1. 19.1 UNDERSTANDING POPULATIONS

2. 1. POPULATION PROPERTIES Size (often hard to measure) Density– amount of population per unit of area (population crowding) # of individuals = population density area (units 2 ) Dispersion – spatial organization of the population

3. 1. POPULATION PROPERTIES Dispersion – spatial organization of the population

4. 1. POPULATION PROPERTIES Dispersion – spatial organization of the population Clumped – population is clustered together, usually around resources or from social behavior ex/ school of fish

5. clumped

6. 1. POPULATION PROPERTIES Dispersion – spatial organization of the population Uniform – the population is evenly dispersed from each other usually from social interactions ex/ bird nesting sites or solitary predators

7. uniform

8. 1. POPULATION PROPERTIES Dispersion – spatial organization of the population Random – the population is randomly scattered throughout the area ex/ trees in a forest with seeds dispersed by wind or animals

9. random

10. 2. SURVIVORSHIP CURVES Survivorship Curve probability of individuals surviving to a certain age

11. 2. SURVIVORSHIP CURVES Survivorship Curve probability of individuals surviving to a certain age I – Low birth rate, low infant mortality, survives to old age (Humans & large mammals)

12. 2. SURVIVORSHIP CURVES II – Survivorship rate equal at all ages (Birds & reptiles)

13. 2. SURVIVORSHIP CURVES III – High birth rate, high infant mortality rate (Fish, Insects, Plants)

15. 3. MODELS OF GROWTH Exponential birth and death rates are constant (b > d)

16. 3. MODELS OF GROWTH Exponential birth and death rates are constant (b > d) the rate increases as the population gets larger limited by density- independent factors Ex: Bacteria

17. 3. MODELS OF GROWTH Logistic (K): the number of individuals the environment can support over time. This is when b rates equal d rates (zero population growth) limited by density- dependent factors

18. Most organisms such as seals, and whales follow this model

19. 4. REGULATING POPULATION GROWTH Limiting factors: restrains population growth

20. 4. REGULATING POPULATION GROWTH Limiting factors: restrains population growth (2 types) Density-independent factors: no regard for population density EX. Weather, seasons, natural disasters

21. 4. REGULATING POPULATION GROWTH Density-dependent factors: increase or become more prominent when the population density increases EX. predation, pollution, food shortage