion Pattern • Clumped • Organisms are aggregated in patches • Most Common • Associated with uneven food distribution • Uniform • Organisms are evenly dispersed • Plants • Random • VERY VERY Rare in nature

  6. Sex Ratio • Def: Proportion of Males to Females • A 50/50 Ratio maximizes population growth • An uneven ratio leads to negative population growth

  7. REMEMBER THIS??? • Developing Countries • Lower average incomes • Simple and agricultural based economies • Rapid population growth • Developed Countries • Higher average incomes • Slow population growth • Diverse, industrial economies

  8. World Population Over Time

  9. Age Structure • Def- the distribution of ages in a specific population at a certain time. • Is shown visually in Population Pyramids

  10. 5.Age structure– relative #’s of organisms of each age within a population Age (years) Mostly younger organisms  positive growth Even age distribution  stable population Mostly older organisms  negative growth #2.2 Aim: How do we describe populations? Agenda QOD (5) Lesson: populations(15) Activity: (15) Summary (5) HW #9

  11. Population Pyramids • A double-sided bar graph • Ex: Countries that have high rates of growth usually have more younger people than older people

  12. Age Structure Cont. • Mostly Younger: Positive Growth • Even Age: Stable Population • Mostly Older: Negative Growth

  13. Survivorship • Def: The percentage of members of a group that are likely to survive to any given age. • Used as a way to predict population trends.

  14. Survivorship Curves • TYPE I: Most people live to be very old • TYPE II: Similar death rates at all ages • TYPE III: Many children die

  15. Fertility Rates • Def: The number of babies born each year per 1,000 women in a population • Total fertility rate: The average number of children a women gives birth to in her lifetime.

  16. Fertility Rates

  17. Imagine a population with positive growth… 1. Describe the size, density, distribution, sex ratio, age structure, and birth/death rates of your population. 2. Work in pairs to make a mini-poster showing a picture and a diagram of either the age structure or the survivorship type. For example…

  18. Example: Subway rats Size: about 1,000 organisms and increasing (positive growth) Density: medium (not high or low). Not a lot of competition for resources, not too hard to find mates. Distribution: clumped. The rats like to be near the stations where they find more food. Sex ratios: even. Since there are just about as many males as females, the population is increasing at a rapid rate. Age structure: mostly young. Since most of the rats in the population are in their reproductive prime years, the population is increasing at a rapid rate. Birth and death rates: The birth rate is higher than the death rate. The rats have Type 1 survivorship where they don’t usually die until old age. #2.2 Aim: How do we describe populations? Agenda QOD (5) Lesson: populations(15) Activity: (15) Summary (5) HW #9

  19. Example: Subway rats Rats have Type 1 survivorship #2.2 Aim: How do we describe populations? Agenda QOD (5) Lesson: populations(15) Activity: (15) Summary (5) HW #9

  20. Sampling Techniques

  21. Direct Counting • Method to estimate the size and density of population • Impractical due to size of ecosystem, the number of plants involved, and the movement of animals

  22. Sampling Technique • A more practical way • Enables us to estimate the total population size of the organism • 1: Quadrat Sample Method • 2: Mark and Recapture Sampling

  23. The Quadrat Sample • Used for estimating the size of plant population and immobile animals • A quadrat: A wooden frame which forms a square of a known area (1 m2). • Placed randomly in a population where sampling is carried out.

  24. Quadrat

  25. Quadrat Sampling • Used to find DENSITY: The mean number of organisms per unit area.

  26. Quadrat Sampling • Used to find PERCENT COVERAGE: an indication of how much the area of quadrat is occupied by a species.

  27. The Capture, Mark, Release, and Recapture Technique • Used to estimate mobile animals • Procedure: • First Capture: A random sample of animals is selected. • Mark: Each animal is marked in a distinctive way • Release: The marked animals are released back into nature • 2nd Capture: Only a proportion of the 2nd capture sample will have animals that were marked in the 1st capture.

  28. Mark and Recapture

  29. Survey 2: Survey 1: M = 12 C = 15 R = 4

  30. M = R N C N = M C R What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2nd sample M = 12 C = 15 R = 4

  31. N = 12 * 15 4 What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2nd sample M = 12 C = 15 R = 4

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